[Closed] Beginners guide to nuclear power stations ?

By default the current reactors are all unsafe-by-default. If left to their own devices without active-cooling they go super-critical.

A better way would be safe-by-defualt, where being left alone cause the reaction to slow to a stop without external input of power or otherwise.

LFTR does this, well worth watching some of the videos (mostly the same talks, various different lengths with associated brevity) on YT. http://www.youtube.com/results?search_query=liquid+thorium&aq=f

Unfortunately current regulation is not setup for either these or travelling wave reactors, so even starting development again has been a no-no since the late 70s.

I read that India was developing Thorium. And Thorium is more abundant than Uranium. Why not Thorium then?

The google tec talk was very interesting. I liked:

As the grid demands more from the fluid it goes back colder. The colder the fluid gets, the denser it is, the more energetic the reaction. So the reaction is to an extent, demand lead.

The solid "plug" of reactive material at the bottom of the core is maintained by fan cooling. If the core overheats, or if external electrical supply fails, the plug melts and the fluid pours into a separator catch tray, where it is non-reactive. You then re-heat the fluid in the tray and re-start the pump to put it back in the core to resume. At the Oakridge experimental plant, they did this over every weekend so they could have the weekends off.

That is very operationally flexible and safe. The barriers would seem to be setting up the infrastructure. The Uranium-based infrastructure we have today was largely paid for by the weapons programme.

My point is that nuclear has a very good safety record, and if it goes wrong it's not quite as horrific as you might be lead to believe and the consequences of other forms of generation going wrong are just as bad.

[url= http://en.wikipedia.org/wiki/Cumbre_Vieja ]i wonder what would happen?[/url]

There are other unstable landmasses around, i wonder if any coastal nuclear plants have anything in the emergency manual just in case?

Some of the comments on the first page are starting to look very silly. Laughable even were it a laughing matter. Forums are great in the way posts stick around and some people demonsrate how easily duped they are.

Keep up the good work. What I know about this stuff could be written on the back of an envelope, however, I've been listening for the word "boron", haven't heard it and can't help wondering why not.

Every single system designed by human beings, thus far, has, at some point, failed.
Humans make mistakes - it's in our nature.

Sounds much cooler if you imagine it in Darth Vaders voice.

I reckon that if an older generation nuclear reactor can take a hit from one of the largest earthquakes in history, it is a remarkable success and my best wishes are with them all.

I reckon that if an older generation nuclear reactor can take a hit from one of the largest earthquakes in history, it is a remarkable success.......

Yeah well I think it is now pretty well established that an older generation nuclear reactor [i]cannot[/i] take a hit from one of the largest earthquakes in history - or at least the [i]consequences[/i] of one of the largest earthquakes in history. Otherwise there wouldn't any problems today with three nuclear power plants in Japan.

I've been listening for the word "boron", haven't heard it and can't help wondering why not

Is boron still used as control rods? It's been a long time since I studied Nuclear reactors, and even then it was AGRs which I'm guessing isn't the type of reactor that's causing the problems in Japan.

What happens when a coal one breaks down how many people get cancer and for how long can you not live in the vacinity with conventional power?

Well there are plenty of other nasties that get given off by conventional power stations, and I'm going to go out on limb and say that quite a few of them are carcinogens. Apparently about 20-30 years is how long you have to stay out the area. There are people who live in that area now. Granted not everything there is sweetness and light but there is life doing rather well there. Bear in mind that it is very difficult to get a proper idea of just how many people have died as a direct result of the disaster. What can be said however is that that, the worst nuclear disaster in history doesn't even come close to the worst industrial disaster.

[url= http://www.theregister.co.uk/2011/03/14/fukushiima_analysis/ ]And the other side[/url] A good read

Otherwise there wouldn't any problems today with three nuclear power plants in Japan.

To be fair they are taking all the right precautions and the story comes out sounding like they might pull it off. If they can keep the damage to a minimum I am sure it will more than justify it's service to the people of Japan.

Not saying it is a foregone conclusion, and I wish them all the luck, but it could turn out to be a bit of cracking PR for the nuclear industry.

the story comes out sounding like they might pull it off.

