Will China convert existing coal plants to nuclear using HTR-PM reactors?
It would be a huge benefit to the earth’s atmosphere if China, India, Brazil and the US could reduce direct coal burning while still making use of much of the capital that they have invested in building coal fired power plants. It would make an even larger difference in reducing air pollution in the areas downwind of the coal stations.
Converting coal-burning supercritical steam plants to nuclear power plants by replacing the furnaces and boilers with high temperature gas cooled reactors might become a routine power plant improvement in the relatively near future. The High Temperature Reactor – Power Module (HTR-PM) project is aimed at demonstrating the feasibility of this evolutionary concept.
At the recent High Temperature Reactor 2016 (HTR2016), held in Las Vegas, NV, Prof. Zhang Zuoyi, Director of China’s Institute of Nuclear and New Energy Technologies (INET), briefed his colleagues in the international community of high temperature gas reactor enthusiasts on the current status of the HTR-PM. That project is one of the more intriguing clean air projects underway in the world today.
The end of Zhang Zuoyi’s brief resulted in a sustained round of clapping; there were even a few hoots from the attending scientists and engineers that would have been more expected at a football match. (Most attendees at this talk were not from the US, the word “match” is intentional.)
Some of the audience members were able to trace their involvement and excitement about HTRs back more than 40 years to hands-on experience in the construction and operation of the Peach Bottom 1 nuclear plant, a project that was planned, constructed and operated in the US during the period from 1958 – 1978. The attendees were nearly unanimous in their appreciation of the fact that someone, somewhere was building commercial plants using the technology they had been working on for so long.
Target Market
China’s HTR-PM project is squarely aimed at being a cost-effective solution that will virtually eliminate air pollution and CO2 production from selected units of China’s large installed base of modern 600 MWe supercritical coal plants.
This is not a “pie-in-the-sky” long range plan to eventually replace those built facilities and leave idle capital rotting away. Instead, it is a deployment program with the first of a kind commercial demonstration approaching construction completion and commercial operation by mid to late 2018. Major parts of the machinery will be able to be merged into the existing infrastructure.
Schedule
The commercial operation date is six to nine months later than scheduled when construction began, but Prof. Zhang Zuoyi proudly explained that the HTR-PM first-of-a-kind delays were much shorter than the 3-4 year delays that have plagued the EPR and AP1000 construction projects in their country.
The current critical path item is the completion of the steam generators — one for each of the two reactors. The shells and internals have been completed, but the final stages of attaching the piping to the thick-walled, large diameter pressure vessels will delay site delivery until sometime close to the middle of 2017.
Development Challenges
Zhang Zuoyi gave an excellent overview of the design and testing challenges that the project has faced and overcome. Nearly every item on the list of critical steps for design and testing had been completed.
For example, the development effort included building four different prototypes for the helium circulators. The primary design included magnetic bearings, but the developers knew that they were well past the size limits of proven uses of magnetic bearings so they had a couple of fall back designs. They did not want the project to fail because of failure to deliver on a single component.
In another example, the reactor pressure vessels weigh in at 600 tons, making the act of installing them a very heavy lift that exceeded previously existing capabilities.
The learning that has been gained during the challenging task of construction and component manufacturing and the learning that will be gained during the operation of a plant that uses two nuclear heated boilers to power a single steam turbine will form a solid foundation for the next step.
As operational experience is gained with the first unit, the developers will be building more boilers and installing them in configurations of six to twelve boilers providing steam to a single steam turbine.
One of the items that was learned during construction of the lead unit was that the plant footprint could be reduced by about 50% by arranging the boilers in circles with three boilers in each circle instead of lining them all up side by side.
Increasing Value Of Existing Infrastructure
In some cases, these nuclear boiler installations will be part of entirely new power stations. The more intriguing aspect of the concept, however, is the fact that the high temperature atomic boilers produce steam conditions that are identical to the design conditions for a large series of modern, 600 MWe steam plants that currently use coal as the heat source.
During the question and answer period, Prof. Zhang Zuoyi responded to my questions by confirming that some of the pebble-bed atomic boilers will be installed as replacement heat sources for existing steam plants. Those installations will be able to take advantage of the switchyards, the installed transmission networks, the cooling water systems, the sites and in some cases the entire steam plant including the steam turbine.
The priority for replacing coal boilers with nuclear boilers will be at power plants in areas with major pollution problems. Those plants are often located very close to population centers; that reality is one of the reasons that China has invested in developing reactors that can be tested and proven to be safe.
The HTR-PM modules can withstand complete loss of pressurization and helium flow without a forced shutdown and still not release enough radioactive materials to exceed the very conservative dose limits in place today.
Cost And Value
The overall cost of this first of a kind nuclear plant will be in the neighborhood of $5000.00/kw of capacity. That number is based on signed and mostly executed contracts, not early estimates. It is about twice the initially expected cost. According to Zhang Zuoyi, 35% of the increased cost could be attributed to higher material and component costs that initially budgeted, 31% of the increase was due to increases in labor costs — which Zhang Zuoyi noted were rising rapidly in China — and the remainder due to the increased costs associated with the project delays.
