Studies in the frame of the EC pilot dismantling project BR3 Mol

Directorate-General For Research And Innovation European Commission

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Nuclear energy and safety

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• Publié par: DIRECTORATE-GENERAL-FOR-RESEARCH-AND-INNOVATION-EUROPEAN-COMMISSION
• Nombre de lectures: 43
• Langue: English
• Poids de l'ouvrage: 3 Mo

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ISSN 1018-5593
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European Commission
nuclear science
and technology
Studies in the frame
of the EC pilot dismantling
project BR3 Mol European Commission
nuclear science
and technology
Studies in the frame
of the EC pilot dismantling
project BR3 Mol
J. Ruiz Martinez, E. Arguez Pérez - Lainsa, Spain,
V. Massaut, M. Klein - SCK/CEN, Belgium**
*Calle Francisco de Rojas 3, E-28010 Madrid
**Boeretang 200, B-2400 Mol
Contract No FI2D/CT91/0070
Final report
This work was performed in the framework of the European Atomic Energy Community's
research programme on the decommissioning of nuclear installations (1989-93),
Section C 'Pilot Projects?
Directorate-General
Science, Research and Development
1995 EUR 16645 EN LEGAL NOTICE
Neither the European Commission nor any person acting on
behalf of the Commission is responsible for the use which might be made of the
following information
Cataloguing data can be found at the end of this publication
Luxembourg: Office for Official Publications of the European Communities, 1995
ISBN 92-827-5114-7
© ECSC-EC-EAEC, Brussels · Luxembourg, 1995
Reproduction is authorized, except for commercial purposes, provided the source is acknowledged
Printed in Luxembourg ABSTRACT
The study consisted in the assignment of one of LAINSA's engineers to the EU
BR3 Pilot dismantling project, belonging to SCK/CEN and relating to two main
activities.
First, decontamination tests have been performed on different metallic pieces
coming from the primary circuit. Two techniques have been selected to compare
parameters such as a chemical efficiency, decontamination factor, waste treatment
and radiological aspects. The aim was to choose the most suitable technique to
decontaminate up to values below the permitted levels. This will reduce
considerably the quantity of the wastes from the dismantling of the BR3.
Second, the implementation of the ALARA principle in all dismantling activities was
considered very important. The application of some techniques to optimise the
radiological protection has been one of the key points in the dismantling project to
reduce collective and individual dose. Preliminary results showed that the
methodology used for predictings had been reliable and useful. By means of
various records, a data base was created and will certainly be useful for future
applications in other dismantling projects.
Ill INDEX
Page
I. INTRODUCTION 1
II. ACTIVITES 2
III. THOROUGH DECONTAMINATION OF COMPONENTS 4
1. Objectives and scope 4
2. Characteristics of the contamination 5
3. Selection of decontamination processes 6
4. Description of then method tested
4.1. Modified CORD process
4.2. CONAP
4.3. Ce(IV) process with no-regeneration.
4.4 HF/HN03 process
5. Laboratory scale decontamination tests 8
5.1. Selection of metal parts
5.2. Description of the installation
5.3. Experimental procedure
5.4. Radioactivity measurements
6. Laboratory tests 10
6.1. Treatment of piece with modified CORD
6.2.t of piece with CONAP
6.3. Treatment of piece with Ce (IV)
6.4.t of piece with the HF/HN03
7. Analysis of results 14
8. Conclusions5
IV. ALARA7
1. Introduction
2. Optimisation of the Radiological Protection 18
3. Dose estimate 19
4. Application of the ALARA tools 20 4.1. Study case I. Cost-benefit analysis
4.2. Study case II. Decontamination of the refuelling pool walls.
5. Optimisation of the refuelling pool space. Removal of the reactor 24
vessel collar support and its lead shielding
6. Dismantling activities 27
6.1. Dismantling of the reactor collar and instrumentation basket.... 2
6.1.1. Removal of the rod shroud tubes support plate (RSSP)
6.1.2.l of collar and instrumentation basket
6.2. Dismantling of upper Internals 33
6.3.g of the lower core support assembly (LCSA) 3
7. Conclusions 37
V REFERENCES8
Tables9
Figures 5
VI I. INTRODUCTION
This report was developed within the framework of the contract n° FI2D-CT91-0070,
between the European Community Commission and the Spanish company
"Logística y Acondicionamientos Industriales S.A."(LAINSA),consisting of the
assignment of one of LAINSA's chemical engineers to the dismantling project to be
carried out on the Belgian reactor BR3 belonging to CEN/SCK (Mol).
LAINSA's co-operation in the BR3 dismantling project consisted of appointing the
above-mentioned engineer in order to gain practical experience through his active
involvement within the existing working team at the BR3.
The working programme scheduled during the period of his appointment, by mutual
agreement with CEN/SCK, was as follows:
BR3 Pilot dismantling project Phase II.
The second phase of this Pilot project involved the remote dismantling of all the
reactor internals.
This co-operation is mainly focused on radioactive effluent treatment and
characterisation and radiological protection optimisation.
This report focuses on active co-operation in the ALARA study concerning
phase two of the BR3 dismantling Pilot project.
Within the framework of this task the aim was to carry out the ALARA
methodology , and keep a record of collective and individual doses during the
tasks in phase two. This allowed to define how they deviate from the expected
values and how better optimisation could be envisaged.
- BR3 Pilot dismantling project Phase III.
This phase shall involve the dismantling of the primary circuit including the
reactor pressure vessel. LAINSA's involvement would consist of its participation
in preliminary research to assess the radiological impact and the generated
secondary waste .
- Thorough Decontamination of metallic components.
LAINSA's participation was called for in the selection of a several suitable
decontamination processes to be applied to contaminated components
resulting from the dismantling of the BR3, and assessment of these processes
from the radiological and secondary waste production points of view. II. ACTIVITIES
The activities carried out during the period covered by this work have been the
following:
1- Decontamination techniques
Active participation in the execution and assessment of laboratory tests with the
objective of selecting a suitable decontamination method for components resulting
from the dismantling of the BR3.
Bearing this aim in mind .three kinds of chemical decontamination processes have
been studied.
Redox.
Two similar techniques have been used.
One of them is Siemens's CORD system, which has been modified to a certain
extent.
The other is Westinghouse's CONAP which differs from the former as it involves
a pre-treatment stage in the first cycle and different concentrations of chemicals.
These methods are normally peformed in three cycles and they basically remove
and dissolve the oxide layers without attacking the base metal.
- Oxidation with Ce4+.
This is a method based on the oxidation with Ce4+ which not only dissolves the
oxide layers but also attacks the base metal by oxidation-Ce4+ is reduced to
Ce3+. This hard decontamination technique is applied in only one cycle.
- Fluoronitric mixture, based on a HF/HN03 mixture attacking the base metal.
2- ALARA studies
During the period covered by this report , most of the dismantling tasks
corresponding to phase 2 of the BR3 Pilot dismantling project were carried out.
The works started with certain operations inside the refuelling pool to allow more
space available for the dismantling activities that had to be carried out.
First of all, the report details a case corresponding to the decontamination of the
refuelling pool walls by various decontamination methods and a comparison of the
collective and individual dose estimate made.