Yep, let's hope they do. And let's also hope that lessons are learnt. Although by their very nature, unforeseen circumstances are very difficult to plan for.

So the Japanese are efficiently working through problems caused by a once in 200year or more earthquake and the tsunami. Meanwhile, the media and people who didn't go to school are running round in a flap.

We shut down the nukes and we have to burn more coal.

[b]A coal power station emits 100x more radioactive material than a nuclear station that generates the same energy.[/b]

Coal contains uranium and thorium, both radioactive elements. They occur in trace amounts in natural coal, and so are not a problem whilst the coal is in the ground. However, when coal is burned into fly ash, uranium and thorium are concentrated at up to 10 times their original levels.

This fly ash spreads further and blankets a wider area than the radiation produced by a nuclear plant.

Nice to be a hippy sitting in a warm house whinging about the environment, dude. But you want your house warm, and the internet working to chat to the other dudes online.

Nuclear fuel is the most environmentally friendly choice we have at the moment. As others have said, in 30 years time renewables might be a go-er, but not yet.

The operators must have been horrified when they saw the primary coolant levels dropping away and no means to pump around fresh coolant. There's a certain amount of improv going on e.g. using fire pumps to put sea water into the core. I bet that isn't in the manual. I read that they are going to "ventilate" i.e. drill holds in the outer building before steam venting again, to prevent explosive build up of hydrogen.

I hope they get medals.

Meanwhile, the media and people who didn't go to school are running round in a flap.

I bet I'm a darn sight more relaxed and sleeping better than the nuclear bods in Japan.

The answer isn't producing ever more electricity, it's cutting demand, particularly peak demand. I bought a 30s house which already had double glazing and roof insulation,and reduced gas consumption from 600m3/year to 220m3/year just by futher insulating and adding a solar hot water heater. I could have cut it to about 150m3/year by changing to a condensing boiler but cut the gas off and fitted a wood burner instead. Wood consumption is curently 4m3/year but with yet more insulation that will go down.

Now if everyoen does the same then renewables become viable now.

Assuming the absolute worst case scenario statistics, how many deaths from Chernoble? I seem to remember 10,000 being banded about? And we're unlikely to repeat that.

who are you who is so wise in the ways of science 🙄
Cancer is negligible amd makes you die 10 mins early?

The digest, based on a three-volume, 600-page report and incorporating the work of hundreds of scientists, economists and health experts, assesses the 20-year impact of the largest nuclear accident in history

I've just been reading about Chernobyl. It was a dreadful disaster because the reactor design was poorly behaved so that operator errors could and did lead to overheat. And the design lacked a vessel strong enough to contain an overheated core. Very shonky design.

What happens when a coal one breaks down how many people get cancer

How many people suffer short term or long term effects of pollution from coal fired power stations every day? How many more may be affected or displaced by the long term effects of climate change if the predictions are true.

and for how long can you not live in the vacinity with conventional power? etc

As for the hoover dam at 600 ft thick at its base and 45 foot at its top it is hard to think what could be done to break it.

In fact, although not as sexy a story as the nuclear issue, just along the road [url= http://www.hydroworld.com/index/display/article-display/5036367493/articles/hrhrw/News-2/2011/03/dam-breaks_following.html ]a dam[/url] (don't know if it was for hydro or water) broke in the quake and washed away thousands of houses.

And that problem is [url= http://www.hydroworld.com/index/display/article-display/357756/articles/hydro-review-worldwide/volume-16/issue-4/articles/technical/evaluating-earthquake-safety-for-large-dams-in-southeast-turkey.html ]not unique to Japan[/url]. Indeed you may remember the quake in China last year [url= http://www.internationalrivers.org/en/node/5285 ]damaged a dam[/url] which threatended the homes and lives of at least 100,000 people.

Yes it could happen [ i suppose a meteor could hit it] but nuclear ones have occured numerous times.

I am not certain that it is wise to compare hypothetical scenarios with ones that have occured when assessing risk

dmjb4 - Member

So the Japanese are efficiently working through problems caused by a once in 200year or more earthquake and the tsunami. Meanwhile, the media and people who didn't go to school are running round in a flap.

