Office for Nuclear Regulation

Hunterston B - SBI16 Inspection

Executive summary

Purpose of Intervention

The purpose of this intervention was to undertake a System Based Inspection (SBI) at EDF Nuclear Generation Limited’s (NGL’s) Hunterston B power station (HNB) in line with the planned 2018-19 Intervention Strategy for the site. The inspection was undertaken by two Fuel and Core Inspectors, and the Nominated Site Inspector and concentrated on the Irradiated Fuel Dismantling Facility (IFDF) and associated intermediate waste vaults. The aim of the inspection was to confirm that the IFDF, with its associated operating instructions and maintenance schedule, is able to meet the safety case functional requirements.

The function of the IFDF is to blow down the charge machine to atmospheric pressure, dismantle irradiated fuel stringers, dispatch the fuel elements to the cooling pond and to crop tie-bars and transfer them, together with other stringer components, to the debris vault.

Interventions Carried Out by ONR

The system based inspection of the IFDF was conducted against compliance with the following Licence Conditions (LCs):

The inspections were based on sampling the implementation of arrangements for the IFDF against each licence condition.

Explanation of Judgement if Safety System Not Judged to be Adequate

Not applicable.

Key Findings, Inspector's Opinions and Reasons for Judgements Made

LC 10 (Training) – In order to examine LC10 compliance, the training records of a number of fuel route and Nuclear Safety Group staff who work on the IFDF were sampled against their role profile. We also examined the training records associated with emergency response actions in relation to a dropped fuel event. In our sample, the IFDF operators were judged to be knowledgeable and there was good awareness of recent procedural changes. During the inspection EDF NGL could not provide adequate evidence that demonstrated that the persons in control of the plant had competed the required training associated with a particular temporary modification. Considering that the plant at the time of the inspection was under embargo and not available for handling irradiated fuel, we judged that the impact on nuclear safety to be low. Consequently, we judged this to be a minor shortfall against the requirements of LC10, and therefore we rated LC10 as GREEN (no formal action). However, since similar findings have been identified on other EDF sites this will be raised at a fleet level.

LC 23 (Operating Rules) – Technical Specifications and associated surveillance records were sampled. We found that the limits and conditions of operation (LCOs) were appropriately specified and that the operators were able to demonstrate a clear understanding of the governance arrangements. Therefore, based on our sample, we judge that a rating of Green for LC 23 is appropriate.

LC 24 (Operating Instructions) – We sampled a number of Plant Item Operating Instructions (PIOIs) and the pre-checks carried out before the operation of the IFDF. During our discussion with an IFDF Operator and the fuel route records team we were able to confirm that processes are diligently applied and the completion of the records was adequate. Therefore, we have assigned a rating of GREEN for LC 24.

LC 27 (Safety Mechanisms, Devices and Circuits) - Based on the areas sampled in our inspection of LC 23, LC 24 and LC 28, we were satisfied that suitable and sufficient safety mechanisms, devices and circuits (LC 27) were connected and in working order to meet the requirements of the safety case and identified operating limits and conditions.  Appropriate arrangements where observed to be in place regarding the embargo on the operation of the IFDF system. Therefore, we assigned a rating of GREEN to LC 27.

LC 28 (Examination, Inspection, Maintenance and Testing) – We sampled records of recent and past maintenance activities, functional tests, work order cards, camera inspections of the vaults and records of borehole sampling and analysis. We were satisfied that the equipment was being adequately maintained and that adequate records were present. We therefore judged that a rating of GREEN to LC 28 is appropriate.

LC 34 (Leakage and Escape of Radioactive Material and Radioactive Waste) – We sampled the inventory records of the materials disposed to the vaults and we found that EDF NGL maintains adequate accountability of the vaults’ contents. We also found that EDF NGL monitors internal and external boreholes to confirm that no leakage is occurring. We therefore assigned a rating of GREEN to LC 34.

Based on the inspection of the physical IFDF plant and equipment the facility was judged to be in good condition. However, it was noted that, at the time of the inspection, the IFDF at HNB was under embargo for the handling of irradiated fuel pending a revised safety case in relation to dropped fuel faults.

Conclusion of Intervention

After considering all of the evidence presented by EDF NGL we concluded that the arrangements and their implementation, associated with the IFDF system met the requirements of the safety case and were deemed to be adequate. An overall rating of GREEN (no formal action) was assigned to the system based inspection.