San Onofre NPP

The first unit of the station is the first generation PWR reactor from Westinghouse , which was finally shut down in 1992 after 25 years of operation. In 2002, the reactor vessel was dismantled ^[9] . Used as storage for spent nuclear fuel . ^[10] The reactor is enclosed in a spherical container made of concrete and steel 1.8 and more meters thick. The maximum net power was 436 MW (gross 456 MW). ^[eleven]

Blocks 2 and 3 are designed by Combustion Engineering and they are a two-loop PWR with a gross power of 1127 MW (net power of 1070 MW). ^[eleven]

In 2011, the ten-year process of replacing steam generators at blocks 2 and 3 was completed, the cost of which amounted to $ 671 million. Due to the two-loop design, which is not typical for such powerful reactors of the 1980s, steam generators were one of the largest in the industry (each weighing about 640 tons) ^[12] . One of the drawbacks of huge steam generators is the increased wear of the pipes, due to which replacement is required before the expiration of the originally planned 40 year service life. ^{[12] The} installation of steam generators, one of the largest components of the reactor, requires the creation of a temporary hole in a concrete and steel pressure vessel ^[13] measuring about 28 by 28 feet ^[14] . Replacement on the second block was completed in 2009, on the third - in 2011. According to the company, modernization could save consumers about $ 1 billion, provided that the NPP was operating until the end of the licensed period - 2022. ^{[15] [16]}

During operation, SONGS provided about 20% of the electricity needed in areas of Southern California . ^[17]

In 1982, Time magazine wrote that during the construction of the station in 1977, Bechtel installed a 420-ton reactor vessel at San Onofre with a 180-degree rotation. ^[18] In 2008, the station received several comments due to non-functioning emergency generators, incorrect battery connections and falsification of safety data. ^{[19] [20]} .

In November 2011, an ammonia leak ^[21] occurred, eliminated after three hours. The operation of the reactors was not interrupted ^{[22] [23]} .

Environmental Risk

Station Operator Southern California Edison said the plant could withstand an earthquake with a magnitude of 7 points in the immediate vicinity of the station. ^[24] In addition, a 25-foot wall was built along the coast to protect against tsunamis . ^[25] The former nuclear power plant is located near the Interstate 5 motorway, the railway line used by the National Railroad Passenger Corporation ( Amtrak ), and the Marine Corps Base Camp Pendleton .

Unlike most American PWR reactors, San Onofre uses sea water for cooling. ^[26]

The station stores about 4 thousand tons of spent nuclear fuel. ^[27]

Reactor

The San Onofre-2 block was scheduled to be shut down in early January 2012 to replace fuel and the reactor vessel cover. ^[28] January 31, 2012 at the San Onofre-3 block in one of the steam generators, a small leak of radioactive water from the first circuit (radioactive) to the second was discovered ^{[29] [30]} . For the most part, radioactive materials remained inside the container, and the reactor was manually shut down within three hours after the leakage sensor was triggered. ^{[31] [32] [33]} When inspecting both blocks, premature wear of more than 3 thousand heat transfer tubes (in more than 15 thousand places) was discovered inside the new steam generators installed in 2010-2011. ^[34] The station operator stated that the reactors would remain shut off until the causes of leakage and wear on the tubes were discovered. ^[28] Further, both reactors did not start. Due to the shutdown of the nuclear power plant, no forced outages were made, however, to compensate for the lost power, the load on the thermal stations increased. In addition, the cost of electricity to consumers has increased. ^[35]

NRC Reaction

On March 27, 2012, the NRC issued a Confirmatory Action Letter (CAL) prohibiting the resumption of NPP operations until the causes and deterioration of the tubes were clarified and corrected. ^{[36] [37]}

In 2013, the NRC explained that Mitsubishi Heavy Industries (MHI) made a lot of mistakes when designing and calculating steam generators. For example, when calculating the thermal-hydraulic regime using the FIT-III program, incorrect input parameters were used, ^{[38] [39]} it was used in the area for which the calculation model is not applicable. MHI also changed the bending shape of the heat transfer tubes and the anti-vibration system; there were welding defects ^[40] . In fact, the supplied steam generators were defective, and legal proceedings between SCE and MHI are ongoing ^[41] .

• Southern California Edison SONGS
• History of steam generator replacement events
• Virtual Tour
• VLADIMIR RYCHIN . Children's disease of San Onofre , ATOMINFO.RU (10.25.2012). Date of treatment December 28, 2013.
• VLADIMIR BERGUNKER, OKB HYDROPRESS . New problems of vertical steam generators , Atominfo (06/03/2013). Date of treatment December 27, 2013.
• San Onofre - launches without profit , Atominfo (12/14/2013). Date of treatment December 27, 2013.
• Root Cause Analysis Report for tube wear identified in the Unit 2 and Unit 3 Steam Generators of San Onofre Nuclear Generating Station (64 pages)
• San Onofre Nuclear Generating Station, Units 2 & 3 REPLACEMENT STEAM GENERATORS - Supplemental Technical Evaluation Report (68 pages)