Chinese reactor design evolution

The growth of nuclear power in China has been characterised by the evolution of several domestic and imported reactor designs.

Today, there are 20 reactors in operation: two pressurised heavy water reactors (PHWRs) and 18 pressurised water reactors (PWRs). A further 28 units are under construction. The mainstay of the Chinese reactor programme has been and remains the PWR. There are a number of different Chinese-developed PWR models under construction, with more advanced versions in the design stage. Click here for a table showing the different characteristics of the Chinese PWRs under development.

“The current mix of nuclear technology in China is not based on any particular decision," said Huang Wei, minister counsellor and alternate to the resident representative at the Chinese Permanent Mission to the International Atomic Energy Agency (IAEA) in a recent interview with the agency.

“Due to some historic reasons, such as financing, bilateral cooperation and others, different nuclear technologies from France, Russia, Canada and the USA were introduced in the past decades," he explains.

In addition to its PWR construction programme, China is building a demonstration high temperature gas cooled reactor, the HTR-PM. While the first HTR-PM project only began construction in late 2012, the design should be considered a serious future contender given that it has big investment by China Huaneng Group, which is one of the largest listed power producers in China and wants to develop nuclear power. It is also significant that Shidaowan in Shandong province, the site of the first HTR-PM, is set to become a major nuclear centre, showcasing the latest Chinese reactor technology. This will include the first Chinese evolution of the Westinghouse AP1000 - the CAP1400 - which is scheduled for first concrete this year.

The development of Chinese reactor design has a consistent strategy: China has imported a reactor design, learned from it and then used its own and international experience and feedback to improve its own 'domestic' reactor technology. “Cross-fertilization of reactor technology concepts between the imported designs and local designs is still happening today," say Jonathan Hinze and Yun Zhou of Ux Consulting.

The big three nuclear developers in China

There are three authorised nuclear power plant developers in China. They are:

• China General Nuclear Corporation (CGN)
• China National Nuclear Corporation (CNNC)
• China Power Investment Corporation (CPIC).

These developers are licensed to invest as controlling shareholders and operate nuclear power plants in China. Any other public or private companies are to have minority shares in new Chinese nuclear projects.

Could China Huaneng Group join these three? In 2012 it began work on the HTR-PM demonstration project in partnership with China Nuclear Engineering Group (CNEG) and the Institute of Nuclear & New Energy Technology (INET) at Tsinghua University. However this is considered a research programme, and despite holding a majority stake in the project Huaneng is still not licensed to invest in and operate nuclear power plants.

China Huaneng Group was split off from the State Power Corporation in 2002, along with China Datang Corp., Huadian Power International and China Guodian Corp. Like Huaneng, each of these have minority shares in projects under construction and development.

In addition to these developers, China's State Nuclear Power Technology Corporation (SNPTC) was founded in 2007 as the national body responsible for transfer of generation III nuclear power technology into China. SNPTC is responsible for engineering design and project management, and formation of a Chinese brand of nuclear power technology via 'digestion, absorption and re-innovation of the imported advanced technology' (currently the Westinghouse AP1000).

China General Nuclear Corporation (CGN)

CGN is responsible for over half of China's nuclear programme. It was founded in 1994 as China Guangdong Nuclear Power Holding Corporation (CGNPC) but changed its name to China General Nuclear Corporation in April 2013 as a reflection that its operations extend beyond Guangdong Province. However, as would be expected, CGN still retains some priority within that region.

The company now has 11 reactors in operation (10.5 GW) and 13 under construction (16.6 GW). It is not solely a nuclear company. CGN's core business is defined as the development of clean energy projects, which include solar, wind and hydro as well as nuclear. The company has capabilities in engineering, construction, operation & maintenance of nuclear power plants, as well as nuclear technical services and industrial products divisions. Its research and development is focused on nuclear safety, construction, equipment and nuclear fuel.

All of CGN's reactors are based on French technology. Most have evolved from the first 900 MWe units that were exported by Framatome in the 1980s for Daya Bay. The CPR-1000 design is described as a 'significantly upgraded version' of those first M310 units, which were based on Gravelines 5&6 in France. Fifteen CPR-1000 units are currently under construction at six different sites in China.

