China's HTR-PM demonstrates inherent safety

Industry Discussions Nuclear Power
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One of China’s newest nuclear facilities is the HTR-PM pebble bed plant at Shidao Bay. Two gas-cooled reactors of 250 MW (thermal) capacity produce steam that drives a single common steam turbine/generator.

Last year, a series of tests took place to demonstrate the inherent passive safety of the pebble bed design. With one of the reactors at 200 MWt, the reactor coolant flow was intentionally turned off. The passive safety systems then demonstrated the ability to keep the reactor temperature well below any dangerous level.

I can’t find a free detailed description of these tests, but the following links provide some information.

The following scientific papers also provide a little more insight.

https://www.cell.com/joule/abstract/S2542-4351(24)00290-3

From the link:
Two safety tests were conducted on the two reactor modules of the HTR-PM plant, each at a power of 200 MWt. During the tests, the active power supply was totally switched off to see if the decay heat can be removed passively. The responses of nuclear power and temperatures within different reactor structures show that the reactors can be cooled down naturally without active intervention. The results of the tests manifest the existence of commercial-scale inherent safety for the first time.

Another source here:
https://www.sciencedirect.com/science/article/abs/pii/S2542435124002903

The first test began at 9:16 a.m. August 13, 2023. Before the test, #1 and #2 modules operated at the power levels of 200 and about 5 MWt, respectively. The test was started by switching off the power supply of the primary helium circulator and feed-water pump. As a result, the reactor protection system was activated, triggering the emergency shutdown signal that induced the dropping of control rods.

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The pebble-type TRISO fuel used in the HTR-PM is much different than that used in water-cooled nuclear plants. The pebbles consist of layers of uranium, graphite and silicon carbide that produce a very stable structure, and can also withstand very high temperatures. The reactor core actually has a rather low power density, which is also an advantage during accident conditions.

  • Pete
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Here in the US, efforts are underway to begin making TRISO pebble fuel on a large scale, as well as the power reactors to use the fuel.

In 2022, construction started on a TRISO fuel fabrication facility in Tennessee. The company that will own and run the facility is X-Energy, which will also produce the power plants.

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More recently, X-Energy was awarded a federal tax credit for construction of (evidently) a different TRISO fabrication plant, also in Oak Ridge, Tennessee.

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DOW Chemical intends to install an X-Energy pebble bed plant at its chemical facility in Seadrift, Texas. Since the XE-100 is a high temperature reactor, it is capable of producing higher temperature steam that is often required for chemical manufacturing operations.

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There is still much work to do, since the X-Energy reactor design is not yet licensed by the NRC. However, it continues to look like plans are progressing.

_Pete

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What are the for cost and schdule numbers? Will it be ready to give firm cost and schedule by 2040? Will it start construction by 2040?

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When the DOW project was announced in 2023, they said construction will begin in 2026.

I have my doubts the 2026 date is still good, but if X-Energy and the NRC can get it licensed, it shouldn’t be too much later.

As for cost, since DOW Chemical plans to use these reactors for heat, at least partially, costs cannot be directly compared with a pure electric power plant.

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Another X-Energy project in the planning stages is with Energy Northwest at the Hanford reservation. The quoted cost for 320 MWe is $2.4 billion. This comes to $7500 per kw, which is not exorbitantly high. I figure the LCOE cost, assuming operation and maintenance costs similar to a light water plant, would be around 7 cents per kwh.

_Pete