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«Is Entombment an Acceptable Option for Decommissioning? An International Perspective – 13488 Helen Belencan1, Vincent Nys2, Andrey Guskov3, Patrice ...»

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WM2013 Conference, February 24 – 28, 2013, Phoenix, Arizona USA

Is Entombment an Acceptable Option for Decommissioning? An International Perspective

– 13488

Helen Belencan1, Vincent Nys2, Andrey Guskov3, Patrice Francois4, Bruce Watson5,

Vladan Ljubenov6

1

US Department of Energy

2

Federal Agency for Nuclear Control (Belgium)

3

Scientific and Engineering Centre on Safety in Nuclear Energy

4

Institut de radioprotection et de sûreté nucléaire (France)

5

US Nuclear Regulatory Commission, 6 International Atomic Energy Agency

ABSTRACT

Selection of a decommissioning strategy is one of the key steps in the preparation for decommissioning of nuclear facilities and other facilities using radioactive material. Approaches being implemented or considered by Member States include immediate dismantling, deferred dismantling and entombment. Other options or slight modifications of these strategies are also possible.

Entombment has been identified in the current International Atomic Energy Agency (IAEA) Safety Standards as one of the three basic decommissioning strategies and has been defined as a decommissioning strategy by which radioactive contaminants are encased in a structurally long lived material until radioactivity decays to a level permitting the unrestricted release of the facility, or release with restrictions imposed by the regulatory body.

Although all three strategies have been considered, in principle, applicable to all facilities, their application to some facilities may not be appropriate owing to political concerns, safety or environmental requirements, technical considerations, local conditions or financial considerations.

The IAEA is currently revising the decommissioning Safety Standards and one of the issues widely discussed has been the applicability of entombment in the context of decommissioning and its general objective to enable removal of regulatory control from the decommissioned facility.

The IAEA recently established a consultancy to collect and discuss experience and lessons learned from entombment projects, to identify regulatory requirements and expectations for applying entombment as a decommissioning option strategy, in compliance with the internationally agreed standards.

INTRODUCTION: IAEA SAFETY FRAMEWORK

To understand why the question of the applicability and or appropriateness of entombment is being asked, it is first important to understand the context within which the question is being raised.

1 WM2013 Conference, February 24 – 28, 2013, Phoenix, Arizona USA The IAEA was set up as the world´s "Atoms for Peace" organization in 1957 within the United Nations. The Agency works with its Member States and multiple partners worldwide to promote safe, secure and peaceful nuclear technologies. The IAEA Secretariat is headquartered at the Vienna International Centre in Vienna, Austria. Operational liaison and regional offices are located in Geneva, Switzerland; New York, USA; Toronto, Canada; and Tokyo, Japan. The IAEA runs or supports research centers and scientific laboratories in Vienna and Seibersdorf, Austria;

Monaco; and Trieste, Italy. The IAEA's mission is guided by the interests and needs of Member States, strategic plans and the vision embodied in the IAEA Statute. Three main pillars - or areas of work - underpin the IAEA's mission: Safety and Security; Science and Technology; and Safeguards and Verification.

The IAEA safety standards have a status derived from the IAEA’s Statute [1], which authorizes the IAEA “To establish or adopt, in consultation and, where appropriate, in collaboration with the competent organs of the United Nations and with the specialized agencies concerned, standards of safety for protection of health and minimization of danger to life and property... and to provide for the application of these standards” [Article III, Functions, Statute of the IAEA]. Although not mandatory, the IAEA safety standards provide a framework of fundamental principles, requirements and guidance to ensure safety for use by its member states. They are developed through an open and transparent process for gathering, integrating and sharing the knowledge and experience gained from the actual use of technologies and from the application of the safety standards, including emerging trends and issues of regulatory importance.

These safety standards are organized in a hierarchy as illustrated in Table I [2] and described

below:

 Safety Fundamentals: As the primary publication in the Safety Standards Series, Fundamental Safety Principles establishes the fundamental safety objective and principles of protection and safety.

 Safety Requirements: An integrated and consistent set of stable Safety Requirements publications establish the requirements that must be met to ensure the protection of people and the environment, both now and in the future. The requirements are governed by the objectives and principles of the Safety Fundamentals. If they are not met, measures must be taken to reach or restore the required level of safety. Their format and style facilitate their use by Member States for the establishment, in a harmonized manner, of their national regulatory framework.

Safety Guides: Safety Guides provide recommendations and guidance on how to comply with the requirements, indicating an international consensus that it is necessary to take the measures recommended (or equivalent alternative measures). The Safety Guides present international good practices, and increasingly they reflect best practices, to help users striving to achieve high levels of safety. Table I illustrates the full hierarchy and lists the titles of the general and specific requirements.





2 WM2013 Conference, February 24 – 28, 2013, Phoenix, Arizona USA

–  –  –

IAEA, DOE, AND NRC DECOMMISSIONING ALTERNATIVES

According to the IAEA decommissioning safety standards [3] (herein after referred to as WS-R-5) ‘decommissioning’ refers to the administrative and technical actions taken to allow the removal of some or all of the regulatory requirements from a facility (except for a repository, for which the term ‘closed’ and not ‘decommissioned’ is used). A facility, as used in WS-R-5, means a building and its associated land and equipment in which radioactive material is produced, processed, used, handled or stored on such a scale that consideration of safety is required. The requirement goes on to acknowledge that a “a facility is considered decommissioned when an approved end state has been reached” and also recognizes that the “end state” cannot be globally defined but must rather be “tailored to address the safety and environmental needs in each situation.” Article 1.5 of the WS-R-5 also describes three strategies for decommissioning based on

approaches being implemented or considered by Member States. These are:

Immediate dismantling: the strategy by which the equipment, structures and parts of a facility containing radioactive contaminants are removed or decontaminated to a level that permits the facility to be released for unrestricted use, or with restrictions imposed by the regulatory body. In this case decommissioning implementation activities begin shortly after the permanent cessation of operations. This strategy implies prompt completion of the decommissioning project and involves the removal of all radioactive material from the facility to another new or existing licensed facility and its processing for either long term storage or disposal.

