Not much. This is actually a common reactor type, and you don't have to worry about things like cooling pumps going bad or high-pressure pipe breaks.
> The water acts as neutron moderator, cooling agent and radiation shield. The layer of water directly above the reactor core shields the radiation so completely that operators may work above the reactor safely. This design has two major advantages: the reactor is easily accessible and the whole primary cooling system, i.e. the pool water, is under normal pressure. This avoids the high temperatures and great pressures of nuclear power plants. Pool reactors are used as a source of neutrons and for training, and in rare instances for processing heat but not for electrical generation....Most research reactors are of the pool type.
I think this comment shouldn't be downvoted because it's a common misunderstanding rooted in how unintuitive it is that water is so good at blocking radiation.
> But just to be sure, I got in touch with a friend of mine who works at a research reactor, and asked him what he thought would happen to you if you tried to swim in their radiation containment pool. “In our reactor?” He thought about it for a moment. “You’d die pretty quickly, before reaching the water, from gunshot wounds.”
>> 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 this pool if they want to keep things under 100c. That's fine. Just don't pretend this is going to hum along quietly like a research reactor. And don't tell me thing will remain at 100c should that flow of water be interrupted. Any non-boiling, low-pressure, reactor is going to need exponentially more cooling (by volume) than an equivalent traditional reactor. Let us hope they keep a lake nearby as backup.
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.
Correct me if I'm wrong but isn't the idea of safe pool reactors that hydrogen-neutron heat transfer is more efficient than normal radioisotope-water heat transfer. If you shut down the pumps and heat increases, spectral hardening cools the reactor faster and disperses the energy into larger volume than convection using pumps.
Is that really true? My understanding is that ordinary boiling water reactors contain safety systems that work just by boiling. Reading the wikipedia article[1], the Isolation Condenser, the Automatic Depressurization System, and the Gravity-driven Cooling System all work just by water boiling and with natural convection in the water, without any active pumps, and they are supposedly enough to keep the core from melting.
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.
> The decay heat produced by a reactor shutdown from full power is initially equivalent to about 5 to 6% of the thermal rating of the reactor. This decay heat generation rate diminishes to less than 1% approximately one hour after shutdown. However, even at these low levels, the amount of heat generated requires the continued removal of heat for an appreciable time after shutdown.
At 400 MW it takes about 4 hours to boil the water in an olympic swimming pool[1], so there should be some safety margin for the power to drop. Then once it is down to 1% decay heat it could boil for a couple of weeks before running dry.
No reactor is a calm place. The heat capacity of water changes with pressure, but not by orders of magnitude. So any 400 MW reactor has to pump similar amount of water to keep the T constant.
So the pumps have to be similarly sized, except you no longer need a pressure vessel.
using a specific heat of 4184 J/ kg*°C, those 400 megawatts can heat 1200 kilograms of water from 20°C to 100°C every second. That's a lot of hot water.
You would need a 1 meter diameter pipe flowing at 1.5 meters/sec to supply this.
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.
>> Stuff like this makes me feel western countries really underestimate Chinese tech chops.
The west largely underestimates Chinese tech chops b/c they steal so much of our IP...
Their ability is evident in the number of Ph.D's they turn out, so why don't they invest in developing their own technology instead of stealing everyone else's? "Catching up" is not an acceptable answer with how much intellectual firepower they have.
Because it's easier to 'steal'? Their laws are different so they don't see it as stealing and have no problem with it. Each country is unique and I'm happy US can't force their IP laws to everyone around the world.
It's coined "piggyback economy" where the first move innovator ends up absorbing all the risks in developing the product and getting it to the market. The second mover then simply improves on the original product likely with ton of issues as they have to distribute their resources throughout the full journey the product makes it from the drawing board to the consumer. The market is there and the second mover is able to "catch up" when the product is as good if not better in quality which finally leads to the exit of the first innovator signaling new entrants that will put pressures on the second innovators margins.
Lots of original research in the US is done by Chinese PhDs. Have you not done your research? So is it really stealing? Or the US is taking advantage of the best and brightest from China?
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.
