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 Heysham Power Station available to the public. It is for distribution to members of the Heysham Local Community Liaison Council and covers activities associated with the regulation of safety at Heysham. These reports are distributed quarterly. Site Inspectors of HM Nuclear Installations Inspectorate attend LCLC meetings and will respond to any questions raised there by members of the LCLC. Any other person wishing to enquire about matters covered by this report should contact the HSE, Nuclear Directorate Information Centre on 0151-951-4103
The Nuclear Installations Inspectorate (NII) site inspectors made visits to Heysham on the following dates during this quarter:
|
Heysham 1 |
Heysham 2 |
|
6, 7, 8, 13, 14 & 15 July 2004 |
5, 15, 21, 26, 27 & 29 July 2004 |
|
3, 4, 24, 25 & 27 August 2004 |
11, 25, 26 & 27 August 2004 |
|
3, 7, 15, 17, 23 September 2004 |
17, 22, 29 & 30 September 2004 |
Other members of the NII, including the Chief Inspector, Deputy Chief Inspector and specialist inspectors visited the Heysham site during the period, as follows.
The NII Chief Inspector and Deputy Chief Inspector visited site on 23 September for a tour of the plant. Station gave a presentation on how Heysham 1 is implementing the British Energy Performance Improvement Programme followed by visits to areas of the turbine hall and reactor building associated with the boiler closure units and impulse line projects and the hazards safety case. The NII site inspector, superintending inspectors and specialist inspectors attended site on a number of occasions during the period in relation to matters associated with: planned and reactive inspection activities; the 2004 Periodic Shutdown of Reactor 1; events on the site; the unplanned trip on 25 July; and development of the hazards safety case.
The NII site inspector and specialist inspectors attended site on several occasions during the period to inspect matters associated with events on the site and to conduct an inspection to assess the readiness of the site to implement Technical Specifications to replace Operating Rules and Identified Operating Instructions.
As part of our routine work we inspect for compliance against the requirements of the Stations' Nuclear Site Licence Conditions and the arrangements made under them, the Health and Safety at Work Act and other relevant safety legislation. We sample activities on site that may affect safety, and in this report include details of the following matters.
Emergency Planning Consultative Committee. The NII site inspectors attended the Emergency Planning Consultative Committee meeting, which took place on 17 September 2004.
Proposal to Appoint a Single Site Director at Heysham. Stations are considering revising the current management structure for the Heysham site to move to a single site director overseeing a plant manager at each of the Heysham power stations. These higher-level management changes are likely to be accompanied by additional changes to the lower tier management structures at both stations. These proposed changes will be subject to the stations' arrangements to control organisational changes and NII oversight.
Reactor 1 Periodic Shutdown The triennial periodic shutdown of reactor 1 commenced on 3 September 2004. The NII site inspector and specialist inspectors have commenced a programme of inspections that will inform a judgement on the readiness of Heysham 1 to return the unit to service for a further period of operation. NII will attend the start up meeting scheduled for 14 October.
Implementation of Technical Specifications at Heysham 2. Station proposes to implement Technical Specifications to replace the current Operating Rules and Identified Operating Instructions at Heysham 2. They have been preparing for this change for some time and NII recently carried out an inspection, which confirmed, subject to a number of preconditions being met, that they were ready to make the transition. They plan to implement the revised arrangements in October following NII granting Approval.
We respond to non-routine matters arising on site that may affect safety, and in this report include details of the following matters.
Routine examination of Hartlepool Reactor 1's prestressed concrete pressure vessel (PCPV) has revealed that a tendon, which had been exposed to wetting from the pressure vessel cooling water (PVCW), has corroded leading to wire failures. The PCPV has many thousands of tendon wires and can tolerate local failures of the type observed at Hartlepool. However, this failure mechanism was unexpected and therefore British Energy has considered the potential impact of such corrosion on the integrity of those prestressed concrete boiler closure units (BCUs) that have also been exposed to PVCW. Heysham 1 has completed an extensive programme of verification inspections, which has established that the accessible steel components are protected with grease and in good condition. The station has reviewed the safety case for operating reactors with BCUs exposed to PVCW and prepared a justification for their continued operation. Heysham 1 has also given NII a commitment to give further consideration to the potential impact of exposure to PVCW on the integrity of the BCUs. The NII site inspector is satisfied that station's response to discovery of the failed tendon wires is appropriate.
The failure of the cast iron essential cooling water main in 2003 highlighted the potential threat posed by deep flooding in the turbine hall basement. Heysham 1 has reviewed the existing hazards safety case and identified other initiating events that have the potential to cause deep flooding of the turbine hall basement. It has emerged that the threat of flooding may be bounded by a scenario that is initiated by the failure of a turbine located in the turbine hall. Turbine failure is an infrequent event but the potential consequences are such that NII has asked both Heysham 1 and Hartlepool to provide a safety case which demonstrates that, following such an event, the reactors can be shutdown and maintained in a safe condition. Currently, all four reactors at Heysham 1 and Hartlepool are shut down and will not be returned to service before NII is satisfied it is safe to do so.
