Disposal Of Long-lived Radioactive Waste Research Articles

Preserving awareness for oversight – towards a resilient system at social level over centuries and millennia

Abstract. A resilient system at social level can be understood as one where society, at any point in time, takes responsibility for the repository system and acts to preserve the basic conditions for future generations to take responsibility and responsible decisions. The idea of societal responsibility is included in the notion of oversight, which was introduced by the Nuclear Energy Agency (NEA, 2011) and taken up by the International Commission on Radiological Protection (ICRP, 2013) for its guidance in the field of geological disposal of long-lived radioactive waste. In ICRP (2013) oversight is defined as “`watchful care' [that] refers to society `keeping an eye' on the technical [repository] system and the actual implementation of plans and decisions”. Oversight is a crucial concept in the ICRP's system of radiological protection, since “the level of oversight affects the capability to control the source, i.e. the waste and the repository, and to avoid or reduce potential exposures”. Three categories or “levels” of oversight are distinguished: “direct oversight”, when the waste is still easily accessible; “indirect oversight”, when sections or all of the repository is sealed, and the waste is no longer readily accessible; and “no oversight”, when there is no “watchful care” of the repository anymore. In a collective statement on the preservation of records, knowledge and memory (RK&M), the Radioactive Waste Management Committee (RWMC) of the NEA asserts the relevance of maintaining oversight over geological repositories for as long as practicable and states that there is no intention to abandon geological repositories, either before or after closure. The RWMC adds, “Preparing for future RK&M preservation is best addressed while waste management plans are being designed and implemented, and funding is available for this important component of long-term planning” (NEA, 2014); i.e. it is considered a relevant topic today. But while the RWMC has explicitly adopted the ICRP position on the relevance of maintaining oversight for as long as practicable, some other institutions do not mention oversight in their guidance, leaving the degree to which the guidance mentioned is approved of in the community somewhat open. While societal decisions on how to organise and exercise post-closure (i.e. “indirect”) oversight may be decades away, the discussion on preservation strategies for RK&M has indeed started, a first milestone being NEA (2019). At a recent conference in Dessel, Belgium, organised by the NEA's Expert Group on Awareness Preservation (EGAP), new ideas and aspects were presented. The discussions revealed, however, that participants felt that a “common vision” in the community (meaning both the international expert community and any interested parties) would be beneficial to help focus discussions on RK&M preservation strategies. At the panel session, it should be discussed – by international experts in the fields of awareness preservation and oversight and the plenary – whether the ICRP and NEA position on oversight could be the conceptual basis for such “vision building” in the community. If so, the original question of what needs to be done today with respect to the preservation of RK&M would be projected onto the question of what needs to be done in the future with respect to organising and exercising post-closure oversight. Hence, the panel session aims to facilitate an exchange on the concept of indirect oversight promoted by the ICRP (2013) and its relation to the preservation of RK&M today.

Long-term prediction for seismic hazard for radioactive waste disposal

We consider possible approaches to the long-term prediction for seismic hazard in relation to the practical need for the safety of geological disposal of long-lived radioactive waste. The required period of prediction significantly exceeds the one reflected in the set of maps of General Seismic Zoning of the territory of the Russian Federation (GSZ-97). The first geological repository in Russia is planned to be set up in the Nizhnii Kan granite massif in the Krasnoyarsk Krai. This region is an intraplate territory with a relatively high seismic activity. We summarize the analysis of the known empirical generalizations and theoretical principles underlying the seismic hazard prediction. Real seismic events constantly violate forward-looking statements even for relatively short periods of time. These and other arguments suggest that the hypothesis of stationarity of the seismic regime, which is the basis of long-term prediction today, has limited and uncertain applicability in time. Intraplate earthquake prediction is especially uncertain because of the uncertainty in the factor responsible for generating tectonic stresses in these regions. The short horizon of the prediction, based on statistical methods, can be attributed to the nonlinearity of seismic geodynamic processes. Fundamental laws of tectonic processes should be used as the scientific basis for long-term predictions for seismic hazard at the sites chosen for geological disposal of long-lived radioactive waste. These processes can be reflected in models for the migration of the seismically active boundaries of lithospheric plates and the occurrence of seismic activity in intraplate regions.

