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2013-07-02 REMOVAL OF OPERATIONAL WASTE FROM BUGEY 1 GAS-COOLED REACTOR

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Tuesday, 02 July 2013 13:41

Luc LAFANECHERE, Christophe DORIER, Thierry BALON, Antoine DELORT (EDF) - This email address is being protected from spambots. You need JavaScript enabled to view it.
Jean-Louis QUIRANTE, Alain GAGNOR (AREVA/STMI) - This email address is being protected from spambots. You need JavaScript enabled to view it.
Copyright owned by the American Nuclear Society, La Grange Park, Illinois 
 
1 –INTRODUCTION
After a quick description of the EDF dismantlingprogram, this paper focuses on special developmentsaccomplished in terms of organization, design of specifictools, containment, waste conditioning for the removal ofoperational waste from the reactor pressure vessel atBugey 1 gas cooled and graphite-moderated power plant.
This waste removal process is planned to take placebetween 2012 and 2015.

2 - EDF’S DISMANTLING PROGRAM
Electricité de France (EDF) is currentlydecommissioning nine Nuclear Power Plants (NPP).Mostof them are first generation units that started operating inthe 60s and were definitively shutdown between the endof the 80s and the beginning of the 90s.[1].
In 2001, EDF decided to completely dismantle its 8first generation nuclear plants, as well as the fast breederreactor of Creys-Malville within the following 25 years, EDF has set up a specific organization and defined adetailed program in order to implement this new strategycf. [1].

3 - BUGEY 1 POWER PLANT PRESENTAION
Constructed between 1965 and 1972, EDF Bugey 1NPP was the last in the line of the natural uraniumfuelled, gas cooled, and graphite-moderated reactors(known as UNGG) to be built in France. With an output of 540 MWe it was the largest UNGG reactor in Franceand was operated successfully until its closure in 1994.

The Bugey 1 dismantling project is considered as thelead project for 5 other EDF UNGG reactors located atChinon and St. Laurent in the Loire region. More information on the Bugey 1 reactor dismantling projectcan be found in [2] and [3].

Since the final shutdown of Bugey 1 (1994), the operational waste such as control rods, bins, shockabsorbers etc… has been stored inside the upper part ofthe reactor pressure vessel protected by a thick layer ofconcrete, as illustrated on the figure below.

qq20130702133551
         Bugey 1 pressure vessel-Location of operational waste
This paper deals with all the technical developmentsproposed by AREVA/STMI as well as regulatoryrequirements necessary for the removal of the operationalwaste.

4 - SCOPE AND DESCRIPTION OF OPERATION
During plant’s operation, 19 tons of LILW (Low andintermediate level waste) was created. This waste is madeup of 10 components with both short and long half lives depending on the time spent inside the reactors neutronflux.
This waste is mainly composed of control rods (173),shock absorbers (96), shock bins (26) and control roddampers (96). Its contact dose rate is up to 10 Sievert’sper hour, thus requiring a high level of biologicalshielding and treatment via remote control.
The more activated wastes will be stored in R73®containers with an overall activity of about 200Tera-Becquerel’s per container (each container will containabout 17 control rods).
This waste has to be removed from the reactor’schannels and vaults, (where it is currently stored) andtransferred beneath the reactor pressure vessel, 55 metersdown for waste management processing, includingcutting, packaging and removal from site. Furthermore,samples have to be taken from the majority of the wastein order to complete the radiological characterization.
The removal of operational waste is divided into fivemain steps described in the next chapters:
(1) Preliminary arrangements.
(2) Dismantling of the existing zone.
(3) Preparation for waste removal work.
(4) Waste removal, cutting, packaging andtemporary storage.
(5) End of work.
The next figure gives a general view of the wastemanagement processing necessary for its removal andtreatment. The waste is taken from vaults located insidethe top of the reactor pressure vessel. Then, they are carrydown to the treatment area (cutting and packaging) usingthe tubular channel inside the reactor pressure vessel (anidentical process to that used during the plants operationfor the transportation of fuel assemblies). Finally, they arepacked in appropriate containers in the waste routegallery.
qq20130701173045 
                                  Waste location and management path

4.1 - Step 1 - Preliminary arrangements
The “Preliminary arrangements” consist mainly ofthe preparation of the controlled area, the fire protectioninstallation, the improvement of the ventilation systemand upgrading of waste transfer containers.
The EUVv ventilation system used during the plantsnormal operation and stopped many years ago will be totally upgraded and recommissioned.
The waste transfer containers (cf. next figure) usedfor fuel transportation (during operation) on the top of thereactor pressure vessel, will be decontaminated andupgraded before use.
qq20130701173015 
   Waste transfer containers used on the top of thereactor pressure vessel