We have had nuclear power for what 50 years? How many serious accidents and releases of radioactivity? How many more "nearly" until one blows properly?

A coal power station emits 100x more radioactive material than a nuclear station that generates the same energy.

Only so long as you ignore the issue of waste - low medium and high level.

There remain too issues that mean nukes are not the answer. Waste and decommissioning.

coal is intresting as the mining is dangerous for sure but not sure this is rlevant pr se as we are discusssing the actual power genration stations not the method you get the fuel. You would need to give deaths for coal fired fuels stations to compare them to nucleur or we are not really comparing the same thing.
climate change is not a debate for here but oil is far more critical than coal as is is eating meat.
how many nucleur reactors would survive an earthquake? I suspect a dam is more likely to survive but I dont actually know. Nor do I expect google to answer it for either of us. i assume they dont build them anywhere near know fault areas.

there have been very few nuclear accidents which have caused significant casualties (and even fewer members of the public have been killed). You are simply remembering the nuclear incidents over the others.

In many ways they are like planes we all know they are safe if nothing goes wrong but when they go wrong the effects are fairly catastrophic.
i accept this one has not gone wrong and is still contained and highly likely to remain so.

Junkyard - Member

coal is intresting as the mining is dangerous for sure but not sure this is rlevant pr se as we are discusssing the actual power genration stations not the method you get the fuel. You would need to give deaths for coal fired fuels stations to compare them to nucleur or we are not really comparing the same thing.

I ain't buying that. Surely theh only faior comparision is total deaths per kilowatt hr of leccy we get out. Mining ( some folk die urainium mining as well I guess) transporting, generating, emmssions deaths.

that what i was [trying to] saying TJ
perhaps we both spell so badly no one can understand us?

TJ - We have had nuclear power for what 50 years? How many serious accidents and releases of radioactivity? How many more "nearly" until one blows properly?

But I agree with you it is waste (and decomissioning) which are the barriers to nuclear rather than safety per se.

junkyard - A fair point but you may be doing the opposite. I assume if we blow up all the dams and all the nucleur power stations more of us would die from the later than the former. I am less sure that this proves my point or has any baring but I it seems like a noc epice of hyprbole so it can stay

[quote=double award science student]We have had nuclear power for what 50 years? How many serious accidents and releases of radioactivity? How many more "nearly" until one blows properly?

Do you also refuse to travel by plane? I mean, it must be way more dangerous than driving, wasn't there a plane crash on TV last year?

A few sensational nuclear disasters get the news, but the tonnes of carbon and radiation emitted over the same period from burning coal have caused more harm.

[quote=double award science student]There remain too issues that mean nukes are not the answer. Waste and decommissioning.

Only if you ignore the issue of waste - low medium and high level.

I'd prefer nuclear waste buried several miles below my house to a slag heap next to it? Wouldn't you?

some estimates suggest 12000 people die EVERY year worldwide from coal mining

That is a shocking figure. On the plus side, that's probably not that far from the maximum possible figure. You might get a 10% or 20% increase in any given year, but you would not get 100% or 200% increase in any one year. Well, not without some sort of pre warning that fatalities were stacking up. So that's fairly reassuring.

Another shocking figure is that, a large meteorite killed off 90% of all species and it took life on Earth 30 million years to recover. The good news is, that almost no one has died as the result of a meteorite for 250 million years.

Which all goes to prove, that I have absolutely no idea whatsoever what my chances are, of dying from a coal, nuclear, or meteorite, related death. I am surprisingly unbothered though......maybe I should be?

Whatever the merits (or not - and I'm still inclined to view the industry as a massive white elephant) of nuclear.... hats off to the bravery of the engineering & other personnel on the ground.

I've been scouting for the most alarmist/innacturate press and this is the best I've come up with: [url= http://www.mirror.co.uk/news/2011/03/15/japan-quake-and-tsunami-48-hours-to-stop-a-nuclear-disaster-115875-22990301/ ]The Mirror[/url]. Surely they should be reporting celeb gossip, not serious news?

"How many more "nearly" until one blows properly?"

Reactor fuel is not explosive. The burning reactor core exposed to the atmosphere at Chernobyl was almost the worst that can happen.

