Researchers advise caution as a commercial-scale nuclear reactor known as HTR-PM prepares to become operational in China


Construction of the Xipu fast neutron reactor nuclear power demonstrative project in east China’s Fujian province is designed to start at the end of 2017, China Business News quoted Xu Mi, an academician with Chinese Academy of Engineering, as saying.

The demonstrative nuclear power project, designed with 600,000kw (600 MWe) installed capacity, will be a fourth generation reactor designs.

The Shanghai newspaper speculated that this newest facility, because of its planned full scale size, will be the long anticipated joint commercial venture between China National Nuclear Corp. and TerraPower, a firm based on Bellevue, WA. Gates has been instrumental in funding the development of a type of fast reactor called a “traveling wave reactor” through TerraPower, a company he founded in 2008 and chairs. Gates has visited China at least three times in recent years for possible cooperation on nuclear power.

On his last trip to Beijing, which took place last February of this year, Gates met with Nur Bekri, a vice chair of China’s National Development and Reform Commission, and with China National Nuclear Corp chairman Sun Qin. China National Nuclear Corp is one of the country’s largest nuclear power company and a major Chinese partner of TerraPower.

The two firms first announced an intent to cooperate on fast reactor designs in 2012.

The Chinese newspaper did not cite a confirmation statement from Terrapower about the Fujian pilot project.

Fast neutron reactors

China’s research and development on fast neutron reactors started in 1964.

A 65 MWt sodium-cooled fast neutron reactor – the Chinese Experimental Fast Reactor (CEFR) – at the China Institute of Atomic Energy (CIAE) near Beijing, started up in July 2010.1 It was built by Russia’s OKBM Afrikantov in collaboration with OKB Gidropress, NIKIET and Kurchatov Institute.

It was grid connected at 40% power (8 MWe net) in July 2011, and ramped up to full 20 MWe power in December, then passed ‘official’ checks in October 2012.

It has negative temperature, power reactivity and sodium void coefficients. Its fuel cycle is designed to use electrometallurgical reprocessing. It is reported to have high-enriched (65%) UO2 fuel.

The CDFR-1000, a 1000 MWe Chinese prototype fast reactor based on the CEFR, was envisaged with construction start in 2017 and commissioning 2023 as the next step in CIAE’s program.

This would be a three-loop 2500 MWt pool-type, use MOX fuel with average 66 GWd/t burn-up, run at 544°C, have breeding ratio 1.2, with 316 core fuel assemblies and 255 blanket ones, and a 40-year life.

This is CIAE’s ‘project one’ Chinese Demonstration Fast Reactor (CDFR). It is to have active and passive shutdown systems and passive decay heat removal.

The reactor would use MOX fuel with average 66 GWd/t burn-up, run at 544°C, have breeding ratio 1.2, with 316 core fuel assemblies and 255 blanket ones.

This could form the basis of the Chinese Commercial Fast Reactor (CCFR) by 2030, using MOX + actinide or metal + actinide fuel. MOX is seen only as an interim fuel, the target arrangement is metal fuel in closed cycle.

However, in October 2009, an agreement was signed by CIAE and China Nuclear Energy Industry Corporation (CNEIC) with Russia’s Atomstroyexport to start pre-project and design works for a commercial nuclear power plant with two BN-800 reactorsc (see section on Sanming in the information page on Nuclear Power in China).

These reactors are referred to by CIAE as ‘project 2’ Chinese Demonstration Fast Reactors (CDFRs), with construction originally to start in 2013 and commissioning 2018-19.

In contrast to the intention in Russia, these would use ceramic MOX fuel pellets.

The project was expected to lead to bilateral cooperation of fuel cycles for fast reactors.

However, according to the Beloyarsk plant Director late in 2014, “The main objective of the BN-800 is [to provide] operating experience and technological solutions that will be applied to the BN-1200,” and no further Russian BN-800 units are planned.

The project is reported to have been suspended indefinitely, though this is unconfirmed.

The CIAE’s CDFR-1000 is expected to be followed by a 1200 MWe China Demonstration Fast Breeder Reactor (CDFBR) by about 2028, conforming to Generation IV criteria.

This will have U-Pu-Zr fuel with 120 GWd/t burn-up and breeding ratio of 1.5 or more, with minor actinide and long-lived fission product recycle.

PWR capacity in China is expected to level off at 200 GWe about 2040, and fast reactors progressively increase from 2020 to at least 200 GWe by 2050 and 1400 GWe by 2100.

