The Dismantling of the DELPHI Experiment

Table: Dimensions and main composition of the DELPHI Forward detectors.

I.2.    General approach for the dismantling

Originally it was foreseen to dismantle the complete DELPHI detector and the counting houses D1, D2 and D3. Recently the proposal has been made to keep part of the DELPHI experiment as a museum site. This has significantly changed the dismantling project. It is planned to dismantle only the 2 endcaps, as well as the counting barracks B1, B3, A1, C1, C2 and the platforms A3, B4, C3 and D3. All other counting barracks will be used in a different configuration by LHCb.

The dismantling of the DELPHI endcaps follows roughly the inverse order of its installation. After a preparatory phase which is not much different from the start of a normal winter shutdown, the actual dismantling and removal of sub-detector units starts, beginning with the innermost detectors and the LEP vacuum chamber and ending with the magnet  yoke segments and the counting barracks. 

The overall schedule, which is imposed by the end of the LEP running and the start of LHC civil engineering work in the UX cavern, requires to work in parallel work on the barrel and the 2 endcaps. Therefore the position of these 3 units and of the counting barracks will be changed several times, in order to provide the optimum configuration for access and material flow.

The sub-detectors will be dismantled by the individual detector groups. Every group will provide a sufficient number of physicists and technicians which are familiar with the hardware of the detector. They assure the availability and correct funtionning of all necessary equipment. The detector groups will be assisted by a team of technicians and crane drivers, which take care of the erection of necessary scaffoldings, handling and lifting. The dismantling and removal of cabling, pipework and structural elements will also be affected by this team. All activities will be coordinated by a small team of CERN staff (B. Corajod, C. Joram, J. Renaud). During the dismantling regular meetings will be held to fine tune the collaboration with the detector groups, to follow up the progress and to identify zones of problems.

In the UX cavern the material will be handled using the 2 overhead cranes of the UX cavern (capacities: 1 x 80 tons, 2 x 40 tons respectively) and the movable heavy load platform (100 tons).  Most of the material will be evacuated through the shaft PX with its 80 tons overhead crane installed in the SX hall. Only small components (electronics / portable equipment) can be removed through the personnel elevator PZ. The materials elevator PM is reserved for the teams dismantling LEP and must in general not be used by us.

Once lifted to the surface the material the further approach depends on the destination of the material. Detector components which are planned to be reused in any form, have to be immediately removed from the site. Storage, even outside, is in general excluded by the very limited available space. All other detector components will be removed by an industrial recycling company, either directly from the DELPHI site, or after cutting of big components on a central zone, situated on the CERN Prevessin site.

The DELPHI control room and the online cluster is planned to stay operational until at least end 2000. This is in order to give the detector groups the possibility to analyse detector (calibration) data and to migrate programs and data to other machines or storage media. All infrastructure and safety systems in the control room stay operational during that time.

The DELPHI exhibition in the SX building has to be dissolved at the end of the LEP running to create space for the handling of detector components. All detector groups have to recuperate their module and transport it off site.

I.3.    The INB question

The LEP accelerator is being operated under an agreement with the French authority in charge of all nuclear installations in France. Have a look under DSIN and ISPN for more details.

LEP and to some extent also the 4 experiments are treated as INBs (Installation Nucleaire de Base), i.e. as basic nuclear installations. This has major consequences for the dismantling of the LEP machine, but possibly also some consequences for the dismantling of the experiments.

The LEP dismantling document which describes the strategy and the procedure of the LEP dismantling (zoning, waste study, risk analysis) has been presented to INB in September 1999 but was rejected for various reasons. One of the main points of criticism was that the  experiments were not treated in an adequate way. 

It was felt that the fastest way to solve this problem, is to write a number of annex documents:

• The zoning analysis (i.e. a classification of the various parts of the experiments as conventional or radioactive zones), common for the 4 experiments, is mainly based on calculations performed by TIS (M. Silari et al.) in collaboration with the experiments (Many thanks to Vincent Hedberg who represented DELPHI in this team). In some cases the calculations have been verified by various activity measurements during the 1999/2000 shutdown. The main result is that, with the exception of the very forward luminosity monitors VSAT, any material may be classified as conventional. According to the calculations, a small level of induced radioactivity may be expected for the VSAT detectors, so that they have to be classified as "TFA" (très faiblement active).

• A waste study and risk analysis has been made for each of the 4 experiments individually. The DELPHI document (click here for the latest version), written by Christian Joram and Jean Renaud, describes the detector, the overall dismantling planning and discusses then in detail the various sub-detectors and their disposal paths. Special care has been given to detectors carrying radioactive sources.

The goal of these documents is to convince INB, that the expected and also measured radioactivity levels justify to dismantle the experiments without following the full set of strict regulations which are applied to the LEP machine. In particular a complete inventory and subsequent tracing of all dismantled pieces has to be avoided. The experiments should be considered as INB^light. The tracability requirement for all material coming from LEP and other INB constraints may have indirect implications for DELPHI since we are sharing the same site and in particular the same access to the site.

The modified LEP document together with the annex documents for the experiments have been presented to ISPN and subsequently to DSIN in January 2000. A final and firm approval of the proposed procedure can however only be expected by summer 2000. Semi-official information indicates however that the French authorities will accept the experiment

II.    Planning

During the last 18 months a detailed planning of all aspects of the dismantling has been established and graudually refined and adjusted to emerging constraints. It comprises a detailed schedule of all tasks, the detector specific dismantling methods, the logistics (transport and intermediate storage), and the provision of tools and special dismantling equipment. 

The time table for the dismantling assumes that LEP is operated until end of September 2000. The dismantling activities are foreseen to start on Monday, 2 October 2000. This date (week 40) serves as T_o. A lot of preparatory work will of course have to be performed already before T_o.

A possible extension of the LEP running will essentially result in a T_o shift, with some adjustments due to the christmas stop. The planning of the individual detector groups and, in particular, all contracts with industrial partners have to allow for this possibility.  

The planning of the LHC project assumes the DELPHI cavern to be available for civil engineering work as of June 2001. This date has to be considered as a hard limit. Its violation will result in penalty payments from CERN to the civil engineering contractors.

According to the planning which we discuss below, the available period of 8 months is sufficient to dismantle and remove the detector and the counting barracks D1, D2 and the platform D3. In case some of the assumptions and estimated turn out not to be fully realistic, a reserve of 4 weeks is included. The planning is based on a weekly working time of 40 hours. Longer working time or work in shifts can be envisaged to catch up unforeseen delays.    

II.1    The dismantling phases

DELPHI will be dismantled in 7 phases. Each phase corresponds to a specific configuration of the barrel, the endcaps, and the counting houses A-D. The configurations optimise the access and the material flow, taking into account the sub-detector specific constraints. The time loss due to the relatively slow displacement of the barrel and endcaps (typically 1 day per movement) is compensated by the possibility of in parallel work on the barrel and endcaps.

