US nuclear refueling outages show effects of aging maintenance

London (Platts)--2Mar2006

US nuclear operators ran the median refueling outage in a record time of
735 hours in the last six months of 2005, seven hours better than the previous
best in fall 2002, but the average time offline, at 934 hours, was well above
the 752-hour average three years before, according to utility data.
     That meant virtually no change in the overall pattern of US refueling
outages in the last three years. Longer outages were attributed largely to
steam generator and reactor pressure vessel head replacements, which help
ready power reactors to operate for extended lives.
     With only 23 of the 103 operating US nuclear units refueling in the
last six months of 2005, outage times ranged from 17 to 79 days. Outages in
the first half of 2005 ran 17 to 99 days for the 43 units that refueled then.
In the first half, 81% of units refueled in less than 40 days of outage, while
in the second half, only 65% did, the data showed.
     Two world records were claimed in the last half of 2005: one by
AmerenUE for a four-loop steam generator replacement in under 64 days at
Callaway, and one by PSEG Nuclear for a 25-day outage that included a vessel
head replacement.
     Five of the seven shortest outages were turned in at units operated by
Exelon Nuclear or, in the Salem-1 case, an outage co-managed by Exelon.
Shortest was Byron-2, at less than 17 days. The longest outage was Arkansas
Nuclear One-1's replacement of its steam generators, at just under 79 days.
Entergy said that outage included vessel head replacement as well, according
to the data.
                                    ---Margaret Ryan, margaret_ryan@platts.com

A full version of this story was published in Platts Nucleonics Week. Request
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