Office for Nuclear Regulation

Dungeness B - Fire Protection System Based Inspection (SBI11)

Executive summary

Purpose of Intervention

In accordance with the Office for Nuclear Regulation (ONR) Strategy, each year ONR performs a series of planned System Based Inspections (SBIs).   In line with the operating Facilities Division (OFD) strategy, a planned fire protection SBI at Dungeness B (DNB) was conducted in June 2018.  The purpose of this inspection was for ONR to determine the adequacy of implementation of the safety case claims in respect of this system.

The planned LC4 (Restrictions on nuclear matter on the site) compliance inspection was cancelled due to lack of station availability.  It has now been re-arranged to take place during the July 2018 site engagement week.  

Interventions Carried Out by ONR

In order to determine the adequacy of implementation of the Licensee’s safety case claims in respect of the fire detection, suppression and protection systems, ONR examined evidence to determine compliance against five key Licence Conditions (LCs), which are applicable provisions of the Energy Act 2013.  These LCs (listed below) have been selected in view of their importance to nuclear safety and in providing a structured approach to determining whether the safety case has been implemented adequately through the system being inspected.

ONR assessed compliance against the following LCs using applicable inspection guidance:

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

The inspection examined the applicable safety case claims and sampling, through a combination of document reviews, discussions with plant operators, internal nuclear assurance and plant inspections to determine compliance against the selected LCs.  In this case, the inspection plan did not cover any area where fire protection systems could lead to leak and escape of radioactive material and radioactive waste and hence LC 34 did not form part of the inspection.

ONR held a meeting with NGL representatives from the station and from Barnwood headquarters regarding the proposed installation of a replacement nitrogen storage and vaporisation plant. This meeting was followed by a plant tour of the installation area..

The Reactor 22 2018 Statutory Outage is planned to commence on 27th August. A routine outage intentions meeting was held where NGL explained its planned maintenance, overhaul, testing and inspection work and how it planned to manage the outage, which will involve many contract workers as normal. In addition, discussions were also held regarding the stations proposed safety case justification for extending the operating period for Reactor 22.

The new nominated site inspector held routine engagements with the licensee’s internal safety regulator, TSSM, Plant Manager and Maintenance Manager. The discussions were informative in introducing the site inspector to Dungeness B.

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

From the areas targeted and the evidence examined during the SBI, ONR considers that NGL has adequately implemented those safety case claims that relate to the fire detection, suppression and protection system. 

Whilst some minor deficiencies and anomalies against NGL’s compliance against LC10 - Training, LC 27 – Safety Mechanisms and LC 28 – EIM&T were identified, ONR considered the significance of these deficiencies to be low.  As such, inspection ratings of Green were awarded.

ONR also considered NGL provided an adequate level of assurance and evidence to demonstrate compliance against LC 23 – Operating Rules, LC - 24 Operating Instructions.  As such, inspection ratings of Green were awarded for the fire system as a whole.

Updates were provided, as part of on-going ONR engagement, regarding safety case production and preparatory installation work of the replacement nitrogen storage and vaporisation plant.  Plans for essential work required to be undertaken during the forthcoming statutory outage was also provided.

An agreed way forward was established for the proposed extended operating period for Reactor 22.There was good representation from station staff, clearly knowledgeable in the work planned to be undertaken for Reactor 22 2018 Statutory Outage.  Lessons learnt from previous outages as well as wider learning, including from across the fleet was being used to enhance outage processes and procedures, as part of continuous improvement.

Conclusion of Intervention

From the evidence gathered during this SBI, it was judged that there were no matters that have the potential to impact significantly on nuclear safety.  Consequently, an overall rating of Green was awarded for the system as a whole.  The inspection findings were shared and accepted by NGL as part of normal inspection feedback.  ONR considers NGL adequately demonstrated ownership and implementation of the fire detection, suppression and protection system safety case to ensure and maintain nuclear safety.