Nuclear Inspection Team Highlights Failures at San Onofre

http://www.utsa...esign-failures/

A months-long inspection of the sidelined San Onofre nuclear plant found
inaccurate computer modeling and construction shortcomings by an equipment
manufacturer are behind rapid degradation of steam generator tubes that serve
as a crucial barrier to radiation, nuclear safety regulators announced Monday.

A team of inspectors from the Nuclear Regulatory Commission told a packed
public meeting in San Juan Capistrano that higher than expected steam flow
velocities were rattling tubes within steam generators manufactured by
Mitsubishi Heavy Industries.

"The computer simulation used by Mitsubishi to design the steam generators
had underpredicted velocities of steam and water in the generators by factors of
three and four times," said Greg Werner, a branch chief for the nuclear
commission.

He added that manufacturing tolerances left the tubes sitting too loosely within
support structures -- a problem that was especially pronounced in the Unit 3
reactor at the plant.

"So essentially the tubes are not held in place securely enough, so it allows
them to slide or vibrate," Werner said. A full written report from the inspection
team is due out within 30 days.

Original steam generators at the plant's twin 30-year-old reactors were
replaced starting in 2009. Evidence of unusual wear on generator tubing turned
up in January, with some of the equipment in service for only one year.

Read the full article at:
http://www.utsandiego.com/news/2012/jun/18/nuclear-inspection-team-
highlights-design-failures/