Executive summary
- Inspection date(s): 11/10/22
Aim of inspection
In accordance with the Office for Nuclear Regulation’s (ONR’s) Operating Facilities Strategy, each year ONR undertakes a series of planned compliance inspections of selected licence conditions (LCs), targeted at those facilities with significant importance to nuclear safety. Some compliance inspections may be themed, such as where the subject of regulatory interest reads across more than a single LC.
This was a themed compliance inspection of flooding hazards at EDF Energy Nuclear Generation Limited’s (NGL) Sizewell B (SZB) nuclear power station. The aim was to examine EDF NGL’s compliance with arrangements made under LCs from the perspective of controlling risks from flooding hazards.
The intervention was planned in accordance with ONR’s Operating Reactors sub-division Integrated Intervention Strategy (IIS) for 2022/23. The intervention enabled ONR to also:
- Follow-up on a long-standing regulatory issue (RI) 3167 relating to internal flood sources.
- Gather intelligence with respect to the potential flooding implications for lifetime extension of SZB and from development of SZC.
Subject(s) of inspection
The following actives were the subject of this inspection:
- LC10 – Training – Rating – Green
- LC23 – Operating rules – Rating – Green
- LC24 – Operating instructions – Rating – Green
- LC27 – Safety mechanisms, devices and circuits – Rating – Green
- LC28 – Examination, inspection, maintenance and testing – Rating – Green
- LC34 – Leakage and escape of radioactive material and radioactive waste – Rating – Green
Key findings
Nuclear safety risks from flooding hazards can be significant if not adequately controlled. ONR inspected EDF NGL’s compliance with arrangements made under the following LCs to form a judgement on their adequacy from the perspective of controlling risks from flooding hazards:
- LC10 – I sampled training records for several roles relevant to flooding hazards, and compared these with the role profile requirements. Based on my sample, EDF NGL operators have received required training. I recommended that EDF NGL introduce a training module on internal flooding that has been developed in response to RI-3167. Overall, I judge that EDF NGL is adequately implementing its training arrangements from the perspective of flooding and award a Green rating.
- LC23 – I sampled the technical specification (Tech. Spec.) for segregation barrier doors. The doors are important for segregating safety trains from hazards. I was able to trace operational limits and conditions to relevant safety cases, and into more detailed surveillance and local instructions. I judge that EDF NGL is adequately implementing its arrangements with respect to operating rules relevant to flooding, and award a Green rating
- LC24 – I sampled several instructions including for demountable flood barriers. I am satisfied that the instructions clearly communicate the required actions that operators need to undertake in the safe execution of work. I judge EDF NGL is adequately implementing its arrangements with respect to instructions relevant to flooding and associated protection measures, and award a Green rating.
- LC27 – I sampled instructions and maintenance routines for a priority sump alarm, relevant to internal flooding. I saw evidence that the safety device is available and routinely maintained. EDF NGL operators described the actions to be undertaken in response to this alarm. I judge EDF NGL is adequately implementing its arrangements with respect to safety devices, mechanisms and circuits relevant to flooding, and award a Green rating.
- LC28 – I sampled several areas to ensure EDF NGL were adequately implementing their maintenance and surveillance routines. I found examples of good practice, but also examples of poor practices including inadequate maintenance of nuclear safety classified building roofs and the surge chamber tidal flaps have never been inspected. We sampled specific evidence demonstrating that measures are in-place to address the shortfalls. However, I have raised a level 4 regulatory issue (RI-11079) to track these LC28 shortfalls. The ONR civil engineering specialist inspector will follow-up on them during the forthcoming RO. I award a Green rating despite these poor practices, as I judge that they are not significant enough to warrant an amber rating, given the low likelihood of any safety consequences.
- LC34 – Based on my sample no significant sources of radioactive inventory were identified relevant to flooding. I judge this licence condition was not sufficiently relevant to the safety SSCs sampled. No rating is awarded.
Overall, I found that EDF NGL’s existing arrangements made under the inspected LCs are adequate for controlling risks related to flooding hazards. During the inspection I have identified some matters for improvement. I have raised a level 4 issue (RI-11079) to ensure required corrective actions are undertaken. I judge that these matters are not of sufficient significance to warrant an amber rating. I will also engage with the Design Authority to understand safety case updates forming part of PSR3 that could impact the extant arrangements and flooding protection strategies. On this basis I award EDF NGL a GREEN rating.
Judgements made
Overall, I found that EDF NGL’s existing arrangements made under the inspected LCs are adequate from the perspective of controlling risks related to flooding hazards. During the inspection I have identified some matters for improvement and follow-up:
- I have raised level 4 issue RI-11079 to address the observed LC28 shortfalls and ensure EDF NGL undertake required maintenance activities relating to the EDG building roof and surge chamber tidal flaps.
- I will engage with the Design Authority to understand safety case updates forming part of PSR3 that could impact the extant arrangements and flooding protection strategies.
These matters will be followed up by the relevant ONR specialist inspectors. With respect to the extant arrangements, I judge that the identified matters are not of sufficient significance to warrant an amber rating. On this basis I award EDF NGL a GREEN rating.