Review of the adequacy of the implementation of the arrangements to control the Installation, Testing and Commissioning of the Replacement of the Secondary Shutdown Guardline (SSGL) Top Dome Differential Pressure (TDDP) Trip Group Equipment (NP/SC 7524)

Executive summary

Purpose of intervention

This is a planned inspection at EDF Energy Nuclear Generation Ltd’s (NGL’s) Heysham 1 power station, undertaken as part of the planned assessment of a category 1 safety case to replace the existing top dome differential pressure trip group equipment.  This equipment is used to initiate a reactor trip which shuts down the reactor in case of excessive rate of change of pressure across the top dome and its replacement requires a new licence instrument from ONR.

Interventions carried out by ONR

I undertook planned compliance inspections against the following nuclear site licence condition (LC):

LC 22:  Modification or experiment on existing plant, considering adequacy of the arrangements to control the installation, testing and commissioning of this replacement equipment.

I visited the existing installation and reviewed progress on the site preparatory work associated with the implementation of the modification.

Key findings, inspector’s opinions and reasons for judgements made

I was satisfied that station staff were fully aware of their responsibilities with respect of this modification and had demonstrated compliance with procedures for the preparatory work.  The site documentation required for implementation had not, as yet, been written or finalised. However the inspection provided me with confidence that this will be adequately undertaken at an appropriate time closer to the intended installation because: 

• The Neoprene Replacement Programme Project Safety Review Group (PSRG) has oversight of the Test & Commissioning Panel (T&CP) in charge of controlling the Installation and Commissioning. The aim of the Neoprene Replacement Programme arrangements and outcomes were inspected by ONR in the past and considered to be carried out to a good standard.
• The station personnel have a good knowledge of the site installation and experience in the Neoprene Replacement Programme.
• The complexity of this modification is limited and precautionary measures are in place to minimise the risks.

From the evidence gathered during this intervention, I am confident that the procedures planned or in place for controlling the installation, documentation, training and commissioning of the replacement of TDDP trip group equipment are appropriate for nuclear safety. The licensee demonstrated adequate compliance with respect to the arrangements made under LC22.

Conclusion of intervention

From the evidence obtained during this intervention, no matters have been identified that are likely to have a significant impact on nuclear safety on the station at this time. No corrective actions were raised during this inspection.  Therefore, no additional regulatory action arising from this visit is considered necessary at this time.

Recommendations

The planned interventions set out in the integrated intervention strategy for Heysham 1 remain valid and will be followed for future inspections.