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Sanmen Nuclear Power Station China map
Japanese (Toshiba) owned Westinghouse announced (26-May-2016) completion of a cold hydrostatic pressure test for Sanmen Nuclear Power Unit 1 (AP 1000) in China. The reactor unit is more than three years behind schedule, and has been under construction for over 8 years.

The test showed that welds held at a pressure of 3,107 psig (21.4 MPa) for a whole 10 minutes didn’t appear to leak. This was apparently not at operating temperatures, so is not reflective of the real system stresses. The entire test was completed within 4 hours.

Compare to the California Code which says 30 minutes “without leakage, undue distortion, excessive permanent expansion or evidence of impending failure“. The Westinghouse press release merely says that “Inspection of the more than 1800 welds found no leaks“.

This 10 minutes of maximum pressure was around 1.48 times the operating pressure for the AP 1000 reactor. 1.5 times the operating pressure is minimum for hydrostatic testing for the California Code. Wikipedia’s article on hydrostatic testing says that “The test pressure is always considerably higher than the operating pressure to give a factor of safety. This factor of safety is typically 166.66%, 143% or 150% of the designed working pressure, depending on the regulations that apply.

Shouldn’t the regulations be more strict for nuclear applications and not the bottom end of safety?

While they do not give the temperature, it was probably the upper end of room temperature (36C). Operating temperatures would be in the range of 227 C to 321 C. Thus, this test tells us little. They plan to follow this cold test with a hot functional test, presumably at operating temperature. (See references and more details after discussion of Sanmen Nuclear Power Station).

It is noteworthy that Japanese owned Toshiba (Westinghouse) is building a nuclear power station in China. Japan and China appear really friendly, though the media wants you to believe otherwise.

Chinese workers undergoing training for the AP1000 reactor in 2007, US NRC via Wikimedia
Chinese workers undergoing training for the AP1000 reactor in 2007, US NRC via Wikimedia. The US NRC being there probably has to do with Shaw Group (now CBI) involvement in the project.

Four AP1000 reactors are under construction in China, at Sanmen Nuclear Power Plant in Zhejiang, and Haiyang Nuclear Power Plant in Shandong.[25] The Sanmen unit 1 is expected to be the first AP1000 to begin operating, in 2017 more than three years after the original plan date.[1]… The first four AP1000s to be built are to an earlier revision of the design without a strengthened containment structure to provide improved protection against an aircraft crash.[28]… In 2008 and 2009, Westinghouse made agreements to work with the State Nuclear Power Technology Corporation (SNPTC) and other institutes to develop a larger design, the CAP1400 of 1,400 MWe capacity, possibly followed by a 1,700 MWe design. China will own the intellectual property rights for these larger designs. Exporting the new larger units may be possible with Westinghouse’s cooperation.[31] In September 2014 the Chinese nuclear regulator approved the design safety analysis following a 17-month review.[32]/ In December 2009, a Chinese joint venture was set up to build an initial CAP1400 near the HTR-10 Shidaowan site.[31][33] In 2015 site preparation started, and approval to progress was expected by the end of the year.[34][35]/ In 2014, China First Heavy Industries manufactured the first domestically produced AP1000 reactor pressure vessel, for the second AP1000 unit of Sanmen Nuclear Power Station.[36]https://en.wikipedia.org/wiki/AP1000

The Sanmen Nuclear Power Station (Chinese: 三门核电站) is a nuclear power station under construction in Sanmen County, Zhejiang Province in China. Groundbreaking for the first and second units was held February 26, 2008.[2][3]/ Sanmen NPS will be the first implementation of the AP1000 pressurized water reactor (PWR) developed by Westinghouse Electric Company. The contract was agreed in July 2007.[4] Announcement of the project start came roughly twelve months after Westinghouse won a bidding contest over other companies. The contract for the new plant involved The Shaw Group (now Chicago Bridge and Iron), a minority shareholder in Westinghouse. Westinghouse is controlled by Japanese Toshiba. The Shaw Group will provide engineering, procurement, commissioning, information management and project management services.[4]The first pair of reactors will cost more than 40 billion yuan (US$5.88 billion).[5] / Excavation for the first unit was completed in September 2008… Construction of Sanmen Unit 1 began on April 19, 2009, as the first 5,200 m³ of concrete were poured for the foundation,… The units were originally projected to begin operation in 2014 and 2015. As of April 2015, a start date of 2016 is projected for both. [11] One month later, the start date was put back to 2017.[12][13]https://en.wikipedia.org/wiki/Sanmen_Nuclear_Power_Station

Toshiba (87%) (majority owner), Kazatomprom (10%), IHI (3%)
https://en.wikipedia.org/wiki/Westinghouse_Electric_Company (Shaw Group-CBI appear to have sold their shares.)