Phase I is of special importance since it includes all measures required to secure the experiment, the cavern and the other work places

• switch off all HV/LV and fastbus

• purge flammable gases (see also II.8)

• empty detector fluids (RICHes)

• demagnetize magnet yoke

• warm up solenoid (see also II.8)

• empty cooling water circuits 

• disconnect barracks from electrical power

• disconnect all gas, smoke/fire detection systems on the detector, in the barracks and on the platforms, and also in the gas building (SG)

• remove the HALON fire extinguishing equipment

• disconnect the telephones in the barracks and on the platforms

The smoke detection systems in the cavern and in the DELPHI control room stay operational.

Phase I week 1    purge flam. gases demagnetize solenoid  preparatory tasks
Phase II week 2 - 4   open endcaps  warm up solenoid  dismantle  * Beampipe * MUB periph. chambers  * STIC  * TAG, LASER  * MVTX  * FCA
Phase III week 5 - 8   endcaps in garage position dismantle * RIF * FCB  * FEMC  * MUB outer chambers * Platf. B4 + Bar. B3
Phase IV week 9 - 12   dismantle  * Bar. B2 (store) * Bar. B1 (scrap)  * MUF  * HOF * MUB cont.
Phase V week 13 - 17   dismantle  * FHAC thin endcap * FHAC thick endcap
Phase VI week 18 - 20   dismantle  * Platf. A3 + C3 * Bar. C2 + C1  * Bar. A2 (store)  * Bar. A1 (scrap)
Phase VII week 21 - 24   dismantle  * Platf. D3 * Install B2 + A3 on top     of D2

II.2 Detailed planning

A detailed planning of all dismantling tasks has been established using MS Project. The ".mpp" file can be found here. For those who are not able to use MS Project we inlcude the corresponding listing of all tasks .

II.3     Resources and organisation

The dismantling project will be organised as follows: The individual sub-detetcor groups are responsible for the dismantling of their equipment, including electronics. A sub-detector group consists of a number of hardware experts (physicists/engineers/technicians) sufficient to complete the dismantling in the time allocated in the planning. Each group names a technical responsible and contact person. They agree with the technical coordinator, the GLIMOS and the foreman ("chef de chantier") on the dismantling method and the detailed work schedule. Whenever possible the team should include persons which were already present during the detector installation.

A support team of 4 - 6 electro-mechanical technicians will be permanently present. They work under the supervision of the "chefs de chantier" and assist the sub-detector groups. They will also take care of  the dismantling and removal of infrastructure (cables, pipework, structucal elements) and the preparation of the necessary scaffolding and work platforms.

For each of the 3 overhead cranes (2 in UX, 1 in SX) there will be 2 cranemen. One of the 6 cranemen will act as foreman for the lifting and handling tasks.

The overall responsibility for the dismantling planning and execution is with the technical coordinator. The GLIMOS is in charge of all saftey aspects of the complete project.

Non-CERN personnel must be registered as CERN user (user office) and have a valid CERN access card. Only persons which have attended the TIS safety course  are allowed to work in the cavern. For persons which have not been working in the cavern for some time the attendance of the safety course is highly recommended. All persons have to carry a film badge when they work in the underground area. Non-CERN personnel without a film badge can obtain a visitor film badge at the dosimetry and calibration service TIS/RP-DC (J. Fraisse) in B24-E-011. In this case a special medical examination is not required.

Newly arriving sub-detector teams will be briefed in a short DELPHI specific meeting about safety precautions, access formatlities and INB regulations.

Regular meetings will be held to follow up the progress of the work and to discuss the detailed planning for the following week. The contact persons of the sub-detector groups have to attend these meetings one week before and during their dismantling task. 

II.4    Logistics

Due to the construction work of the hall SHM8 the available space on the DELPHI site is very limited. The main rules are therefore:

• dismantled material must be removed from the DELPHI site immediately after the dismantling

• except of special cases no material can be stored on site

• sub-detector specific dismantling tools / material has to be   brought to the site just in time and removed immediately after completion of the dismantling

Dismantled material will be evacuated through the shaft PX with its 80 tons overhead crane installed in the SX hall. Only small components (electronics / portable equipment) can be removed through the personnel elevator PZ. The materials elevator PM is reserved for the dismantling of LEP and must in general not be used by us.

The material removal rate is to a large extent determined by the crane speeds. As a rule of thumb, the evacuation of an element with a weight above 5 tons through the PX shaft takes about 1 hour. Material has therefore to be conditionned in a proper way.

For the collection and lifiting of general material (cables, pipework, structural elements) skips of 5 and 9 m³ capacity are will be placed in the SX cavern. Sub-detector specific handling details will be discussed below.

Once the material is available in the SX hall, three main paths are foreseen:

• Removal by the sub-detector team for later use. In this case the transport has to be organized by the team.

• Removal by a contracted recycling company. Direct loading on a truck, or removal of material in skips of 5, 9, or 30 m³ is foreseen. A number of skips for different material types will be placed around the SX building.

• Very large or heavy components which will be transported by the CERN transport service to a central cutting zone on the CERN Prevessin site. The contractor will cut the components in transportable pieces and remove them.

For the transports carried out by CERN or the contractor, provisional schedules have been established. A final schedule for the following week will be provided one week in advance. It is expected that the CERN transport service and the contractor follow these schedules with a precision of 1 day. The same rule has to be applied to transports organised by the sub-detector teams.

II.5 Dismantling tools and materials

It is the responsibility of the sub-detetcor teams to provide the specific tools and materials required for their detector. All equipment has to be conform with CERN safety regulations. Its correct functioning has to be verified in advance. In case of missing equipment, solutions have be discussed with Jean Renaud and Christian Joram as soon as possible.

CERN will provide all general tools required for the dismantling. In addition special cutting tools (pneumatic, hydraulic) for cables, cable bundles and pipework have been purchased. A sufficient number of standard pallettes (ca. 150) will be available for moudules of the FEMC. It is foreseen to set up a number of small (<1m³) and medium size (5 and 9 m³) containers in the cavern for the collection of small items, like bolts, nuts etc., but also cable and pipework (see below). These containers will be lifted to the surface either with the PZ lift or through the PX shaft. 

II.6    Cables and pipework

Cables and pipework are in general not subject to later re-use. Their removal method is therefore optimised for speed. Cables will in general be cut directly behind the detector modules. The connectors stay on the detector if they don't hinder the dismantling of the detector. The cables / cable bundles will be cut in pieces of appropriate length and be collected in skips available in the cavern. A separation between power and signal/coaxial cables may be made. It is estimated that 80% of the cables are multi wire signal cables, 10% coax and HV cables, and about 10% power cables.

Depending on the material type and cross-section, pipework will be similarly dismantled as cables. Large diameter tubes will be dismounted and removed as a whole.

