British Energy's PWR performance

Tuesday, 15 April 2008

Presenting to investors yesterday, British Energy announced progress in engineering issues at its gas-cooled reactors, while celebrating the performance of its newest pressurized water unit.

 

The company's CEO, Bill Coley, said that it had been hit by some 'large loss events' in the last financial year. Chief among these had been ongoing boiler inspections and operational limits at Hinkley Point B and Hunterston B and the separate issue with boiler closure units (BCUs) at Hartlepool and Heysham 1.

 

A BCU binding is found to be intact

Advanced Gas-cooled Reactors have their eight boilers (steam generators) fitted inside the reactor's reinforced concrete containment structure, making them hard to manage as they age. At Hinkley Point B and Hunterston B, problems with the boilers have restricted output to around 60%, althought this could rise to 70% during this financial year with the addition of 'clamshell' insulation. At both of Hartlepool 1's reactors, wire windings in the BCUs - which form part of the pressure boundary - have been found to be corroded. Heysham 1 shares the same BCU design, and one wire related to the first reactor there has failed.

 

BE has been inspecting the wire bundles, taking around 10,000 radiographs and removing fillite to reach them for visual inspection. The components cannot be replaced, so BE will place circumferential bands around the BCUs to 'lock in and enhance the existing pre-stress'. This effectively provides a tenth layer of binding over and above the nine in the BCU itself. Further protection will be added by a bolted steel restraint to go on top of the BCU. A team of 500 is working on the project and all four reactors should return to service by the end of 2008.

 

Breaker-to-breaker

 

In contrast to troubles at some of its older units, BE highlighted the performance of its only pressurized water reactor (PWR), Sizewell B. The 1196 MWe station recently completed a breaker-to-breaker run, BE said, operating without any unplanned shutdowns during the 516 days between two refuelling outages.

 

The run gave the unit a capability factor of 89.3% over the last 18 months (including one refuelling) and helped plant staff enjoy a low collective dose rate. BE is keen to build more PWRs, or their cousins, boiling water reactors.

 

Keith Parker, chief executive of the UK Nuclear Industry Associaiton, described Sizewell B's run as an outstanding performance. He told World Nuclear News: "This goes to show how important nuclear is in supplying secure, reliable, base-load electricity – and why the UK should be a part of the worldwide nuclear renaissance."