Health and Safety
Executive / Commission
Nuclear
LLC reports
This report is issued as part of the Health and Safety Executive's commitment to make information about inspection and regulatory activities relating to the above site available to the public. It is for distribution to members of the Dungeness Local Community Liaison Council and covers activities associated with the regulation of safety at Dungeness B Nuclear Power Station. Site Inspectors of HM Nuclear Installations Inspectorate (part of the Health and Safety Executive's Nuclear Directorate) attend LCLC meetings and will be happy to respond to any questions raised there by members of the LCLC. Any other person wishing to inquire about matters covered by this report should contact the HSE's Nuclear Directorate Information Centre on 0151 951 4103.
1. The Nuclear Installations Inspectorate (NII) Site Inspector visited Dungeness 'B' on the following dates during the quarter covered by this report:
21 to 24 January,
5 to 7 and 26 to 28 February, and
4 to 7 March.
2. Other NII inspectors with specialist technical expertise also visited site during the period so as to support the Site Inspector by performing inspections of the Seismic safety case and assisting with an investigation into an incident.
3. Compliance Inspections: During the visits listed above the Site Inspector carried out planned inspections of the licensee's compliance with: (i) the conditions attached to the Site Licence; (ii) the Ionising Radiations Regulations; and (iii) other relevant health and safety legislation.
4. Procedural Adherence was introduced by the site management from 4 February 2002 for all work activities which may impact upon safety. It is anticipated that this will reduce the number of events of the type reported in Paragraph 8 below. The Site Inspector will monitor the impact of this initiative. He anticipates that it will have a positive impact on safety culture at the power station.
5. Emergency Planning Consultative Committee Meeting: This meeting took place at Kent Constabulary Headquarters, Maidstone on 7 February 2002. It was a routine meeting which was attended by the Dungeness B Site Inspector. Following it, there was a tour of the newly refurbished LEC which was thoroughly tested during a Level 3 Exercise (based on Dungeness A power station) on 27 March 2002.
6. Local Community Liaison Committee Meeting: The Site Inspector attended the 44th meeting on 7 March 2002. The Station Director reported that staff/apprentices are being recruited during 2002. This is a matter which NII is monitoring at all nuclear installations so as to ensure adequacy of site resources both now and in the future.
7. Incidents on Site: As part of routine, planned inspections the Site Inspector examined the licensee's arrangements for the recording and investigation of incidents at the power station and, where appropriate, undertook independent investigations to the extent that was warranted by the significance of the incident.
8. The power station experienced a significant number of events during this quarter which have been rated at Level 1, variation from permitted procedures (anomaly), on the International Nuclear Event Scale:
The Reactor 21 automatic protection system tripped the reactor on 4 February 2002 when boiler gas temperatures increased above their normal values. It was determined that the trip had been due to failure of the main boiler feed pump. Further investigation found that the pump's oil system had been affected by debris which had reduced flows. It was also found that some instrumentation thermocouples on the pump had been incorrectly installed. The Site Inspector has monitored the efforts on site to remove debris from both oil and water systems while the feed pump cartridge is replaced. Quality checks which should ensure that the pump work is completed correctly this time have been discussed with system engineers. The recently introduced Procedural Adherence initiative (see Paragraph 4) should ensure that a quality job is completed this time and that the risk of further boiler temperature excursions due to feed pump failure is minimised.
On 9 January 2002 the Water Spray Fire System sprang a leak at a flanged joint within the reactor building. Unit 22 had to be shutdown and the water was removed. During start-up on 12 January another joint failed on the same system. The unit was tripped again and the water was dealt with. However, this time the consequences were greater as a gas circulator motor had been drenched and had to be dried out carefully. Water had also entered a fuel store. When trying to return Unit 22 to power on 14 January the Station Transformer tripped on over-current protection. An NII team carried out an initial investigation into these events from 22 to 24 January 2002. As a consequence Direction No 2 was issued on 1 February 2002 (see Paragraph 10 below) and the Station Director has been formally requested to provide the NII with reassurances with regard to safety relief valves on the power station. The investigation continues.
Routine testing on 5 January 2002 found that a number of safety relief valves on the Buffer Storage Tubes, where irradiated fuel is often stored, were lifting at too high a pressure. Despite the lift pressure drifts which had occurred since the valves were last reset, the actual lift pressures found were still within safety case assumptions. Nevertheless, the safety relief valves were reset to the correct lift pressures immediately. Possible causes and solutions have been discussed with the system engineer. The Site Inspector is concerned because this is a repeat event and the exact cause has not been established.
Routine checks on 6 February and 22 March found Maintenance Schedule tests which had not been carried by the required date. The testing has now been carried out.
A Nitrogen Vaporiser became unavailable on 28 February and it left a plant configuration that was not consistent with the safety case requirement for several hours. The situation was rectified once the Operators recognised the problem.
On 20 March 2002 it was recognised that a Fuelling Machine Interlock test had not been placed on the Maintenance Schedule as had been assumed in the safety case. The interlock was tested and the Maintenance Schedule amended.
These last three events should be prevented in the future as Procedural Adherence becomes normal practice at Dungeness B.
9. Seismic Safety Case: NII specialist assessors visited site on 28 February so as to discuss the long term seismic safety case which is currently being developed for Dungeness B. Associated plant modifications were inspected. BEGL reported further programme slippage as they do not believe that certain masonry wall modifications will be completed by the agreed deadline of end of June 2002. NII has warned BEGL that failure to complete the PSR project (which this is part of) before the next formal reactor start-up may result in regulatory action.
10. The NII has powers within the standard Nuclear Site Licence Conditions to issue Consents, Approvals and Directions. In addition NII uses Licence Instruments to issue Specifications and Agreements under the conditions attached to the Licence. In accordance with formal regulatory procedures under Site Licence No. 61 the NII issued the following:
Direction No. 2, issued under Licence Condition 15(4) on 1 February 2002, directing the licensee to carry out a review and reassessment of safety with respect to the Water Fire Spray Ring Main, in particular taking due account of modern standards and the condition of the rubber gaskets used within the 10" Ring Main, their possible failure and/or break-up mechanisms and consequences of debris that could arise from them should the system enter a dynamic condition, and report the results of this review and reassessment to the Executive by the end of March 2002.
[The licensee has reported that this work was completed by the end of March - the Inspectorate has not yet completed assessment of the technical reports produced.]
Published on the HSE web site 8 July 2002