Xi Jinping never practiced as a chemical engineer, however, being an anointed princeling destined for officialdom (and of course, he had to delay his education because of the CR). Hu Jintao and Jiang Zemin are better examples, actually having worked as engineers for a number of years before becoming politicians.
Hard to use princeling in the sense to convey privilege here. His father was sentenced to labor camp during the Cultural Revolution and he himself worked in forced labor for seven years:
"The father was detained and imprisoned and spent 16 years in a labor camp, plunging the family into poverty. During the Cultural Revolution, a 15-year-old Mr. Xi was banished to a poverty-stricken village in northern China where, for seven years, he labored with peasants, eating corn chaff bread and sleeping in a flea-infested bed."
Yes, but he was quickly rehabilitated after Mao’s death, and anyways, everyone was in the same boat.
Xi is the canonical example of his so named “lost generation:” forced to leave high school early, sent down to the country side, rehabilitated and given basically an cursory education as a legacy admit to Tsinghua. He is the first Chinese leader since Mao who can’t speak a word of English, less educated than his predecessors, more autocratic (vs. Hu), less outspoken (vs. Jiang) and more on ideological message.
They have a different perception towards the human life. There's no way anyone would allow this in America because of the potential for catastrophic failures outweigh the benefits.
You have to understand the fundamental difference between the two countries on a cultural and government level. Chinese people are more than happy to submit to the government as in the neo-confucian sense, the state is the provider, the father, the protector. This is what most Koreans thought too during the early days of dictatorship era that brought tremendous economic uplift.
So it's obvious that China would be more daring in areas where the US would not but because they view the cost of human lives differently.
For instance, the leave no man behind, is not unique to the US military but seldom executed because of the sheer logistical and cost-benefit analysis. In any case, you hear routinely hear Russian soldiers being left to die in Chechnya, Crimea, and now Syria.
> There's no way anyone would allow this in America because of the potential for catastrophic failures outweigh the benefits.
The perception of the potential for catastrophic failure outweighs the benefits.
Given it’s an unpressurised rector that doesn’t boil the working fluid the potential for a serious accident is very low compared to a high pressure reactor. It can easily be passively cooled and shutdown heat decay can be handled without much fuss. That’s why most research reactors are of this type.
The problem with nuclear power, and in this case heating, is humans are extraordinarily bad at estimating risk.
Because of the design? None. In fact the Canadian-designed SLOWPOKE reactor (https://en.m.wikipedia.org/wiki/SLOWPOKE_reactor) is licensed to run unattended overnight - it is only passively cooled and increased temperature results in a negative feedback loop.
An unpressurised light water reactor is an inherently safe design. The rate of reaction depends on liquid water being present, steam will stop the reaction.
Nuclear power doesn't have to be dangerous, and even now more people die due to coal power (including mining and pollution effects) each year than ever have due to nuclear power.
I'm sure the Chinese government doesn't care about human lives that much, but it's irrelevant when talking about nuclear power. The total radiation-related death by Fukushima disaster is estimated to be ~130[1]. For comparison, "A 2013 study by MIT indicates that 53,000 early deaths occur per year in the United States alone because of vehicle emissions."[2]
Most likely, using these reactors and having a nuclear accident will still kill less people than using fossil fuels to heat the same homes and not having any accident.
When a government doesn't care about their citizens because there's "too many of them" you get stuff like this (http://www.cnn.com/2016/06/23/asia/china-organ-harvesting/in...). So, of course they are going to be more willing to ignore basic human rights to achieve their goals. I'm not saying the US is innocent either, privatized prisons targeting African and Latin Americans to benefit shareholders of those private companies is legalized genocide (how many fatherless black children growing up in the ghetto are equipped to adjust to mainstream society)?
There is a lot of misinformation regarding the Fukushima disaster if you dig around and the long term effect on the population near that region is not being addressed and being covered up. Their exposure to the radiation will not show immediately as in most nuclear disasters but at a delayed rate after it takes a toll on their bodies. This type of silence is typical of the Japanese where they will hide mistakes for as long as it's tolerated (ex. Kobe Steel etc).
I don't think it's safe to look at Fukushima and say "oh only 100 ppl died its safe" to justify proliferation of nuclear reactors because the damages are not limited to those loss of life. Germany understands this and lot of European countries are moving away from Nuclear power altogether.
