A statement of nuclear incidents at nuclear installations in Britain during the fourth quarter of 2002 is published today by the Health and Safety Executive (HSE). It covers the period 1 October to 31 December 2002. There are two Installations mentioned in the statement: Harwell; Dounreay.
The statement is published under arrangements that came into effect from the first quarter of 1993, derived from the Health and Safety Commission's powers under section 11 of the Health and Safety at Work, etc. Act 1974.
1. The arrangements for reporting incidents were announced to Parliament by the Parliamentary Under Secretary of State for Energy on 30 April 1987 (Hansard col. 203-204). A minor modification to arrangements for reporting on nuclear incidents was announced in HSE press notice E108:93 of 30 June 1993.
2. Normally each incident mentioned in HSE's Quarterly Incident Statements will already have been made public by the licensee or site operator either through a press statement or by inclusion in the newsletter for the site concerned.
Statement of Nuclear Incidents at Nuclear Installations: Fourth Quarter 2002 - single copies of each free from the Information Centre, Health and Safety Executive, Room 004, St Peter's House, Stanley Precinct, Bootle L20 3LZ.
The Health and Safety Executive (HSE) presents the attached statement of nuclear incidents at nuclear installations published under the Health and Safety Commission's powers derived from section 11 of the Health and Safety at Work, etc. Act 1974.
On 6 November 2002 during operations in a glove box in B220, the over pressure alarm sounded. The operators evacuated and shortly afterwards the airborne activity monitors also sounded. The building emergency arrangements for airborne activity alarms was initiated to ascertain the source and to manage the operations. An investigation by UKAEA confirmed that a release of Americium 241 into the working area had occurred at a quantity in excess of Schedule 8 column 4 of the Ionising Radiations Regulations 1999 (IRRs). A number of personnel have received intakes including the two operators and the health physics personnel who attended the event. The highest dose (up to 6 mSv.) was received by the Health Physics charge hand.
UKAEA placed an embargo on the use of similar systems and have completed their own management investigation and produced an internal report. It concludes that the likely cause of the event was over-pressurisation of the vacuum equipment used in the process. The report also highlights improvements required to the ventilation system in the laboratory and adjoining areas. An action plan has been developed for this work and progress is being made.
NII has followed the UKAEA investigation and carried out its own study including a visit by a ventilation specialist. This has confirmed the problems with the ventilation system. It is a complex issue that may have a wider impact across the building. A letter has been sent to UKAEA detailing a series of short-term requirements and the need to review implications and produce a longer-term action plan. UKAEA is cooperating fully with these requirements.
On 12 November 2002, two contractors leaving the D2001 Intermediate Level Waste Processing facility were found to have contaminated shoes and one had contamination on his hands. All personnel in the building were withdrawn and monitored, and as a result contamination was revealed on the shoes of a further fifteen individuals. Of these, one other person had contamination on his hands and face. The two individuals with personal contamination were sent to the Occupational Health Department where decontamination was successfully carried out the following day.
In parallel with UKAEA's investigation, an investigation into
the incident was carried out by NII commencing at site on 13 November
2002. The investigation concluded that the source of the
contamination was the leakage of a small quantity of contaminated
Zinc Bromide liquid from a flask. This had been swabbed up from the
inside of a shielded waste cell and placed in a waste container which
was then posted out of the cell into the flask for processing and
consignment for storage. The flask, waste container and the
associated bagging system is not designed to provide containment of
free liquids and the Zinc Bromide leaked to the outside of the flask
and was spread around the working area on the shoes of the
The actual doses received by the individuals affected by the incident were confirmed to be very low. In addition, checks of the discharge stack monitors concluded that there was no evidence of a release to the environment.
NII's investigation report revealed a number of shortcomings which are being addressed by UKAEA. An Improvement Notice was served under the Ionising Radiation Regulations 1999 (IRRs) requiring improvements to be made to the flasking system design and operations.
The incident has been classified as Level 0 on the International Nuclear Event Scale.