In September 2016 the Office for Nuclear Regulation (ONR) closed an Improvement Notice that had been issued to AWE the previous year. The notice said they had to choose a plan for dealing with the stocks of Higher Activity Waste (HAW) stored at Aldermaston, an issue regulators have been trying to get AWE to address for sixteen years.
While few details of the proposed process have been made public, an assessment by the ONR shows that serious questions remain over whether AWE can stick to their timetable.
HAW is the term used for radioactive waste that cannot be disposed of in the Low Level Waste (LLW) repository in Drigg, Cumbria. HAW consists of the two most dangerous categories of waste: High Level Waste (HLW) and Intermediate Level Waste (ILW) as well as some types of LLW that Drigg is unable to accept.
From the 1950s until 1983, radioactive waste generated at AWE was simply dumped at sea, so the waste currently stored on site has been produced during operations and decommissioning since 1983. It is mainly comprised of ILW, and is not thought to contain any HLW.
The safest way to store radioactive waste is to treat it so that it is immobile and passivated, meaning that it has been processed into a solid form where it is unlikely to chemically react with its surroundings and corrode or degrade. None of the HAW at AWE has been treated in this way.
According to the ONR many of the containers storing the waste are “already several decades old and well beyond their normal design life”. There is also a risk that corrosion of the containers could compromise their safety features or make it more difficult to treat the waste in the future.
In the year 2000 the Nuclear Installations Inspectorate (NII), ONR’s predecessor organisation, required AWE to repackage 670 drums of Intermediate Level Waste (ILW) into safer containers by 2006. In 2007, after the deadline had passed, a new regulatory requirement was adopted at AWE’s suggestion: that the contents of 1000 ILW drums should be reduced in size & encapsulated by 2014.
For most of the 2000s, AWE’s preferred option for dealing with their HAW issue revolved around plans for an on-site facility containing a supercompactor, which would have been used to compress the contents of waste containers before storing them in new containers which are safer than the ones currently used.
In 2008 AWE presented plans to the MoD for a £17m project to refit an existing building to create a solid ILW treatment plant and the process of procuring a supercompactor began. However, by 2010 it was clear that standards for seizemic resiliance and other safety issues meant that the refit project could not go ahead as intended, but a decision was still taken to purchase the supercompactor, which was planned to be sited in a new building instead.
However, the requirement for a new building significantly increased the cost of the project, and the MoD was unwilling to allow some of the costs to be offset by allowing civilian nuclear waste to be processed in the facility, as that would make AWE subject to International Atomic Energy Agency safeguards inspections.
Due to these factors, in Sept 2011 the MoD facilities review board stopped any further spend on developing options, which effectively put an end to the supercompactor project and any hope of AWE meeting the 2014 regulatory deadline. The supercompactor itself had already been purchased by AWE and was sold to the Nuclear Decomissioning Authority for use at Dounreay.
Following the failure to meet the 2014 deadline, the ONR launched an enquiry. Although the HAW at AWE was not judged to be an immediate risk to the public, a serious accident could result in members of the public receiving a radiation dose of over 5 mSv, five times the recommended annual level.
As AWE had failed to produce a long-term strategy to keep risks as low as reasonably possible, they were judged to be in breach of their legal duties and asked by the ONR to attend an interview under caution. AWE did not attend the interview, but instead sent a letter defending their actions.
Despite AWE’s failure to address the HAW issue over 14 years, a decision was taken by the ONR not to prosecute them. Instead, ONR decided to target much shorter-term miletones and issued a new Improvement Notice. This requiring AWE to decide on a firm plan by September 2016 for dealing with all their of HAW streams, including waste that they expect to produce in the future.
Options considered for the 2016 plan
The documents AWE prepared in response to the improvement notice considered two options: the supercompactor proposal and the proposal that was eventually adopted. Both options included a number of common elements: improvements to storage facilities and better monitoring of waste, direct encapsulation of some waste into waste containers on-site and ongoing work to re-categorise some HAW waste as LLW. Re-categorisation is the only area where AWE has made some progress since 2000, with more than 3,800 waste drums being designated as LLW and sent to Drigg by early 2016.
Although details about the chosen proposal have been removed from the ONR documents, the main element of the plan appears to involve some form of treatment or processing of the ‘higher hazard’ waste drums in the short term, and it seems that an organisation other than AWE will be contracted to undertake this work. In 2012, when the proposal was being developed, it seems to have involved up to 5,000 drums of waste being compacted and encapsulated. It is not clear whether the hazard reduction work will be undertaken on site at Aldermaston or whether some of the waste will be transported elswhere.
Whatever is proposed for the higher hazard drums, a substantial number of drums will still not be dealt with using this method, and a processing facility will need to be available to deal with them in the future. At present AWE has no firm plan for this and it appears that processing at an off-site facility is one of the options under consideration.
Is AWE’s plan realistic and are contingencies in place?
ONR have expressed concerns about the potential for delay in the proposed option, in part because of the complexity of orchestrating contracts and managing a project across multiple organisations. There is also potential for delay in the plans for several of the other HAW waste streams.
Although production of nuclear waste at AWE has reduced in recent years, they are still predicted to run out of storage space for waste drums in the next 10 years. Another potential problem with delays to the timetable is the potential degradation of the containers. This could lead to more of the drums being classified as 'problematic waste' - a term applied to part of the HAW holdings which AWE does not currently have a plan for dealing with.
Despite the risks of the plan that AWE has adopted, ONR decided to endorse it because, although in the long run the supercompactor option would have delivered a greater risk reduction, it could also have been supject to delays and if AWE is able to stick to the timetable for dealing with the higher hazard drums, the overall risk profile of the HAW will be reduced faster.
Although total lifetime costs of the plan AWE has adopted are said to be equivalent to the supercompactor plan, it involves much less expenditure in the short term.
ONR’s assessment closing the Improvement Notice stated that, due to the potential for delays and problems, AWE needed to put much more detailed contingency plans in place. It also recommended that they should retain the capacity to build a compactor facility until it was clear that their chosen option could deliver the promised reduction in risk from the HAW holdings.
Given that the MOD has already killed off the supercompactor plan once, despite 16 years of regulatory measures, it is questionable how realistic these recommendations are. At present ONR states there is only “limited evidence of workable contingencies”.
While ONR have closed the Improvement Notice, they have left open the option of further enforcement action if there isn’t sufficient notice on implementing the plan. Time will tell whether AWE will deliver on the plan they have chosen. In the meantime, the waste drums that were the subject of regulatory action in 2000 are still untreated.