Office for Nuclear Regulation

Sizewell B – Inspection ID: 52073

Executive summary

Date(s) of inspection:

  • March 2023

Aim of inspection

To meet the requirements of the Sizewell Statutory Outage Project as defined in the ONR Outage Inspection Plan.

To provide regulatory confidence in relation to RP and compliance with Ionising Radiations Regulations 2017 (IRR’17).

To inform the ONR decision relating to the issue of a Licence Instrument for Consent for return to service of the Sizewell B Reactor.

Subject(s) of inspection

  • IRR17 – Rating: Green
  • LC18 – Radiological protection – Rating: Green

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

This report is on ONR’s assessment of EDF Energy Nuclear Generation Ltd.’s (NGL) radiological risk management arrangements during the 2023 (RO-18) statutory outage of the Sizewell B reactor. The site intervention sought to establish if the license’s statutory outage work programme was being conducted in compliance with the Ionising Radiations Regulations 2017 (IRR17).

The intervention focussed on the following:

  • Operational dose management, specifically day-to-day dose management and profiling during the outage.
  • NGL RP personnel organisation including level of support available and outage contractor selection, training  and competence
  • Supervision and control of work including inputs from HP staff and RPS as well as contractor control and supervision.
  • Radiological event investigation and follow-up
  • Radiation survey instrument maintenance and support arrangements including adequate monitoring equipment resources for the outage.
  • Radioactive source management
  • Radiation protection input to outage work planning including risk assessment and explanation of how mitigations identified in the ALARP report are implemented at the working level.

The inspection found adequate arrangements were in place for RO-18 and it was judged an overall inspection rating of green was appropriate.


The inspection findings were presented to NGL at the close of the inspection.

The inspection found adequate arrangements relating to operational doses management, contractor supervision and control, availability and maintenance of radiological protection survey instruments, radioactive source management and assessment of risk.