Hunterston B - Inspection Week
- Site: Hunterston B
- IR number: 16-190
- Date: December 2016
- LC numbers: 10, 23, 24, 27, 28, 34
Purpose of intervention
The purpose of this intervention was to undertake planned inspections at EDF Nuclear Generation Limited's (NGL's) Hunterston B power station in line with the planned inspection programme contained in the Hunterston B Integrated Intervention Strategy (IIS) for 2016/17.
Interventions Carried Out by ONR
We undertook a system based inspection of the solid and gaseous radwaste systems, during which we assessed compliance against the following licence conditions:
- LC 10: Training
- LC 23: Operating Rules
- LC 24: Operating Instructions
- LC 27: Safety Mechanisms
- LC 28: Examination, Inspection, Maintenance, and Testing (EIM&T)
- LC 34: Leakage and escape of radioactive material and radioactive waste
We undertook a compliance inspection against licence condition 23 (LC 23 - Operating Rules). During this intervention, the nominated site inspector attended the quarter 4 Hunterston site stakeholder group meeting on 1st December 2016 at the Lauriston hotel, Ardrossan.
Explanation of Judgement if Safety System Not Judged to be Adequate
Based on the sample made during this inspection we judged that the solid and gaseous radwaste systems adequately meet the requirement of the safety case.
Key Findings, Inspector's Opinions and Reasons for Judgements Made
In relation to the system based inspection of the solid and gaseous radwaste systems, we made the following observations and judgements:
- LC 10 - Training: we sampled the training records of the two system engineers responsible for the Gas Blowdown and Debris Vaults systems and that of a relevant generation Operator Technician. In all instances we observed appropriate evidence of competency assessment and monitoring through respective qualification manuals, and to an extent that is commensurate with their time in post.
- LC 23 - Operating Rules: we observed appropriate alignment and consistency between safety case claims referred to within the system based views and Technical Specifications for the gas blowdown system and debris vaults. We further observed that the requirements of the radwaste safety case for the debris vaults are being met, however there were some discrepancies evident in the alignment between debris vaults SBV & Radwaste safety case. The station has committed to address these during the next equipment reliability review in 2017.
- LC 24 - Operating Instructions: we observed good quality operating instructions for the gas blowdown system, and observed evidence of good procedural use and adherence for operations observed during the inspection. We further noted that different sampling procedures were utilised for these boreholes compared to those boreholes on the perimeter of the site whose results are reported to SEPA. This was discussed with the station who committed to review.
- LC 27 - Safety Mechanisms: we observed that the gas blowdown route was demonstrably available and in good working order. During the inspection a misconfiguration of instrument valves was detected which resulted in a delay to a planned reactor blowdown. However, we were assured that the route would still have been available for blowdown within the 4 hour limit, notwithstanding the misconfiguration. The misconfiguration was captured in a condition report and we were assured will be subject to an adverse condition investigation.
Overall system health appears to be good for both systems inspected. We further observed that a long-standing claim on an automatic water detection system in the vaults is no longer relevant; the system has never been successfully commissioned and the station uses the results of annual camera inspections as a surrogate measure. The station committed to update its safety case claim.
- LC 28 - EIM&T: We were satisfied from the plant maintenance schedule entries sampled that EIM&T is being undertaken to schedule and to the right standard. 43. We observed that only two out of the five station solid waste debris vaults are inspected every five years. Following shutdown anticipated in 2022/23, the vaults will require increase attention to support the near-term ILW waste strategy and to support defuelling. The station accepted there is a need to consider a longer term strategy for inspection and characterisation of the condition of all five vaults. To this end, a regulatory issue has been raised.
- LC 34 - leakage and escape of radioactive material and radioactive waste: We were satisfied that the routine sampling of the bore holes is being undertaken in line with the maintenance schedule requirements. Elevated tritium levels identified during the routine sampling and testing of the groundwater in October 2016 are currently under investigation. We considered that there is a structured approach to the investigation being carried out, which is in line with corporate arrangements. A potential source of the tritium has been identified and work is on-going to confirm this.
In relation to the LC 23 compliance inspection, we made the following observations:
- The station is demonstrably controlling refuelling operations in accordance with safety case derived limits and conditions.
- Engineering Changes produced on the station, pursuant to category 3 modifications, are not supported by fit-for-purpose standards and procedures, coaching and mentoring arrangements commensurate with the nuclear safety significance of the modification. For modifications towards the higher end of Category 3 in classification, this shortfall appears to be more pronounced given the step-change in rigour of central design authority support and independent nuclear safety assessment oversight that would be attributed to Category 2 modifications. A regulatory issue has been proposed as a mechanism for monitoring the licensee's progress.
- The station did not identify the expiration of the time-limited charge machine gantry and pond flask handling safety cases in a suitable and timely manner. We concluded overall that the station's arrangements for ensuring appropriate visibility of safety case expirations do not appear to be adequate. A regulatory issue has been proposed as a mechanism for monitoring the licensee's progress.
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
From the evidence gathered during the system based inspection of solid and gaseous radwaste systems, we allocated inspection ratings of ‘Green' for LC 10, LC 23, LC 24, LC 27, LC 28 and LC 34.
From the evidence gathered during the LC 23 compliance inspection, we allocated an inspection rating of ‘Amber'.
There are no findings from this inspection that could significantly undermine nuclear safety.