I am quite taken with this liquid fluoride thorium reactor mentioned earlier. Although the chemistry and reactions are more complex, it's operations seem way simpler and safer.

The pebble bed reactor is another worthwhile self-moderating design. I think SA are building some of these.

A pebble-bed reactor thus can have all of its supporting machinery fail, and the reactor will not crack, melt, explode or spew hazardous wastes. It simply goes up to a designed "idle" temperature, and stays there. In that state, the reactor vessel radiates heat, but the vessel and fuel spheres remain intact and undamaged. The machinery can be repaired or the fuel can be removed. These safety features were tested (and filmed) with the German AVR reactor.[6]. All the control rods were removed, and the coolant flow was halted. Afterward, the fuel balls were sampled and examined for damage and there was none.

Why not Thorium then?

Answered by:

The Uranium-based infrastructure we have today was largely paid for by the weapons programme.

Exactly. Nuclear power was a nice side-product discovered while making weapons-grade materials. The legislation, especially in the US and Europe, is very much geared towards Uranium infrastructure, with other options being ignored as a result.

Bill Gates is a big investor in travelling-wave research, and had been hoping that Japan would give permission for some small-scale experimental reactors.

I've been scouting for the most alarmist/innacturate press and this is the best I've come up with

Well if alarmist is what you want, then this takes some beating :

[url= http://www.****/news/article-1366055/Japan-earthquake-tsunami-America-nuclear-alert-Fukushima-explosion.html ]U.S.S. Ronald Reagan hit by month's radiation in just one hour[/url]

[i]The U.S.S. Ronald Reagan was around 100 miles (160km) offshore when low-level radioactive contamination was detected from the stricken Fukushima plant.

Low radiation levels were detected on 17 members of the crew on three helicopters as they returned to the ship after delivering aid to the devastated city of Sendai.

Most of the radiation was found on the clothing of the 17-man crew, but also on one's skin. The sailors were said to not have experienced ill-effects following the incident.

Contamination was found on the helicopters, which were scrubbed down on landing.[/i]

Lots of interesting thoughts in regard to nuclear power, most people forget the Windscale fire - the most probable source of the Cs-137 in the Cumbria / Lake District area rather than the fall out from Chernobyl.

What happens in Japan will depend on the ability of the people on the ground to maintain cooling to remove the residual decay heat from the core and prevent the loss of fuel pin geometry (the clad melts). If this happens there is the risk of fission product release to the environment through either bypass of the containment boundary (eg relief valve lift) or damage to the primary containment.

As an aside the Japanese nuclear industry has a history of misleading the public or attempting to cover up nuclear incidents, which is why the Japanese public seem a bit nervous.

The accidents at Windscale, Three Mile Island, Chernobyl and Tokaimura all had different root causes but none has covered the nuclear industry in glory. The near miss with the Davis Besse reactor head is another example of how things can go wrong.

I am not certain that it is wise to compare hypothetical scenarios with ones that have occured when assessing risk

Well if alarmist is what you want, then this takes some beating :

U.S.S. Ronald Reagan hit by month's radiation in just one hour

Top quote from that in a picture caption - just in case you'd missed the connection between a nuclear reactor and nuclear bombs:

The towns destroyed by the tsunami look very similar to Hiroshima in 1945

Maybe a better picture caption would have been :

The towns destroyed by the tsunami look very similar to how Ronald Reagan would have liked North Korea to look

Well there has been an explosion at reactor 3, this is of greater concern than the others as it contains mixed oxide fuel - a mixture of uranium and plutonium oxides. With Tepco having admitted to having uncovered the fuel on 2 separate occasions it is likely that a zircaloy fuel element will have ruptured leading to fission product release within the primary containment. As they have been venting to the secondary and tertiary containment, it is likely that there will have been fission product release following the recent explosion.

Ps The accident progression is what would be expected for the loss of cooling scenario that has occurred.

So given there hasn't been an accident with a current generation nuclear generator, that's a purely hypothetical risk, and you can't compare with more dangerous methods of energy production in which fatal accidents have occurred, like hydropower

Whether or not more modern reactors are safer isn't really the point.

