Practices for Interim Storage of Research Reactor Spent Nuclear Fuel

By IAEA

This publication provides an introduction to the management of research reactor spent nuclear fuel (RRSNF). Five key areas are discussed: types of RRSNF, characterization data, wet storage considerations, dry storage considerations, and lessons learned and current practices. Information on internationally accepted standards as well as information on aspects such as drying treatment and surveillance programmes are presented, as well as suggestions for further optimization of effective and safe storage of RRSNF through the application of new approaches. The intended users of this publication include industry professionals at operating research reactors and at RRSNF storage facilities who need to identify the most suitable approach for interim storage of spent fuel.

• Language: English
• Publisher: International Atomic Energy Agency
• Release date: Sep 28, 2022
• ISBN: 9789201233226

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Practices for interim storage

Of research reactor

spent nuclear fuel

IAEA NUCLEAR ENERGY SERIES No. NF-T-3.10

Practices for interim storage

Of research reactor

spent nuclear fuel

INTERNATIONAL ATOMIC ENERGY AGENCY

VIENNA, 2022

COPYRIGHT NOTICE

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© IAEA, 2022

Printed by the IAEA in Austria

September 2022

STI/PUB/2007

IAEA Library Cataloguing in Publication Data

Names: International Atomic Energy Agency.

Title: Practices for interim storage of research reactor spent nuclear fuel / International Atomic Energy Agency.

Description: Vienna : International Atomic Energy Agency, 2022. | Series: IAEA nuclear energy series, ISSN 1995–7807 ; no. NF-T-3.10 | Includes bibliographical references.

Identifiers: IAEAL 22-01508 | ISBN 978–92–0–123122–2 (paperback : alk. paper) | ISBN 978–92–0–123222–9 (pdf) | ISBN 978–92–0–123322–6 (epub)

Subjects: LCSH: Spent reactor fuels — Storage. | Radioactive wastes — Management. | Reactor fuel reprocessing. | Nuclear reactors — Safety measures.

Classification: UDC 621.039.74 | STI/PUB/2007

FOREWORD

The IAEA’s statutory role is to seek to accelerate and enlarge the contribution of atomic energy to peace, health and prosperity throughout the world. Among other functions, the IAEA is authorized to foster the exchange of scientific and technical information on peaceful uses of atomic energy. One way this is achieved is through a range of technical publications including the IAEA Nuclear Energy Series.

The IAEA Nuclear Energy Series comprises publications designed to further the use of nuclear technologies in support of sustainable development, to advance nuclear science and technology, catalyse innovation and build capacity to support the existing and expanded use of nuclear power and nuclear science applications. The publications include information covering all policy, technological and management aspects of the definition and implementation of activities involving the peaceful use of nuclear technology.

The IAEA safety standards establish fundamental principles, requirements and recommendations to ensure nuclear safety and serve as a global reference for protecting people and the environment from harmful effects of ionizing radiation.

When IAEA Nuclear Energy Series publications address safety, it is ensured that the IAEA safety standards are referred to as the current boundary conditions for the application of nuclear technology.

In recent years, international activities related to the back end of the nuclear fuel cycle have been focused on spent fuel take-back programmes, namely the Foreign Research Reactor Spent Nuclear Fuel Acceptance Program of the United States of America (USA) and the Russian Research Reactor Fuel Return programme. The objective of these respective take-back programmes for fuels originating in the USA and the Russian Federation is to eliminate inventories of high enriched uranium by returning research reactor spent nuclear fuel (RRSNF) to the country where the fuel was originally enriched. Eventually when these programmes have achieved their objective and research reactors no longer store high enriched uranium and the demand for high enriched uranium for research reactors has decreased, it is almost certain that the take-back programmes will cease operation. Countries with one or more research reactors but no nuclear power programme will either need to manage the relatively small amounts of spent fuel generated in their research reactors or permanently shut down their research reactors before the take-back programmes come to an end.

It is probable that hundreds of research reactors worldwide, both operational and shutdown but not yet decommissioned, will continue storing RRSNF for a long time. As a consequence, safe, secure, reliable and cost effective handling and interim storage of RRSNF will remain crucial issues for Member States with research reactors.