II.7    Counting houses and electronics

The counting houses D1, D2, A2, B2, including the racks, are planned to be reused by LHCb and will therefore stay in the cavern. The counting barracks A1, C1, B1, and B3, as well as the platforms A3, B4, C3 and D3 are planned to be removed from the cavern. For mechanical reasons it is necessary to empty the barrack modules before they can be lifted to the surface. Some empty racks can in principle be left in the barracks and be removed only at the surface.

All counting houses will be completely separated from electrical power in week T_o + 3. At the same time the existing Neon tubes in the barracks will be re-connected via mobile distribution boxes. These distribution boxes may also be used to provide electricity to hand held tools or similar electrical devices.    

The dismantling of the electronics, crates (DAS and slow control), and the transformation of the online cluster is co-ordinated by Philippe Gavillet. He is supported by Yvon Miere (DAS hardware) and Andre Augustinus (SC hardware). Two technicians will be supplied by LHCb for a period of a couple of months to help the central and the detector teams.

The removal of the electronics has to be organized such that interference with the detector dismantling and the use of the cranes is minimized. Whenever possible the PZ lift should be used to lift up electronis stored on palettes.

The electronics, i.e. the crates, the fans, the fastbus and other modules, belong either to the electronics pool, to DELPHI (common fund) or to the individual detector groups (collaborating institutes, incl. CERN).

During the first 2 weeks after  T_o a central team will first mark and then remove all central fastbus and slow control hardware. Then it is the responsibility of the detector teams to remove their specific electronics. If possible, priority should be given to fastbus modules, then to non-fastbus one. Electronics in labs (at CERN or on top of the control oom) must not be forgotten. Containers will be available to dispose obsolete electronics which will then be scrapped. Pool modules will be grouped according to their type and sent back to the pool. Two central persons will support the detector teams in recuperating power supplies, fans and crates (>> pool).  Electronics recuperated by the detector groups for later use must not be stored at the pit or in outside barracks, but has to be transported off site as soon as possible. A more detailed planning was given by Philippe Gavillet during the June 2000 TP. Please consult the general planning (MS Project, Task list) for updates.

The detector groups should co-ordinate with the other groups working in the same barrack to avoid space/access conflicts.

The list of all racks and the associated responsibles is to be found here (pdf file).

Since DELPHI and the individual detector groups may have to pay compensation for missing pool modules all instititutes are requested to make an effort to search for modules, not only in CERN labs, but also in their home institutes. 

Online Cluster

The Online Cluster is planned to stay operational in Pit8 until the Christmas holidays minus 2-3 days, however detector stations are available for immediate removal with prior notice.
The nodes AXDES1, AXDES2 and AXDEOP will be transferred to building 13 just before christmas 2000. A reduced, but functionally identical Online Cluster will be reconfigured in early January 2001.

A questionnaire will be soon sent to the detector groups to inquire their plans to recuperate electronics and ALPHA stations.

II.8    Gas and cryogenics platforms

In the first 2 weeks after T_o the detectors will be purged from flammable gases. The purge is under the responsibility of Ferdi Hahn (FGSO = Flammable Gas Safety Officer). The purge flow rate may be increased compared to a normal shutdown in order to have a complete removal of any flammable gases. This is of great importance since some detector components may be dismantled or cut with a cutting torch. During the purge period, work on the gas platforms A3, B4 and C3, which risks to interfere with the purge is not allowed.

At the end of the purge period all gas bottles have to be removed from the platforms. The gas bottles and batteries in the SG building will be sent back to the supplier.

The mixer lab in the SG building is planned to serve as a storage room for gas racks dismantled form the platforms A3, B4, C3. The racks in the mixer lab will be dismantled and stored in the adjacent gas battery rooms. This task is planned for the weeks 3 and 4 after T_o (ca. 4 man weeks).

Most of the gas racks are planned to be dismantled and and partly recuperated by the gas group. This includes also the controls (G64, PCs). The removal of the material on the platforms is foreseen to happen in two steps. After the gas purge is finished and the electrical power is cut, technicians from the gas group isolate the individual racks (pipework and cables) and prepare them for lifting and transport. This task should be finished before Christmas (2000 ?). During this time detetcor groups may recuperate items from the racks which are owned by them.

It is not froeseen to recuperate any safety relevant material for later use (like IGD, SDN). CERN is planning to replace these systems by more modern devices.

Currently discussions are going on concerning the reuse of the gas installations of the detectors MUB and MUF (CosmoLHC, K. Eggert) and of HPC (HARP experiment, L. Linssen).

Important: The gas racks of HPC, HAC and FHAC contain in total 4 radioactive sources. The sources in the racks have to removed as soon as possible after T_o and given back to TIS/RP (see below).

The cryogenics installations and all related services will be kept operational for about 2-3 weeks after T_o . During this period the solenoid will be used to demagnetize the iron yoke (HCAL) and finally it will be warmed up by exploiting its ohmic resistivity. A suitable power supply (250V, 50A DC) will be provided by A. Beuret (SL/PO). The LHC/ECR group (K. Barth) is planning to recuperate the complete cryogenics equipment (cold box, dewars, controls) installed on D3. After preparation of the equipment by LHC/ECR the removal of the equipment is planned for March 2001.

The SL/PO group plans to recuperate the main power supply (6000 A) of the solenoid. Recuperation of other equipment (main cicuit breaker, discharge resistors) is under study. The trim coil power supplies are of no interest for them. SL/PO will prepare the equipment for removal in March 2001.

II.9    Detector specific dismantling information

The following table summarises the detector specific dismantling information which is based on the analysis of the questionnaire (sent out in April 1999), discussions and email exchanges. It represents the current status of our knowledge. Detectors which will stay in place for the DELPHI Exhibition project are marked with a yellow background.

1) CCZ = Common Cutting Zone, CERN Prevessin site.

III.   Use of material after the dismantling

III.1     Recuperation by the collaborating institutes

As indicated in the below table, a certain fraction of subdetectors are planned to be recuperated by the institutes which have built and operated the devices. In some cases the detectors may be used in lab tests or test beams. The institutes are in charge of both preparing the material for the transport and organising the transport. Temporary technical support can be provided and transports inside CERN can be handled by the CERN trsnsport service. Storage of detectors at the pit is in general excluded for space reasons. The material has to be shipped right after its dismantling.  

III.2    Re-use in future exeriments or exposition for pedagogical purposes

A number of firm requests have been received for the use of large parts of DELPHI in future experiments.

The CosmoLHC project (possible approval in late 2000) aims at the installation of a muon chamber array in the ALEPH cavern after ALEPH is dismantled and the civil engineering work for LHC are finished (early 2002).

The multi-purpose underground muon detector at the CUPP centre in Finland plans to install large area muon detectors for cosmic ray physics in an underground cavern.