Oh yes, people surely love to claim Fukushima is being covered up, and I'm sure many Japanese politicians and businesspeople are being dishonest and trying to cover up their asses, but let's be real. Japan is a dense and well-connected country, and it's been six years. If the deaths and destruction predicted by doomsayers have any basis in reality, we should have seen a glimpse of it by now.
(But the very fact that no such thing is happening is of course considered an evidence of cover-up. How you are going to cover up a thousand leukemia deaths in Japan is left as exercise for the reader.)
Sadly, I do believe many Fukushima residents will suffer long-term health effects, which is inevitable when you've been told a hundred times how your body was irradiated by death rays and you will have cancer as a result. It was a major issue following Chernobyl as well[1]:
> A number of adolescents and young adults who have been exposed to modest or small amounts of radiation feel that they are somehow fatally flawed and there is no downside to using illicit drugs or having unprotected sex. To reverse such attitudes and behaviours will likely take years (...)
I hold those anti-nuclear activists at the same level of contempt as peddlers of homeopathy and other natural woo. These activists likely caused greater harm to children of Fukushima prefecture than the accident itself, by making them believe they are irrevocably harmed and their lives will be stunted.
Thank you for writing that.
We need more people like you to help the human species mitigate this race to the bottom (no technology, no healthcare, no compassion/humanity in activism).
Yeah, it certainly wags its tongue suggestively towards the old idea of a benevolent & competent dictatorship as the most effective form of government.
If you compare US an Chinese total coal usage, the US is actually down significantly more than China. This is despite the US price being cut in half since 2008 peak.
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.
Solar doesn’t work that well in northern China during the winter because there is hardly any sun. Even discounting the pollution, the area would be mostly foggy and overcast, it would be like trying to use solar in Seattle.
An apartment complex I lived in had solar hot water and I absolutely hated it, I could never take a “hot” shower during Beijing’s cold winter, just a luke warm one.
Implementation can make a huge difference, people do install these systems in Alasca and then supplement for a few weeks in the middle of winter which is still a huge fuel savings and cost reduction.
But, if your going to base this on a central location then sizing the system and maintain the desired temperature output is simplified.
There isn’t much space for solar panels, so sizing is intrinsically constrained. Also, these are 32 story towers with approximately 130 units...it’s not rocket science why it doesn’t work out.
Ouch, with 32 stories roof space is not good by to be nearly enough. But, if you're going off site you no longer space constrained.
Which is why I say implementation is so important. 90% reduction in fuel used and lower costs is IMO a better trade off than nuclear which is only useful ~9 months out of the year and has high ongoing costs.
Russia on the other hand is even further north and could probably see more value from such a system.
Yes, the amount of solar heating is affected by the angle of insolation more than the amount of visible sun. They work when overcast just fine, but they won’t work so well in winter at higher latitudes - such as northern China.
Yes, just insert control rods and wait for things to cool down.
I assume the design is something to the tune of "put a reactor at the bottom of a water filled pit, put a big heat exchanger at the top, pump fluid through the heat exchanger and into the city's heating system and let convection do the rest"
I'm sure with some creative engineering you could do some tricks with attaching something of a specific density that changes with temperature at a rate different than the cooling medium to your control rods you could have a system that self regulates based on the temperature of the water being input (control rods sink when temperature increases) so the system self regulates output.
it is just shocking that they did the trial run of the nuclear reactor in Beijing where there are over 20 million people. on the other hand, they were actually allowed to carry out such trial run close to where those most powerful live.
to figure out what other crazy stuff is happening in Beijing, did a quick search and it turns out that there are dozens of experimental nuclear reactors in Beijing, with the first one built in 1964 in Beijing. Tsinghua alone operates many of them.
KTH (the Royal Institute of Technology) was running a nuclear reactor[1] in Stockholm from 1954 to 1970. So if it's crazy, it's at least not unprecedented.
I wonder if this smaller reactor size would prove safer in earthquakes? There is a lot of tectonic activity in Norther China (though I'm not sure if that is where these are planned to be deployed).
