Sizewell B - System Based Inspection - SBI 11
- Site: Sizewell B
- IR number: 15-152
- Date: February 2016
- LC numbers: 10, 23, 24, 27, 28, 34, 36
Purpose of intervention
The purpose of this intervention was to undertake a system based inspection and a site licence compliance inspection at EdF Nuclear Generation Ltd’s Sizewell B power station in line with the inspection programme contained in the Sizewell B Integrated Intervention Strategy for 2015/16.
Interventions Carried Out by ONR
The ONR Site Inspector, Mechanical Engineering Inspector and Fault Studies Inspector, referred to as “we” within this report, conducted a System Based Inspection of System 11 (Residual Heat Removal System and Reactor Building Spray System) at Sizewell B 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 (EIM&T) 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.
The ONR Site Inspector, Leadership and Management for Safety Inspector and Outage Project Inspector also undertook a routine LC 36: Organisational capability, inspection as part of this intervention.
Explanation of Judgement if Safety System Not Judged to be Adequate
From the inspection we judged that overall the Residual Heat Removal System (RHRS) and Reactor Building Spray System (RBSS) met the requirements of the safety case and are adequate.
Key Findings, Inspector's Opinions and Reasons for Judgements Made
- LC 10 (Training) – We reviewed the training skills register for maintenance team A, which provides a record of the current training status for individuals against each task/duty. The register identifies the SQEP (fully trained – suitably qualified and experienced persons) level required with a corresponding ‘green’ and ‘blue’ system (fully trained and in training). From the evidence gathered during this part of the inspection, we considered an Integrated Intervention Strategy (IIS) rating of 3 (adequate) was appropriate.
- LC 23 (Operating Rules) – We sampled the licensee’s compliance with a number of key system surveillances, under its Technical Specifications (Tech Specs). All records examined indicated that these surveillances had been adequately completed and had been accurately recorded. A potential further improvement to the records was acknowledged by the Station, who took an associated action to implement a change to the document. We judged that compliance with LC 23 was adequate meriting an IIS rating of 3.
- LC 24 (Operating Instructions) – During this part of the inspection we sampled a number of instructions including a test verification of emergency core cooling system valve position and an Operations shiftly surveillance to check on the RHRS suction isolation valve. The records were found to be in order and from the evidence gathered during this part of the inspection, we considered an Integrated Intervention Strategy (IIS) rating of 3 (adequate) was appropriate.
- LC 27 (Safety Mechanisms, Devices and Circuits) – The RBSS is considered a safety system as it sprays water into the reactor building to reduce pressure and temperature. It also traps contamination by the removal of fission products and controls the pH of the coolant to ensure material compatibility. The RHRS pumps act as a backup to this system. The Tech Specs clearly define the number of systems that must be available dependent on the reactor operating mode. Compliance with LC 27 was hence judged to be adequate with an IIS rating of 3.
- LC 28 (Examination, Inspection, Maintenance and Testing) – We examined a selection of maintenance records for key equipment within the RBSS and the RHRS and found the documentation to be in order. Maintenance of pumps consists mainly of condition monitoring and testing, with no significant requirement for intrusive maintenance. Although there has been some minor leakage from pump seals it is not significant and we were satisfied that the on-going practice of condition monitoring and testing was appropriate. Overall we considered compliance with LC 28 was adequate and awarded an IIS rating of 3.
- LC 34 (Leakage and Escape of Radioactive Materials and Radioactive Waste) – The licensee has taken action to regularly inspect and clean traces of boric acid from the plant and equipment. This was evidenced during the plant walk down, with no obvious signs of white boric acid crystals apart from a minor staining in a tundish below a steam leak drain. Waste generated through EIM&T activities is consigned to the SZB radwaste route. The system engineer has also developed a leak monitoring check list where the extent of leakage is recorded which we considered as a positive initiative. No significant leaks were identified and we judged that compliance with LC 34 was adequate, with an IIS rating of 3.
- LC 36 (Organisational capability) – During this intervention a number of areas relating to the organisational capability were reviewed including the Station nuclear baseline, periodic safety review 2 PSR2 observations, organisational governance arrangements, management of change process, outage organisation and financial resources. A disconnection between PSR2 observations and the HR function was raised for which an ONR issue has been raised to track resolution. However, based on the evidence sampled during this inspection we consider that overall NGL’s arrangements to ensure compliance with LC36 have been implemented to an adequate standard, warranting an IIS rating of 3.
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 sample inspections undertaken against LCs 10, 23, 24, 27, 28 and 34 we considered that the Residual Heat Removal System and Reactor Building Spray System both met the requirements of the safety case.
From the information gathered and evidence obtained during this intervention there are no matters that could significantly undermine nuclear safety and no change is necessary to the planned interventions and inspections at Sizewell B. An ONR issue has been raised to monitor and track resolution of the PSR2 observation relating to organisational capability.