The The ADONIS idea or the plan to use the MUF chambers in the OPERA experiment are not pursued any longer.

It is understood that the institutes which request detectors clarify all formal, legal, and fiscal details with the actual owners. If required, they provide support (manpower and/or financial) to dismantle the detectors and associated equipment. Once the detetcor is lifted to the surface, the packaging and transport of the equipment is under the responsibility of the requesting institute. Storage on the DELPHI site, even for short periods, is excluded for space reasons.  In case a future project is not approved by the funding authorities or the scientific committees, the requesting institute is in charge of the final disposal of the equipment.   

Some subdetector teams are in touch with science museums or similar organisations which are interested to expose detector components for pedagogical purposes. One example is the MVTX, for which the London Science Museum has expressed interest,  Uppsala university and the royal science museum in Stockholm would like to expose an arangement of a large number of RICH mirrors. The Prague technical museum would like to expose modules or parts of the following detectors: FEMC, TOF/HOF, HPC and MVTX.

III.3    Sale of material

Togther with CERN's SPL division we are preparing the sale of detector components to companies specialised in the field of scrapping and recycling of materials. In a market survey (MS-2771/SPL-LS) about 15 European companies have been identified which expressed strong interest in buying material salvaged from LEP and the 4 LEP experiments. Meanwhile 5 independent calls for tender have been submitted (1 for LEP and 1 for each of the 4 experiments). The total weight of the offered material is about 30.000 tons (LEP 20.000, experiments 10.000). The DELPHI document (IT-2771-DELPHI-SPL/LS) comprises more than 3.100 tons arranged in 9 different material groups. The bidders specify a price per ton for each of the material groups. The price is composed of the pure raw material value and the overhead costs which the bidder has to take into account, like cutting, transport and administration. For some groups a negative price is expected, i.e. we have to pay for the disposal of the material. A further unknown is the variation of the raw material prices due to economical fluctuations. Between  the deadline for bids and the date when the material will actually be sold the raw material component of the bidder's prices will therefore be indexed according to a raw material index.

For the formal sale act CERN considers all material as its property. The income from sales or the cost of the material disposal will be handled via the DELPHI M&O budget. It is then DELPHI's responsibility to redistribute the income/costs.  

The STIC has been included by mistake in this list. It will not be sold but recuperated by its owners. Also the OD team has in the meantime indicated that they want to recuperate their hardware.

IV.    Safety

A successful collaboration of the DELPHI detector groups, people from various CERN divisions, and industrial partners during the dismantling phase does not only require an extensive and careful planning but also a strict application of safety rules in order to work without endangering other people or ourselves. The following sub-chapters will address different aspects of a safe dismantling of the DELPHI detector.

IV.1     Safety organisation and applicable documents

CERN’s policy concerning occupational health, work safety and environmental protection – here used with the general term Safety - has been drawn up by the Safety Policy Committee (SAPOCO) and is described in the document SAPOCO42: Safety Policy at CERN. For its operation, CERN bases its own Safety regulations on the European Directives and the rules in force in the Host States. CERN favours the most advanced safety regulations, which must respect the rules of public policy in force on the territory of the Host States and which have to insure a level of safety which is at least equal to that offered by these States’ own regulations.

The organisational structure concerning safety is also described in SAPOCO42. For Safety matters, the DELPHI collaboration is represented by a Group Leader in Matters of Safety (GLIMOS), who undertakes responsibility for Safety during the operational stages of the equipment and the final dismantling of the experiment. The GLIMOS has appointed Safety Linkmen to ensure continuity during the dismantling work in accordance with the safety requirements and procedures set out in the Divisional Safety Plan.

CERN staff, registered visitors, and temporary labour personnel are accountable for safe behaviour to their immediate supervisor or to other persons specifically named as being in charge of matters of safety during the dismantling of the detector.

Outside Firms and their employees working on the dismantling of DELPHI on the CERN site are bound by the occupational health and safety regulations of the French Host Country. They are also subject to the specific CERN rules by virtue of the firm’s contractual obligations. The safety rules to be applied for industrial enterprises are defined in the document CERN/TIS-GS/98-10.

Additional documents deal with special applications (safety codes, safety instructions, safety notes, divisional safety plans, operational instructions, etc.) of SAPOCO42 and these are published by the TIS Division. The Safety Note NS 20 in French ("Travaux de demolition et demontage"), gives guidelines for demolition and dismantling work in general.

IV.2    Preparatory safety relevant tasks

An important task in the dismantling of the DELPHI detector consists in the careful preparation of all tools and in the testing of all equipment necessary for the dismantling.

Nearly all of these devices were already used during the installation phase and were tested for safety by TIS at that time. As no major modifications were applied to these tools since then, TIS agreed on using this special equipment without any further formal safety tests by the TIS division. Nevertheless, the ensemble of all the equipment needed for the dismantling is going to be or has been tested by the DELPHI technical staff for completeness and proper operation.

DELPHI will make available a certain number of safety helmets, gloves, and harnesses for the dismantling period, though all persons working in the cavern during that time are obliged to have their own personal equipment with them.

IV.3     The dismantling zone

The dismantling zone consists of the DELPHI experiment in the UX cavern and the SX and SG areas on the surface, where the dismantled parts of the detector will be stored for a while or prepared for transport. These zones have to be equipped with warning displays: Dismantling zone, Access for authorised persons only. Barriers have to separate storage space for material and tools from access and emergency escape routes, which must be clearly marked with standard signs and be always kept free from obstacles.

Because of the heavy working load and the very tight schedule during the dismantling phase of the detector visits to the former experimental area will not be possible. It may be envisaged that restricted visits in time and number of participants are exceptionally allowed by using the gallery in the cavern.

IV.4     Securing the experiment

Before starting the dismantling work in the UX cavern all flammable gas systems of DELPHI are flushed with Nitrogen. It is under discussion whether in a second step the Nitrogen in these gaseous detectors has to be replaced by air.

The yoke of the superconducting solenoid will be demagnetised by repeatedly inverting the magnetic field. The magnet and its cryogenics will then be switched off.

All water cooling devices will be stopped and the piping systems will be emptied. The fluorocarbon radiator fluids of the Forward and Barrel RICH counters will be recuperated in their appropriate storage tanks.

All high voltage circuits, preamplifiers, electronics, etc. of the experiment will be switched off at the beginning of dismantling. All electricity circuits including uninterrupted power supplies for the detector elements and for the lights in the counting rooms will be cut. Moveable power plants for the lights in the counting rooms will be installed for a safe dismantling of all the electronics and RICH fluid systems equipment therein. A ‘Service work protocol’ with signature of the person in charge will be established in order to assure that all systems are in a safe state before dismantling work starts.

The activities concerning the securing of the experiment will take place in parallel to a great extent. This Phase I of the general dismantling planning is scheduled for the first three weeks after the experiment's data taking has stopped. Only after the experiment is in a safe status the dismantling of individual detector parts will start and only then technical help and support of outside CERN groups is foreseen.