火山・マグマ活動長期安定性の将来予測と地層処分：現状と今後の課題

火山・マグマ活動長期安定性の将来予測と地層処分：現状と今後の課題

On the absence of appreciable half-life changes in alpha emitters cooled in metals to 1 Kelvin and below

The recent suggestion that dramatic changes may occur in the lifetime of alpha and beta decay when the activity, in a pure metal host, is cooled to a few Kelvin, is examined in the light of published low temperature nuclear orientation (LTNO) experiments on such sources cooled to as low as 25 mK, with emphasis here on alpha decay. In LTNO observations are made of the anisotropy of radioactive emissions with respect to an axis of orientation. Correction of data for decay of activities in metallic samples held at temperatures at and below 1 Kelvin for periods of several days has been a routine element of LTNO experiments for many years. No evidence for any change of half-life on cooling, with an upper level of order 1%, has been found, in striking contrast to the predicted changes, for alpha decay, of several orders of magnitude. The proposal that such dramatic changes might alleviate problems of disposal of long-lived radioactive waste is shown to be unrealistic.

Geoscientific R&D for high level radioactive waste disposal in Sweden — current status and future plans

SKB (Svensk Kärnbränslehantering AB) is responsible for all handling, transport and storage of the nuclear wastes outside the Swedish nuclear power stations. According to Swedish law, SKB is responsible for an R&D-programme needed to take care of the radwastes. The programme comprises, among others, a general supportive geo-scientific R&D and the Äspö Hard Rock Laboratory (HRL) for more in-situ specific tasks. Sweden is geologically located in the Fennoscandian shield which is dominated by gneisses and granitoids of Precambrian age. The Swedish reference repository concept thus considers an excavated vault at ca. 500 m depth in crystalline rocks. In this concept (KBS-3), copper canisters with high level waste will be emplaced in deposition holes from a system of tunnels. Blocks of highly compacted swelling bentonite clay are placed in the holes leaving ample space for the canisters. At the final closure of the repository, the galleries are backfilled with a mixture of sand and bentonite. This repository design aims to make the disposal system as redundant as possible. Although the KBS-3 concept is the reference concept, alternative concepts and/or repository lay-outs are also studied. The main alternative, currently under development at SKB, is disposal in boreholes with depths of 4–5 km. The geoscientific research will to a great extent be guided by the demands posed by the performance and safety assessments, as well as the constuctability issues. Some main functions of the geological barrier are fundamental for the long-term safety of a repository. These are: bedrock mechanical stability, a chemically stable environment as well as a slow and stable groundwater flux. The main time-table for the final disposal of long-lived radioactive waste in Sweden foresees the final selection of the disposal system and site during the beginning of next decade.

Knowledge development since the Seventies

This paper deals with the development of technical and scientific knowledge related to the disposal of long-lived radioactive waste in deep geological repositories since the 1970s, evaluates the progress achieved during the last two decades, and mentions the main orientations of current activities. Wider issues are also addressed briefly, such as the environmental and ethical background for geological disposal, and the strategies currently followed for the implementation of this concept. The starting point is to recall the situation in the early 1970s with regard to the thinking on deep geological repositories. A few important milestones and examples which have marked knowledge development during this period are described. In this respect, the complementarity of national research and the international evaluation of the results is stressed. Finally, an attempt is made to describe today's situation with regard to the level of current knowledge and the extent to which further progress can be anticipated and in which directions.

