Heysham (United Kingdom)

Map of Heysham

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Unit A: 2 * AGR 625 MW grid connection 1983/84
Unit B: 2 * AGR 625 MW grid connection 1988

Facilities in Heysham

plantreactor typconstruction startoperation startshut down
Heysham -1BAGR19701984
Heysham -2AAGR19801988
Heysham -2BAGR19801988
Heysham- 1AAGR19701983
2002-03-11

"British Energy reported an event at Heysham 1 on 11 March involving a fuelling machine operation at a Fuel Storage Tube. The machine had collected a new fuel assembly from the tube and had replaced this with a short shield plug. Unknown to the operators, and contrary to the indications at the fuelling machine, the shield plug had not disconnected from the machine grab. A mechanical interlock designed to prevent the machine moving until safe to do so had failed. This allowed the machine to move sideways which resulted in impact between the shield plug and the storage tube. The shield plug was severed into two parts with the lower part falling into the storage tube.

The NII Site Inspector visited the site within a few hours of the event being reported. He confirmed that the nuclear safety significance of the actual event was low, but that it could have been more serious if the fuelling machine had been operating at the reactor. There are, however, other interlocks to provide protection in this case. He also confirmed that a full investigation was underway and that the refuelling safety case would be revalidated before the machine was used again over the reactor. The event was subsequently categorised as a level 2 event (an incident) on the internationally used INES scale of nuclear events, due to the implications of multiple failures of safety provisions.

NII has closely scrutinised the licensee's investigation and safety case revalidation process. We also used our regulatory powers to prevent the refuelling machine being returned to service without our agreement. We eventually allowed BE to return the machine to service following our assessment of the revalidated safety case. We continue to monitor the longer term actions arising from the event as part of our routine regulatory business."
(source: http://www.hse.gov.uk/nuclear/quarterly-stat/2002-1.htm)

1996-01-29

Just 18 months after low power refueling was established at Nuclear Electric's (NE) Heysham-B advanced gascooled reactor (AGR) station, helping it become the star performer of the company's five AGRs, an incident involving a distorted standpipe caused NE to return last month - for the time being - to its old regime of refueling with the reactors shut down.
Moreover, because it is not yet clear whether such distortion is a one-time occurrence or an inherent design weakness, Heysham-B´s sister station, Torness, run by Scottish Nuclear Ltd. (SNL), has also had to quit on load refueling.
Hinkley Point-B and Hunterston-B are continuing their on-load refueling regime because they have a different standpipe design, even though their overall plant design served as a base model for Heysham-B and Torness.
Hunterston-B´s ability to refuel its twin reactors on-load has given an increase in load factors of some 10% above off-load refueling, according to a 1991 report by the professional journal, Nuclear Engineer.
A 7-metric ton, 70-foot-long fuel assembly snagged as it was being lowered into the core of reactor 2, automatically tripping the reactor.
The assembly is constructed in two parts, the lower part being the assembly of fuel rods and the upper part being a rather wider plug unit which normally makes a complete seal with the top of the reactor so the pressure circuit is maintained.
"The operators were assuming that when it snagged, what was happening was that the fuel rod assembly (on the lower part) was snagging on old fuel debris, something that crops up from time to time." said NII spokesperson Peter Morgan."So they tried again to get it in, but that didn't work. Then they decided just to plug the top with an empty plug unit without any fuel beneath it. But that snagged too. So they realized then that it wasn't anything down in the fuel channelectrical It was further up. And it turned out to be, on investigation, a distortion in the standpipe above the reactor roof through which the fuel assembly is lowered - a sort of guide tube - before it reaches the fuel channel".
NE sources said that until this incident occurred, some 55 fuel assembly exchanges were being made a year, per reactor, at Heysham-B. Altogether, some 150 refuelings had been carried out on-load and this was the first incident of its kind.

1994-12-25

Shutdown because of a generic reheat cracking phenomenon in steam pipe welds. Hairline cracks monitored for 6 years showed an increase in the growth rate.