Office for Nuclear Regulation

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System Based Inspection (SBI) of High Level Waste Plants Steam Systems (WEDH26) and intelligence gathering meetings

Executive summary

Purpose of intervention

The Office for Nuclear Regulation (ONR) undertakes all regulatory interaction with the Sellafield site licensee (Sellafield Limited, SL) against a strategy defined by ONR's Sellafield, Decommissioning, Fuel and Waste Programme. In accordance with that Strategy, a Steam System Based Inspection (SBI) of the High Level Waste Plants (HLWP) was planned and undertaken in September 2016. The purpose of this inspection is for ONR to examine whether the licensee's safety case claims in respect of this system have been adequately implemented.

This inspection comprised examination of the steam system within the HLWP which is supplied, at high and low pressures, from the site ring mains. Constant supplies of high and low pressure steam are needed to support the highly active liquor (HAL) vitrification process. The continued processing of HAL into an immobile, vitrified product is a key aspect of Sellafield's hazard and risk reduction activities.

ONR's System Based Inspection process examines evidence to determine compliance against six key licence conditions (LCs). These licence conditions (listed below) have been selected in view of their relevance to ensuring nuclear safety and in providing a structured approach to determining whether the safety case has been implemented adequately through the system being inspected.

Interventions Carried Out by ONR

I carried out this SBI of the HLWP Steam System over the course of two days. I was assisted with technical support from an external consultant with expertise in the field of control and instrumentation engineering. I was also supported on this inspection by SL staff from its internal regulatory organisation. The inspection comprised discussions with SL staff, physical viewing and inspections of targeted structures, systems and components, and review of SL's records and other safety documentation.

Explanation of Judgement if Safety System Not Judged to be Adequate

I judge the safety case supporting this system to be adequately implemented.

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

From the areas I targeted and the evidence I examined during this inspection, I consider that SL has adequately implemented those safety case claims that relate to the HLWP Steam System and supporting safety systems requiring steam. As such I awarded inspection ratings of Green (No Formal Action) for LCs 10, 24, 27, and 28.

I have not awarded any rating for LC23 during this inspection. SL has not declared any Operating Rules for this system. I have nevertheless reviewed the limits and conditions SL is applying to control safety for this system, and my regulatory consideration is encompassed within my rating for LC24 above.

I have not awarded any rating for LC34 during this inspection, since I judged this licence condition was not sufficiently relevant to the system under consideration.

In the course of my inspection I did not identify any significant concerns with the adequacy of the licensee's safety case for this system that would necessitate an earlier than planned assessment by ONR.

I raised five Regulatory Issues (Actions) in this inspection, all relating to minor matters and none of which detract from my overall inspection conclusions. These will be followed up during my future routine regulatory engagements.

Conclusion of Intervention

I consider that SL has adequately implemented those safety case claims that relate to the HLWP Steam System and has a good understanding and control of the physical condition of the structures, systems and components reviewed during this inspection.