Recognizing these needs, this publication captures valuable experience using wet and dry methods for interim storage of RRSNF that have been used for many decades with excellent results at different sites. Aluminium clad RRSNF has been kept intact in wet storage with properly maintained water quality for more than 60 years. Dry storage of RRSNF is also a reliable technology that, when properly implemented, ensures the long term integrity of RRSNF.

This publication is a collection of Member States’ experiences and case studies to help the research reactor community manage their issues related to the extended storage of RRSNF. The publication is also intended to assist decision makers in Member States with operating research reactors to identify solutions for RRSNF storage under the economic and technological realities of their countries and with due consideration of the safety and security concerns usually associated with RRSNF.

The IAEA wishes to thank all the contributors to this publication, in particular J.W. Lian (Canada), M. Verberg (Netherlands), N.C. Iyer and D.W. Vinson (USA). The IAEA officers responsible for this publication were P. Adelfang, S. Tozser, F. Marshall and S. Geupel of the Division of Nuclear Fuel Cycle and Waste Technology.

EDITORIAL NOTE

This publication has been edited by the editorial staff of the IAEA to the extent considered necessary for the reader’s assistance. It does not address questions of responsibility, legal or otherwise, for acts or omissions on the part of any person.

Although great care has been taken to maintain the accuracy of information contained in this publication, neither the IAEA nor its Member States assume any responsibility for consequences which may arise from its use.

Guidance provided here, describing good practices, represents expert opinion but does not constitute recommendations made on the basis of a consensus of Member States.

The use of particular designations of countries or territories does not imply any judgement by the publisher, the IAEA, as to the legal status of such countries or territories, of their authorities and institutions or of the delimitation of their boundaries.

The mention of names of specific companies or products (whether or not indicated as registered) does not imply any intention to infringe proprietary rights, nor should it be construed as an endorsement or recommendation on the part of the IAEA.

The IAEA has no responsibility for the persistence or accuracy of URLs for external or third party Internet web sites referred to in this book and does not guarantee that any content on such web sites is, or will remain, accurate or appropriate.

The authoritative version of this publication is the hard copy issued at the same time and available as pdf on www.iaea.org/publications. To create this version for e-readers, certain changes have been made, including a the movement of some figures and tables.

CONTENTS

1. INTRODUCTION

1.1. Background

1.2. Objectives

1.3. Scope

1.4. Structure

2. WET STORAGE OF RESEARCH REACTOR SPENT FUEL

2.1. Wet storage technology

2.2. Wet storage facility considerations

2.3. Storage pool maintenance

2.4. Storage pool inspection and surveillance

2.5. Facility lifetime extension

3. TRANSITION FROM WET TO DRY STORAGE

3.1. Predrying conditioning

3.2. Drying of spent nuclear fuel for transitioning to dry storage

3.3. Inert gas considerations

4. DRY STORAGE OF RESEARCH REACTOR SPENT FUEL

4.1. Dry storage technology

4.2. Dry storage package design considerations

4.3. Dry storage system infrastructure

4.4. Operational considerations for dry storage

5. CHARACTERIZATION FOR STORAGE

5.1. Fuel data needs

5.2. Baseline characterization needs

5.3. Characterization tools

5.4. Fuel condition assessment

6. SAFETY ISSUES FOR RESEARCH REACTOR SPENT FUEL STORAGE

6.1. Safety Guide on storage of spent nuclear fuel

6.2. Regulatory requirements

6.3. Commissioning

6.4. Physical protection

6.5. Safeguards

6.6. Emergency planning

6.7. Decommissioning

7. LESSONS LEARNED FROM RESEARCH REACTOR SPENT FUEL STORAGE

7.1. Centralized wet storage at Savannah River Site

7.2. Centralized dry storage at HABOG

7.3. Wet and semidry storage at the Budapest Research Reactor

7.4. Wet storage remediation at Vinča Institute of Nuclear Sciences

8. CONCLUSIONS

REFERENCES

ABBREVIATIONS

CONTRIBUTORS TO DRAFTING AND REVIEW

STRUCTURE OF THE IAEA NUCLEAR ENERGY SERIES

1. INTRODUCTION

1.1. Background

For over 60 years, research and test reactors have made valuable contributions to the development of nuclear power, basic science, education, training, materials development, and radioisotope production for medicine and industry.

