Approval to Amend Operating Rule 5.6 to Remove the 250 Empty Channel Limit on Reactor 2

Executive summary

Permission Requested

Magnox Ltd, the site licence company (the Licensee) that operates and maintains Wylfa Power Station, has requested ONR approval of an amended operating rule to remove the limit of 250 empty fuel channels in Reactor 2 as required by Licence Condition 23(5) of nuclear site licence 58A. 

Background

Wylfa Power Station consists of two Magnox reactors, with one pre-stressed concrete pressure vessel (PCPV) for each reactor.  To optimise the remaining fuel for the reactors, Magnox Limited has permanently shutdown Reactor 2 and is transferring partly used fuel from Reactor 2 to Reactor 1.  Currently there can only be 250 empty fuel channels in Reactor 2, in accordance with Operating Rule 5.6.  Fully irradiated fuel from Reactor 1 is being transferred from Reactor 1 to Reactor 2 to ensure that this limit is being met.

Magnox Limited has done some further analysis that demonstrates that the empty channel limit can be relaxed, which will give it additional flexibility during refuelling and the ability to despatch irradiated fuel from the site rather than returning it to Reactor 2.  It therefore wants to amend Operating Rule 5.6 to remove the limit.  Under the nuclear site licence the licensee must seek ONR approval of the amendment to the operating rule. 

Assessment and inspection work carried out by ONR in consideration of this request

ONR has assessed the safety case for amendment of the operating rule.  Assessment has been completed by specialist inspectors in the following technical disciplines:

• Fault studies
• Human factors 

Matters arising from ONR’s work

There are no significant findings from the work that would prevent approval of the amended operating rule. 

Conclusions

The ONR programme of assessment gives sufficient confidence to allow ONR approval of the amended operating rule.