Environmental issues. Following a number of events recently reported to NII and EA involving compliance with environmental regulatory requirements, a joint site inspection was carried out with the EA site inspector for Heysham 2 to obtain further information on the events identified for consideration. While it was recognised that station was taking steps to improve the performance of plant, which has the potential to affect the environment, they were reminded particularly of the need to improve their arrangements for performing examination, maintenance, inspection and test on such plant. Station has confirmed that they are working to improve the performance of plant, which may affect the environment.
For part of the period of this report, Reactor 7 has been shutdown for an unplanned outage to carry out remedial work to plant and equipment associated with providing feedwater flow through the steam-raising boilers. In addition two circulator impellers have been inspected, as agreed with NII following the discovery of indications of possible defectiveness on one circulator impeller during the recent reactor 8 periodic shutdown. Station reported that the inspections carried out did not reveal any evidence of defectiveness in the impellers examined. Prior to return to service of the reactor repairs were also carried out to a flash vessel, following the agreement of the station independent insurance inspector. The reactor has now returned to service.
As part of our inspection activities at the site we investigate safety related events that occur and follow-up those which are perceived, initially, to have the potential to be more significant, we particularly examine the licensee's response to such issues and events. From our inspections in this quarter we are satisfied that events which occurred did not represent a significant challenge to the safety case, and response by stations has been in accordance with appropriate arrangements. We summarise our reaction to the selected events as follows.
The NII has followed up the following event during this quarter
Prestressed Concrete Pressure Vessel - CO2 in Vertical Tendon. On 25th July 2004 Heysham 1 manually tripped Reactor 2 in response to elevated CO2 levels in a prestressing tendon duct. The trip and shutdown sequence was completed normally. Subsequent investigation of the leak revealed the source to be an impulse line used to measure gas pressures. Experience at Hartlepool has demonstrated that a leaking impulse line can rapidly escalate leading to significant damage to the tendon. Heysham 1 has taken the decision to implement a modification, similar to that previously implemented at Hartlepool, to plug all eight above-dome impulse lines and provide an alternatives means of pressure measurement via external tappings connected to top cap penetrations. This modification removes the potential threat of gas release and tendon damage. Station will complete the modification on Reactor 2 before it returns to power and on Reactor 1 during the Periodic Shutdown. Heysham 1 is seeking NII agreement to implement the modification before return to service of the units.
The following events were followed up at the station during this quarter.
Station HP CO2 Supply System. Station has reported events affecting operation of the system to supply clean CO2 to the reactors. NII has written to station on two occasions requesting further information about the circumstances of the events and details of proposed corrective actions. The most recent event involved multiple lifting of small-bore pressure relief valves on the HP CO2 supply ring main, with the consequential loss of a quantity of clean gas. The site inspector and the NII conventional safety inspector attended site to follow up this matter. Station reported that they responded to this event in accordance with the site incident arrangements and had investigated this matter thoroughly, with corrective actions identified to help prevent a recurrence.
The site inspector and an NII radiological protection (RP) specialist have followed up events at site involving non-compliance with RP requirements. These have included failures to prevent spread of contaminated material and discovery of food wrappers, drinks containers and smoking materials in the RCA. Additional events involving control of persons accessing the site and RCA have also been followed up. NII has written to station confirming agreed actions for station to take to help prevent recurrent events, and they have confirmed that these points will be addressed in full.
During the periodic shutdown of reactor 8 earlier this year station discovered that safety rods held out of the core to provide protection against an unplanned reactivity excursion had been inadvertently dropped into the core. Station investigated the event and identified a number of corrective actions, which they are currently working, to complete. Following a separate NII investigation a letter was sent requiring the licensee to provide confirmation that appropriate steps will be taken to remedy deficiencies that contributed to the event and implement measures to help to prevent a recurrence. Station has confirmed that the NII requirements outlined in the letter will be addressed in full.
The following regulatory documentation was issued during the quarter:
Licence Instrument Number 66, issued 9 July 2004, gave HSE's agreement to replace neutron flux low log trip group equipment.
Licence Instrument Number 67, issued 21 July 2004, specified that the nuclear safety proposal "Reactor 1 Statutory Outage (August 2004). Revised Safety Case for Shutdown Depressurised reactor in an Air Atmosphere." shall not be implemented without the agreement of the Health and Safety Executive.
Licence Instrument Number 68, issued 26 August 2004, gave HSE's agreement to replace neutron flux high linear trip group equipment.
Published on the HSE web site 10 January 2005
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