Certain dismantling tasks imply working on the detector in areas up to 12m over ground. Whenever possible scaffolding or platforms will be installed for safe working conditions.

IV.5     Safety relevant services

After having disconnected all electrical power in the counting rooms, the fire and smoke detection system DEF and VESDA will be disabled. The same applies for the SDN and BINOS systems, which detect smoke, fire, and flammable gas inside the DELPHI detector. The system of catalytic IGD detectors, which sense gas leaks mainly inside the gas distribution racks on top of the counting rooms A, B, and C, will also be disabled and then dismounted. All PERREN halon systems for fighting fires in the counting rooms and in between the barrel and forward parts of the detector will be removed. All telephones inside the counting rooms will be disabled.

Purging the detector from flammable gas mixtures and removing all electrical power inside the counting rooms reduces the risks of explosion or fire considerably. Hence all safety relevant services in the counting rooms and inside the DELPHI detector itself are cut and removed. Nevertheless, all services inside the underground cavern which guarantee safety to a certain extent will be kept operational.

Portable fire extinguishers will remain before all counting rooms and on top of the detector. A sufficient number of BIOCELL breathing apparatus are available in the cavern before counting room B3 and on top of counting room D3 close to the staircase to B4. The telephone system inside the cavern and the so-called ‘red telephone’ will remain operational during the dismantling period. It is also guaranteed that the portable GSM phones will continue to work.

The ventilation systems for the DELPHI cavern and the elevators, the system against inundation of the UX area, and the smoke detection system in the cavern will continue to operate without any modifications. The evacuation alarm system remains installed and operational outside counting room C1 and at both entrance doors to the UX cavern.

The safe environment in the DELPHI cavern is monitored by GSS (General Surveillance System). This system will be modified as certain channels for detecting anomalies, especially in the counting rooms, are no longer activated and available during dismantling time. But all safety relevant level-3-alarms remain operational.

Conventional risks (fire, explosion, etc.) are minimised by cutting all electricity lines in the counting rooms, purging the detector with inert gas, and disposing all hazardous chemical products.

IV.6     Protection of persons and safety briefings

All persons working, even temporarily, in an underground area must be informed about safety rules, hazards present, alarm characteristics and emergency routes. For that reason it is indispensable that all persons working for the dismantling of the detector have UX-clearance. To obtain access permission to the DELPHI cavern all persons have to follow a specific safety briefing, covering the particular safety problems encountered in underground areas. The duration of this briefing is about three hours, and it is given by the CERN Fire Brigade. DELPHI specific information about safety issues (access to the pit, emergency exits, safety relevant services, names of contact persons and supervisors, etc.) will be made available in written form to all persons working underground. In addition, the GLIMOS of the DELPHI experiment will give regular safety briefings to all external people from universities, institutes, and contractors. In this context the new access system to the cavern will be presented and explained. All people working in the DELPHI cavern during the dismantling phases have to wear a film badge which can be obtained for short term visitors from the TIS radioprotection group without any medical consultation.

All activities concerning the dismantling of the DELPHI detector are coordinated by a small team of CERN staff. The members of that team will supervise the work of all those who come from outside CERN institutes, universities or firms, either to dismantle a specific detector part or to take care of the safe handling and transport of material. In order to guarantee the safety of personnel and material, various protective measures and adequate planning and coordination of the operations are established in advance.

The coordination team has determined the period and duration of the different operations needed for a safe dismantling, and they are in charge of the tools and equipment which are indispensable for this task. By keeping an adequate working speed safety risks are kept low for persons involved in the dismantling of the detector.

In addition to these collective precautions all persons working in the DELPHI area are obliged to take individual measures as to protect themselves. It is obligatory to wear a protective helmet and safety shoes during any dismantling activity; gloves, glasses, and noise protection devices have to be worn under special conditions. Persons working on the detector itself must be equipped with harnesses to avoid falling from great heights, if scaffolding or platforms are not available. The qualification and knowledge of the personnel will reduce safety risks considerably during the dismantling activities.

For reasons of different tracing of all dismantled pieces DELPHI and LEP zones are strictly separated. Therefore all persons working on the DELPHI side should only use the PZ-elevator to enter the UX area. It is formally forbidden to take any dismantled material or working tools through the rear exit of the DELPHI cavern into the LEP area. This rear exit is only to be used in emergency situations.

The general working hours during the dismantling of the DELPHI detector are the same as foreseen for the dismantling of the LEP machine itself, i.e. from 7a.m. to 7p.m. from Mondays to Fridays. After short notice should it however be possible to extent this working time for the dismantling of the detector up to midnight in case of necessity. In this case at least two people have to work together and one of them will be briefed for taking responsibility as SLIMOS during these extended working hours.

IV.7    Radiological zoning analysis

As already mentioned above the radiological zoning analysis and several control measurments during the shutdowns show  that the LEP detectors have not been significantly activated as a consequence of the LEP operation. For by far the biggest part of the detector the expected induced activities are below 1 mBq/g. The only exception is the VSAT detector for which the calculations show that activities in the range of several Bq/g can be expected for some specific isotopes. The VSAT is therefore classified as "TFA" (très faiblement active) and will be handled like LEP equipment coming from a TFA zone: it will receive a bar code sticker, will appear in the LEP equipment database, and has to be tracable until its final destination (which may be the TIS/RP service).

IV.8    Nuclear risks and precautions

Although significant levels of radioactivity are not expected during the dismantling of DELPHI, a number of precautions and safety measures will be applied. All people working on the dismantling have to permanently carry their film badge, i.e. they will be under indvidual radiological monitoring. The access control to the experimental caverns (turnstiles with card readers) stays operational until the completion of the dismantling. Every single dismantled component will undergo a radiation check, normally before the component leaves the cavern. In exceptional cases the checks can be done at the surface, however in any case before the material leaves the DELPHI site. A dedicated radioprotection technician under TIS supervision will be in charge of these checks, the bookkeeping and labelling of the controlled equipment. The radiation monitors at the site gate stay operational. Additional random radiation checks will be performed on the Prevessin central cutting zone. A final global check is performed for material with destination recycling company: The loaded truck has to pass a weigh bridge and a nearby radiation monitor before it can leave the CERN site.   

IV.9    Radioactive sources

As detailed in the  INB document DELPHI contains in total 507 calibration sources with a total activity at the time of the dismantling of about 48.7 MBq. Most of these sources (503) are installed in the subdetectors TPC, HPC and VSAT. In the gas racks of HPC, HAC and FHAC in total 4 sources are used. The sources in the racks have to removed as soon as possible after T_o and given back to TIS/RP.  The RP technician will verify that the area around the source is not contaminated before other equipment in the rack can be removed.

