Office for Nuclear Regulation

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A review by the Health and Safety Executive's Nuclear Installations Inspectorate of the strategy of Imperial College of Science, Technology and Medicine for the decommissioning of its nuclear site


This report sets out the findings of a review by the Health and Safety Executive's (HSE) Nuclear Installations Inspectorate (NII), in consultation with the Environment Agency (EA), of the strategy of Imperial College of Science, Technology and Medicine (Imperial College) for decommissioning its nuclear licensed site. NII is that part of HSE responsible for the regulation of safety on nuclear licensed sites, including radioactive waste management and decommissioning activities. The EA regulates the disposal of radioactive waste from the nuclear sites.

Government policy, set down in the 1995 White Paper "Review of Radioactive Waste Management Policy: Final Conclusions", Cm 2919 [1], requests nuclear operators to draw up strategies for the decommissioning of their redundant plant, including justification of the timetables proposed and the adequacy of the financial provision. Government policy is for HSE, in consultation with the environment agencies, to review these strategies on a quinquennial basis to ensure they remain soundly based. This review is one of the series that HSE is undertaking for the UK nuclear licensees.

Imperial College has provided HSE with a document [2] presenting a summary of its decommissioning strategy; enquiries concerning that document should be made to the licensee.


Imperial College operates the Consort reactor on the nuclear licensed site at Silwood Park, Ascot. It is a low power research reactor used for research and teaching purposes. The licensed site comprises the main hall, containing the reactor, and an adjoining annex housing support systems and offices. The reactor is the only remaining research unit in the UK and, subject to workload and commercial factors, it is currently planned to continue operation until at least 2009 and possibly as long as 2028. Whenever it is shutdown, Imperial College proposes to defuel and dismantle the reactor over a period of five years. After an initial period of two years to allow for radioactive decay, the used reactor fuel and other fissile material will be transferred off the site. The remaining radioactive material will be removed from the site and disposed of over the next three years. Imperial College states that its aim is to reduce the residual radioactivity to levels that will allow the site to be delicensed and thereby released for other use.

In undertaking these reviews HSE aims to assess the proposed decommissioning strategy to determine whether it is adequately comprehensive, technically practicable and appropriately timed. In particular it considers whether the strategy is consistent with Government policy that 'decommissioning should be undertaken as soon as it is reasonably practicable to do so, taking account of all relevant factors', and also that the 'hazards presented by the plant (or site) are reduced in a systematic and progressive way'. It also considers whether arrangements are in place to quantify the costs of decommissioning and to make available funds to undertake the work to the proposed timescales in order to assess 'the adequacy of the financial provision being made to implement the strategy'.

HSE has based this review on the information provided in Imperial College's document describing its decommissioning strategy [2], together with the outcome of discussions held with its staff. The EA has been consulted throughout the review.

Technical Assessment

Imperial College has identified all the liabilities that will have to be addressed and described the manner in which it intends to deal with them. In terms of the UK's nuclear licensed sites the Imperial College site is very small and contains a relatively small amount of radioactive material. HSE notes that a number of research reactors have been successfully decommissioned in the UK, and internationally, and that Imperial College has based its decommissioning strategy on the experience from those projects. As a result there is no reason to believe that decommissioning of the Consort reactor will present any significant technical challenges.

Imperial College is investigating the options for managing the spent reactor fuel, other fissile material, and intermediate level waste that will need to be transferred off the site and the destination for this material needs to be established. In addition, decommissioning will generate low-level radioactive waste, and Imperial College will need to ensure that there is an authorised disposal route for this material.

With respect to timing, the strategy is based on early decommissioning following final shutdown of the reactor. Two years, are allowed, for radioactive decay, prior to de-fuelling the reactor, which is not a decommissioning operation, but it is not intended to introduce any further delay. The overall decommissioning timescale of five years is considered to be consistent with Government policy that decommissioning should be carried out as soon as reasonably practicable. Imperial College currently expects the final shutdown of the reactor to be well in the future, but there are uncertainties, that could result in earlier closure. However, the strategy is flexible enough to be applied at any time and does not foreclose the option of earlier decommissioning. The sequence in which Imperial College proposes to remove the radioactive material is logical and consistent with reducing the hazard in a systematic and progressive way.

Imperial College acknowledges that prior to decommissioning more detailed planning will be required, and it has identified work that will be need to be carried out. As decommissioning is not planned to start for at least another 8 years HSE considers that the current level of development of the strategy is reasonable. HSE expects more detailed plans to be progressed such that they are fully developed for the start of decommissioning.

Financial Assessment

At this time the cost estimates prepared by Imperial College are indicative values based on its knowledge of recent decommissioning projects at other research reactors. HSE believes that Imperial College has a broad understanding of the magnitude of its decommissioning costs but supports its undertaking to refine the estimates. Imperial College has noted a contingent liability in its accounts and is considering how to translate this into a provision. In the meantime HSE believes that Imperial College's financial position provides confidence that decommissioning could be taken forward on a shorter timescale if necessary.


HSE regards the strategy proposed by Imperial College for decommissioning its nuclear site at Silwood Park, Ascot to be appropriate at this time. It is technically practicable, consistent with experience on other similar projects, and the timescale is in line with Government policy. HSE expects Imperial College to continue to develop its plans for decommissioning, to refine its estimates of the costs, and to create an appropriate provision in its accounts. It also needs to establish the destination of the spent fuel, other fissile material, and intermediate level waste that will be transferred off the site.


[1] Review of Radioactive Waste Management Policy - Final Conclusions, UK Government Cm 2919, HMSO 1995.

[2] The Decommissioning Strategy for the Consort Reactor: The 1999 Quinquennial Review Submission, ICRC 140/21/01, August 1999.

Published on HSE website 22 May 2002