By Russell Bruce
Following on from a previous article on Hunterston B which was shut down last Friday I decided to have a look at one of the smaller nuclear power stations in Scotland to see how work was progressing on decommissioning.
Chapelcross nuclear power station occupies a 92 hectares site on the location of a former World War II training airfield in Annan. Chapelcross had 4 Magnox reactors, each with a 48MW output. Chapelcross was linked to sister plant Calder Hall in Cumbria which is now the site of the NDA’s Sellafield operation. Calder Hall closed in 2003 and Chapelcross in 2004. Both plants were originally operated by the UK Atomic Energy Authority. Their main purpose was to produce weapons-grade plutonium although they also generated electricity for the National Grid.
The four cooling towers at Chapelcross were demolished in 2007. Cooling towers were common in early nuclear plants and similar to those for coal and wood pellet power stations in Yorkshire. The reactors are spent-fuel free and the building is currently partly demolished. The defuelling work on the 4 reactors was completed in February 2013, nine years after Chapelcross closed. Work on all stages of decommissioning is carried out by Magnox Ltd a subsiduary of the Nuclear Decommissioning Authority (NDA) The NDA is a regulatory authority, a Non-Departmental Public Body (NDPB), created as a result of The Energy Act of 2004.
There are three main levels of nuclear waste that have to be deal with when a nuclear power station is decommissioned. These are the classifications as described, mainly, by the Nuclear Decommissioning Authority.
Higher Activity Wastes
Higher Activity Waste (HAW) includes High Level Waste (HLW). Less than 1% of all radioactive wastes (by volume) are in the HLW category. HLW is produced as a by-product from reprocessing spent fuel from nuclear reactors. Spent nuclear fuel is sent to Sellafield. HLW typically occurs in liquid form and a process called ‘vitrification’ converts the liquid HLW into a solid product. The vitrification process is also carried out at Sellafield.
Although accounting for only for only 1% of waste by volume High Level Waste accounts for up to 95% of radioactivity from a nuclear power plant and is the stuff with the really long ‘shelf life’.
Intermediate Level Waste (ILW)
Intermediate Level Waste exceeds the upper boundaries for Low Level Waste but does not generate a significant amount of heat but enough for it to need time to cool. About 6% of all radioactive wastes (by volume) are in the ILW category. The major components of ILW are nuclear reactor components, graphite from reactor cores and sludges from the treatment of radioactive liquid effluents. NDA use a system of ‘packaging’ to contain, store and handle Intermediate Level Waste. This is stored above ground in specially constructed units for a period of 120 years. So long after the power plant building has been demolished.
Low Level Waste (LLW) contains relatively low levels of radioactivity, not exceeding 4 gigabecquerel (GBq) per tonne of alpha activity, or 12 GBq per tonne of beta/gamma activity.
Most LLW comes from the operation and decommissioning of nuclear facilities. The waste includes items such as scrap metal, paper and plastics. Some smaller amounts of LLW also come from hospitals and universities. About 94% of all radioactive wastes (by volume) are in the LLW category.
Most Low Level Waste from across the UK has been disposed at the Low Level Waste Repository (LLWR) in Cumbria since 1959. Waste was initially placed into landfill-style trenches but is now grouted (cement fill) in metal containers before being stacked in concrete lined, highly engineered vaults. A cap will cover the containers when the vaults are full.
In the North of Scotland, the Dounreay site also has a new LLW repository. This repository will only accept solid waste from Dounreay site operations and the nearby Ministry of Defence’s Vulcan Naval Reactor Test Establishment.
Very Low Level Waste (VLLW)
The NDA have a fourth disposal category for Very Low Level Waste. They describe this alternative as: Alternative Disposal – Permitted landfill sites can accept some Very Low Level Waste (VLLW) alongside non-radioactive wastes. There are strict controls on the amount of radioactive waste that can be disposed of at regular landfill sites.
This indicates the state of play as at 1st April 2019. Chapelcross had been defuelled and all High Level Waste moved to Sellafield. At that point, almost three years ago, the Intermediate Level Waste as well as LLW had still to be dealt with. The VLLW would appear to be close to the end of the decommissioning process. The LLW is destined for containers in Cumbria and the estimated 4,900 cublic metres of Intermediate Level Waste will be left onsite in specially constructed containers for a period of 120 years, pending a Scottish Government decision around 2145 on disposal of the containers and contents.
The interim storage facility for storing Intermediate Level Waste at Chapelcross began 2014 and was completed by May 2021 when the first ‘package’ was placed in the facility. In announcing this progress Magnox Ltd and the NDA said in a news release;
“The Interim Storage Facility (ISF) can hold over 700 waste packages of four different approved package types, and will be filled over the next five years as part of decommissioning work. Standing at 57m long and 23m wide, it has been constructed to safely and securely store packages for 120 years.”
Whilst Low Level Waste (LLW) is sent off-site for treatment and disposal, the purpose-built ISF [Interim Storage Facility] will securely store all the ILW on-site until such time when the Scottish Government decides on disposal of the ILW interim storage facility and contents. In the case of Chapelcross that will be in 124 years time in 2146. The site will need to be continually monitored during that period.
Timeline for Chapelcross
The process at Chapelcross started in 2004 with defuelling and with Higher Level Waste sent to Sellafield, followed from 2021 with work on the Intermediate Level Waste which is due to complete in 2026. The storage facility is then sealed for 120 years when a decision will be made by the Scottish Government on final disposal of ILW storage and contents. Whilst it can be argued that the core decommissioning work will take around 22 years, the end game is still 120 years away making 144 years in total for final clearance at the site.
The situation in Scotland is different from England and Wales
Although energy is controlled by Westminster, planning and environment come under the control of the Scottish Government. Scotland’s radioactive waste policy was set out in January 2011.
Chapelcross operated for 44 years. The ILW will remain on the site until 2146 although the buildings will be long gone by then. It is essential we deal with the legacies of the past and do so to the highest possible standard because we owe that to our own and future generations. The question for policy makers is do we really want to contemplate building new nuclear power stations when the legacy will be with future generations for 102 years, nearly two and a half times beyond any new nuclear plant’s operational life. The cost of nuclear electricity generation is high and future costs of dealing with the legacy are also passed on to at least four future generations.
The Scottish Government has decided no new nuclear plants will be built in Scotland. At the present time only one new nuclear plant is currently approved and under construction in England. When they were planned and built back in the 1950s people were told the electricity would be so cheap it would not be worth sending out electricity bills. Well we know how that turned out.
The Higher Level Waste at Sellafield will be stored in perpetuity in specially constructed containers.
UPDATE 10 January 2022 20.30 pm
We have added the second map from Scottish Government’s policy document as that lists the nature of material at nuclear sites in Scotland. These are only brief summaries. The Scottish Government is presently engaged with the Hunterston Site Stakeholders Group. The SG radioactive waste policy is 10 years old. We will update again when we hear back from the Scottsh Government if they have any plans to update policy on nuclear storage in Scotland.