Both district heating and drinking water desalination plant did ran on nuclear reactors. Desal plant in Kazakhstan ran over a decade until the Aral sea moved to far away. There are few nuclear district heating plants with single loop design still running in Russia
61 comments
[ 1.4 ms ] story [ 117 ms ] thread> The water acts as neutron moderator, cooling agent and radiation shield. The layer of water directly above the reactor core shields the radiation so completely that operators may work above the reactor safely. This design has two major advantages: the reactor is easily accessible and the whole primary cooling system, i.e. the pool water, is under normal pressure. This avoids the high temperatures and great pressures of nuclear power plants. Pool reactors are used as a source of neutrons and for training, and in rare instances for processing heat but not for electrical generation....Most research reactors are of the pool type.
https://en.wikipedia.org/wiki/Pool-type_reactor
https://what-if.xkcd.com/29/
> But just to be sure, I got in touch with a friend of mine who works at a research reactor, and asked him what he thought would happen to you if you tried to swim in their radiation containment pool. “In our reactor?” He thought about it for a moment. “You’d die pretty quickly, before reaching the water, from gunshot wounds.”
There's no pressure vessel and a massive thermal inertia. Not child's play, but very safe.
The big issue is the waste.
>> 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 this pool if they want to keep things under 100c. That's fine. Just don't pretend this is going to hum along quietly like a research reactor. And don't tell me thing will remain at 100c should that flow of water be interrupted. Any non-boiling, low-pressure, reactor is going to need exponentially more cooling (by volume) than an equivalent traditional reactor. Let us hope they keep a lake nearby as backup.
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.
[1] https://en.wikipedia.org/wiki/Boiling_water_reactor_safety_s...
> The decay heat produced by a reactor shutdown from full power is initially equivalent to about 5 to 6% of the thermal rating of the reactor. This decay heat generation rate diminishes to less than 1% approximately one hour after shutdown. However, even at these low levels, the amount of heat generated requires the continued removal of heat for an appreciable time after shutdown.
At 400 MW it takes about 4 hours to boil the water in an olympic swimming pool[1], so there should be some safety margin for the power to drop. Then once it is down to 1% decay heat it could boil for a couple of weeks before running dry.
[1] https://web.archive.org/web/20110316042315/http://www.hss.do...
[2] http://www.wolframalpha.com/input/?i=(specific+heat+of+vapor...
So the pumps have to be similarly sized, except you no longer need a pressure vessel.
You would need a 1 meter diameter pipe flowing at 1.5 meters/sec to supply this.
The west largely underestimates Chinese tech chops b/c they steal so much of our IP...
Their ability is evident in the number of Ph.D's they turn out, so why don't they invest in developing their own technology instead of stealing everyone else's? "Catching up" is not an acceptable answer with how much intellectual firepower they have.
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"
"The father was detained and imprisoned and spent 16 years in a labor camp, plunging the family into poverty. During the Cultural Revolution, a 15-year-old Mr. Xi was banished to a poverty-stricken village in northern China where, for seven years, he labored with peasants, eating corn chaff bread and sleeping in a flea-infested bed."
http://www.nytimes.com/2012/02/13/opinion/chinas-heir-appare...
Xi is the canonical example of his so named “lost generation:” forced to leave high school early, sent down to the country side, rehabilitated and given basically an cursory education as a legacy admit to Tsinghua. He is the first Chinese leader since Mao who can’t speak a word of English, less educated than his predecessors, more autocratic (vs. Hu), less outspoken (vs. Jiang) and more on ideological message.
You have to understand the fundamental difference between the two countries on a cultural and government level. Chinese people are more than happy to submit to the government as in the neo-confucian sense, the state is the provider, the father, the protector. This is what most Koreans thought too during the early days of dictatorship era that brought tremendous economic uplift.
So it's obvious that China would be more daring in areas where the US would not but because they view the cost of human lives differently.
For instance, the leave no man behind, is not unique to the US military but seldom executed because of the sheer logistical and cost-benefit analysis. In any case, you hear routinely hear Russian soldiers being left to die in Chechnya, Crimea, and now Syria.
The perception of the potential for catastrophic failure outweighs the benefits.
