Office for Nuclear Regulation

This website uses non-intrusive cookies to improve your user experience. You can visit our cookie privacy page for more information.

Installation and Commissioning of Variable Speed Drives

Executive summary

Purpose of intervention

This planned intervention at EDF Energy Nuclear Generation Limited's Torness power station was undertaken as a follow up to ONR's Agreement to a modification to partially replace variable frequency converters (VFCs) with variable speed drives (VSDs). This intervention allowed me to review the licensee's activities associated with installation and commissioning of the first two drives and progress with developing a through life management strategy for the new VSDs.

Interventions carried out by ONR

My intervention included a compliance inspection against the following nuclear site Licence Conditions (LCs):

Explanation of judgement if safety system not judged to be adequate.

Not applicable

Key findings, Inspector's opinions and reasons for judgements made

The licensee confirmed that installation and commissioning had been completed to schedule. The licensee stated that no issues had occurred that would preclude declaring the units suitable for service in April 2014 when Reactor 1 is scheduled to return to power following its statutory outage. After discussing the issues that occurred during installation and commissioning, I agree with this conclusion. I also took positive note that the licensee was recording these lessons learnt and would incorporate them into future replacements at both Torness and Heysham 2.

The licensee described the approach taken to manage the commissioning of the equipment. I consider that securing the right people on the commissioning team and having that team in place sufficiently in advance of the commissioning contributed to the successful completion of the work.

I discussed with the licensee the lifetime management of the new VSDs. Based on a lifetime management document previously shared with me and the continued work to develop a commercial arrangement with the equipment manufacturer, I consider the licensee has taken appropriate action.

Conclusion of intervention

From the evidence obtained during this intervention, I identified no matters of concern that are likely to affect nuclear safety at Torness. I consider that the licensee is undertaking appropriate action in relation to the installation and commissioning of the replacement VSDs.


I consider that no further regulatory action associated with the VSD replacement project from an electrical engineering perspective is necessary at this time and further replacement can be monitored as part of normal regulatory business.