The sources of the VSAT are very weak (²⁴¹Am, total activity ca. 5.6 kBq) and can not be separated from the detector because they have been deposited as thin surface films. Special care has to be taken during the dismantling of the VSAT in order to exclude the risk of contamination of perosns, tools or other equipment.

The follwoing two paragraphs became obsolete due to the DELPHI museum project:

Each of the 144 HPC modules contains three   ²⁴¹Am sources with a total activity of 4.15 MBq. These sources can only be removed once the HPC modules are dismantled. For this purpose the outer skin of the modules (copper coated G10) has to be cut open. The precise extraction procedure will be optimised together with TIS/RP in order to avoid the danger of contamination.

The TPC is equipped with 36 sources (⁵⁵Fe, total activity at the time of the dismantling 42.5 MBq). The sources can only be extracted once the TPC is dismantled and opened up. The opening of the TPC will be performed in a hall on the Meyrin site. Appropriate hall space still has to be found. The transport of the TPC from the pit to the Meyrin site has to follow the applicable safety rules.

IV.10    External contractors

As already mentioned in chapter IV.1 "Safety organisation and applicable documents"  outside firms and their employees working on the dismantling of DELPHI on the CERN site are bound to the occupational health and safety regulations of the French Host Country and to the additional safety rules which CERN itself as an organisation has put forward.

In the document CERN/TIS-GS/98-10 "Safety Regulations Applicable to the Work of Contractors at CERN / Regles de securite applicables aux activites des entreprises sur le domaine du CERN" all procedures and safety rules are defined for all those contractors executing  projects and work in the name of CERN. All principal obligations of the contractors in matter of safety are described in there, as:
- registration of personnel and access demand
- obligatory safety session and access card
- individual professional competence and medical fitness
- announcement of starting work to the Host Countries
- coordination of safety
- utilisation of safe materials and their control, etc.

Concerning safety all employees of outside CERN firms (and institutes and universities) are treated in the same way than full time members of CERN personnel. The GLIMOS of the DELPHI experiment is responsible for the proper application of all safety rules which concern outside CERN contractors. Therefore all temporary personnel is -in addition to the UX clearance course by the CERN fire brigade- also obliged to follow the DELPHI specific safety briefing by the DELPHI GLIMOS.

V.    Securité

(version francaise du chapitre 4, original anglais)

Une collaboration réussie des groupes des détecteurs DELPHI, personnes travaillant dans différentes divisions au CERN et partenaires industriels durant la phase de démontage, ne demande pas seulement un planning vaste et soigné mais aussi des mesures de sécurité strictes pour assurer un travail sans danger pour l'entourage et pour nous-mêmes. Les sous-chapitres suivant décrivent les différents aspects du démontage en toute sécurité du détecteur DELPHI

V.1.     Organisation de la sécurité et documents à appliquer

La politique du CERN en matière de santé professionnelle, sécurité du travail et protection de l'environnement - ici utilisée sous le terme général de "Sécurité" - a été élaboré par le "Safety Policy Committee (SAPOCO)" et est décrit dans le document SAPOCO42 : politique de sécurité au CERN. Pour son fonctionnement le CERN a basé son propre règlement de sécurité sur les directives européennes et les statuts en vigueur dans les Etats Hôtes. Le CERN favorise les règlements de sécurité les plus avancés lesquels doivent respecter la politique publique en vigueur sur le territoire des Etats Hôtes et assurer un niveau de sécurité au moins égal à celui offert par les règlements de ces Etats.

L'organigramme concernant la sécurité est aussi décrit dans SAPOCO42. Pour les questions de sécurité, la collaboration DELPHI est représentée par le Chef de groupe en matière de sécurité (GLIMOS), qui a la responsabilité de la sécurité durant la phase opérationelle de l'équipement et le démontage final de l'expérience. Le GLIMOS a désigné des "Personnes de liaison" pour assurer la continuité durant le démontage en accord avec les directives et procédures établies par le plan de sécurité de la division.

Le personnel du CERN, les visiteurs enregistrés et le personnel temporaire sont responsables d'une conduite sûre envers leur superviseur immédiat ou une autre personne spécialement désignée comme étant en charge des questions de sécurité durant le démontage du détecteur.

Les entreprises externes et leurs employés travaillant au démontage de DELPHI sur le site du CERN sont limités par les règlements de santé professionnelle et de sécurité de l'état hôte français. Ils sont aussi assujettis aux règlements spécifiques du CERN suivant les obligations contractuelles de l'entreprise. Les règlements de sécurité à appliquer aux entreprises industrielles sont définis dans le document CERN/TIS-GS/98-10.

Des documents supplémentaires traitent des applications spéciales (codes de sécurité, instructions de sécurité, notes de sécurité, plans de sécurité divisionnaires, instructions opérationelles, etc.) de SAPOCO42 et sont publiés par la division TIS. La note de sécurité NS20 en français ("Travaux de démolition et de démontage") donne les instructions pour la démolition et le démontage en général.

V.2.     Tâches utiles à la préparation

Une tâche importante du démontage du détecteur DELPHI consiste à préparer soigneusement les outils et tester tout le matériel nécessaire au démontage.

Presque tous ces appareils ont déjà été utilisés durant la phase d'installation et testés par TIS à ce moment-là. Comme aucune modification majeure n'a été effectuée sur ces outils depuis, TIS a accepté l'utilisation de cet équipement spécial sans autre test formel de sécurité par la division TIS. Néanmoins, l'ensemble de tout l'équipement nécessaire au démontage sera ou a déjà été testé par le personnel technique de DELPHI pour utilisation complète et correcte.

DELPHI mettra à la disposition un certain nombre de casques, gants et harnais de sécurité pour la période de démontage, mais toute personne travaillant dans la caverne devra avoir son propre équipement.

V.3.    Zone de démontage

La zone de démontage comprend l'expérience DELPHI dans la caverne UX et les parties SX et SG en surface, où les parties démontées seront stockées en attendant le transport. Ces zones doivent être signalées : Zone de Démontage, Accès à personnel autorisé. Les espaces de stockage pour matériel et outils doivent être séparés par des barrières de routes d'accès d'urgence. Les accès d'urgence doivent être clairement marqués avec des signes standard et doivent toujours être dégagés.

A cause de la charge de travail importante et d'un programme serré pendant la phase de démontage du détecteur, les visites à l'ancienne zone d'expérience ne seront pas possibles. Il peut être envisagé que des visites restreintes en temps et en nombre de participants pourront exceptionnellement être accordées en utilisant la galerie de la caverne.

V.4.     Mise en sécurité de l'expérience

Avant de commencer le travail de démontage dans la caverne UX, tous les systèmes de gas inflammable de DELPHI seront purges et remplace par de l'azote. Pour le moment des discussions sont en cours pour déterminer si en deuxième étape l'azote dans certains détecteurs gazeux doit être remplacé par de l'air. La bobine du solenoïde supraconducteur sera démagnétisée par des inversions repetitives du champ magnétiquet; ensuite l'aimant et ses cryogeniques seront débranchés.

