Office for Nuclear Regulation

SBI 03 – Boiler Feed System

Executive summary

Purpose of Intervention

The main purpose of this intervention was to conduct a system based inspection (SBI) of EDF Energy Nuclear Generation Ltd.’s (NGL) Heysham 2 Power Station in relation to the boiler feed system.

This intervention was undertaken as part of a series of planned interventions that are listed in the Heysham 2 Integrated Intervention Strategy 2018/2019. The inspections were undertaken by the ONR nominated site inspector and three ONR nuclear specialist inspectors for structural integrity and chemistry, which for the purpose of this intervention report shall be referred to as “I”. 

Interventions Carried Out by ONR

I performed a safety case informed SBI of the boiler feed system.  Through examination of these systems, compliance inspections were performed against the following Licence Conditions (LC):

The objective of the inspection was to determine whether the licensee’s arrangements were adequately implemented and in accordance with the systems’ safety case requirements. The boiler feed system is the source of the secondary coolant which provides a heat sink to the primary coolant. 

In addition to the SBI of the boiler feed system, the following inspections were also undertaken by the nominated site inspector.

The interventions were performed in line with the requirements of ONR’s guidance (as set out in ONR’s technical inspection guides which can be found at

Explanation of Judgement if Safety System Not Judged to be Adequate

From the system based inspection, I judge that overall the boiler feed system meets the requirements of the safety case.

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

Based on the areas sampled during this system based inspection, I consider that Heysham 2 has met its legal requirements that ensure that the boiler feed system is maintained and operated in accordance with the safety case and the station’s arrangements.

In summary, the outcome of the SBI of the system was as follows:

Conclusion of Intervention

After considering all the evidence examined during the sample inspection undertaken against LCs 10, 23, 24, 27 and 28, I judged that the requirements of the safety case have been adequately implemented at Heysham 2, with a rating of green assigned against licence conditions 10, 23, 24, 27 and 28.

A number of minor gaps were identified relating to the system ownership and the maintenance regime of the Back Up Emergency Feed System (BUEFS). Further, a number of observations were made and fed back to the licensee from the plant walk. The licensee raised Condition Reports (CRs) following ONR’s feedback and I have captured the findings through a regulatory issue to monitor progress.

There were no findings from this inspection that could significantly undermine nuclear safety.  At present, no additional regulatory action is needed over and above the planned interventions of Heysham 2 power station as set out in the Integrated Intervention Strategy.