Skip to main content

PILOT DISMANTLING OF THE KRB-A BWR. DISMANTLING OF CONTAMINATED COMPONENTS OF THE REACTOR BUILDING AND OF ACTIVATED INTERNALS OF THE REACTOR PRESSURE VESSEL; DEVELOPMENT AND APPLICATION OF CONCRETE SAWING AND MELT ENCAPSULATION (ONION PACKA

Objective

The prototype Boiling Water Reactor Gundremmingen A (KRB-A BWR) of the Kernkraftwerk RWE-Bayernwerk GmbH (KRB) had a capacity of 250 MWe and was operated from 1966 to 1977. Dismantling work has been started for some time (especially the turbine hall has been dismantled), and complete removal of the power station is foreseen to be completed by 2000. The 2 foregoing EC programmes have been involved by 4 R&D contracts in the past dismantling work on KRB-A. KRB-A dismantling is a European undertaking according to the definition of the Euratom Treaty.

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 KRB-A 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 CEN/SCK Mol and VAK-GmbH, which are decommissioning the Pressurised Water Reactor BR-3 and the VAK BWR, respectively. The results and conclusions of the assessment work undertaken in contract FI2D0002 are taken into account for the implementation of work in this contract.

As a BWR, KRB-A is representative for such reactors, existing elsewhere in the Community. The first phase of the contract involves the dismantling and segmenting of contaminated components of the reactor building in air (partly with subsequent decontamination), and of activated internals of the reactor pressure vessel (RPV) in remotely controlled underwater operation. Estimations of maximal values for specific contamination or activation are in the order of 10 superscript 4 and 10 superscript 6 Bq/square cm, respectively. The second phase contains the development of specific tools and the segmentation of further steel components and concrete structures as well as the development of procedures for the conditioning of molten steel (onion package) and of decontamination waste.
As a boiling water reactor (BWR), Kernkraftwerk Rwe Bayernwerk GmbH (KRB)-A is representative for such reactors, existing elsewhere in the Community. The first phase of the contract involves the dismantling and segmenting of contaminated components of the reactor building in air (partly with subsequent decontamination), and of activated internals of the reactor pressure vessel (RPV) in remotely controlled underwater operation. The second phase contains the development of specific tools and the segmentation of further steel components and concrete structures as well as the development of procedures for the conditioning of molten steel (onion package) and of decontamination waste. The following activities have been carried out:
preparation of the dismantling of a secondary steam generator;
dismantling of a shutdown cooler;
dismantling of a primary cleanup cooler;
presegmenting of the head of the reactor pressure vessel.
The main targets were the application of the ice sawing technique and the preparation of underwater cutting of the steam dryer.
WORK PROGRAMME

1. Dismantling in air of contaminated and low-activated components of the reactor building, partly with subsequent decontaminating/melting.

1.1. Dismantling of a secondary steam generator with various tools (band saw, flame cutting)
1.2. Dismantling of a primary circulation pump by band saw.
1.3. Dismantling of a primary clean-up cooler with various tools (band saw, diamond-tipped wire saw)
1.4. Dismantling of a shutdown cooler with various tools (band saw, shears, flame cutting)
1.5. Dismantling of the RPV-cover by flame cutting
1.6. Decontamination of segmented components by dipping technique and meltling for recycling and disposal.

2. Underwater dismantling of activated and highly contaminated components of the RPV

2.1. Segmenting of the steam-dryer by various tools (shears, plasma-arc torch, consumable electric electrode torch)
2.2. Segmenting of the water-steam separator with the core head by various tools (saw, shears, plasma arc torch with special gripping system)

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, 6, 7, 8 and 9.

4. Development and application of a carrier and handling system for automated segmenting of thick-walled pipes and pipe fittings in limited space,

5. Remote-operated underwater segmenting of internals of the reactor core,

6. Development and application of a facility for the conversion of iron-oxalate, generated during decontamination,

7. Qualification and large-scale testing of a wire saw device for the dismantling of reinforced concrete walls,

8. Development and qualification of a procedure for the pre-conditioning of metallic dismantling waste by melting (optimized "onion package");

9. Qualification and application of underwater segmenting of control rods by shearing.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Kernkraftwerk RWE - Bayernwerk GmbH
Address
1,Dr.-august-weckesser-strasse
89355 Gundremmingen
Germany