Given it’s an unpressurised rector that doesn’t boil the working fluid the potential for a serious accident is very low compared to a high pressure reactor. It can easily be passively cooled and shutdown heat decay can be handled without much fuss. That’s why most research reactors are of this type.
The problem with nuclear power, and in this case heating, is humans are extraordinarily bad at estimating risk.
but how many nuclear accidents have we had because of this "safe" design?
An unpressurised light water reactor is an inherently safe design. The rate of reaction depends on liquid water being present, steam will stop the reaction.
Nuclear power doesn't have to be dangerous, and even now more people die due to coal power (including mining and pollution effects) each year than ever have due to nuclear power.
Most likely, using these reactors and having a nuclear accident will still kill less people than using fossil fuels to heat the same homes and not having any accident.
[1] https://en.wikipedia.org/wiki/Fukushima_Daiichi_nuclear_disa...
[2] https://en.wikipedia.org/wiki/Exhaust_gas
There is a lot of misinformation regarding the Fukushima disaster if you dig around and the long term effect on the population near that region is not being addressed and being covered up. Their exposure to the radiation will not show immediately as in most nuclear disasters but at a delayed rate after it takes a toll on their bodies. This type of silence is typical of the Japanese where they will hide mistakes for as long as it's tolerated (ex. Kobe Steel etc).
I don't think it's safe to look at Fukushima and say "oh only 100 ppl died its safe" to justify proliferation of nuclear reactors because the damages are not limited to those loss of life. Germany understands this and lot of European countries are moving away from Nuclear power altogether.
(But the very fact that no such thing is happening is of course considered an evidence of cover-up. How you are going to cover up a thousand leukemia deaths in Japan is left as exercise for the reader.)
Sadly, I do believe many Fukushima residents will suffer long-term health effects, which is inevitable when you've been told a hundred times how your body was irradiated by death rays and you will have cancer as a result. It was a major issue following Chernobyl as well[1]:
> A number of adolescents and young adults who have been exposed to modest or small amounts of radiation feel that they are somehow fatally flawed and there is no downside to using illicit drugs or having unprotected sex. To reverse such attitudes and behaviours will likely take years (...)
I hold those anti-nuclear activists at the same level of contempt as peddlers of homeopathy and other natural woo. These activists likely caused greater harm to children of Fukushima prefecture than the accident itself, by making them believe they are irrevocably harmed and their lives will be stunted.
[1] https://en.wikipedia.org/wiki/Chernobyl_disaster#Other_healt...
https://www.quandl.com/data/EIA/COAL-US-Coal-Prices-by-Regio...
They mention it's going to be plugged into existing heating networks, but temperature of 100C is not all that hot.
An apartment complex I lived in had solar hot water and I absolutely hated it, I could never take a “hot” shower during Beijing’s cold winter, just a luke warm one.
You're not going to get much solar heating out of that... Unless you want to block your neighbor's solar heating array.
But, if your going to base this on a central location then sizing the system and maintain the desired temperature output is simplified.
They were definitely not supplementing enough.
Which is why I say implementation is so important. 90% reduction in fuel used and lower costs is IMO a better trade off than nuclear which is only useful ~9 months out of the year and has high ongoing costs.
Russia on the other hand is even further north and could probably see more value from such a system.
Nuclear normally sucks for fluctuating demand, but presumably a 6 month on/off cycle is slow enough to work.
I assume the design is something to the tune of "put a reactor at the bottom of a water filled pit, put a big heat exchanger at the top, pump fluid through the heat exchanger and into the city's heating system and let convection do the rest"
I'm sure with some creative engineering you could do some tricks with attaching something of a specific density that changes with temperature at a rate different than the cooling medium to your control rods you could have a system that self regulates based on the temperature of the water being input (control rods sink when temperature increases) so the system self regulates output.
to figure out what other crazy stuff is happening in Beijing, did a quick search and it turns out that there are dozens of experimental nuclear reactors in Beijing, with the first one built in 1964 in Beijing. Tsinghua alone operates many of them.
crazy
[1] https://en.wikipedia.org/wiki/R1_(nuclear_reactor)
http://www.drgeorgepc.com/EarthquakesChina.html