- Site: Sizewell B
- IR number: 21-106
- Date: November 2021
- LC numbers: 10, 23, 24, 27, 28
Executive summary
Purpose of Intervention
The purpose of this intervention was to undertake a systems based inspection at EDF Energy Nuclear Generation Limited’s Sizewell B power station, in line with the planned inspection programme contained in Sizewell B’s Integrated Intervention Strategy (IIS) for 2021/22.
Interventions Carried Out by ONR
This systems based inspection examined evidence to judge the duty holders compliance against five key Licence Conditions (LCs), selected to determine whether the safety case requirements of the system concerned are adequately implemented, and safety systems and structures are fit for purpose and will fulfil and continue to fulfil their safety functional requirements. The licence conditions assessed were: Licence Condition 10 (Training), Licence Condition 23 (Operating Rules), Licence Condition 24 (Operating Instructions), Licence Condition 27 (Safety Mechanisms, Devices and Circuits), Licence Condition 28 (Examination, Inspection, Maintenance and Testing). Licence Condition 34 (Leakage and Escape of Radioactive Material) was not included in the scope of this inspection.
The system-based inspection of system 07, Reactor Make-Up Water and 19, Clean Air Systems was conducted by two mechanical engineering inspectors, one being a nuclear associate and the Sizewell B nominated site inspector who attended for part of the first day.
The inspection comprised discussions with the licensee staff, a review of the licensee’s records, safety documentation and a physical walkdown of plant areas on the station. Throughout this intervention record “I” refers to all the ONR Inspectors identified above.
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
The safety systems inspected as part of this systems based inspection was judged to be adequate.
Key Findings, Inspector's Opinions and Reasons for Judgements Made
From the areas sampled and the evidence I examined during this inspection; I consider that the licensee has adequately implemented the safety case claims relating to the Reactor Make-up Water and Clean Air Systems. I am content that the areas of the system I sampled are inspected, maintained, and operated in accordance with the safety case. I identified a minor area of improvement regarding the clarity of an operating instruction relating to the use of beyond design basis backup equipment. I will follow this up through normal regulatory business as I did not consider this shortfall to be of detriment to overall nuclear safety. The ratings I have assigned for each of the Licence Conditions are detailed below.
LC 10 (Training) – I examined the training records for individuals involved in the operation, maintenance, inspection and testing of the Makeup Water and Clean Air systems. From my sample, I judged that the personnel undertaking and supervising these activities were suitably trained. I therefore assigned a rating of Green (No formal action) for License Condition 10 compliance.
LC 23 (Operating Rules) – I sampled limits and conditions identified in the safety case for the air quality of the clean air system and isolation limits and conditions on the makeup water system. From the areas sampled, I considered the operating rules in the safety case were clearly identified, understood and compliance was demonstrated via appropriate surveillances.
From my sample, I judge that the Licensee has an adequate process in place for identifying and implementing the operating rules to demonstrate the safety and operation of the Makeup Water and Clean Air systems. I judged therefore, that a rating of Green (No formal action) is appropriate for this licence condition.
LC 24 (Operating Instructions) – I examined completed Operating Instructions used for carrying out shifty and weekly surveillance of limits and conditions important to the safety and operation of the clean air system. I confirmed that operations had been carried out as stipulated in the Operating Instructions. I sampled Operating Instructions used for connecting back-up supply equipment important to nuclear safety. I consider that the Licensee has adequate arrangements in place for the production and implementation of Operating Instructions. I therefore judge that a rating of Green (no formal action) is appropriate for this licence condition, License Condition 24.
LC 27 (Safety Mechanisms, Devices and Circuits) – I reviewed the maintenance and test records associated with safety mechanisms on the clean air system and reactor makeup water systems. I physically walked down the systems, identifying key safety mechanisms devices and circuits. The licensee adequately demonstrated that Safety Mechanisms, Devices and Circuits were connected, in good working order and appropriate periodic inspection and testing to confirm plant condition and availability was being undertaken, in accordance with the licensee’s arrangements. I judged therefore, that a rating of Green (No formal action) was appropriate for License Condition 27.
LC 28 (Examination, Inspection, Maintenance and Testing) – I sampled the licensee’s maintenance arrangements through reviewing records and discussions with the system engineers. I sampled completed work order cards and the associated maintenance and inspection procedures identified on the plant maintenance schedule. I judged that the licensee’s requirements were being implemented adequately.
Overall, I judge the evidence sampled demonstrated the licensee is undertaking examination, inspection, maintenance and testing in accordance with the specified arrangements and frequencies. Therefore, I judge that a rating of Green (no formal action) to be appropriate for licence condition 28.
Conclusion of Intervention
Based on my sample, I judge that the Reactor Make-up Water and Clean Air Systems (Systems 07 and 19) met the requirements of the safety case. The inspection findings and observations were shared and accepted by the licensee during the feedback session.
I judge the licensee adequately demonstrated ownership and implementation of its safety case. In addition, the licensee demonstrated an adequate understanding of its arrangements to ensure and maintain the safety of its Make-up Water and Clean Air Systems.