China considers transforming coal-fired plants into HTGR NPPs

30 November 2016

From 2018, China could begin transforming some coal-fired power plants into NPPs, Professor Zhang Zuoyi, Director of China’s Institute of Nuclear and New Energy Technologies (INET), told the recent High Temperature Reactor 2016 (HTR2016) conference, held in Las Vegas. He outlined the current status of the HTR-PM project, which is aimed at demonstrating the feasibility of high-temperature gas cooled reactors (HTGRs). Under the proposed a plan, China could remove the furnaces and boilers from its 600MWe super-critical coal plants and replacing them with HTGRs. Only super-critical steam plants could withstand the high operating temperatures HTGRs require.

The deployment programme with two first of a kind commercial demonstration units is approaching construction completion and commercial operation by mid to late 2018, Zhang said. Major parts of the machinery will be able to be merged into the existing infrastructure. The commercial operation date is six to nine months later than scheduled Zhang noted but added that the first-of-a-kind delays were much shorter than the 3-4 year delays that have plagued the EPR and AP1000 construction projects in China.

The current focus is on 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.

The project has not been without its difficulties. Zhang said the development effort included building four different prototypes for the helium circulators. The primary design included magnetic bearings, but because they were above the size limits of proven uses of magnetic bearings some fall back designs were prepared to avoid problems which might arise from failure to deliver on a single component. Lifting the 600t reactor pressure vessels exceeded the weight limit of previously existing capabilities, and new methods had to be found.

As operational experience is gained with the first two units more reactors will be built and installed in configurations of six to 12 providing steam to a single steam turbine. Experience gained during construction of the lead units means that the plant footprint can be reduced by about 50% by arranging the reactors in circles with three in each circle instead of lining them up.

While some reactor installations will be part of entirely new power stations, others will be used to adapt the 600MWe steam plants that currently use coal as fuel. These installations will be able to take advantage of the switchyards, the installed transmission networks, the cooling water systems, the sites, and possibly the steam plant including the steam turbine. The first adaptations will be at power plants in areas with major pollution problems, often located very close to population centres, making safety a key priority. The HTR-PM modules can withstand complete loss of pressurisation and helium flow without a forced shutdown and still not release radioactive materials in excess of the current stringent dose limits.

The overall cost of the HTR-PM will be around $5000.00/kw of capacity, Zhang said. The final estimate is based on signed and mostly executed contracts and is about twice the initially expected cost. He noted that 35% of the increased cost could be attributed to higher material and component costs than initially budgeted, 31% of the increase was due to increases in labour costs and the rest to project delays. However, new techniques are expected to reduce costs in future to $2,000 to $2,500/kw capacity.

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