CGN and Xiamen University are reported to be cooperating on R and D for the travelling-wave reactor (TWR). The Ministry of Science and Technology, with CNNC and SNPTC, are skeptical of it.

(This is a fast reactor design using natural or depleted uranium packed inside hundreds of hexagonal pillars.

In a ‘wave’ that moves through the core at only one centimetre per year, the U-238 is bred progressively into Pu-239, which is the actual fuel. However, this design has now radically changed to become a standing wave reactor with the fuel shuffled in the core.)

In January 2013 a prototype TWR-P was being discussed as a TerraPower-SNERDI joint project, and in December 2013 a US Federal Register notice said that the USA had negotiated an agreement with China “that would facilitate the joint development of TWR technology”, including standing wave versions of it.


IAEA review of fast reactors in 2015

In Russia, the BN-600 sodium-cooled fast reactor (SFR) has shown an impressive operational performance by reaching an 86% load factor last year, while the Russian light water reactor (LWR) fleet reaches 82% on average. The multipurpose sodium-cooled fast neutron research reactor (MBIR), to be built in Dimitrovgrad, obtained the construction license from the Russian government. The BN-800 SFR will be commissioned at the beginning of 2016.

In India, commissioning of the prototype fast breeder reactor (PFBR) at Kalpakkam is expected to start by the end of September 2015. The China experimental fast reactor (CEFR), which was connected to the grid in 2011, reached 100% power in December 2014. In France, the conceptual design phase for the advanced sodium technological reactor for industrial demonstration (ASTRID) is planned to be completed by the end of 2015. In addition, other participating countries reported promising and progressing activities in FR development.

The reactor is a pebble-bed, high-temperature gas-cooled reactor (HTGR), a new design that is ostensibly safer but that researchers in the U.S. and Germany warn does not eliminate the possibility of a serious accident.

Their commentary, publishing August 23 in the journal Joule, recommends continued research, additional safety measures, and an extended startup phase that would allow for better monitoring.

“There is no reason for any kind of panic, but nuclear technology has risk in any case,” says first author Rainer Moormann, a nuclear safety researcher based in Germany.

“A realistic understanding of those risks is essential, especially for operators, and so we urge caution and a spirit of scientific inquiry in the operation of HTR-PM.”

In addition to generating electrical power more efficiently, pebble-bed HTGRs such as HTR-PM avoid some of the safety challenges that earlier reactor designs faced.

They use graphite- and ceramic-coated grains of uranium fuel that can withstand the core’s very high temperatures and passive cooling systems, which together should eliminate the possibility of a core meltdown.

“Pebble-bed reactors have been described by their supporters as ‘free from catastrophes’ and ‘walk away safe,'” he says.

Risultati immagini per scheme HTR-PM china

What this means in practice, however, is that the soon-to-be-operational HTR-PM has been built without the safeguards that nuclear reactors in operation today are usually equipped with: it does not have a high-pressure, leak-tight containment structure to serve as a backup in case of an accidental release of radioactive material.

It also does not have a redundant active cooling system.

“No reactor is immune to accidents.

The absence of core meltdown accidents does not mean that a dangerous event is not possible,” Moormann says.

He and his coauthors, Scott Kemp and Ju Li of the Massachusetts Institute of Technology, argue that with new technology, there is always a higher chance of user error.

And prototype HTGRs have surprised their operators in the past by forming localized hot spots in the core and unexpectedly high levels of radioactive dust.

The pebble-bed design also produces a larger volume of radioactive waste, which is challenging to store or treat.

Moormann acknowledges the potential of HTGRs and supports further research into them. “HTGR designs with what’s known as a prismatic core seem to be less problematic than the pebble-bed one, so development work should concentrate on that,” he says.

But to reduce risk, he and his colleagues advocate for several precautionary steps, including rigorous, continuous monitoring, the installation of containment and cooling systems, and an extended startup phase to allow the reactor to be observed and monitored as it comes to temperature.

They also recommend investigating more secure long-term storage options for the fuel waste, which currently will be stored in aboveground canisters potentially vulnerable to environmental stresses and terrorism.

“There was already some controversy about pebble-bed HTGRs, but my impression was that many problems of them were not sufficiently published and thus not known to some of my colleagues,” says Moormann.

“I hope that the pros and cons will be broadly discussed.”

More information: Joule, Moormann et al.: “Caution is Necessary in Operating and Managing the Waste of New Pebble-bed Nuclear Reactors”

Provided by Cell Press


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