Sim radwaste management30 May 2001
The 9th International High-Level Radioactive Waste Management Conference was held in Las Vegas on 29 April - 3 May, 2001. NEI reports on the proceedings of the conference.
Those of you familiar with computer games (possibly as a result of exposure through children) may be aware of the Sim City games. The premise of these games is that the player has to manage a city, or an ecosystem, or a manufacturing plant. Actions have consequences, and various unexpected external events can have a major impact on the system. If the system can cope, it survives, and if it can’t, it doesn’t. While I was at the 9th International High-Level Radioactive Waste Management (IHLRWM) Conference in Las Vegas in early May, I was struck by the thought that high-level radwaste management has a lot in common with these games. It has to be able to cope with and survive any of a number of extremely unlikely external events.
A number of themes were discussed. Some of these were long-standing issues that have been much discussed in the past.
The first and most obvious feature of the conference was that there was a very strong international presence, and a very strong international theme. This was reflected in the discussions on the viability of an international depository.
National or global?
Different countries have been developing and planning waste repositories. However, a case is being made that suggests that for countries with a relatively small number of nuclear facilities, the cost and complexity of developing an independent repository is excessive. Co-operation on an international repository is one possible solution to this. Since the fuel cycle is already international, there is a logic to this.
However, there are several issues that must be resolved before an international repository can be set up. The most significant is to gain political and social acceptance in the host country. There will undoubtedly be some local resistance to the concept of “acting as a nuclear dustbin for the world”. Such an argument would be very difficult to circumvent, and without public acceptance, there is no chance of the facility being built.
However, an international repository would introduce significantly greater security with regard to the prevention of proliferation of weapons-grade material.
It is a logical but not necessarily obvious consequence that if there is no disposal mechanism for high-level radioactive waste, then decommissioning nuclear weapons, far from increasing security, simply releases significant volumes of weapons-grade material in a form that is less controllable. There would be greater international observance of an international repository, and hence greater assurance that disposed material remains disposed.
The key to getting acceptance of the concept of international repositories is, as is so often the case, that of economics. If it becomes profitable to host such a facility, then there will be interest in the idea.
However, the big limitation of an international repository is the need to transport the radioactive waste to the site. There is always public concern over transport (as has been seen lately in Germany). An international repository would automatically involve an increase in the extent of transport.
A common view at the conference was that pressures towards disarmament would lead to an increased need for a safe and secure place to store the material released by the disarmament. In a slightly unexpected but logical consequence of disarmament, weapons-grade material becomes available, and the risk of this material entering distribution is increased. However, placing this material in a secure depository means that the material is still out of circulation. As a result, the pressure towards disarmament is seen as implying a pressure towards building a disposal site. Thus, non-proliferation is linked to disposal, and disposal facilities can facilitate disarmament.
Salt or not?
Another topic that was of widespread interest was whether or not salt was the best geological medium in which to store high-level waste. The basic discussion centred around the fact that geological salt tends to creep over time. This is considered to be both an advantage and a disadvantage. It is an advantage because the creeping of the salt caverns will tend to result in compaction, and hence closing up potential leaks. On the other hand, creeping implies movement, which provides uncertainties over the proposed life of the depository. Many different opinions on this were expressed, ranging from highly positive to highly negative.
For example, one presentation looked at the long-term life and movement of a containment area in the proposed Yucca Mountain site. This showed estimated movements of the salt over the years, which, if the modelling is accurate, demonstrates that the creep will tend to compact around the drums and thus prevent escape of waste.
One area that resulted in delegates being in general agreement was on the need for greater public transparency and engagement of the public in nuclear issues. This was widely agreed to be a good thing, although a number of delegates did suggest that this was essentially a ‘motherhood statement’, one that states obvious platitudes that no-one would disagree with. However, actually providing transparency and involving the public in the discussions frequently appears to be a lot harder. There is a reluctance in many quarters to actually pay more than lip service to this principle.
One presentation discussed the issue that an increase in pluralism in society tends to lead to a greater distrust in authority, which in turn leads to an increase in uncertainty. The only way of reversing this trend is to get society involved in the discussions. When authority is not automatically trusted, trust has to be earned, and this can only be done by engaging the public.
There were several presentations from groups that had set out to be proactive in involving the public in discussions. In particular, Canada appears to have well-developed means of public consultation. One paper that was presented at the conference was: “Enabling Participatory Decision Making through Web-Based GIS”. This presentation indicated that the public could check on, for example, statistics relating to water quality in a given location. In addition, people could report in indicators of water quality, leading to a widespread involvement in the monitoring process.
The key phrase seemed to be stakeholder involvement; when this is present, there is a great deal more public sympathy and understanding on the issues.
This was also shown in the situation in Sweden, according to a presentation entitled: “Public Participation and Transparency – Theoretical Models and Swedish Experiences”, and which was supported by several other presentations from other Swedish speakers. Because the public has been well involved in discussions, Sweden has a well-developed plan to develop a depository. It was noted that people living in locations that may be suitable for the site, far from objecting to its possible presence in their vicinity, have been eager to encourage the depository to be sited close to them. The present situation is that the siting decisions are well underway. Site selection is expected to take five years, with a decision being made by about 2007. Application to build the site will then be made, and the depository is expected to start operation in 2015, and will be filled by 2050.
Surveys have indicated that 70-85% of the public in Sweden are in favour of SKB building a long-term high-level waste depository to dispose of spent fuel. Site investigations are being carried out at Oskershamm, Nyokping, Forsmark, and Tierp.
Peter Nygards, president of SKB, said that Sweden had been able to get farther than any other country in gaining public acceptance of radwaste disposal: “Because it takes the public seriously, and takes the trouble to explain the situation to them.”
Realism in analysis
Perhaps one of the more contentious areas of discussion at the conference was on whether realistic or conservative calculations should be the basis of any analysis. The difficulty with conservative assessments of risk is that they tend to include scenarios that are impossible simply because a combination of two (or more) unlikely events are not necessarily excluded, even if they would be automatically mutually exclusive. A realistic analysis of risk tends to give a much more plausible view of what might happen. However, given the nature of long-term storage or disposal of radioactive waste, there are considerable difficulties with carrying out tests over the required lifetime, and the complexities of modelling are extensive. Without tests, there is always going to be some doubt over models, and in this situation, one is well advised to adopt very conservative assumptions. This difference resulted in some interesting discussions.
It was certainly the case that the level of modelling and consideration of factors included in calculations was impressively extensive. Factors such as potential climate change were included in the calculations.
Disposal or storage?
There were some interesting presentations that compared the advantages and disadvantages of disposal and storage as means of managing radwaste, and compared open and closed disposal. Interestingly, under most assumptions, qualitative analysis indicated that closed disposal was the best method of dealing with waste. It was only when one placed a very high priority on retaining the ability to recover the waste (because one has a very high confidence that in the future, scientists will be able to develop methods of treating radioactive waste to reduce its activity) that one gets an indication that open disposal might be a superior method of managing the waste.
Overall, the conference continued long-standing discussions, and there was a considerable level of exchange of information. That is exactly what one would expect from a good conference.
And, for those interested in the risk assessments carried out in Las Vegas itself, I have to report that it appears that the casinos do indeed have a shrewd ability to judge risks that exceeds mine, based on the limited evidence available.