CPR-1000

A 1086 MWe capacity, three-loop PWR, the CPR-1000 has a design life that could extend beyond 40 years as a result of efforts to reduce impurities (such as copper, sulphur and phosphorous) in the reactor pressure vessel (RPV) material. Other changes to the original M310 design include eliminating a welded joint in the RPV, which shortens production time and eliminates the need to inspect the weld during operation.

The CPR-1000 reactor core comprises 157 fuel assemblies (active length 12ft), enriched to 4.5% U-235. The fuel assembly design is AREVA's 17x17 AFA 3G M5, which can be fabricated in China. The CPR-1000 operates on an 18-month fuel cycle. It has a digital instrumentation and control system, and is equipped with hydrogen recombiners and containment spray pumps.

The CPR-1000 has evolved rapidly over the last few years and a more advanced version, the ACPR1000, is now under construction at CGN's Yangjiang site in western Guangdong. Yangjiang 1-4 are CPR-1000s (unit 1 is now in operation and unit 2 is expected to enter service this year). Units 5&6, which started construction in 2013, are the first of the ACPR1000 designs.

“Yangjiang itself may become a nice showpiece of evolving Chinese reactor designs," says Steve Kidd, senior partner at East Cliff Consulting.

ACPR1000

The ACPR1000 design has ten major technical improvements over its predecessor the CPR-1000, according to CGN, among them greater capacity, simplified reactor chemical and volume control system, optimized distributed control system, enhanced mitigation capacity of nuclear steam supply system, longer design life and improved resistance to external events.

The core of the ACPR1000 comprises 157 fuel assemblies (active length 14ft). In-core instrumentation is inserted from the top of the RPV. In the nuclear steam supply system the steam generator's heat transfer area is 28% bigger than that of CPR-1000 and the pressurizer cavity has been increased by 26%. A metal core reflector will extend the reactor vessel design life to 60 years.

The advanced design has three independent safety systems with full physical separation, a low-pressure safety injection system in combination with a residual heat removal system and an in-containment refuelling water storage tank. The design also has improved seismic capability (0.3g compared with 0.2g).

Severe accident management measures include passive autocatalytic hydrogen recombiners, and a core catcher. Unlike the CPR-1000, the ACPR1000 has a double containment that is capable of withstanding large commercial aircraft impacts.

In parallel with its own line of reactors, CGN is majority partner in a project to build 2x1750MW AREVA EPR reactors at the Taishan site in Guangdong province, with EDF (30%) and Yudean Group (19%).

China National Nuclear Corporation (CNNC)

State-owned China National Nuclear Corporation (CNNC), whose primary territory is mainly on the east coast near Shanghai and Zhejiang Province, has led the development of a line of reactor technology named CNP. In the past CNNC has also imported reactors from Canada (CANDU 6) at Qinshan III. It also operates two VVER-1000 reactors at Tianwan, and is developing two more at the same site.

The company's reactor development started in the 1970s when the Shanghai Nuclear Engineering Research and Design Institute (SNERDI), part of CNNC, began work to develop a small indigenous reactor based on a submarine reactor. The result was the 300 MW single-loop CNP-300 PWR, which was first built at Qinshan 1 (start-up in 1991). The most recent CNNC reactor design to enter operation is the CNP-600, a 650 MW two-loop PWR.

CNP-600 and ACP-600

Classified as a generation II reactor design, the CNP-600 reactor has a single containment, 40-year design life and operates on a 12-month fuel cycle. CNP-600 was also based on Daya Bay's M310 design, but with just two loops it was downsized to two-thirds the capacity. The CNP-600 has more severe accident protection than its predecessor.

The first CNP-600 reactor began operation at Qinshan II-1 in 2002, and the most recent startup was Qinshan II-4 in December 2011.

Changjiang 1 and 2 are the only two CNP-600s under construction. However, CNNC is developing an advanced version of the design, named the ACP-600, which will have double containment, active and passive safety systems, improved response capability in the case of a station blackout event, digital instrumentation and control, and a 60-year design life. The core of the ACP-600 reactor will also contains 121 fuel assemblies, but will be designed to operate on a longer 18-24 month fuel cycle.

ACP-1000

CNNC's main CNP development is a three-loop 1000 MW version of the design designated CNP-1000. It began work on this in the 1990s with the help of vendors Westinghouse and Framatome (now AREVA).

