Subtitle: Nuclear plants require costly upgrades after 20 to
30 years
Steam generators inside containment structure Purple-cutaway view. source: NRC |
One of the favorite arguments of the nuclear proponents is
that, even though a nuclear plant costs more to build, it lasts for 60
years. The second part of the statement
is not true, although the first part is definitely true. Equipment wears out, and must be replaced at
significant cost. As an example, the
pressurized water reactors, PWR, have an expensive heat exchanger – the steam
generator – that suffers tube degradation over time. see image. NRC requirements cause these steam generators
to be replaced when tube degradation reaches a certain level. For some plants, the replacement works. At California’s San Onofre plant – SONGS –
however, four replacement steam generators failed recently very soon after
startup. The plant owner, Southern
California Edison, SCE, elected to shut down the plant permanently rather than
complete the steps required by the NRC to ensure the steam generators could be
repaired and operate safely.
Details of the SONGS steam generator troubles can be found at
the NRC website: see link.
The NRC described the tube degradation as “unexpected.” Apparently, the type of tube wear and
degradation is one that has never been witnessed before. The
tube wear was due to adjacent tubes rubbing against each other, and tubes
rubbing against retainer bars. The safety concern, unique to nuclear power
plants using the PWR design, is a sudden loss of main steam header pressure. In the words of the NRC, this is a main steam
line break. The reason this is a safety
concern is that radioactive hot water under high pressure flows on the inside
of the tubes in the steam generator. At
a somewhat lower pressure, water flows on the outside of the tubes. The water on the outside of the tubes is
heated, boils, and turns to steam (hence the name, steam generator). The tube walls must retain their strength to
prevent leaks of the radioactive water through the tubes and into the steam
system. The steam system's pipes run outside
the containment building, into the steam turbine, and from there steam flows
into the condenser. With both systems operating normally,
pressurized radioactive water on the inside of the tubes, and lower pressure water/steam on the outside, the tubes have an easier task in keeping the
two water systems separate. But, if a
main steam line breaks, the pressure difference across the tube walls increases
suddenly and dramatically. Weak tubes
would, of course, fail and send radioactive water and steam into the
atmosphere. This is unacceptable, but is
a natural consequence of choosing to generate power using nuclear fission as
the heat source.
Indeed, this is exactly what happened at SONGS when the new
steam generators sprung a leak, radioactive water entered the steam system, and
a small amount of radioactive steam was released into the atmosphere. See link As required, SCE shut down the plant to
investigate.
The sticking point in the order from NRC to SCE was this: “SCE
will determine the causes of tube-to-tube interaction and implement actions to prevent
recurrence of loss of integrity in the Unit 3 steam generator tubes while
operating.” That is a most reasonable
requirement, find out what happened, and implement steps to make sure it does
not happen again. SCE, however, either
could not, or would not take the time and expense to determine the causes. Instead, SCE shut down both reactors in the
plant.
It should be noted that minor tube wear is normal and
expected. Indeed, with the more than
9,000 individual tubes in one steam generator, a tube that is near failure due
to excessive wear can be plugged to remove it from service. The difference in this case was the rapid
tube wear so very soon after the new steam generators were placed in
service. The original steam generators
lasted not quite 30 years, as the SONGS reactors came online in 1983 and 1984, and
the steam generators were replaced around 2010.
The radioactive steam leak occurred in January, 2012.
There is much more to the story of the leaking tubes at SONGS. As time permits, that story will be told. It involves SCE trying to obtain an extension to the operating permit by claiming the replacement steam generators were sufficiently similar to the original equipment to qualify for "like-for-like" status, when the new steam generators were not "like-for-like." A United States Senator became involved. A re-licensing procedure would have been lengthy and the plant would be shut down for the duration of that procedure.
In addition, the 2000 MW of electricity was lost to the grid, and had to be replaced somehow. A part of that story is related at this link. The good news is that at least 75 MW of the power must be from energy storage systems. That will provide a significant boost to the grid-scale energy storage firms.
Other nuclear plants also have been in the news due to tube
wear and degradation, including the St. Lucie plant in Florida. See link Also, the Watts Bar plant has suffered tube
wear and has ordered replacement steam generators. Finally, the Davis-Besse nuclear plant in
Ohio is replacing its steam generators, also.
It’s an exciting time.
How many more nuclear plants will go the way of SONGS, due to faulty
replacement steam generators that have tubes wear on each other?
Conclusion
It can be seen, then, that the nuclear power
plant in California lasted a bit less than 30 years, not the 50 or 60 years as
nuclear proponents claim. Nuclear plants require costly upgrades after
20 to 30 years, but the anticipated added life does not always appear.
Previous articles in the Truth About Nuclear Power series are found at the following links. Additional articles will be linked as they are published.
Part One – Nuclear Power Plants Cannot Compete
Part Three – Nuclear Power Plants Cost Far Too Much to Construct
Part Four – Nuclear Power Plants Use Far More Fresh Water
Part Five – Cannot Simply Turn Off a Nuclear Power Plant
Part Six – Nuclear Plants are Huge to Reduce Costs
Part Seven -- All Nuclear Grid Will Sell Less Power
Part Nine -- Nuclear Plants Require Long Construction Schedules
Part Ten - this article
Part Eleven - Following France in Nuclear Is Not The Way To Go
Part Twelve - Nuclear Plants Cannot Provide Cheap Power on Small Islands
Part Thirteen - Nuclear Plants Are Heavily Subsidized
Part Fourteen - A Few More Reasons Nuclear Cannot Compete
Part Fifteen - Nuclear Safety Compromised by Bending the Rules
Part Sixteen - Near Misses on Meltdowns Occur Every 3 Weeks
Part Seventeen - Storing Spent Fuel is Hazardous for Short or Long Term
Part Eighteen - Reprocessing Spent Fuel Is Not Safe
Part Thirteen - Nuclear Plants Are Heavily Subsidized
Part Fourteen - A Few More Reasons Nuclear Cannot Compete
Part Fifteen - Nuclear Safety Compromised by Bending the Rules
Part Sixteen - Near Misses on Meltdowns Occur Every 3 Weeks
Part Seventeen - Storing Spent Fuel is Hazardous for Short or Long Term
Part Eighteen - Reprocessing Spent Fuel Is Not Safe
Part Nineteen - Nuclear Radiation Injures People and Other Living Things
Part Twenty - Chernobyl Meltdown and Explosion
Part Twenty One - Three Mile Island Unit 2 Meltdown 1979
Part Twenty Two - Fukushima The Disaster That Could Not Happen
Part Twenty Three - San Onofre Shutdown Saga
Part Twenty Four - St. Lucie Ominous Tube Wear
Part Twenty - Chernobyl Meltdown and Explosion
Part Twenty One - Three Mile Island Unit 2 Meltdown 1979
Part Twenty Two - Fukushima The Disaster That Could Not Happen
Part Twenty Three - San Onofre Shutdown Saga
Part Twenty Four - St. Lucie Ominous Tube Wear
Part Twenty Five - Price-Anderson Act Protects Nuclear Plants Too Much
Part Twenty Six - Evacuation Plans Required at Nuclear Plants
Part Twenty Seven - Power From Nuclear Fusion
Part Twenty Eight - Thorium MSR No Better Than Uranium Process
Part Twenty Nine - High Temperature Gas Reactor Still A Dream
Part Thirty - Conclusion
Part Twenty Eight - Thorium MSR No Better Than Uranium Process
Part Twenty Nine - High Temperature Gas Reactor Still A Dream
Part Thirty - Conclusion
Roger E. Sowell, Esq.
Marina del Rey, California
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