Office for Nuclear Regulation

Heysham 2 – Inspection ID: 51357

Executive summary

Date(s) of inspection:

  • February 2023

Aim of inspection

The aim of the intervention is to assess compliance with the nuclear site licence condition 11 (Emergency Arrangements) at EDF Energy Nuclear Generation Ltd.’s (NGL’s) Heysham 2 power station.

The inspection is in accordance with ONR’s integrated intervention strategy for the site. ONR technical inspection guide NS-INSP-GD-011 Issue 7.1 ‘LC 11 – On-site Emergency Arrangements’ will be used as the basis for the inspection, which can be found at

Subject(s) of inspection

  • LC 11 – Emergency arrangements – rating: Green

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

ONR observed and assessed the Level 1 emergency exercise ‘PERSEUS’ at the EDF Energy Nuclear Generation Ltd.’s (NGL’s) Heysham 2 power station.

The scenario involved loss of the decay store cooling and multiple casualties, following a lightning strike.

All of the command centres and intervention staff performed adequately, and overall the licensee successfully:

  • Established three on-site command centres, in addition, the corporate emergency support centre was set-up.
  • Re-established feed water supply to the decay store using the beyond design basis tie-in points.
  • Accounted for all staff on-site.
  • Located all three casualties and retrieved two back to occupational health for treatment. The third casualty (a fatality) was attended at the scene by a simulated paramedic.

ONR were satisfied that the exercise objectives and performance indications in the licensee’s scenario were largely met.


In conclusion, ONR judged that exercise ‘PERSEUS’ was an adequate demonstration of the Heysham 2 emergency arrangements and rated the inspection for Licence Condition 11 as Green (no formal action).