China's Yanlong: a small nuclear reactor strictly for district heating

Post by CompelTechnic » Wed, Dec 20, 2017, 5:03 PM UTC

sandworm101 wrote: post #6

>> around the same volume as an Olympic swimming pool. >> with each 400-megawatt unit capable of warming 200,000 urban households. >> with temperatures not exceeding 100 degrees Celsius, Think about that for a minute. If the water isn't going to exceed 100c but the reactor is still going to pump out 400-megawatts, it isn't going to be a calm pool. They are going to have to pump insane amounts of water in and out of t…

Post by vilhelm_s » Wed, Dec 20, 2017, 5:12 PM UTC

Symmetry wrote: post #16

adrianN wrote: post #9

Earlier quoted context omitted.

It is possible to regulate the output of a nuclear reactor. In case the pool boils off in some freak accident, the chain reaction also stops, because water is acting as a neutron moderator in these designs. So you only have to ensure that the residual heat from normal decay doesn't melt the reactor. That doesn't sound too hard.

Isn't the residual heat from normal decay something like 10% of the reactor output? When you split Uranium you get a lot of byproducts with short half-lives that continue decaying away even when Uranium chain reaction stops. So you've still got 40 MW to deal with, at least until those short-half-lived byproducts finish decaying.

Post by vilhelm_s » Wed, Dec 20, 2017, 5:22 PM UTC

sandworm101 wrote: post #11

adrianN wrote: post #9

Earlier quoted context omitted.

It is possible to regulate the output of a nuclear reactor. In case the pool boils off in some freak accident, the chain reaction also stops, because water is acting as a neutron moderator in these designs. So you only have to ensure that the residual heat from normal decay doesn't melt the reactor. That doesn't sound too hard.

>> you only have to ensure that the residual heat from normal decay doesn't melt the reactor. Not hard if this is a passive-cooling design. My point is that at these power levels passive cooling isn't enough. Stop the pumps and the reactor may build up enough heat to start melting things very quickly, long before the pool boils dry.

Post by seanmcdirmid » Wed, Dec 20, 2017, 5:35 PM UTC

jobu wrote: post #20

xbmcuser wrote: post #18

Stuff like this makes me feel western countries really underestimate Chinese tech chops. They are able to force stuff on the people that most countries have to cajole and negotiate with their citizens. I get cognitive dissonance from the fact that China is doing it's best to decrease coal usage where as US is tried to increase coal usage.

China has been run by technocrats for the last couple decades. Most of the current leadership has more of a political background, but president Xi Jinping has a chemical engineering degree. http://www.scmp.com/news/china/policies-politics/article/211... "from 1997 to 2007, all of the top leaders sitting on the innermost Standing Committee shared an engineering background"

Post by jjoonathan » Wed, Dec 20, 2017, 5:38 PM UTC

Retric wrote: post #22

Seems like a much more expensive option than solar hot water heaters. It's $226.7 million for 400MW and "Each 400-MW unit can heat 200,000 homes" so ~1,133$ per home where basic models are selling in Asia for under US$250. They mention it's going to be plugged into existing heating networks, but temperature of 100C is not all that hot.