Tous les dispositifs de refroidissement d'eau seront arrêtés et les systèmes de canalisations vidés. Les fluides des radiateurs à fluorocarbone des compteurs des "Forward et Barrel RICH" seront récupérés dans des citernes de stockage.

Tous les circuits haute tension, pré-amplificateurs, électroniques, etc. de l'expérience seront arrêtés au début du démontage. Tous les circuits électriques incluant les sources d'énergie pour les éléments du détecteur et pour les lumières dans les salles de contrôle seront coupés. Des groupes électrogènes pour les lumières dans les salles de contrôle seront installés pour un démontage en toute sécurité de toute l'électronique et des systèmes liquides du RICH. Un "Service work Protocole" sera signé par la personne responsable afin d'assurer que tous les systèmes sont en état de sécurité avant que le travail de démontage commence.

Les activités concernant la mise en sécurité de l'expérience seront effectués en parallèl. Cette PHASE 1 du planning général du démontage est prévu pendant les trois premières semaines suivant la fin de la prise de données. Seulement après s'être assuré que l'expérience est en état de sécurité nécessaire, le démontage des parties individuelles du détecteur pourra commencer et seulement à ce moment-là l'aide technique et le support des groupes externes au CERN sont attendus.

Certains travaux de démontage impliquent un travail dans des zones jusqu'à 12 m de hauteur. Chaque fois qu'il est possible, des échafaudages et des plates-formes seront installés pour une sécurité maximale.

V.5.     Services de sécurité

Après avoir déconnecté l'électricité dans les salles de contrôle, les systèmes de détection du feu et de fumée DEF et VESDA seront mis hors service. La même procédure s'applique pour les systèmes SDN et BINOS qui détectent la fumée, le feu et le gas inflammable à l'intérieur de DELPHI.

Le système de détecteur catalytique IGD, qui détecte les fuite de gas principalement à l'intérieur de la galerie de distribution des gas au sommet des salles de contrôle A, B et C sera aussi mis hors service et ensuite démonté. Tous les systèmes PERREN pour combattre le feu dans les salles de contrôle et entre le cylindre et les parties avant du détecteur seront enlevés. Tous les téléphones à l'intérieur des salles de contrôle seront mis hors service.

La purge du détecteur des mélanges de gas inflammables et l'enlèvement de toute installation électrique dans les salles de contrôle réduit le risque d'explosion ou de feu considérablement. A partir de ce moment-là tous les services en rapport avec la sécurité dans les salles de contrôle et à l'intérieur de DELPHI seront coupés et enlevés. Pourtant, tous les services à l'intérieur de la caverne souterraine qui garantissent la sécurité jusqu'à un certain point seront maintenus.

Des extincteurs mobiles resteront devant toutes les salles de contrôle et au sommet du détecteur. Un nombre suffisant d'appareils respiratoires BIOCELL sont disponibles dans la caverne devant la salle de contrôle B3 et au sommet de la salle de contrôle D3 près de la cage d'escalier B4. Le système de téléphone à l'intérieur de la caverne et le "téléphone rouge" vont rester opérationnels pendant la période du démontage. Il est aussi garanti que les téléphones mobiles GSM continueront à fonctionner.

Les systèmes de ventilation pour la caverne de DELPHI et les ascenceurs, le système contre les inondations de la zone UX, et de détection de fumée dans la caverne continueront à fonctionner sans modification. L'alarme d'évacuation reste et fonctionne au dehors de la salle de contrôle C1 et sur les deux portes d'entrée de la caverne UX.

La sécurité dans la caverne DELPHI est surveillée par GSS (Système de Surveillance Général). Ce système sera modifié quand certains conduits pour détecter les anomalies, spécialement dans la salle de contrôle ne seront plus activés et disponibles pendant le démontage. Mais toutes les alarmes de sécurité du niveau 3 restent opérationnelles.

Les risques classiques (feu, explosions, etc) sont minimisés par la coupure de toutes les lignes électriques dans les salles de contrôle, la purge du détecteur avec du gaz inerte, et l'enlèvement de tous les produits chimiques dangeureux.

V.6.      Protection des personnes et instructions de sécurité

Toutes les personnes travaillant, même temporairement, dans des zones souterraines doivent être informées des instructions de sécurité, des dangers présents, des caractéristiques des alarmes et des sorties de secours. Pour cette raison il est indispensable que toutes les personnes travaillant pour le démontage du détecteur aient l'accès UX. Pour obtenir cette autorisation d'accès dans la caverne DELPHI, toutes les personnes doivent suivre un cours de sécurité spécifique, couvrant particulièrement les problèmes de sécurité dans des zones souterraines. La durée de ce cours est d'environ 3 heures, et il est donné par le Service du Feu du CERN. Les informations spécifiques sur la sécurité à DELPHI (accès au puits, sorties de secours, services liés à la sécurité, noms des personnes responsables et superviseurs) seront disponibles par écrit à toutes les personnes travaillant dans les souterrains. De plus le GLIMOS de DELPHI donnera régulièrement des instructions à toutes les personnes de l'extérieur venant des universités, des instituts et aux contractants. Dans ce contexte le nouveau système d'accès dans la caverne sera présenté et expliqué. Toutes les personnes travaillant dans la caverne DELPHI pendant le démontage devront porter un film-badge. Les personnes venant des universités et restant au CERN seulment pour une période limitée en temps peuvent obtenir un film badge "visiteur" au service dosimétrie de la division TIS sans consultation médicale.

Toutes les activités concernant le détecteur DELPHI sont coordonnées par un petit groupe de personnel CERN. Les membres de ce groupe devront superviser le travail de tous ceux qui viennent des instituts en dehors du CERN, universités ou entreprises, soit pour démonter une partie spécifique du détecteur, soit pour s'occuper du traitement du transport de matériel. Afin de garantir la sécurité du personnel et du matériel, différentes mesures de protection, un planning adéquat et la coordination des opérations seront établis d'avance.

L'équipe de coordination a déterminé la période et la durée des différentes opérations nécessaires pour le démontage et elle est responsable des outils et de l'équipement indispensable à cette tâche. En maintenant un rythme de travail adéquat, les risques seront limités pour les personnes impliquées au démontage du détecteur.

En plus de ces précautions collectives, toutes les personnes travaillant dans DELPHI sont tenues à prendre des mesures de sécurité individuelles pour se protéger. Il est obligatoire de porter le casque de protection et les chaussures de sécurité pendant n'importe quelle activité de démontage; gants, lunettes et casques contre le bruit doivent être portés dans des conditions spéciales. Les personnes travaillant sur le détecteur lui-même doivent être équipées de harnais pour éviter de tomber de haut, si les échafaudages ou les plates-formes ne sont pas disponibles. La qualification et les connaissances du personnel réduiront les risques pendant les activités de démontage.