The first CNP-1000 units were due to be built at Fangjiashan (the same site as Qinshan). However, the design was subsequently changed to a CPR-1000. CNNC's focus, meanwhile, switched to development of a more advanced generation III version of the CNP-1000, the ACP-1000. In 2013, China announced that it had independently developed this three-loop PWR, with Chinese authorities claiming full intellectual property rights over the design. China's current aim is to only build generation III and generation IV projects after 2015.

Like its smaller cousin, the 1100 MW ACP-1000 reactor is an advanced PWR with double containment and an expected 60-year design life. The reactor core comprises 177 fuel assemblies (12ft active length), and is designed to operate on an 18-month refuelling cycle for economic competitiveness. The ACP-1000 has active and passive safety systems for emergency core cooling, core residual heat removal and containment heat removal which are said to give it a maximum core damage frequency of 10^-6 per year.

In December 2013, China signed an agreement with the IAEA for a Generic Reactor Safety Review (GRSR) for the ACP-1000 design. The GRSR process reviews the completely- or partially-developed safety cases of new reactor designs that are not yet in the licensing stage. It involves checking the status of the documentation for completeness and comprehensiveness against IAEA Safety Standards. IAEA says the GRSR process typically takes about six months from submission of the design safety documentation to the final report to the requesting party. As the GRSR reports can contain proprietary information they are not made publicly available.

CNNC had planned two ACP-1000 units on at Fuqing 5&6 in Fujian province. However it is now thought that the newer ACC1000 design (see below) will be built there instead.

That means CNNC's first ACP-1000 could be exported, as it is planned for Pakistan's Karachi Coastal Nuclear Power Project.

Joint offering: the ACC1000

CGN and CNNC are working together in a 50:50 partnership on a third-generation nuclear power plant, which they claim will have independent intellectual property rights.

This 1150 MW design will combine the ACPR1000 (CGN) and ACP-1000 (CNNC) designs. It is currently being referred to as ACC1000 or Hualong-1000.

Little technical information is available, but it is believed the ACC1000 reactor core will be based on the core of CNNC's ACP-1000 reactor design, with 177 fuel assemblies (active length 12 ft). The ACC1000 will have an extended refuelling cycle (likely 18-24 months); an extended design life; high availability and reduced construction cost. Some analysts think there will be two different versions of the ACC1000 design, depending on the lead developer of the project.

According to CGN a demonstration project is planned for Fangchenggang phase II. In addition, it might be chosen for Fuqing 5&6.

SNPTC: AP1000 to CAP1000

State Nuclear Power Technology Corporation (SNPTC) is the national body responsible for transfer of generation III nuclear power technology into China. SNPTC is majority-owned (60%) by the State Council. CNNC, CPI, CGNPC and China National Technical Import & Export Corp. each hold a 10% stake. Since its inception in 2007, SNPTC has included the Shanghai Nuclear Engineering Research and Design Institute (SNERDI)-formerly part of CNNC-as a research and development arm.

The Westinghouse AP1000 is the main basis of China's move to generation III technology, with four reactors currently under construction at Sanmen and Haiyang for CNNC and CPI, respectively. SNPTC is responsible for the engineering, design and project management of these first AP1000 projects, which are being built as part of a technology-transfer agreement with Westinghouse.

As part of the agreement, the Chinese supply chain takes an increasingly large share of reactor construction. The next eight units (so-called CAP1000s) will involve higher local content (the aim is for 80%), although they will still contain some critical components from Westinghouse, including digital control systems, fuel and reactor internals. The AP1000 design has also undergone post-Fukushima enhancements, including addition of waterproof doors, 72-hour water supply, enhanced spent fuel pool level monitoring instruments, an improved emergency command centre and incorporation of full-scope severe accident management guidelines.

SNPTC is also leading the development of the Chinese evolution of the AP1000, dubbed the CAP1400. Agreements with Westinghouse stipulate that SNPTC will own the intellectual property rights for any derivatives over 1350 MWe, according to the World Nuclear Association.

