The Environment Agency (EA) have announced that they are planning to approve the Atomic Weapons Establishment’s (AWE) application to to increase the quantity of volatile beta emitters that AWE Aldermaston is permitted to release into the environment. Beta emitters are radioactive elements that produce beta radiation. Volatile is a chemistry term which refers to a substance that tends to vaporise and become a gas.
AWE’s application for the increase to the limit was announced in late January, and there was a consultation on the application which ended in February. The Environment Agency have now released a draft decision which approves the proposed increase to the limit.
Under their current license AWE are allowed to release 4.4 megabecquerels (MBq) of volatile beta emitters into the air as gas every year. The draft decision allows them to increase the limit to 100 MBq a year, an increase of 22 times, or 2200%. A becquerel is a measure of the quantity of radioactive material. One bequerel is the quantity of material where radioactive decay will occur once every second. A megabecquerel means one million becquerels of material.
The EA is running a consultation on the draft decision, which closes on the 6th June.
AWE releases volatile beta emitters as gasses during a process to prepare samples for testing as part of AWE’s nuclear forensics capability.
Since 2005 the UK has participated in joint exercises with other countries where all participants analyse the same samples and compare the results in order to rehearse the testing process and validate their testing methods to assist nuclear non-proliferation efforts.
The radioactivity of the samples in the programme have recently increased. This has caused AWE to come close to breaching the current limit, as the process of preparing a more radioactive sample releases greater quantities of volatile beta isotopes. AWE’s application said that the radioactivity of the samples and other specifics of the programme are determined by ‘key allies’. The possibility of altering the programme to keep discharges within the current limit does not seem to have been considered.
It would be possible to install equipment to reduce the quantity of volatile beta isotopes released into the environment, but AWE has rejected this as “grossly disproportionate”. No costings were given in AWE’s application and in their draft decision document the EA do not comment directly on whether cost benefit analysis has been undertaken.
The EA do say that the proposed arrangements are “compatible with the broader requirement to apply” Best Available Techniques (BAT). BAT is an analysis that involves balancing the detrimental effects of an activity with the cost of mitigation measures. The EA has also said that the increase in the volatile beta limit is consistent with its growth duty, where it is obliged to promote the economic growth of organisations operating nuclear licensed sites.
As part of their application AWE carried out a dose assessment to calculate the radiation dose to the most vulnerable members of the public. The EA carried out their own dose assessment and found the results of the two assessments were consistent with each other. AWE’s assessment has been published as part of the consultation.
The AWE dose assessment calculated that the group of people most affected by radioactive discharges from the Nuclear Forensics Laboratory are those living at Ravenswing Caravan Park, and that if discharges were at the level of the proposed new limit an infant living there would receive a dose of 0.163 microsieverts a year from the laboratory. The vast majority of the dose would be due to consuming contaminated cow’s milk and other dairy products. The model makes the conservative assumption that all the dairy products consumed would be sourced from farms local to AWE, which is unlikely to be the case for most local people.
Aside from the limit on volatile beta emitters, AWE is allowed to release several different categories of radioactive material into the environment. Tritium is the radionuclide released in the greatest quantity, with a limit of 39 TBq (terabecquerels) a year for gaseousness emissions and a limit of 25 Gbq (gigabecquerels) on into the public sewers of liquid containing tritium. A terabecquerel is equal to 1 million megabecquerels, and a gigabecquerel is equal to 1 thousand megabecquerels.
In AWE's permit there are limits on all the categories of radioactive emissions, except for tritium in water released through the North Ponds system, which instead is governed by a ‘notification level’ where AWE has to let the EA know if radioactivity levels go above 30 Bq per litre of water. The limits and levels in the draft permit are the same as in the current permit, except from volatile beta emissions.
When all discharges from AWE Aldermaston were taken into account, the most affected group of people would be those living at the Old Kennels on Paices Hill. An infant there would receive a dose of 7.98 microsieverts/year if all discharges were at the levels in the proposed new permit. Again, the majority of this dose would be due to drinking dairy products.
In both cases the calculated dose is considerably lower than the government’s dose limit for a member of the public (1 milisievert, or 1,000 microsieverts, per year).
As the emissions from the Nuclear Forensics Laboratory do not occur steadily throughout the year, but happen in a series of short-lived releases, AWE also undertook a short-term assessment of dose. They were not obliged to do this as the calculated annual dose is lower than the level at which an assessment of short-term dose is required, but the assessment was carried out as a precaution. It found that each release could potentially give a dose of 0.4 microsieverts in calm weather to someone at the AWE fence-line. However, the calculation did not include ingestion of radioactive material and the model used was not able to include the correct figures for the height at which the release of radionuclides would occur or the distance from the fence.
AWE’s radiological assessment also considered the potential impact on non-human life of increasing the volatile beta discharge limit. It calculated that the greatest risk was to lichen mosses and other similar plants, known as bryophytes, but that it would be too low to be a significant risk.
In the draft decision letter, the EA say that the total calculated potential dose from AWE under the proposed limits would only be 2% of the 500 mSv maximum annual dose allowed for a single site. They also note that actual radioactive discharges from AWE in recent years have been much lower than the maximum allowed by the limits.
For these reasons the EA are proposing to approve the increase in the volatile beta limit, despite the fact it is current government policy to try and progressively reduce radioactive discharges into the environment, even when current scientific knowledge suggests the levels are unlikely to cause harm.
A link to the consultation and points that will be submitted in NIS’s response can be found in the document below.