Pour des raisons de traçabilité des pièces démontées les zones DELPHI et LEP sont strictement séparés. Pour cette raison toutes les personnes travaillant à DELPHI devront utiliser seulement l'ascenceur PZ pour entrer dans la zone UX. Il est formellement interdit de prendre du matériel démonté ou des outils de travail par la sortie arrière de la caverne DELPHI dans la zone du LEP. Cette sortie arrière est à utiliser dans des cas urgents uniquement.

Les heures de travail générales pendant le démontage de détecteur DELPHI seront les mêmes que celles prévues pour le démontage du LEP, c'est-à-dire de 7h à 19h du lundi au vendredi. Pourtant il est possible qu'après préavis le temps de travail soit prolongé jusqu'à minuit si nécessaire. Dans ce cas au moins deux personnes doivent travailler ensemble et l'une d'elles sera formée pour prendre les responsabilités en tant que SLIMOS.

V.7.      Analyse radiologique de la répartitiion des zones

Comme mentionné déjà avant le zonage des expériences du LEP et plusieurs mesures de contrôle pendant les coupures montrent que les détecteurs LEP n'ont pas été activés de manière significative comme une conséquence du fonctionnement du LEP. Pour la plus grande partie des détecteurs l'activite induite attendue est en desous de 1 mBq/g. La seule exception est le détecteur VSAT pour lequel ces calculs montrent que plusieurs Bq/g sont à attendre pour quelques isotopes spécifiques.

Le VSAT est pour cette raison classé TFA (Très Faiblement Actif) et sera traité comme équipement LEP venant d'une zone TFA : il recevra un autocollant au code barre, apparaîtra dans la base de données des équipements LEP, et sera retrouvable jusqu'à sa destination finale (qui peut être le service TIS/RP).

V.8.      Les risques nucléaires et les précautions

Malgré que l'on ne s'attend pas à des niveaux de radioactivité significatifs pendant le démontage de DELPHI, un certain nombre de précautions et de mesures de sécurité seront appliquées. Toutes les personnes travaillant au démontage doivent porter d'une manière permanente leur film-badge, c'est-à-dire qu'ils seront sous surveillance radiologique individuelle. Le contrôle d'accès aux cavernes d'expérimentation (tourniquets avec lecteurs de carte) resteront opérationels jusqu'à la fin du démontage. Chaque pièce démontée devra passer un contrôle de radiation, normalement avant que la pièce ne quitte la caverne. Dans des cas exceptionnels les contrôles peuvent être faits en surface, mais dans tous les cas avant que le matériel ne quitte le site DELPHI. Un technicien de radioprotection désigné sous la supervision de TIS, sera chargé de ces contrôles, de l'enregistrement et de l'étiquetage de l'équipement contrôlé. Les détecteurs de radiation à la porte du site restent opérationnels. Des vérifications de radiation supplémentaires et au hasard seront effectuées sur la zone de decoupe central de Prévessin. Un contrôle final et global sera effectué pour le matériel destiné à des compagnies de recyclage: le camion chargé devra passer par un pont bascule  et par un moniteur de surveillance de radiation avant de pouvoir quitter le CERN.

V.9.      Sources radioactives

Comme détaillé dans  le rapport INB DELPHI contient en totalité 507 sources de calibration représentant une activité totale au moment du démontage d'environ 48.7 MBq. La plupart de ces sources (503) sont installées dans les sous-détecteurs TPC, HPC et VSAT, quatre sources sont utilisées dans les galeries de gaz de HPC, HAC ET FHAC. Les sources dans les galeries doivent être enlevées aussi vite que possible après le T₀ et rendues à TIS/RP. Avant de pouvoir enlever l'équipement restant, le technicien RP vérifiera que les alentours de la source ne sont pas contaminés.

Les sources de VSAT sont très faibles (241 Am, activité totale env. 6.5 kBq) et ne peuvent pas être séparées du détecteur car elles ont été déposées en surface sur des films fins. Des précautions spéciales doivent être prises pendant le démontage du VSAT pour exclure le risque de contamination des personnes, outils ou autre équipement.

Les 2 paragraphes suivants sont maintenant obsoletes:

Chacun des 144 HPC modules contient trois sources de 241 Am d'une activité totale de 4.15 MBq. Ces sources pourront être enlevées seulement après le démontage des modules HPC. Il a été planifié de stocker les modules HPC dans la chambre de mélange du bâtiment des gas sur le site DELPHI, lequel sera vidé des baies contenant les mélangeurs. Une fois que tous les modules HPC seront démontés et stockés dans cette pièce, l'extraction des sources radioactives pourra commencer. Pour ce faire, la protection extérieure des modules (Cuivre enduit de G10) devra être coupée et ouverte. La procédure d'extraction elle-même devra être en collaboration étroite avec TIS/RP afin d'éviter tout danger de contamination.

La TPC est équipée de 36 sources (55 Fe, activité totale pendant le démontage 42.5 MBq). Les sources pourront être extraites seulement quand la TPC sera démontée et ouverte. L'ouverture de la TPC sera effectuée dans un hall sur le site de Meyrin. L'espace approprié devra être trouvé et le transport de la TPC du puits jusqu'au site de Meyrin devra suivre les règles de sécurité.

V.10.      Contractants externes

Comme mentionné au chapitre IV.1 "Organisation de sécurité et documents à appliquer" les entreprises externes et leurs employés travaillant au démontage de DELPHI sur le site du CERN sont régis par le règlement francais en ce qui concerne la santé et les règles de sécurité et en plus par les mesures de sécurité supplémentaires que le CERN a mises en place.

Dans le document CERN/TIS-GS/98-10 "Safety regulations applicable to the work of contractors at CERN/Règles de sécurité applicables aux activités des entreprises sur le domaine du CERN" toutes les procédures et règles de sécurité sont définies pour tous les contractants qui exécutent des projets ou travaillent pour le CERN. Les principales obligations des contractants en matière de sécurité sont expliquées dans le document, telles que :

- enregistrement du personnel et demandes d'accès

- cours de sécurité obligatoire et carte d'accès

- compétences professionelles individuelles et certificat médical

- annonce du début des travaux aux Pays Hôtes

- coordination de la sécurité

- utilisation du matériel de sécurité et leur contrôle, etc.

La sécurité de tous les employés en dehors du CERN, (et instituts et universités) est traitée de la même manière que pour le personnel CERN. Le GLIMOS de l'expérience DELPHI est responsable de l'application correcte des règles de sécurité qui concernent les entreprises exterieures au CERN. C'est pour cette raison que le personnel temporaire est - en plus du cours de sécurité UX par le Service du Feu du CERN - aussi obligé de suivre le cours spécifique pour DELPHI donné par le GLIMOS.