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 System Based Inspection (SBI) of the Highly Active Liquor Evaporation and Storage (HALES) facility’s Steam System was planned and undertaken in December 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 HALES which is supplied, at high and low pressures (HP and LP), from the site steam distribution ring main. Constant supplies of high and low pressure steam are needed to support the highly active liquor evaporation and storage process. The continued processing of the highly active liquor (HAL) into an immobile, vitrified product is a key aspect of Sellafield’s hazard and risk reduction activities.
ONR’s SBI process examines evidence to determine compliance against six key licence conditions (LCs). These LCs (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.
I carried out this SBI of the HALES Steam System over two days. I was assisted with technical support from an ONR internal hazards specialist inspector and an external mechanical engineering consultant. I was also accompanied on this inspection by a representative from SL’s internal independent regulatory function. The inspection comprised discussions with SL staff, a plant walk down where a sample of structures, systems and components was inspected, and sampling of SL’s documentation and records.
SL advised me at the start of my inspection that one of its back-up steam boilers (which is subject to claims and availability assumptions within the HALES safety case) is no longer being maintained due to conventional safety concerns. ONR guidance is clear that the safety case should reflect the current plant configuration and that derived safety claims are both substantiated and implemented. As the availability of the back-up boiler is a key safety case claim, I judge that this system’s safety case is not adequately implemented.
In view of the non-availability of the back-up boiler, I have awarded an Amber (Seek Improvement) rating for LC 23 from this inspection. SL needs to improve its arrangements to remedy shortfalls associated with the implementation of limits and conditions derived from the safety case associated with back-up boiler arrangements.
From the evidence requested and sampled I have however awarded Green (No Formal Action) ratings for LCs 10, 24, 27 and 28. For these LCs, I consider that SL has adequately implemented those safety case claims that relate to the HALES Steam System and supporting safety systems requiring steam.
I raised one Regulatory Issue during this inspection, due to shortfalls with the implementation of SL’s safety case derived limits and conditions associated with the availability of a claimed back-up boiler. The closure of this Regulatory Issue, which SL is already progressing, will be followed-up during my future routine regulatory engagements.
I have not awarded any rating for LC 34 during this inspection, since I judged this licence condition was not sufficiently relevant to the system under consideration.
Although I have awarded a No rating for the implementation of this system’s safety case, I do not consider that the safety case needs an earlier assessment by ONR than would otherwise have been planned. This is because my work to oversee the closure of my Regulatory Issue will entail me reviewing the parts of SL’s safety case that are affected by the identified shortfall.
I consider that SL has not adequately implemented those safety case claims that relate to the HALES Steam System due to shortfalls in back-up boiler availability. I have however examined evidence indicating that SL’s project to introduce another modern back-up boiler system is in an advanced stage of commissioning and the work is planned to be complete by June 2017. The timely completion of this project will be routinely monitored to ensure the timely closure of my Regulatory Issue.
Notwithstanding this shortfall, I am satisfied that HALES has adequate provision with respect to steam supply for the facility, and if necessary can enter a quiescent state if its steam supply is threatened. Following this inspection SL has written to ONR to confirm its opinion that the facility remains safe to operate, and I accept this position, subject to the timely resolution of the associated Regulatory Issue.