Environmentalists and others will heave a sigh of relief after the plug is finally pulled on the last ageing Calder Hall military reactor – Reactor 1 – at Sellafield this month. The first to operate at Sellafield, Reactor 1 was opened in 1956 with a design life of 20 years.
Projected only two years ago to operate until at least 2006, Calder’s early demise has been forced on BNFL by the discovery last year of shrinkage and distortion of the graphite in the cores of Reactors 2,3 and 4, making fuelling/ defuelling and control rod operation unsafe. Low electricity prices have also been quoted by BNFL as a reason for premature closure of the entire station. Calder Hall is survived, albeit temporarily, by its sister station at Chapelcross in Scotland which has also had graphite shrinkage problems. Both stations have recently suffered major defuelling accidents leading to investigations by the Nuclear Installations Inspectorate (NII).
A CORE spokesperson said today. We won’t shed any tears over the passing of these reactors that BNFL pushed 27 years past their sell-by date. A costly and dangerous way to boil a kettle, the site’s tiny contribution to the national grid is steadily being replaced by cheap, clean and safe renewable energy – attributes that Calder never possessed. The sooner all these Magnox stations are put out of their misery the better.
As well as producing electricity, Calder Hall produced weapons grade plutonium for UK’s nuclear weapons programme, taking over the role of the Windscale Piles shut down after the 1957 Windscale fire. Military plutonium was still being produced at Calder in the early 1990’s and it was only in 1995 that a halt to these Ministry of Defence (MOD) contracts was ordered by Government. At Chapelcross, MOD contracts for the production of tritium for weapons use are still undertaken today.
The closure of Calder Hall will necessitate a change to the Sellafield ‘reference’ accident scenario upon which county emergency plans have been based for decades, and for which potassium iodate tablets are issued to the public close to the site, or kept in stock locally. The ‘reference accident’, historically based by BNFL upon a major failure of the coolant circuit on a Calder Hall reactor with subsequent off-site release of radioactive Iodine 131, must now be replaced by another scenario that reflects the potential for a significant accident from another plant on the Sellafield site.
The demise of the power station will also bring to an end a significant source of radiation dose to workers and public. Gamma radiation from the Carbon Dioxide coolant gases and from Argon gas, together with neutron radiation emanating from unshielded roofs and reactor buildings have in the past resulted from doses significantly in excess of those recommended by the UK’s National Radiological Protection Board. The doses from Calder Hall have been significantly greater than from any other magnox power station.
In 1996 CORE undertook its own covert assessment of radiation and doses within the Sellafield site, using the Visitor Centre’s bus tours around the site regularly over a five month period. Readings from a concealed geiger counter and radiation dose meter showed consistantly high levels of radiation and dose in the tour bus close to the reactors.
With decommissioning of the station expected to take up to one hundred years, CORE added “ even with the reactors closed, people should remain wary of the ongoing dangers posed by Calder Hall and BNFL’s plans and ability to dismantle it safely “.