December 01, 2016

China's plans to begin converting coal plants to walk away safe pebble bed nuclear starting in the 2020s

China’s HTR-PM (high temperature pebble bed nuclear reactor) 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.

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.

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 were overcome

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.

As operational experience is gained with the first unit (where two nuclear reactors feed one steam turbine), the developers will be building more boilers and installing them in configurations of six to twelve boilers providing steam to a single steam turbine.

China will replace coal burners with these high temperature nuclear units

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.



On March 20, 2016, the first of two reactor pressure vessels was installed at the demonstration HTR-PM high-temperature gas-cooled reactor unit under construction at Shidaowan in China's Shandong province. The twin-reactor unit is scheduled to start up next year. The vessel - about 25 meters in height and weighing about 700 tonnes - was manufactured by Shanghai Electric Nuclear Power Equipment. It successfully completed factory acceptance on 29 February and was dispatched from the manufacturing plant on 2 March. The pressure vessel arrived at the Shidaowan site on 10 March, plant owner China Huaneng Group announced the following day.



A proposal to construct two 600 MWe HTR plants - each featuring three twin reactor and turbine units - at Ruijin city in China's Jiangxi province passed a preliminary feasibility review in early 2015. The design of the Ruijin HTRs is based on the smaller Shidaowan demonstration HTR-PM. Construction of the Ruijin reactors is expected to start next year, with grid connection in 2021.



Replacing coal

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.

China started building its first supercritical coal plant in 2001. Construction of a first reference plant was Yaomeng power plant.

China currently has over 900,000MW of coal-fired capacity, the equivalent of about 1,300 large coal-fired units. The actual number of coal plants is more as there are smaller 100, 200 and 300 MW plants as well as 600 MW and 1000MW

Sourcewatch has a list of existing coal plants in China. Most of the coal plants completed after 2007 are supercritical plants. About one third of China's coal power is ultracritical or supercritical plants.



China has another 200,000MW of coal-fired capacity under construction, and a new Greenpeace analysis has identified a further 150,000MW of projects potentially able to enter construction.


Converting to nuclear power for just the burner could be done for 300-400 plants at the cost of about $1.2 billion for each that is about 600MW in size. This could be achievable by about 2040.

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.

SOURCES- Sourcewatch, World Nuclear News, Atomic Insights

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