Zhang Zuoyi described the techniques that will be applied to lower the costs; he expects them to soon approach the $2,000 to $2,500 / kw capacity range.
The value proposition of these clean replacement boilers, however, will be more than just economical electricity. The real payoff will be the ability to enjoy the fruits of economic development without as much difficulty in merely taking a breath.
Rod,
Can you elaborate on the techniques / ideas that Prof. Zhang Zuoyi has to cut the cost in half and how long it will take to achieve that cost reduction? For the sake of comparison, did he happen to mention the cost of power production in China (so we could make a statement such as “the 2000-2500 $/kw of capacity using a HTR-PM is X times the cost of capacity for the coal unit it is replacing”)?
@RTK42C
Prof. Zhang Zuoyi is no longer an academic who freely shares everything he knows. He is now a businessman who understands that some information is too valuable to share for free. Specific costs, supply chain details and cost reduction strategies are among the closest hold topics for commercial enterprises.
Well, seeing as he *did* give out that specific cost for the first-of-a-kind build, it seems like that should at least be possible to compare to the costs for coal in China? Or are the coal costs closely guarded secreets?
A few years ago, I found article an article titled, “Economic potential of modular reactor nuclear power
plants based on the Chinese HTR-PM project”, with Zuoyi Zhang as a co-author. The paper can still be found on line and might be behind a paywall now, but I still have the full text.
In that paper, their FOAK estimates are over twice that of a series built PWR, with the target dropping to about parity. The main cost driver for the FOAK are the pressure vessel, reactor internals, and steam supply equipment. In my opinion, their plan for dropping that cost is through economy of scale of those parts.
While this won’t save jobs in coal mining and transportation, this could save some jobs at coal power plants. I have an uncle who recently retired from working at a coal plant, and I know there was concern within the power industry at lost jobs from closing coal plants.
Granted, it’s probably going to require retraining much of the staff, because nuclear technology is a bit different than coal, but these conversions could allow a lot of power plant jobs to be retained, seems like.
That would probably be welcome news to some people.
Rod,
I note the potential for hydrogen production to change the greenhouse gas emissions and global warming causation of existing steel production with this technology. Please refer to a very good paper by Viktor Sivertsson from Uppsala University on Hydrogen production using high temperature nuclear reactors A feasibility study. In this article he compares the benefits of technologies such as high temperature electrolysis with sulphur – iodine
I think you are on to something. It seems like a natural that process heat for industries should quickly follow once the Chinese begin building these things. I also wonder if the plants can receive uprates. Will it be possible to run the hot gas produced by the reactor through a Brayton cycle turbine with the hot exhaust gas then used in a steam generator like a natural gas cogen.
Necessity is the mother of invention and the Chinese have the necessity to clean up their air.
An alternative is a 12-pack of the forthcoming Nuscale modules @ 50 MWe apiece. Cannot reuse the steam equipment but can use the existing electrical equipment at the site. The estimated price is the same, US $5/W, and the estimated total time to mechanical completion is but 51 months from licensing.
These PBMRs are reminiscent of the British AGRs, which were likewise graphite moderated, gas cooled, ran at about 600 C, and were built in pairs to give coal-quality steam. Both types are too large to qualify as Small Modular Reactors. Hence maybe the decision to place them in circles, not in rows – a few of the SMR designs have a row of reactors all under one gantry crane, but these things are too big for that.
The AGRs get about 30% better thermal efficiency than light water reactors, but have a lower burnup on the fuel. They were also designed to be refueled at full power, which proved troublesome because of vibrations in the fuel assemblies. The German pebble bed reactor prototype had refueling problems too, with pebbles sticking in the chute. Hopefully the Chinese have sorted this out, so they might get a higher capacity factor than light water reactors, plus perhaps two or three times a LWR’s burnup by recycling pebbles back through.
Did Prof Zhang say what enrichment the fuel will have, and what burnup they are expecting ?
@John ONeill
Yes, the HTRs have evolved from the AGR line of thinking, with design choices intended to address areas where the AGRs had issues. (It’s worth noting that many of the AGR issues have been mitigated; most of them are still operating today, routinely providing about 15% of the UK’s electricity.)
AGR burnup is limited by low enrichment and by material limitations of the fuel assemblies. HTRs have TRISO coated particles designed to vastly improve fuel durability and they use higher fuel enrichments – nominally 9% fissile. (German AVR testing included all possible fissile isotopes.)
The pebble form puts the moderating graphite into the fuel element and avoids many of the problems associated with the monolithic graphite structure cracking and swelling that has limited AGR performance and projected longevity.
Fuel pebble handling systems have been refined and improved over the AVR. They still might have some operational issues, but not show stoppers.
