Office for Nuclear Regulation

System Based Inspection (SBI) of Heating & Ventilation (H&V) Systems

Executive summary

Purpose of Intervention

The purpose of this intervention was to undertake compliance inspections at EDF Energy Nuclear Generation Limited’s Heysham 2 power station, in line with the planned inspection programme contained in Heysham 2’s Integrated Intervention Strategy (IIS) for 2019/20.

Interventions Carried Out by ONR

Systems based inspections examine evidence to determine compliance against six key Licence Conditions (LCs), selected to help 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 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) and Licence Condition 34 (Leakage and Escape of Radioactive Material and Radioactive Waste).

The nominated site inspector, mechanical nuclear associate and chemical engineering inspector conducted a System Based Inspection (SBI) of Heating and Ventilation (H&V) systems. For brevity in this intervention report all ONR representatives are referred to as “I”. The areas targeted were the H&V systems:

The inspection comprised discussions with the licensee staff remotely via Skype, a desktop review of the licensee’s records and other associated safety documentation and a physical walkdown of plant, conducted by the site inspector and mechanical nuclear associate.

The intervention was informed by ONR technical guidance, which can be found at

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

From the areas targeted and the evidence I examined during this inspection; I consider that the licensee has adequately implemented the safety case claims relating to the H&V 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 minor areas of improvement which I did not consider prejudice 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 H&V Systems. I judged that the personnel undertaking and supervising these activities were suitably qualified and experienced.  I identified a minor shortfall in confirming contractors meet mandatory training requirements in NGL’s Company Technical Standards. I have raised a regulatory issue against this minor shortfall.

LC 23 (Operating Rules) – I judged that the Licensee has an adequate process in place for identifying the operating rules to demonstrate the safety of and operation of the H&V systems. The link between the operating rules and how these rules were complied with was clear.

LC 24 (Operating Instructions) –I confirmed that operations had been carried out as stipulated in the Operating Instructions. I consider that the Licensee has adequate arrangements in place for the production and implementation of Operating Instructions. The requirement to carry out the operating instruction was clearly stated in the technical specifications and the licensee demonstrated the link between these requirements and the safety case.

LC 27 (Safety Mechanisms, Devices and Circuits) – The licensee demonstrated that Safety Devices Mechanisms and Circuits were connected and in good working order. The key safety mechanisms devices and circuits were clearly identified, and adequate surveillance to confirm plant condition and availability was being undertaken in accordance with the licensee’s arrangements.

LC 28 (Examination, Inspection, Maintenance and Testing) – I sampled the licensee’s maintenance arrangements through reviewing records and discussion with the system engineer. Overall, I judge that the licensee is undertaking examination, inspection, maintenance and testing in accordance with the specified arrangements and frequencies.  I am content that there was evidence of adequate implementation of arrangements in the areas sampled with one area for improvement in relation to the implementation of cascade air flow testing. I am content that this does not represent any significant detriment to nuclear safety and have raised a minor regulatory issue to resolve the shortfall.

LC 34 (Leakage and Escape of Radioactive Material) – The Contaminated Ventilation Discharge System was sampled to ensure adequate control and containment of radioactive matter. From discussions with the licensee, sampling of ventilation flow diagrams and review of evidence of appropriate monitoring of radioactive waste discharge, I am content that the licensee has adequate arrangements for monitoring the leakage and escape of radioactive material.

Conclusion of Intervention

Based on my sample, I consider that the H&V met the requirements of the safety case, with minor areas for improvement. The inspection findings were shared and accepted by the licensee during the feedback session. I have raised two regulatory issues to resolve the minor shortfalls identified. I judge that a rating of Green was appropriate for License Conditions 10, 23, 24, 27, 28 and 34 as no significant issues were raised.

I consider that the licensee adequately demonstrated ownership and implementation of its safety case.  In addition, it demonstrated an adequate understanding of its arrangements to ensure and maintain the safety of its H&V systems.