"Potential Exposure" in Practice

Potential exposures are not normally expected to occur, but they can be anticipated, and the probability of their occurrence can be forecast. Early ICRP thoughts about this concept were developed in considerations about final disposal of long-lived radioactive waste, and about major accidents such as nuclear disasters. ICRP has now examined a third situation: accidents affecting one or a few persons only (but sometimes with severe consequences for those affected). Protection against such potential exposures starts with a structured analysis of scenarios. Given probabilities derived from such analyses, the expected detriment from potential exposures can be computed. This risk can be compared to a risk constraint, which need not be particularly complicated.

Nuclear waste transmutation

Accelerators can play a role in the disposal of long-lived radioactive waste: an alternative to the storage in deep underground repositories might be transmuting long-lived elements into stable or short-lived ones into subcritical systems driven by spallation neutrons. These neutrons would be produced by a high intensity, intermediate energy proton accelerator irradiating a heavy target. Similar systems have also been proposed to produce energy with a minimized waste inventory. Since a good knowledge of the spallation process is essential for designing and optimizing the target-blanket assembly, new programmes aimed at studying spallation reactions are in progress.

96/01021 Proceedings of an International Workshop — Environmental and ethical aspects of long-lived radioactive waste disposal, 1–2 September 1994, Paris

96/01021 Proceedings of an International Workshop — Environmental and ethical aspects of long-lived radioactive waste disposal, 1–2 September 1994, Paris

Environmental and Etidcal Aspects Of Long-Lived Radioactive Waste Disposal Proceedings of an International Workshop organised by the Nuclear Energy Agency in co-operation with the Environment Directorate

Environmental and Etidcal Aspects Of Long-Lived Radioactive Waste Disposal Proceedings of an International Workshop organised by the Nuclear Energy Agency in co-operation with the Environment Directorate

Protection of the environment from nuclear fuel waste radionuclides: a framework using environmental increments

Protection of the environment is a key issue in the disposal of long-lived radioactive wastes. To assess the implications of underground disposal, transport models are commonly used to predict radionuclide concentrations in soil and water. However, an appropriate framework needs to be established to ensure that the predicted concentrations do not impose unacceptable environmental impacts. Here, we suggest Environmental Increments (EI) of the most important radionuclides in nuclear fuel waste, which could be added to soil and water without causing detectable effects. The EI values are based mostly on natural variability, but some alternative methods are used for radionuclides that are very rare in nature. The EI values are most useful as a screening tool to help identify potentially unacceptable concentrations arising from a disposal concept. This review focuses especially on concentrations applicable to the Canadian Precambrian Shield, as part of the Canadian concept of nuclear fuel waste disposal in a deep, stable geological formation.

The management of long lived nuclear waste

Disposal of long-lived radioactive waste is often publicized as one of the great unresolved problems of the industrial era. Within the waste management community there is a consensus, however, that safe disposal is perfectly feasible with current technology. This paper reviews concepts for the disposal of such waste with emphasis on using observations from natural systems to justify the applicability of the performance assessment methodology used to demonstrate safety over very long time periods.

Natural radioactivity and radioactive waste disposal

The disposal of long-lived radioactive wastes by deep burial in suitable rock formations is an emotive issue. Although disposal is technically not exceptionally demanding, the demonstration of long-term safety using predictive hydrogeological and geochemical models has proved much more difficult. In order to validate the results of such predictions, the models and associated computer codes and databases are being tested and calibrated on natural radioactive systems. This article looks at how information on natural radiation sources, and the distribution and behaviour of radionuclides in geochemical systems, is being used to evaluate the performance of deep radioactive waste repositories.

High-Level and Long-Lived Radioactive Waste Disposal

No uniform international approach for handling the problem of high-level radioactive waste disposal exists. All the while, the volume of these wastes continues to grow. The only viable solution to the disposal problem is a geologic one. Burial of these wastes in solid form for long periods of time in mined cavities in salt or Precambrian crystalline rock formations is technically possible. Several steps in the burial process have already been demonstrated in Germany. The problem becomes more serious as the number of countries committed to the use of nuclear energy grows. If one considers the problems of seismic stability and worldwide distribution of salt deposits, the overwhelming need for an international solution to the waste disposal problem seems obvious.