Sizewell B - SBI 04 Chemical and Volume Control System
- Site: Sizewell B
- IR number: 15-171
- Date: March 2016
- LC numbers: 10, 23, 24, 27, 28, 34
Purpose of intervention
The main purpose of this intervention was to undertake a system based inspection (SBI) at EdF Energy Nuclear Generation Ltd’s (EdF NGL) Sizewell B (SZB) power station. The system inspected was system 04 – Chemical and Volume Control System - CVCS (System BP) and Emergency Charging System – ECS (System BG). The inspection was conducted in line with the inspection programme contained in the SZB integrated intervention strategy (IIS) for 2015/16.
Interventions Carried Out by ONR
The ONR Site Inspector and two specialist inspectors, referred to as “we” within this report, conducted a SBI of System 04 (CVCS and ECS) at SZB nuclear power station. Through examination of this system, we performed compliance inspections against the following licence conditions of the Nuclear Site Licence i.e. LC 10: Training; LC23: Operating Rules; LC24: Operating Instructions; LC27: Safety Mechanisms, Devices and Circuits; LC28: Examination, Inspection, Maintenance and Testing and LC34: Leakage and Escape of Radioactive Material. The inspection was based on sampling the implementation of the arrangements in place at the station against each licence condition.
During this intervention the Site Inspector also undertook a number of other meetings with the Licensee to review regulatory issues and reported events. The Site Inspector also attended the Sizewell Stakeholders Group meeting during this visit.
Explanation of Judgement if Safety System Not Judged to be Adequate
From the inspection we judged that overall the CVCS and ECS system met the requirements of the safety case and are adequate.
Key Findings, Inspector's Opinions and Reasons for Judgements Made
- LC 10 (Training) – For this part of the inspection we chose to sample a range of operator training material relevant to the CVCS and ECS. For all of the training material reviewed it was evident that a comprehensive structured approach was in place, clearly linking the aims and objectives with the training material. The combination of workbooks, presentations, plant walk-downs and simulator training, as appropriate, was considered adequate. The use of OPEX was also featured prominently in the training materials reviewed. We also observed CVCS operations in the main control room where it was clear that the training material strongly reinforced the key steps in the operating instructions and made the instructed aware of important considerations when undertaking the operations. From the totality of the evidence gathered during the SBI, I consider that an Integrated Intervention Strategy (IIS) rating of 3 (Adequate) is appropriate for LC10.
- LC 23 (Operating Rules) – We sampled the licensee’s compliance with a number of key CVCS and ECS operating rules, under its Technical Specifications (TSpecs). The inspection confirmed that station has made and implemented arrangements to ensure that plant is not operated unless TSpecs provided to implement the limits and conditions derived from the safety case are satisfied. We judged LC23 aspects of the SBI to be good, with Station having identified, implemented and demonstrating compliance with operating rules derived from the safety case, warranting an IIS rating of 2 – Good Standard.
- LC 24 (Operating Instructions) – During this part of the inspection we sampled a number of the associated station and plant operating instructions, to confirm that operations important to safety are carried out in accordance with written instructions. This included a sample relating to the CVCS and ECS TS surveillance requirements. An appropriately clear line of sight from TSpecs at a high level in the safety case through to operating instructions was evident. We found the operating instructions to be well presented, being in a systematic format and relevant to the tasks in hand. Accordingly, we judged that an IIS rating of 3 (Adequate) is appropriate for the LC24 aspects of the SBI.
- LC 27 (Safety Mechanisms, Devices and Circuits) – The inspection reviewed records of Safety Mechanisms to establish how their availability is managed and good working order maintained. The station were able to provide adequate evidence that the devices sampled were maintained and available in line with safety case requirements, based on documented procedures and defined acceptance criteria. The historical records also appeared complete. Therefore, we judged the LC27 aspects of the SBI to be adequate, warranting an IIS rating of 3 (Adequate).
- LC 28 (Examination, Inspection, Maintenance and Testing) – The inspection reviewed the procedures and arrangements in place to ensure Examination, Inspection, Maintenance and Testing (EIMT) is carried out appropriately for the CVCS and ECS. We reviewed the Condition Reports raised in relation to both systems for the past 24 months and also both the maintenance strategy and associated reviews for both the CVCS and ECS. We were content that these represented adequate arrangements; in regard to reports and reviews of maintenance and demonstrated good control of the system EMIT requirements. One maintenance activity associated with valve maintenance was identified as a potential area for improvement. The station accepted an action to respond to this and an ONR issue has been raised to track this progress.
- LC 34 (Leakage and Escape of Radioactive Materials and Radioactive Waste) –This aspect of the inspection considered the Station arrangements for control of leakage and escape of radioactive material or waste. As the ECS system contains borated water separate from the RCS in normal operations and did not meet the definition associated with LC34, this system was excluded. On the basis of the evidence presented for LC34 related aspects of the CVCS we judged that station should have adequate arrangements in place for leak detection and monitoring however this was not adequately demonstrated during the inspection. A previous ONR intervention in January 2016 raised an issue to progress this shortfall and on the basis of the inspection an IIS rating of 4 – below standard was awarded.
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
After considering all the evidence examined during the inspection, we considered that the Chemical and Volume Control System and Emergency Charging System met the requirements of the safety case.
From the information gathered and evidence obtained during this intervention a minor area for improvement was raised with the licensee, which the licensee accepted and will be tracked and closed as a part of the ONR issue management. However, no matters were been identified that are likely to have significant impact on nuclear safety on the station at this time. Therefore we consider that no additional regulatory action arising from this visit is necessary currently, and the interventions for SZB power station, set out in the integrated intervention strategy, should continue to be implemented as planned.