There are two Magnox Reactors at Wylfa Nuclear Power Station. These reactors are designed to operate continuously to provide ‘base load’ electricity.
To continue to operate safely and reliably reactors require examination, inspection, maintenance and testing. Continuous improvement also requires plant upgrades to be implemented. Whilst some of these activities can take place when a reactor is generating electricity, many of them require a reactor to be shut down and be at relatively low temperatures for an extended period. To enable such activities each reactor at Wylfa undertakes a Periodic Shutdown (often referred to as a statutory outage) every two years. Following a statutory outage the reactor cannot start-up without the permission of the HSE’s Nuclear Directorate.
The current statutory outage for Reactor 2 at Wylfa commenced on 8 April 2010.
Assessment and inspection work carried out by ND in consideration of this request
ND has undertaken a number of inspections and assessments in relation to this request, as follows:
- a meeting with the licensee on 3 March 2010 to discuss and agree work to be undertaken during the outage
- an inspection visit by a radiological protection specialist
- an inspection visit to examine quality assurance
- specialist assessment of graphite core inspection results
- an inspection by a structural integrity specialist and assessment of relevant inspection results, particularly internal reactor support structures
- specialist assessment of civil structures inspection results
- an inspection visit to examine control and supervision of contractors during the outage
- an inspection visit to review electrical engineering aspects of the outage
- nine inspection visits by the site inspector and specialist inspectors during the outage to monitor outage activities and
- a start-up meeting on 23 June 2010 to review outage findings and agree actions to be completed before start-up.
The licensee has adequately addressed issues arising out of these inspections and assessments and has satisfactorily addressed actions from formal meetings.
Matters arising from ND’s work
- Inspection and assessment work undertaken by ND has confirmed that the licensee has conducted maintenance activities in accordance with the Station Maintenance Schedule, has undertaken inspections to support the station safety case and has complied with statutory requirements and implemented modifications.
- Where the licensee’s inspection work has revealed deterioration in plant condition, the licensee has assessed the results in accordance with its arrangements and where necessary, has carried out remedial work. ND’s inspection and assessment work has confirmed that none of the licensee’s outage inspection findings prevent start-up of Reactor 2.
- An extensive graphite inspection programme was undertaken and completed by the licensee. Anomalies observed during the inspections were reviewed in detail by ND, and it was confirmed that they were within the current safety case.
- Emergent work identified by the licensee during the outage has required replacement of a number of steam pipe hangers. ND is satisfied that appropriate corrective actions have been put in place by the licensee.
There was one event of note during the outage which concerned the inadvertent withdrawal of a charge chute and attached fuel element. The fuel element remained fully within the reactor at all times during the event and did not introduce any significant risk to nuclear safety. The recovery operation has been successfully completed.
- The Wylfa Reactor 2 statutory outage has been undertaken and completed in accordance with the work described in:
- the current Maintenance Schedule;
- the Outage Intent Document;
- other safety case requirements, and;
- additional ND requirements;
- except for those items due to be completed as part of the reactor’s return to power.
- ND inspection and assessment of the outage and of the key safety case changes has not revealed any concerns that challenge the granting of Consent to start-up Wylfa Reactor 2.
The licensee has provided adequate responses to the start-up actions identified by ND.
It is recommended that Licence Instrument No.544, which gives Consent for the start-up of Wylfa Reactor 2 following the 2010 periodic shutdown, be issued to the licensee.