A statement on incidents at nuclear installations in Britain which meet Ministerial reporting criteria is reported to the Secretary of State for Energy and Climate Change and the Secretary of State for Scotland and is published every quarter by the Health and Safety Executive.
For the period 1 July 2008 to 30 September 2008 there was one incident at a nuclear licensed installation that met the reporting criteria.
On 19 September 2008 a fault occurred on the radioactive Waste Vitrification Plant (WVP) Line 3 shield door interlock system. Nobody was injured or received any radiation dose.
During a planned changeover of hydraulic supply units in Line 3, an uncontrolled movement of two shielded trap doors and other hydraulic-drive components was observed. These components protect against the inadvertent exposure of workers to radiation and so are designated Safety Mechanisms.
One movement was of the trap door between the Line 3 Control Cell and Decontamination Cell. Neither cell was occupied at the time, though personnel access to these cells is permitted and it is possible for personnel to be working in one cell while a container of vitrified waste is present in the other. The radiation dose rate from a container of vitrified waste is very high and hence the incident had the potential to cause a significant radiation dose.
The root cause of the incident has not yet been established and is the subject of ongoing work by Sellafield Limited. Meanwhile Sellafield Limited has suspended all of Line 3 shield door operations.
NII is investigating the incident taking into consideration the implications for safe operation of other facilities at the Waste Vitrification Plant, and also the implications of previous shield door incidents. NII is considering enforcement action.
Single copies of statements are available free from the Health and Safety Executive, Nuclear Directorate, Division 4A, Building 4N.G, Redgrave Court, Merton Road, Bootle, L20 7HS,