Office for Nuclear Regulation

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Improvement Notice served on Rolls-Royce Submarines Ltd

8 July, 2020

The Office for Nuclear Regulation (ONR) has served an Improvement Notice on Rolls-Royce Submarines Ltd (RRSL) for procedural safety breaches at its Derby site.

The notice was served after shortfalls were identified against the safety case requirements at a nuclear fuel production facility on the site.

ONR is satisfied that significant safety margins remained in place at the plant, and that public and worker safety was not compromised.

However, the regulator requires a number of improvements to be made to ensure sustained compliance with ONR Licence Condition 23 (Operating Rules).

To secure the necessary high standards of safety at all licensed nuclear sites in Great Britain, those who use such sites must operate them in accordance with a safety case which sets out clear limits and conditions for such operations.

The Notice was served after RRSL operators brought 21 units of fissile material into the facility – thereby exceeding the limit of 16 units defined within the safety case, and set out in the Criticality Control Certificate for the facility. The breach was identified by RRSL and reported to ONR in line with required procedures.

The limits specified were extremely conservative, so the breach in itself did not present any immediate risk to safety. In addition, the facility in question features other measures to ensure a criticality hazard cannot occur.

However, adherence to the conditions set out in a safety case is required by law and, as a consequence, ONR has served the Improvement Notice to prevent any recurrence of the breach.

RRSL is required to comply with the Improvement Notice by 31 May, 2021.