Conceptual design of the CAP1400, a 1530 MWe two-loop advanced PWR was completed in 2010, with the basic design completed in 2011. In January 2014, SNPTC announced that the technology had passed a design review by the China National Energy Administration, and that the key parameters of CAP1400 had been "fixed and approved" by the state. The construction design was 60% complete as of January 2014.

Site preparation works for the first CAP1400 demonstration project began in March 2013, and first nuclear concrete is expected this year (April 2014) at the Shidaowan site in Rongcheng, Shandong Province. SNPTC chairman Wang Binghua said in September 2013 that drawings would be 75% completed by first nuclear concrete. Grid connection is anticipated in 2018. Some 80% of the components for the demonstration project are expected to be made in China.

The CAP1400 design will have a larger core than the AP1000, with 193 fuel assemblies rather than 157. The fuel assembly design will either be the AP1000 Robust Fuel Assembly (RFA), or a new Chinese-developed design.

Beyond the CAP1400, SNPTC is conducting preliminary R&D for a larger three-loop PWR (CAP1700), with a further demonstration project also planned for the Shidaowan site. Plans also envisage other 'CAP' designs, potentially a CAP2100, if the passive cooling system can be scaled-up and an 150 MW integral PWR, CAP150, if the passive cooling system can be scaled-down.

HTR development

China's quest for a high-temperature reactor (HTR) began in the 1970s with fundamental research into the technology. Construction of a 10 MW high-temperature gas cooled reactor (HTR-10) was approved in 1992, and started in 1995. The project achieved first criticality in 2000 and began operation in 2003.

In December 2012, first concrete was poured for the HTR-PM demonstration power plant, a 200 MW commercial demonstration plant based on the HTR-10. The small HTR-PM units with pebble bed fuel and helium coolant are 2x105 MWe reactors, so that they can retain the same core configuration as the prototype HTR-10. The twin units, each with a single steam generator, will drive a single steam turbine.

The HTR-PM project is being managed by Huaneng Shidaowan Nuclear Power Co. Ltd (HSNPC), which comprises China Huaneng Group (via subsidiary Huaneng Nuclear Power Development Co, 47.5%), China Nuclear Engineering Group (32.5%), and Tsinghua University (20%).

As of the end of 2013, the civil work for the underground part of nuclear island buildings had been completed. The main components, including reactor pressure vessels, core internals and steam generators are being fabricated by domestic manufacturers. A fuel factory that will supply 300,000 fuel elements each year to the HTR-PM is also being built in northern China. According to the project schedule HTR-PM is expected to be commissioned in 2017.

China's future choice of nuclear technology?

What is the plan for future nuclear power development in China, and what will be the technology of choice?

Following the Fukushima accident and the release of the Chinese nuclear safety plan, China will build "a few" Gen II+ projects between now and 2015, says Yun Zhou of Ux Consulting. These are projects that were either already under construction, or are paired with existing units.

After 2015, China aims to only build Gen III and Gen IV projects. "Currently, officially, the National Energy Bureau only supports AP1000 as the only Gen III model to mass-produce and CAP1400 as the only Gen III model to export. However, of course the government will not oppose other models to develop and export, if any. China is developing its own Gen III ACC1000, which could serve as a supplement for both domestic and exporting uses," she adds. (The CAP1400 has been chosen for export because the Chinese claim it has 100% Chinese intellectual property.)

Steve Kidd agrees. "AP1000s are expected to constitute the main part of the Chinese domestic programme (for now at least). The other mainstay of the Chinese programme will be the ACC1000, which is the outcome of the battle between CNNC and CGN for the Chinese Gen III-qualified 1000 MW unit."

As the ACC1000 design is derived in part from the French M310s at Daya Bay and Ling Ao Phase I, it is believed that it cannot be exported due to French intellectual property concerns. But Kidd says the ACC1000 is expected to remain very important within China, and can be built far more cheaply than the AP1000 until the latter's localisation rate is much higher.

With respect to Chinese high-temperature reactor (HTR) technology, the goal is eventually to export the HTR-PM design with independent IP rights. However, since existing Gen III reactor lifetimes could be as long as 60 years, the HTR will be at most a supplement to the domestic market in the next several decades.

China is investing in small modular reactor R&D programmes in order to be prepared for a potential international market. However, the nature of China's electricity demands and geography mean SMRs will not play a significant role in China in the near future.

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