Office for Nuclear Regulation

Statement of nuclear incidents at nuclear installations

A statement of nuclear incidents at nuclear installations in Britain during the first quarter of 2001 is published today by the Health and Safety Executive (copy below). It covers the period 1 January to 31 March 2001.

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.

Statement of Nuclear Incidents at Nuclear Installations: First Quarter 2001 - single copies of each free from the Information Centre, Health and Safety Executive, Room 004, St Peter's House, Stanley Precinct, Bootle L20 3LZ


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.

3. The location of the installations mentioned in the statement are as follows:

Hunterston B (British Energy Generation UK plc)
Sellafield (British Nuclear Fuels plc)
Chapelcross (British Nuclear Fuels plc)


The Health and Safety Executive 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.

INCIDENT 01/1/1 - HUNTERSTON B (British Energy Generation (UK) plc)

During routine monitoring of Hunterston B, it was discovered that there was radioactivity in the ground water in the bore holes associated with reactor 4. This event was reported under the site arrangements, initially to the Nuclear Installations Inspectorate (NII) and Scottish Environment Protection Agency (SEPA), and later to other government departments.

The licensee continues to investigate this matter with the assistance of company specialists and external contractors. The findings so far suggest that the levels of radioactivity present in the ground water are low and are decreasing. The source of the activity has not yet been conclusively identified, and this continues to be investigated by the licensee. Indications are that it was a one-off rather than continuous or recurring event.

So far there are no detectable off-site effects, and steps are being taken to remove the arisings as they build up in the bore holes. Currently the evidence suggests that this event is not of radiological significance for workers and the public.

The incident was classified as Level 1 on the International Nuclear Event Scale (INES). The NII and SEPA are being kept informed of developments in this matter.

INCIDENT 01/1/2 - SELLAFIELD (British Nuclear Fuels plc)

On 6 March 2001, during a routine glove change operation on a glovebox in the plutonium processing section of the B205 Magnox reprocessing plant at Sellafield, plutonium contamination was released into the working area.

This occurred when a seal weld on a waste export bag failed, releasing contaminated waste items onto the floor. Two workers were exposed to elevated levels of airborne plutonium, and BNFL's early estimate is that they have each received an effective internal exposure of about 4 mSv.

BNFL's best estimate of the amount of radioactive material spilled is 24 Mbq of plutonium-239 and 720 Mbq of plutonium-241. This is 24 times the reporting level specified in IRR99 for plutonium-239 and seven times that specified for plutonium-241. BNFL has recovered the spilled material and decontaminated the working area. There was no release of radioactivity to the environment following the event or during the clean up activities.

HSE investigated the event and required BNFL to undertake a site wide review of similar operations. This confirmed that there was a wide variation in the methods used for work within plutonium glove boxes on the site. BNFL has developed an action plan to prevent a recurrence in B205. In addition, BNFL is reviewing its methods for carrying out plutonium glovebox operations.

HSE is considering taking formal regulatory action. The incident was classified as Level 1 on the International Nuclear Event Scale (INES).

INCIDENT 01/1/3 - CHAPELCROSS (British Nuclear Fuels plc)

During refuelling operations on Reactor 2, an irradiated fuel element failed to release from the grab (this is used to hold an element while it is withdrawn from a reactor). Routine methods were used to release the grab. However, the irradiated fuel element snagged during the operation and was lifted out of its shielding resulting in the operators on the pile cap being exposed to the intense radiation being emitted from the irradiated fuel element. Personnel responded quickly, and the radiological dose received by them was small.

The event revealed shortfalls in the safety of the refuelling operation and the licensee took the immediate step of halting all refuelling operations while it investigated the event and reviewed the safety of the equipment. The NII investigated the event and judged that it was due to inadequate design and operation of the equipment. The licensee has modified the equipment and procedures in accordance with the nuclear site licence requirements and NII has agreed to fuelling operations continuing.

The incident was classified as Level 1 on the International Nuclear Event Scale (INES).