The Westinghouse press release for the cold hydrostatic test (CHT) for Sanmen Nuclear Power Station Unit 1 states: “Initiated on May 25, the test was completed within four hours with the unit’s reactor systems successfully maintaining a test pressure of 3,107 psig (pounds per square inch gauge) for 10 minutes without leakage. Inspection of the more than 1,800 required welds in the reactor coolant system test boundary found no leaks at that pressure. The CHT leads the way to the next two critical commissioning milestones, hot functional test and initial fuel load. The hot functional test, which tests all plant systems prior to loading fuel in the reactor, will begin in the next several weeks. Once complete, it will be followed by initial fuel load.https://web.archive.org/web/20160527170908/http://www.businesswire.com/news/home/20160526006454/en/Westinghouse-AP1000®-Completes-Cold-Hydro-Test-Sanmen They state that “lessons learned” will be used for the US AP 1000s still under construction in Georgia (Vogtle) and South Carolina (VC Summer).

3107 pounds-force per square inch = 21.4 megapascals
23.6 megapascals = 3423 pounds-force per square inch

AP 1000 specifications for reactor operating pressure:
2,250 psia (15.513 MPa abs), meaning that the test was around 1.38 times the operating pressure. Temperature specifications: “Hot leg temp is 610°F (321.11°C)
Steam generator design pressure 1200 psia (8.274 MPa abs), Main feedwater temp 440°F (226.67°C)
” See these and other AP1000 specifications here: https://web.archive.org/save/_embed/http://www.westinghousenuclear.com/Portals/5/Documents/documentation%20pdfs/Chapter%201%20Section%201-3.pdf

The test pressure is always considerably higher than the operating pressure to give a factor of safety. This factor of safety is typically 166.66%, 143% or 150% of the designed working pressure, depending on the regulations that apply.https://en.wikipedia.org/wiki/Hydrostatic_test

The piping between the RPV and the steam generator is called the “hot leg.

Based on a paper discussing a hydrostatic pressure test at another Chinese Nuclear Power Station and the fact that they call this “cold” and mention that they will later do a “hot functional test” it was probably the upper end of room temperature, i.e. 36 C (97 F). The operating temperature would be much hotter with the Hot Leg temperate at 321 C, and the Main Feed-water Temp of 226.67C.

A paper by Lin Lei, et. al., on testing the pressurizer at another Chinese Nuclear Power station states that: “The highest hydrostatic test pressure is 23.6 MPa, and the temperature of external surface during the hydrostatic test is maintained at 36 C. During the hydrostatic test, the internal pressure increases from 0 to 23.6 MPa, and maintained for at least 10 min at 15.4 MPa and 17.13 MPa…. During the hydrostatic test, the final pressure is about 1.5 times the operating pressure, which leads to potential failure risk…
In this paper, actual strain of a CPR1000 unit’s pressurizer during the pre-delivery hydrostatic test is acquired. The strain and stress data acquired can be used as the basic data for the pressurizer ageing condition assessment or structural integrity assessment during its long-term operation. The conclusions of this study are summarized as below:
(1) The longitudinal and hoop strains of base metal in the cylinder are very uniform, and the stress values match well with the thick-walled theoretical values. However, the strains of girth and longitudinal welds vary with location. The strains decrease from lower head to upper head, and have the same trend with the circumference deformation variation. (2) The longitudinal and hoop stresses near the centerline of cylinder middle longitudinal weld are much lower than the stresses at other locations. This indicates the possibility of compressive residual stresses at both longitudinal and cir-cumferential directions. (3) The principal stresses of symmetrical locations in upper head welds vary a lot. There is possibility that the weld thick-ness is not uniform along the weld circumference. Also, residual stresses may have contribution to this phenomenon. The principal stresses of symmetrical locations in the surge line nozzle weld agree well. It indicates a good geometric uniformity of this weld. (4) The maximum general primary membrane stress is at the spray nozzle weld in upper head. The stress value is lower than the allowable value. So the structural integrity is maintained at the highest hydrostatic test pressure. The fatigue usage factor is far less than one, which indicates that a single hydrostatic test cycle has little effect on the total pressurizer fatigue life
” Excerpted from “Strain test and stress intensity assessment of a CPR1000 Nuclear Power Plant pressurizer during pre-delivery hydrostatic test“, Case Studies in Structural Engineering, Lin Lei, Xu Decheng, Yu Min, Xue Fei, Jiang Jiawang, Zhang Guodong, Zhao Wensheng, Suzhou Nuclear Power Research Institute, Suzhou, China http://dx.doi.org/10.1016/j.csse.2014.09.002 2214-3998/ Copyright 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/3.0/, emphasis our own).


From the California Code: “Updated 2015 Boilers and Pressure Vessels Act Cap. B-5 Regulations“, p. 22-23 “7.03 The hydrostatic or pneumatic testing of boilers, pressure vessels or pressure piping shall be carried out in accordance with the following procedures ….. (e) for hydrostatic testing, the pressure component shall be completely filled with water or a liquid having a viscosity similar to water and pressure shall be gauged at the top of the pressure component and applied in accordance with these regulations; (f) a pressure component has passed the hydrostatic or pneumatic test if it has retained the applicable test pressure for at least thirty minutes without leakage, undue distortion, excessive permanent expansion or evidence of impending failure. (EC234/85)http://www.gov.pe.ca/law/regulations/pdf/B&05G.pdf

Scandalously, ASME codes must be bought for a fortune, even though it is based on volunteerism. They clearly don’t want people to access their recommendations “American Society of Mechanical Engineers Section III Rules for Construction of Nuclear Facility Components” Shame on them!