Deferred dismantling (sometimes called safe storage, safe store or safe enclosure): the strategy in which parts of a facility containing radioactive contaminants are either processed or placed in such a condition that they can be safely stored and maintained until they can subsequently be

–  –  –

decontaminated and/or dismantled to levels that permit the facility to be released for unrestricted use or with restrictions imposed by the regulatory body.

Entombment: the strategy by which radioactive contaminants are encased in a structurally long lived material until radioactivity decays to a level permitting the unrestricted release of the facility, or release with restrictions imposed by the regulatory body.” Article 1.5 of the WS-R-5 goes on to state that “these strategies are, in principle, applicable to all facilities; however, their application to some facilities may not be appropriate owing to political concerns, safety or environmental requirements, technical considerations, local conditions or financial considerations.” And further, that “the preferred decommissioning strategy shall be immediate dismantling.” The IAEA approach of allowing local conditions, needs, and expectations for future uses define the end state is consistent with requirements applied in the decommissioning of former US defense nuclear facilities. For these facilities, decommissioning takes place after deactivation and includes surveillance and maintenance, decontamination, and/or dismantlement. These actions are taken at the end of the life of a facility to retire it from service with adequate regard for the health and safety of workers and the public and protection of the environment. The ultimate goal of decommissioning is unrestricted release or restricted use of the site [4]. Although DOE does not specifically recommend a decommissioning strategy for its facilities, it has issued a strategy document [5] that endorses the application of entombment and describes a series of steps that could be applied to select candidates for entombment.

According to a 1995 policy [6], decommissioning of DOE defense nuclear facilities is conducted by the US DOE Office of Environmental Management and driven by the requirements of CERCLA [7], which establishes a risk-based end state in consideration of future use, such as residential, industrial, or recreational. This policy is the result of a joint effort by EPA and DOE to develop an approach to decommissioning that ensures protection of worker and public health and the environment that is consistent with CERCLA, that provides for stakeholder involvement, and that achieves risk reduction without unnecessary delay.

For its licensed nuclear power plants, Title 10 of the Code of Federal Regulations, Section 50.2 defines decommissioning as the safe removal of a facility from service and reduction of residual radioactivity to a level that permits termination of the NRC license. Three alternatives are considered: DECON, SAFSTOR, or ENTOMB. Table II provides the definition of each alternative.

4WM2013 Conference, February 24 – 28, 2013, Phoenix, Arizona USA

Table II: NRC Decommissioning Alternatives [8] DECON: This alternative represents immediate dismantlement. Under this alternative, equipment, structures, and portions of the facility containing radioactive contaminants are removed or decontaminated to a level that permits release of the property and termination of the license.

SAFSTOR: This alternative is also referred to as “delayed DECON.” Under this alternative, a nuclear facility is maintained and monitored in a condition that allows the radioactivity to decay;

afterwards it is dismantled.

ENTOMB: Under this alternative, radioactive contaminants are encased in a structurally sound material such as concrete and maintained and monitored until the radioactivity decays to a level allowing release of the property. The NRC has deferred rulemaking that would clarify the use of the ENTOMB option for reactors pending completion of research studies on entombment viability issues.

While these three organizations all recognize entombment, they also recognize that its application is very situational, and so within the IAEA framework, it may not be appropriate to maintain it as a prescribed strategy. To that end, the IAEA is working on a revision to WS-R-5, wherein entombment is no longer considered on the same “level” as immediate and deferred dismantlement, that is, not a “strategy” and not a solution for normal planned shutdown, but should only be considered a solution under exceptional circumstances (such as severe accidents) for existing facilities. This position is supported by an IAEA publication issued in 1999 concerning on site disposal as a decommissioning strategy [9].

APPLICATIONS OF ENTOMBMENT EXPERIENCES TO DATE

With very few decommissioning projects to date having used this strategy, limited practical experience is available and is concentrated in several Member States only. Table III summarizes experiences to date.

–  –  –

Due to the limited application of the entombment strategy, detailed guidance on the technical and safety aspects of entombment has never been developed within the IAEA framework.

In the recent years several Member States have renewed their interest in application of the entombment strategy in decommissioning. Further, the recent US experience with entombment of former production reactors, and the challenges facing Japan in the recovery from the accident at the Fukushima-Daiichi, has brought this option to the forefront. Discussions at several international meetings showed that entombment cannot be ignored as an option and that an effort to consolidate international experience with entombment is needed. Regulatory expectations on evaluation and demonstration of long term safety of entombed facilities needs to be identified and explained in order to provide operators with a basis for consideration of this option in the strategy selection process.

In August 2012, the IAEA hosted its first consultancy meeting on this topic. Five representatives from four member states (Belgium, France, Russia, and the United States) came together to share experiences and perspectives on the applicability, challenges, and considerations associated with the use of entombment.

THE FUTURE OF ENTOMBMENT – FITTING A SQUARE PEG IN A ROUND HOLE?

After a discussion of experiences with entombment, the members of the consultancy team began a discussion of how the entombment option fits, or doesn’t fit, within the IAEA framework of safety standards. The team considered entombment from three perspectives: (1) decommissioning, (2) radioactive waste management, and (3) remediation. These three perspectives cross the



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