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PILOT DISMANTLING OF THE BR-3 PWR. DECONTAMINATION OF A PRIMARY CIRCUIT, REALIZATION OF CUTTING EQUIPMENT, SEGMENTATION OF ALL REACTOR INTERNALS

Objective

The BR-3 Pressurized Water Reactor had a capacity of 11 MWe and had been operated from 1962 to 1987. CEN/SCK has started the dismantling and decontamination of certain parts of the plant and is examining the possibility of its complete dismantling.

Considering that the experience to be gained from the dismantling of the first representative nuclear installations in the Community should be made available to all Member States, the Commission selected BR-3 as a pilot dismantling project for the 1989-93 R&D programme on the decommissioning of nuclear installations. The Commission, through shared-cost participation in specific parts of the project, intends promoting the use of advanced techniques and the performance of collateral investigations, in order to enhance the generation of useful knowledge and experience to serve in subsequent decommissioning tasks. In particular, the generation of specific data on costs, working hours and job doses as well as on the amount of created secondary waste is considered as an important objective of this project.

The assessment of techniques and procedures will be performed in collaboration with Kernkraftwerk RWE-Bayernwerk GmbH (Gundremmingen), which is decommissioning the Boiling Water Reactor KRB-A and with VAK GmbH which is decommissioning the VAK BWR.

As a Pressurized Water Reactor, the BR-3 is representative of the reactor type most frequently used in the Community in Phase 1. The contract involves the decontamination of the primary circuit of the reactor and the dismantling of the thermal shield, a highly radiating steel component (specific activity 10 superscript 8 - 10 superscript 9 Bq/g, estimated contact dose rates 10 superscript 2 - 10 superscript 3 Sv/h, estimated radioactive inventory 10 superscript 4 - 10 superscript 5 Ci at plant shut-down) and in Phase 2 the dismantling of the lower and upper core support assembly and of the reactor collar with the instrumentation basket.

The contract is implemented in close cooperation between SCK/CEN as main contractor and Siemens-KWU (FRG) and Framatome (F) as associated contractors, with an agreement for cooperation with Belgatom.
As a pressurized water reactor, the BR-3 is representative of the reactor type most frequently used in the Community. In Phase 1 the contract involves the decontamination of the primary circuit of the reactor and the dismantling of the thermal shield, a highly radiating steel component and in Phase 2 the dismantling of the lower and upper core support assembly and of the reactor collar with the instrumentation basket.

Using the CORD process the BR3 primary loop and associated auxiliary circuits have been decontaminated. The CORD process was applied in 3 successive cycles, using the BR3 primary pumps to circulate the chemicals at low pressure and to reach the required primary water temperatures. A mean decontamination factor of the order of 10 has been obtained in the primary loop, the radioactivity being removed from the circuits and trapped on ion exchange resins.

The main objectives were first to test in cold conditions the segmenting equipment and afterwards to demonstrate this equipment in a radioactive environment, dismantling the reactor vessel thermal shield.

The thermal shield was segmented first in situ, ie inside the reactor vessel, and afterwards rings separated from the thermal shield were transferred and cut into angular segments inside a flooded cutting chamber installed in the reactor refuelling pool. 3 cutting techniques were used: mechanical sawing, electrodischarge machining and plasma arc torch cutting; their performances and harmfulness, more particularly the quantities and properties of the secondary waste resulting from the cutting operation, were compared.
WORK PROGRAMME

1. Chemical decontamination of the primary loop

1.1. Cost benefit analysis and selection of a procedure
1.2. Decontamination operation
1.3. Treatment and removal of decontamination waste

2. Segmenting of the reactor internals

2.1. Concept and design of the segmenting and remote operation equipment
2.2. Manufacturing and procurement of the segmenting and remote-operating equipment
2.3. Inactive testing and commissioning of the segmenting and remote operating equipment
2.4. Segmenting of activated components
2.5. Waste treatment and packaging

3. Generation of specific data on costs, radioactive job doses, working time and secondary waste arisings, derived from the execution of items 1, 2, 4, 5 and 6.

4. Underwater dismantling of the lower core support assembly

5. Underwater dismantling of the upper core support assembly

6. Underwater dismantling of the reactor collar with the instrumentation basket.

Coordinator

BELGIAN NUCLEAR RESEARCH CENTRE
Address
200,Herrmann Debrouxlaan 40-42
1160 Bruxelles
Belgium

Participants (1)

Rolls Royce and Associates Ltd
United Kingdom
Address
Raynesway Park
DE24 8BJ Derby