During operation of these research reactors, thousands of fuel elements were, and continue to be used, composed of different designs, types, shapes, material composition and enrichment [1]. With very few exceptions (such as when there is no provision for fuel replacement), when the spent fuel reaches its burnup limit it is removed from the reactor core and replaced with a new fuel element, allowing the reactor to operate for many years.

Typically, after it has been discharged from the reactor core, the research reactor spent nuclear fuel (RRSNF) is placed into wet storage, either in the reactor pool, or in a pool away from the reactor. The fuel is maintained there until the decay heat and radiation levels are low enough to allow the movement of the material to the next step in the management of the fuel. Depending on the fuel consumption and conditions of the facility, the wet storage can be extended for long periods of time, in some cases more than 50 years, or the RRSNF may be transferred to dry storage sites, which may be suitable for longer periods.

Neither wet nor dry storage is intended to be the end point of the research reactor fuel cycle; the term ‘storage’ implies a temporary situation and that the fuel will be retrieved and moved again. Continued generation and storage of spent fuel without full commitment to a clearly defined end point is not a sustainable policy. The end point of the research reactor fuel cycle is expected to be associated with a geological repository for the disposal of the spent fuel assemblies after their conditioning and/or for the disposal of the vitrified radioactive waste arising from spent fuel reprocessing. In the context of this publication, the term ‘interim’ is used to emphasize that storage is not the final step in the management of spent fuel from research reactors. For the purpose of this publication, interim storage has been defined as any storage period up to 100 years.

Developing a geological repository for spent nuclear fuel (SNF) and high level waste (HLW) is not a simple undertaking; at present, there is no spent fuel repository in operation in the world. The technology and costs involved for the development and maintenance of a geological repository for SNF make it prohibitive for most States, especially for those with only one or two research reactors and no nuclear power programme. It is likely that, for the foreseeable future, wet and dry storage will be options heavily used for the management of spent fuel from research reactors in most States.

Regardless of how long the storage period is, public concerns about the RRSNF remain. In addition to the proliferation, safety and physical security concerns, the organization operating a research reactor or the government has the responsibility to ensure the safe, secure and economic management of its RRSNF [2].

In 1993, the IAEA organized an Advisory Group Meeting on Storage Experience with Spent Fuel from Research Reactors to identify, discuss and plan activities related to RRSNF storage. For many research reactors, the capacity for spent fuel storage had reached or was close to reaching the design storage limits, raising concerns about the feasibility of expanding storage capacity and, from a materials science point of view, about ageing materials in ageing storage facilities, with the related consequences for the integrity of the fuel elements.

Following the recommendations of the experts, the IAEA initiated a series of programmatic activities to assist organizations operating research reactors in dealing with spent fuel management issues. These activities included workshops, technical meetings and coordinated research projects (CRPs), which resulted in several IAEA publications made available to the research reactor community. Examples of such activities are:

— Exchange of experience in options, procedures and practices for RRSNF storage [ 1, 3 ];

— Ageing management of materials in RRSNF storage facilities [ 4, 5 ];

— Study of corrosion and other forms of material ageing leading to the degradation of mechanical and physical properties of RRSNF [ 6, 7 ];

— Study of regional solutions for research reactors in Latin America [ 8 ];

— Exchange of experience in the two international RRSNF take-back programmes: the USA Foreign Research Reactor Spent Nuclear Fuel (FRRSNF) acceptance programme and the Russian Research Reactor Fuel Return (RRRFR) programme [ 9 ].

1.1.1. Options for the management of spent nuclear fuel from research reactors

After having been discharged from the reactor core, the RRSNF is usually stored under water for cooling. This typically occurs in at-reactor (AR) facilities for three to five years, in order to allow for radioactive decay of spent fuel fission products and to remove the residual decay heat. Following this, the fuel may be moved to another storage location or moved to a disposal facility. In general, organizations operating a research reactor have the following options for the next step in their spent fuel management programme:

— Continue to store the fuel in wet storage;

— Transfer the fuel to a dry storage facility;

— Send the fuel for reprocessing with a domestic or international commercial service provider;

— Return the fuel to the country where it was originally enriched (in this way transferring the responsibility for disposal to others);

— Dispose of the fuel directly into a national or regional geological repository, with or without conditioning.

Additional