Substitution solution16 February 2004
The UK government is considering shipping high- rather than intermediate-level waste back to BNFL’s overseas reprocessing customers. Does it make good economic, ethical and environmental sense?
The UK government’s Department of Trade and Industry (DTI) published a consultation document on 30 January to gather opinions from all interested parties on the analysis carried out by independent consultants NAC International on a proposal made by BNFL. In the document, NAC recommends that BNFL exercise their ability to return high-level waste (HLW) instead of intermediate-level waste (ILW) to countries that have commissioned them to reprocess spent nuclear fuel – a process known as substitution.
The deal is that the UK will keep – and ultimately dispose of – the low-level waste (LLW) and the ILW but will send back a radioactively equivalent amount of HLW.
The report comes against a background of indecision on the UK’s long-term waste strategy. The possibility of waste substitution has been associated in previous reports and consultations with an assumed decision on a final repository to be operated by Nirex, the body created by the government to design, build and operate a disposal facility for ILW and some LLW not suitable for disposal at the existing Drigg facility.
The UK government’s 1995 white paper, Review of Radioactive Waste Management Policy, described BNFL’s substitution situation as that: “BNFL may engage in waste substitution for LLW now, but any arrangements they now enter into and implement with their overseas customers for the substitution of ILW must be conditional upon confirming at the time a Nirex repository receives planning permission, that waste equivalence has been properly calculated.” Nirex had proposed using the Sellafield site as the UK’s final deep repository solution, but in 1997, planning permission was refused for a research facility to be built on a farm adjacent to the Sellafield site to further assess the site’s qualities as a potential deep repository.
The setback caused the UK government to take a fresh look at radwaste management, commencing a new consultation in 2001 which resulted in a 2003 decision to commission NAC “to assess the environmental case for implementing ILW substitution on existing BNFL reprocessing contracts now in terms of the overall costs and benefits, rather than waiting until there is greater certainty on the long-term management strategy for ILW.”
In the absence of such certainty, NAC’s advice to the UK government now is based on three long-term timescales: the earliest possible date for a repository to be ready, 2025; a reference case of readyness in 2040 and the latest repository date, 2100.
Analysis performed by BNFL in 1994 suggested that under Thorp contracts, an approximate environmental neutrality could be obtained when 15% extra HLW is returned to the customer country. For Magnox contracts, between 60 and 100% extra HLW could be returned. The higher figure for Magnox represents the fact that different reprocessing work is involved and that less HLW is produced per unit of spent fuel. Correspondingly, a greater percentage of extra HLW is required to balance the toxic potential of the ILW.
Figures in the consultation document show the UK’s total ILW inventory to be 237,021m3 with 3238m3 (1.4%) of overseas origin which could be earmarked for retention, while total UK HLW inventory comes to 1071m3 with 50m3 of UK origin HLW to be returned under substitution.
Exactly how much extra HLW will be returned depends on the integrated toxic potential (ITP) approach to determining equivalent amounts of radioactivity between different grades and batches of waste. ITP has formed the basis of negotiations between BNFL and its international customers and was endorsed by the UK government’s 1995 policy statement (see Panel).
BNFL stated in 1994 that the effect of substitution on members of the public would be an additional exposure of less than 0.3mSv per year, 8000 times less than UK background radiation. A 2003 report from Nirex also found that the effect of foreign ILW caused negligible environmental impact. Although these reports were based on the effects of the waste once situated in a repository, mention was made of the effects of transport and handling, which were also held to be small.
If the environmental impact of the extra ILW can be shown to be negligible compared to the UK’s own waste stock, with uncertainties well understood and within acceptable limits, the NAC consultants propose that there is no benefit in delaying a decision on substitution further while other benefits stand to be gained.
To demonstrate that the environmental burden on the UK of the retained ILW is equivalent to the returned HLW could prove to be quite a problem. The UK’s stance up until this consultation has been that a decision on ILW substitution can only be made in the light of approval of the UK’s long-term repository plans, but although that concern has been sidelined due to delays, it remains that BNFL’s customer countries may not have finalised their own long-term plans by the time the HLW is returned.
Although the UK government does not wish to discourage other nations from finding their own disposal solutions following the general principle of self-suffiency, it is rather unlikely that other countries will make final decisions anytime soon. Different treatment for nations at different stages of repository development would not be acceptable. In the absence of final repository designs, calculations of environmental impact will have to be made against a reference case repository and the resulting equivalence ratios applied to waste transactions between all customer countries. In addition, ITPs of wastes may be viewed to be equal, but their peak doses would vary over time, further complicating the issues surrounding public acceptance of the substitutions in both nations.