4.2 - Step 2 - Dismantling of the existing zone
The “dismantling of the existing zone” consists of thedismantling and packaging of 35 tons of waste present indifferent zones that will be used during the next steps ofthe project.
Among this work, a difficult dismantling operationconsists of removing the 55 meter long tube installedinside the reactor tubular channel (cf. figure below) usedduring operation for the removal of spent fuel from thetop of the reactor to the treatment room. This tube has tobe removed to allow the larger waste components andmaterials to pass down the tubular channel.
qq20130701173127 

                         55 m long tube installed the tubular channel
This dismantling procedure will be carried out fromthe pile cap using a special containment airlock (cf. figurebelow). The tube will be lifted by the main reactor crane,flipped horizontally with a specially designed tool, cutinto pieces and transported to the packaging workshop.
qq20130701173237 
                        Special airlock for 55 m long tube dismantling

4.3 - Step 3 - Preparation of waste removal work
All the necessary remote control tools are installedduring this step, including:
- Waste container automatic transporter andhandling cranes. Two different types ofcontainer have to be transported, a 5 m3container and cylindrical R73® container(depending on short on long half life waste).
- About 150 tons of lead biological shielding hasto be installed to protect operators during wastetransport.
- Remote manipulators.
- Automated manipulators for control rods andother waste during the cutting process.
- Automatic cutter for control rods and otherwaste, five different cutting tools will bedeveloped and installed depending on wasteshape.
- Table and remote manipulators for waste sortingand conditioning.
- Necessary measurements taken for wastecontainer control.
- Control room for remote control of all processes.

qq20130701173315 
                                    Waste sort table and manipulators

qq20130701173256 

                               Waste container filling and transportation

qq20130701173332 
                                            Waste container transportation

4.4 - Step 4 - Waste removal, cutting and packaging
During this step, the waste removal and treatmentwill be undertaken. At the same time sampling will becarried out in order to document the waste radiologicalcharacteristics.
The waste treatments are described in the next figure:
qq20130701173505 
                                   General view of waste management

1 - Cutting and packaging of waste in the waste container.
2 - Mechanical docking of waste container.
3 - Transfer airlock for waste container.。

Between 3 and 4 shielded doors for radiation protection,areas 1, 2 and 3 are totally remote controlled, areas 4, 5, 6& 7 are accessible by the operator.
Because of the high levels of radiation, the doors betweenareas 3 and 4 / areas 4 and 5 are not allowed (by I&C) tobe opened at the same time.
4 -Protection of waste container from contamination.
5 - Opening and closing of waste containers (the closureof full containers is possible in this area (access ispermitted for operators), because of the shielded cap putin place in 2).
6 - Waste radiological control area.
7 - Waste container transfer area.
Waste containers are placed in transitory wastestorage before their final removal.
All this work will be undertaken in two 8 hour daysin order to reduce the waste treatment duration. This stepof waste removal is planned to take approximately 1.5years.
4.5 - Step 5 - End of work
The last step consists of the cease of operation, andremoval of all installed components.


5 - PROJECT STATUS
Step 1 “Preliminary arrangements” is currently inprogress and step 2 “Dismantling of the existing zone” isplanned to begin during summer 2012.
The main step, “Waste removal, cutting andpackaging” presently planned from 2014 to 2015.

5 - AREAS OF CONCERN
The major concerns regarding the preparation of thisoperation are:
- Safety requirements to avoid the spread ofcontamination.
- Supply and installation of 150 tons of shielding inorder to limit radiation.
- Upgrading existing tools and development of newtools for gripping and cutting components remotely.
- Handling of components with high reliability toavoid security and safety related incidents.
- Use of radiological measurements for wastemanagement by category and choice of packaging.

The basic operational design has been defined. Itprovides that one of the essential project data are theradiological figures.
In order to measure radiation and contaminationvalues, a heavily shielded specific shutter (cube ofapproximately 1.5 meters square and 30 tons in weight)has been designed (cf. figure below).
Furthermore, during cutting processes, about fiftymetal samples will be taken for complete radiologicalcharacterization.
qq20130701173433 
Specific shutter for radiation and contaminationmeasurements

Another major issue of the waste removal is thecontrol of zoning radiation (the waste contact dose rate isup to 10 Sievert’s per hour for the control rods).
To avoid an accident a carefully planned process withseveral safety features (lead shielded automatic doors)will be necessary。

REFERENCES

1. J.J GRENOUILLET, “EDF Strategy for the
Decommissioning of first generation of Nuclear
Power Plants” EPRI International Decommissioning& Radioactive Waste Workshop, Lyon (2004).
2. F. TARDY, P. LEFEVRE, A. WILLIS, “Dismantlingof Bugey UNGG Reactor,” 6th EPRI InternationalDecommissioning & Radioactive Waste Workshop,Vienna (2007).
3. L. LAFANECHERE, C. DORIER, “EDF Bugey1Reactor Dismantling Project Status - Management ofRadioactivity Products Containment”, ANSDecommissioning Decontamination and ReutilizationConference, Idaho Falls (2010).


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