Using these type reactors to “re-power” existing power plant.s for me is where the money will be in the future. As stated in the article the capital has already been sunk for the TG sets turbine hall switch boards transformers etc therefore you are only paying for the steam generators and reactor which even on a LWR may only be 50% of the cost.
As a stand alone new build I struggle to see the economics of gas cooled reactors compared to a LWR plant due to the higher cost of the reactor compared to the LWR otherwise AGR reactor would have been significantly cheaper than a LWR back in the 70’s (in the end costs were probably comparable)
There are substantial savings to be made using conventional steam turbines compared to the low temp wet turbines used on nuclear plants which are generally one off custom built and very expensive in comparison, however this doesn’t tend to make up for the higher reactor cost due to low power density.
Excellent report Rod, very informative as always.
It will be interesting to see if the new U.S. administration takes up the recommendation of the SecE task force report on the future of nuclear energy, with this technology being highlighted ( at least initially ) as one of the most advanced , – along with the sodium fast design.
I also read your brief on who may be appointed as the new SecE , very interesting !
Diarmuid
In the same vein, would it be possible for existing CCGTs to be converted to nuclear air combined cycle (NACC)?
If so, the economics of marrying a MSR to a gas turbine makes even more sense.
https://www.youtube.com/watch?v=2zD0m_ci-oo
@benjamin weenan
Modern CCGT’s operate with turbine inlet temperatures in the range of ~1500 ℃. The highest proposed MSR reactor outlet temperatures that I am aware of are in the range of 700 ℃. Unless you are willing to accept a substantial boost from natural gas combustion to raise turbine inlet temperature to the 1500 ℃ range, you would be better off using MSRs in supercritical steam plants or in old fashioned gas turbines that don’t have exotic materials, blade cooling systems and compressors that produce pressure ratios in the range of 25:1.
Here is a useful article from Power Engineering describing the evolution of high efficiency CCGTs. It includes a discussion about the steps used to increase turbine inlet temperature from ~540 ℃ in the late 1938s to the 1500 ℃ used in CCGTs that approach thermal efficiencies of 60%.
http://www.powerengineeringint.com/articles/print/volume-18/issue-3/features/ccgt-breaking-the-60-per-cent-efficiency-barrier.html
Or you could use a helium gas reactor & turbo-compressor to drive the gas turbine’s air compressor, yielding a ~959 MWe power plant using an advanced gas turbine like a GE 7HA. Yields the cleanest and most efficient fossil power plant ever proposed. All this from a single gas turbine and steam turbine.
This objective of the technology is to significantly improve a gas turbine while using a simplified helium gas reactor (~630 MW thermal). Natural gas or coal gas can be used.
Relative to an existing coal plant, everything but the switchyard and coal handling equipment would have to be junked – would also need a relatively small gasification plant. However, emissions end up being about the same as a natural gas fired gas turbine.
This is a patented US developed technology.
@Mike Keller
Your proposed system seems quite complicated and filled with new components that have to be developed and tested.
Good luck.
The only new item is a helium turbo-compressor, which from a process industry standpoint is pretty straightforward.
Everything else is an adaptation of existing technology.
Also, can provide power using steam turbine without the gas turbine and reactor, which yields a very reliable plant. A bypass stack and forced draft fan are used with the Heat Recovery Steam Generator. Have managed plants like that and we routinely switched back & forth on the fly.
Providing steam to a single turbine using a number of reactors is operationally complicated –also not allowed in the US by NRC regulations.
Also, using a gas reactor to drive an existing coal boiler’s super-critical steam turbine is not a very good fit for a variety of thermodynamic and design reasons. The superheat/reheat conditions do not fit very well with the reactor’s boiler. Better to use a steam turbine designed specifically for the gas reactor.
@Mike Keller
Unlike China, the US doesn’t have a large inventory of nearly new super-critical steam plants whose steam conditions almost exactly match those available from HTR-PM modules.
The HTR-PM is a step towards resolving the “operationally complicated” task of supplying steam to a turbine from multiple passively safe reactors that can be continuously refueled while operating.
I’m not sure why you say regulations in the US would prevent such a system from operating here. Obviously, there are no current regulations covering such a system, but that is true of almost every reactor technology other than light water cooled and moderated systems that are only refinements of currently operating reactors.
As I said before, good luck to you and whatever team you are working with on this project. It seems like a worthy effort that will have plenty of challenges.
Ever wonder why NUSCALE is using one steam turbine per reactor? Could use 2×1 configuration without too much trouble (kind of like what the Chinese are doing). NRC will not allow it – I suspect is a Reg.Guide and possibly the Standard Review Plan item. As near as I can tell, does not appear to be in General Design Criteria. Might be easier just to ask the NUSCALE folks directly.
Operationally, when you string a bunch of boilers together, the various feedwater control and fuel control systems start chasing each other in response to changing steam conditions (transients). Much easier to just go with a 1×1 configuration from a simple operations standpoint.
Ps I vaguely recall Enterprise had several reactors per steam plant. However, Navy is exempt from NRC requirements, thank God.