Difficulty in Site Selection
According to the current basic policy for HLW disposal in Japan, the siting process is to be carried out with three stages (Fig. 24.5). The first stage is “literature survey,” the second is “preliminary investigation,” and the third is “detailed investigation.” Then, construction of the repository will start. At each stage,
Fig. 24.4 HLW disposal scheme in Japan (multi-barrier concept) (Modified from NUMO )
Fig. 24.5 Three stages of site selection process for HLW disposal in Japan (Modified from NUMO )
decisions will be made by selection criteria, taking into account the opinions of the local mayor (municipality) and local governor (prefecture).
In reality, there has been no occurrence of the first literature survey, although more than 10 years have passed since the siting process started. As mentioned before, a scheme of open solicitation was adopted for volunteers to apply for the literature survey, but after the failed attempt of Toyo Town in 2007, another scheme was added in which the government invited municipalities for the literature survey. However, the situation did not improve; rather, after the Fukushima accident the situation is becoming worse.
Facing these difficult situations, the government of Japan decided to take a more positive role in site selection. It is expected that a promising area could be more narrowly defined by screening sites on the basis of existing geological and geographical information.
Six Proposals by the Science Council of Japan
In September 2010 the Science Council of Japan (SCJ) received a deliberation request from the Chairman of the Japan Atomic Energy Commission, and SCJ formed a Review Committee for Disposal of High-Level Radioactive Waste. The author participated in the Review Committee as a member of SCJ. The Review Committee made a Reply on Disposal of High-Level Radioactive Waste  in September 2012.
The Review Committee of SCJ pointed out the following six proposals to search for a path toward consensus formation: (1) fundamental reconsideration of policies related to disposal of HLW with extended definition, which includes spent nuclear fuels as well as vitrified HLW canisters; (2) awareness of the limits of scientific and technical abilities and securing scientific autonomy; (3) rebuilding a policy framework centered on temporal safe storage and management of the total amount of HLW; (4) necessity of persuasive policy decision procedures for fairness of burdens; (5) necessity of multiple-stage consensus formation by establishing opportunities for debate; and (6) awareness that long-term persistent undertakings are necessary for problem resolution.
Considering the SCJ report, the Japan Atomic Energy Commission, however, expressed its intention to maintain a policy of implementing the geological disposal on December 2012 with extension of the scope to include the direct disposal of spent nuclear fuel .
Setting a Moratorium Period by “Temporal Safe Storage”
Proposals of the SCJ report, particularly, the concepts of temporal safe storage and management of total amount, triggered many discussions widely concerning the issue of HLW disposal.
The temporal safe storage is characterized by securing a moratorium period of several dozen or several hundred years to establish appropriate handling measures for the problem. It provides the advantages of using this period to refine technological developments and scientific knowledge, guaranteeing the possibility of creating handling measures that target a longer period; for example, improvement of the durability of containers, development of nuclear transmutation technology to reduce volume and toxicity of HLW, and research related to the stability of geological layers.
In addition, the temporal safe storage makes it possible to keep various options for future generations to choose for final disposal of HLW.
The concept of safe storage, however, still has a wide range of uncertainties in technical specifications; for example, duration of storage, location characteristics such as on ground or underground, and number of storage facilities. The concept ranges from currently available interim storage of spent fuel to retrievable geological disposal. In fact, the response of Japan Atomic Energy Commission mentioned retrievable geological disposal in the context of temporal safe storage.
SCJ had set up a Follow-up Committee as an extension of the Review Committee in August 2013 to clarify the concept of the temporal safe storage.
“Management of the Total Amount” of HLW
As clearly stated in the SCJ report, “management of the total amount” has two connotations: “setting an upper limit for the total amount” and “controlling increases of the total amount.” “Setting an upper limit for the total amount” corresponds to the withdrawal from nuclear power, and the level of upper limit depends on the tempo of that withdrawal. On the other hand, “controlling increases of the total amount” corresponds to keeping nuclear power in the future with strictly controlling increases of the total amount, and the amount of disposed waste per unit of generated power must be controlled to the smallest amount possible. There are many technical options to control the increase of the total amount of HLW, for example, increasing burn-up of fuels, transmutation of radioactive nuclides, and longer temporal storage of HLW, which secure time for radioactivity to decay.
However, in fact, many readers of the SCJ report mistakenly recognized that management of the total amount means setting an upper limit for the total amount, and thus believed that SCJ proposed withdrawal from nuclear power: this is a complete misunderstanding. At the background of the proposal of management of the total amount, there is recognition that we should respond to the concerns on the limitless increase of HLW.
Awareness of the Limits of Scientific and Technical Abilities
The Review Committee of SCJ consists of various experts from wide-ranging academic fields from physical science, engineering, life science, social science, and humanities. The proposal concerning awareness of the limits of scientific and technical abilities was formed through interdisciplinary discussions among the experts. Some readers of the SCJ report seem to have felt uneasiness with this proposal because this proposal apparently cast a scientific doubt on the feasibility of the geological disposal of HLW. To the author's understanding, this proposal is a rather general statement that there is no perfect scientific evidence to support the safety of HLW disposal for more than 10,000 years.
Having heard the discussions related to this proposal, the author recognized there are many different academic approaches depending on the field of science. For example, natural scientists seek truths in natural phenomena, whereas engineers try to make things and/or systems that are valuable and acceptable for human society. HLW issues are related not only to various fields of science, but also to value systems shared by society. Here again, the author was convinced that we need to reflect more deeply on the relationship between science and society.