Initial press reactions to the consultation document have done little to promote public understanding, with the use of attacks on BNFL’s links to the authoring consultants and headlines such as “Britain set to become ‘nuclear dustbin of the world’ in policy shift” (The Independent), a view broadly matched by the BBC. It was interesting to note that the stories made much of BNFL’s potential increase in profit but little of the benefits in terms of transport risk, and the simple fact that Britain would be host to less HLW.
BENEFITS AND SAVINGS
The principal benefit of substitution would be a significant reduction in the number of international waste shipments, from 225 to 38, including both sea and rail (see Table). In addition, the transportation process would most probably end at least 10 years earlier.
Such a reduction in transportation will be accompanied by a proportionate reduction in dose to the public and to transportation workers. Combining the entire journey from Sellafield to the country of origin and to a repository, collective dose is estimated to be reduced ninefold under substitution, from 0.33Sv to 0.038Sv. The figures are based on actual dose records from previous shipments, with few additional assumptions. In line with ITP calculations, work by Nirex has concluded that the extra dose from more ILW flasks would indeed be balanced by the radioactivity of fewer HLW flasks, while the risk of radiological accidents would be halved.
The risk of an accident at sea releasing radioactive material has been considered by BNFL as virtually nonexistant while the IAEA puts the risk at “very low or negligible.” And, while a rail accident is the only scenario which would affect radiological dose, the dose from such an accident would be about 100 times lower than the dose from normal operations.
Radiological issues aside, the risk of fatal accidents among workers returning foreign waste would be reduced by a factor of six simply because of the reduced workload. 30,000t of oil would also be saved, along with 27,000t of carbon emmissions.
Besides the gains in security, safety and international relations, increased logistical efficiency could save BNFL up to £200 million – even including some £50 million in lost transport earnings.
The main increase in cost to the UK would come from the greater amount of ILW that must be disposed of. Even assuming that the cost of ILW disposal doubles from the £87 million estimated in the document, those costs would be overshadowed by the £650 million payable by BNFL’s customers. If the government allows substitution, payments could begin to flow from 2005, subject to wastes held in the UK being allocated to customer countries. It is estimated that some 60% of foreign waste will have been allocated by the begining of 2005. BNFL can only allocate a batch of waste to a customer after the customer’s reprocessing order has been completed.
BNFL’s profit increases will come as anathema to green groups who will nevertheless be happy to see a reduction in the number of international waste shipments. Ian Jackson, an independent consultant, told NEI: “If the aim of ILW substitution is genuinely to be environmentally neutral, then it ought to be broadly fiscally neutral too.” The large difference (£563 million) between the costs to the UK of storing the extra waste and the charges to customer countries makes the arrangement begin to “look uncomfortably like a profit centre,” pointing out that this level of profit is approximately double that expected from the Sellafield MOX plant.
The indications from BNFL’s European customers, Germany, Italy, Netherlands and Switzerland are that they will be keen to avoid transport costs and sign up for substitution. In Japan, however, a legislative change will be necessary before returns of either ILW or substituted HLW can be returned.
Interested parties wishing to respond to the document have until 30 April 2004 to reply to the DTI.
Related ArticlesSubstitution approved for Sellafield wastes
The basis of equivalence is the calculation of the toxic potential of each unit of waste. This is calculated for each isotope based on its level of radioactivity multiplied by a weighting factor which is in turn calculated from both the specific energy and the type of radiation emitted (alpha, beta, gamma or neutron) and how the isotope behaves in the body. Considerations for the weighting factor are the the dose to the body and the number of potential pathways the material could take through the body.
When a body of waste contains a number of different isotopes, their individual toxic potentials are summed. This can be done in two ways, the first is simple summing of their gross toxic potential at any given time to produce a total toxic potential for the mixture. A more advanced method is to take into account the different rates of change of toxic potential with time which result from their differing half-lives and combine their toxic potentials over a specified time period, giving an integrated toxic potential (ITP). ITP can vary according to the specific timescale over which the integration takes place.
Toxic potential is a theoretical measure of the potential of the isotopes to cause harm. It is a fundamental value which does not depend on whether the material is stored, transported or disposed of. It can be used to compare what the effect would be if exposure occurred without the need to consider the likelihood of such exposure occurring. The NAC report considers disposal as a means of determining whether the decision to substitute could result in a significant difference in the potential future environmental impact.
Research on equivalence calculation methods has not been great. In part, this is because few countries have ever made exchanges such as this. In any case, the authors of the NAC report have concluded that the environmental consequences of substitution would be small, irrespective of the methodology assumed in calculating ILW/HLW equivalence.