Heysham 1 - SBI026 - Two Day Inspection - Post Trip Logic Equipment
- Site: Heysham 1
- IR number: 16-210
- Date: January 2017
- LC numbers: 10, 23, 24, 27, 28
Purpose of intervention
The purpose of this intervention was to undertake a system based inspection (SBI) of the post trip logic (PTL) equipment at EDF Energy Nuclear Generation Limited’s (NGL’s) Heysham 1 power station in line with the planned inspection programme contained in the Heysham 1 Integrated Intervention Strategy (IIS) for 2016/17.
Interventions Carried Out by ONR
As part of this intervention a control and instrumentation (C&I) specialist inspector performed an SBI of the post trip logic equipment to judge the system performance against its safety function. During the inspection, for training purposes, a second C&I Specialist Inspector and a defence nuclear safety regulator (DNSR) assisted in the inspection. Through examination of this system and associated sub-systems we performed compliance inspections against Licence Conditions LC10 (Training), LC23 (Operating rules), LC24 (Operating instructions), LC27 (Safety mechanisms, devices and circuits) and LC28 (Examination, inspection, maintenance and testing). LC34, which relates to leakage and escape of radioactive material and radioactive waste, was not considered applicable to the post trip logic equipment.
Explanation of Judgement if Safety System Not Judged to be Adequate
From the system based inspection, we judge that the implementation of the arrangements for the post trip logic equipment meet the requirements of the safety case.
Key findings, inspectors’ opinions and reasons for judgements made
Based on the areas sampled during this system based inspection, it was found that Heysham 1 has adequate arrangements to ensure that the post trip logic equipment is maintained and operated in accordance with the safety case and the station’s arrangements.
In summary, the outcome of the SBI of the post trip logic equipment was:
- LC10 Training - We were satisfied that Heysham 1 has implemented adequate arrangements for suitable training for staff with responsibilities for the specific operation and maintenance of the post trip logic equipment. We gave an IIS rating of green against LC10. However, we identified the following area for improvement which does not impact on the IIS rating.
- We identified that three members of staff performing post trip logic associated maintenance activities had not completed the requisite essential training for their role as identified in the training records. An ONR issue has been raised for the licensee to provide a justification as to why the individuals identified are suitably qualified experienced persons to perform the assigned roles. ONR will monitor progress for the resolution of this issue through normal regulatory business.
- LC23 Operating rules - We were satisfied that the safety case conditions and limits have been identified and where necessary have been incorporated into technical specifications. The licensee demonstrated adequate knowledge and understanding of the safety case and how this relates to the operating rules and technical specifications. We gave an IIS rating of green against LC 23.
- LC24 - Operating instructions - A sample of operating instructions was reviewed, a visit to the simulator to observe the operating instructions in use was undertaken and records from reactor trips were inspected. We were satisfied that adequate operating instructions were in place to support plant operations. We gave an IIS rating of green against LC24.
- LC27 Safety mechanisms, devices and circuits - The licensee described the safety mechanism, devices and circuits associated with the post trip logic system. We were satisfied that suitable and sufficient safety mechanisms, devices and circuits (LC27) were connected and in working order to meet the requirements of the safety case and identified operating limits and conditions. This was supported by evidence seen during the plant walkdown. However, we identified the following area for improvement which does not impact on the IIS rating:
- Heysham 1 had identified that the master trip relays originally manufactured by Bonner-Bray were obsolete; no forward action plan was identified to resolve this issue despite it being identified 6 months previously. An ONR issue has been raised for the licensee to provide a strategy to address the obsolescence of Bonner Bray relays. ONR will monitor progress for the resolution of this issue through normal regulatory business.
- LC28 Maintenance - a number of the maintenance procedures were sampled and judged to provide adequate maintenance instructions for the post trip logic system. In addition completed maintenance instructions were sampled and found to have been completed satisfactorily, within specified timescales and appropriately signed off. This was supported by evidence seen during the plan walkdown. We consider that the post trip logic equipment was maintained with adequate arrangements in place to meet the requirements of LC28 and on that basis have assigned an IIS rating of green against the LC28 element of this system based inspection. However, we identified the following two areas for improvement which do not impact on the IIS rating:
- We identified that measurements were taken during maintenance without clear pass / fail criteria within the procedure. Station was unable to provide an explanation for this. An ONR issue has been raised for the licensee to review and amend, as necessary, the work instructions/check-sheet for inspection and maintenance of the post trip logic cubicle equipment to include pass/fail criteria. ONR will monitor progress for the resolution of this issue through normal regulatory business.
- We identified that the master trip relays (MTR) maintenance procedure only related to one type of relay (Clifford & Snell) and only identified seven relays when there were eight on the schematic diagrams presented. Heysham 1 was unable to provide an explanation for this. An ONR issue has been raised for the licensee to review and amend the MTR unit maintenance instructions to ensure all MTR’s are suitably and sufficiently inspected, maintained and tested to deliver the safety functions required within the safety case. ONR will monitor progress for the resolution of this issue through normal regulatory business.
The intervention was performed in line with ONR's guidance requirements (as described in our technical inspection guides) in the areas inspected.
Conclusion of Intervention
After considering all the evidence examined during the sample inspection undertaken against LCs 10, 23, 24, 27 and 28, we considered that the post trip logic system meets the requirements of the safety case and has been adequately implemented at Heysham 1, with a rating of green assigned against licence conditions 10, 23, 24, 27 and 28.
There are no findings from this inspection that could significantly undermine nuclear safety. At present, no additional regulatory action is needed over and above the planned interventions of Heysham 1 power station as set out in the Integrated Intervention Strategy, which will continue as planned. ONR will monitor progress for the resolution of the issues raised through normal regulatory business.