Office for Nuclear Regulation

Sizewell B - SBI12 and other inspections

Executive summary

Purpose of Intervention

The purpose of this intervention was to undertake licence condition (LC) compliance inspections at EDF Energy Nuclear Generation Limited’s (NGL) Sizewell B Power Station, in line with the ONR’s Operational Facilities Division intervention strategy. The intervention was carried out by the ONR site inspector, supported by a number of specialist inspectors.

Interventions Carried Out by ONR

Jointly with the Environment Agency, we performed a System Based Inspection (SBI), of the station’s Heating, Ventilation and Air Conditioning systems (HVAC). During examination of these systems, inspections were performed against the following Licence Conditions (LC), which are applicable provisions of the Energy Act 2013:

The ONR site inspector also carried out a Themed Inspection to gain confidence that standards of engineering governance at Sizewell B are consistent with those observed across the NGL fleet and are not impacted by organisational (or process) differences due to use of PWR technology.

The intervention used NGL’s Fleet Engineering Equipment Reliability (ER) process as a platform to evaluate engineering governance. This was done by holding structured discussions with staff and reviewing documentation to gain insight into aspects supporting effective governance. Relevant Licence Conditions (LCs) applied during this inspection were:

The intervention was performed in line with ONR's guidance requirements (as described in our technical inspection guides) in the areas inspected.

Explanation of Judgement if Safety System Not Judged to be Adequate

From the areas sampled during this inspection, I judged that the overall the HVAC systems met the requirements of the safety case.

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

System Based Inspection

With respect to the SBI against ONR’s approach I was able to make the following judgements;

LC10 (Training) – The records were in date and adequately demonstrated the personnel sampled were appropriately trained. I judged that in the areas sampled ONR’s expectations have been met and therefore have assigned an inspection rating of GREEN for LC10.

LC23 (Operating Rules) and LC24 (Operating Instructions) - Overall, we judged that these arrangements were consistent with relevant benchmarks for LC23 and LC24.  We judge that the following inspection ratings against LC23 and LC24 are appropriate: GREEN.

LC27 (Safety Mechanisms, Devices and Circuits). Our review reassured us that the availability requirements of the sampled HVAC systems were well known and controlled by the Station’s duly authorised persons. Based on the evidence sampled, we judge that NGL was compliant with its legal requirements under LC27 and therefore we judge the following inspection rating appropriate: GREEN

LC28 Examination, Inspection, Maintenance and Testing – I recognise the investments NGL have, and continue to make in their HVAC systems to improve plant reliability and reduce environmentally harmful refrigerant gases. However I found that SZB do not routinely perform tests to confirm the performance of ventilation systems within radiologically controlled areas. In my judgement, this is a shortfall against relevant good practice. I judged that NGL had made insufficient progress in implementing recommendations to optimise maintenance routines arising from Maintenance Strategy Report Reviews. I also judged that there is insufficient technical guidance available to the NGL operating fleet to ensure adequate maintenance of bleed filters used during maintenance changes of main HEPA filter elements. NGL agree to make improvements in these areas which will be tracked via entries on the ONR issues database. I therefore assigned an inspection rating of AMBER to LC28.

L34 (Leak and Escape of Radioactive Material and Radioactive Waste) – Overall based on my sampling, I judged that the arrangements were consistent with relevant benchmarks for LC34. I therefore judge that an inspection rating of GREEN against LC10 is appropriate.

Conclusion of Intervention

From the evidence gathered during this System Based inspection, it was judged that there were no matters that have the potential to impact significantly on nuclear safety. The inspection ratings given in relation to LCs 10, 23, 24, and 34 were all “GREEN”. However the evidence and inspection of the maintenance activities associated with the HVAC in support of LC28 did not meet my expectations and as such I judged that a rating of AMBER is appropriate for the LC28 part of this intervention.