Japan Nuclear Power Plants Off-Line & Being Replaced

Japan's nuclear-power crisis has left the country dependent on aging conventional plants that are being pushed well beyond their normal limits to keep the lights on and businesses functioning. The Fukushima Daiichi accident in March 2011 has increased public opposition to any restarts of the nation's 54 nuclear reactors, which remain idled due to shut down for  periodic maintenance checks.

 

Only three units are now operating and even those will be shut down as early as April. On Monday, Japan said the average nuclear power capacity used for power generation in January was 10.3%.

Among thermal power plants, coal-fired plants generally are operated near full capacity, but gas-fired and oil-fired plants, which use more expensive fuels, typically are brought online only when demand rises to peak levels.

Demonstrating the heavy load, thermal power plants at Japan's 10 regional power utilities were operating an average of 66% of the time last December, up sharply from 45% in the year ended in March 2011.

Japanese utilities are working on small-scale portable gas turbines that can be used in a pinch.  (WSJ, 2/13/2012)

NRC Approves Two New Reactors at Plant Vogtle

Today, in a 4-1 vote, the Nuclear Regulatory Commission (NRC) approved two new nuclear reactors (3 & 4) at the Plant Vogtle facility in Burke County, Georgia.  The reactors are the first to be built in the United States in almost 30 years and are expected to be completed in 2016 and 2017. The project is estimated to cost roughly $14 billion-dollars. The nuclear regulatory commission last gave a utility permission to start building a nuclear plant in 1978.

The NRC Combined Operating License (COL) will authorize Southern Company to build and operate two AP1000 reactors at the Vogtle site, adjacent to the company's existing reactors approximately 26 miles southeast of Augusta, Ga.

Plant Vogle Reactors 1 & 2

Southern Company submitted its COL application on March 28, 2008 and the NRC completed its environmental review and issued a Final Supplemental Environmental Impact Statement for the Vogtle COLs on March 24, 2011. The NRC completed and issued the FSEIS on Aug. 9, 2011.

The NRC certified Westinghouse's amended AP1000 design on Dec. 30, 2011. The AP1000 is a 1,100 megawatt electric pressurized-water reactor that includes passive safety features that would cool down the reactor after an accident without the need for electricity or human intervention. (WTOC11, 2/11/2012)

San Onofre Steam Generator Leak

San Onofre nuclear generating station (SONGS), right, hasn't been generating power since 5:31 p.m. Tuesday, when Southern California Edison shut down its Unit 3 reactor ---- one of two reactors ---- announcing that operators had detected a leak in one of two giant heat exchangers installed in 2010. The leak could be a safety concern because it allows water that can can contain radioactive particles to mix with clean water used to make steam. The steam travels outside the protective concrete domes that are designed to protect the public from a radiation release. Once it leaves the radioactive side of the plant, the water can evaporate and travel through the plant's electricity-generating turbines.

Given that the new components were supposed to last for decades, industry experts were quick to question why the expensive equipment was already leaking at a rate of between 50 and 100 gallons per day. At the time the leak was detected, San Onofre's other reactor ----- Unit 2 ----- was already shut down for refueling and maintenance.

Steam Generator

The vertical steam generators generally have a feedwater ring supply header on the outer edge of the steam generator. The water is directed downward and flows along a wrapper sheet then is directed upwards to flow along the steam generator tubes where the water picks up heat, increasing in temperature until boiling occurs and the water is converted to steam. In the upper part of the steam generator is a moisture separator region which forces the steam-water mixture through channels which allow steam to pass, but not water. A vane arrangement in these steam generators also force a swirling action that enhances the steam-water separation.

The water supplied to the steam generators must be very pure, free of particles, and chemicals. In the boiling environment of the steam generator these chemicals can concentrate resulting in undesired corrosion.

SC Edison began replacing the steam generators at San Onofre in 2009 with new units manufactured by Mitsubishi Heavy Industries. Edison has indicated the new generators would last until the plant's license expires in 2022. But on Tuesday a leak developed in one of the tubes in the number 2 steam steam generator at Unit 3. Radiation monitors detected an increase in radioactivity levels, plant operators diagnosed the leak, and the unit was depowered at 4:30 p.m. and shut down fully at 5:31 p.m.

Steam Generator

While there is still no quantitative information available on the radioactivity release, an NRC spokesman noted that: “all of our information so far indicates it was very, very small, and well within federal regulatory limits. It posed no danger to workers on site or to the public offsite.”  Meanwhile, according to the NRC, SONGS workers doing maintenance at the second reactor, unit 2, checked that new steam generator as part of routine maintenance and found that:

“Two of the tubes have thinning so extensive that they need to be plugged and taken out of service. Sixty nine other tubes have thinning greater than 20 percent of the wall thickness, and a larger number have thinning greater than 10 percent of wall thickness.”

It should be noted that the nuclear power industry, now with 30 years of experience with this problem, is well equipped to plug or sleeve degraded tubes and return the steam generator to service. The generator contains thousands of tubes so even if some must be blocked the generator can still be used.

HOW NUCLEAR PLANTS WORK

(North County Times, 2/3/2012, The Orange Country Register, 2/2/2012,