In the past I've heard plenty of people expounding about how wonderful nuclear power is in Japan, and how they have a flawless safety record. Everybody has a flawless safety record until the very moment that they haven't.

If these old reactors were inherantly less safe than current reactors, then surely it would have been a good idea to either improve their saftey features or shut them down some time ago. But IMO that's not how the nuclear industry works. Instead it relies on the support of a bunch of technophiles who think that everything can be managed, even when the evidence is right in front of them.

I don't give a sh1t if the UK is unlikely to suffer from a 9.0 earthquake. I don't want a new generation of Nuclear Power here, because it is usually not the foreseeable problems that go bad (except in this case!) but the unforseeable ones, and having a bunch of appologists for the nuclear industry telling me how they are going to make sure that 'lessons are learned' or that 'technology is better now' or 'that shouldn't have happened' doesn't comfort me very much.

I'm afraid that no amount of statistics about numbers of coal miners killed will ever convice me that nuclear is a good idea. Surely the correct response would be to call for coal mining to be made safer? Or better still to start to finally accept that our existing energy usage is unsustainable and try to at least start cutting back on consumption?

Anyway, I'm sure I'll be kept warm enough basking in the flames of the forum, but I'm hoping that this latest wake up call will at least rouse a few more people from their technology induced stupors.

No flaming Rightplace. Just a request to pop out to the shops and buy a bagful of 3W LED light bulbs and a couple of 36W strip lights because those "economy bulbs" your government gave you use are energy greedy (as well as providing poor lighting and taking ages to warm up) and you can start reducing your personal consumption today. Sorry, but all those pretty halogen lights have to go to the recycling centre.

Buy some multi-socket blocks with a switch too so it's easy to switch off the amp/TV/sat box/ cable box/DVD player and 3W LED table lamp in one go when you leave the room.

Buy some multi-socket blocks with a switch too so it's easy to switch off the amp/TV/sat box/ cable box/DVD player and 3W LED table lamp in one go when you leave the room.

There we go, ready for a meltdown of my own now 8)

As accidents go, the one at Fukushima was predictable - earthquakes and tsunami tend to go together. The Windscale fire was a result of a drive to produce Plutonium for the nuclear weapons programme hence an air cooled graphite moderated reactor with only a few filters preventing release of radioactive material into the environment.

TMI was the result of a faulty meter reading and the failure of the regulator system in the US that assumes you are safe if you have met certain targets rather than challenging everything to ensure the plant is safe. Again see the Davis besse reactor head - corrosion due to dissimilar metals around the control rod penetrations in the RPV head.

Chernobyl was the product of political pressure and poor design. The reactor had a significant -ve temperature reactivity coefficient below 20% full power that in the operating rules stated that if you went below 20% full power you need to restart the reactor. Political pressure was placed to run a test at 4% full power (a turbine overrun test) and then continue operating at power. To do this the operators had to defeat all the safety systems and pull the control rods out to a position that only the then president of USSR could authorise. Leading to the prompt criticality accident, the explosion and fire.

The generation 4 reactor designs are very different in that previously a lot of safety was reliant on operator action or active control systems. The latest designs have numerous fail safes and are designed with walk away capability ie you put the control rods in and if you walk away and do nothing the plant will passively sit there.

The next evolution of the the Fukushima plant accident will be that as the cooling fails (no one adding water), the fuel will heat up and the steam atmosphere in the reactor will oxidise the zircaloy fuel clad (an exothermic reaction) at between 600 and 800 deg C producing more hydrogen. As the exothermic zircaloy steam reaction drives up the temperature of the clad along with the residual heat in the fuel, at some point there will be further clad failure leading to a loss of reactor core integrity. This is the expected and worst case scenario.

With the clad failure, the boron that has been added and the control rods (which will also mechanically fail) should prevent any criticality issues.

There is potential for fire in each reactor due to the temperatures involved (even concrete will burn if hot enough), and failure of the primary containment through another hydrogen explosion should this not be being vented.

I have never liked the BWR design as I always felt the design was fundamentally flawed from a safety point of view. Having to drive control rods in against gravity rather than having them drop in under gravity to shut down a reactor in an emergency always seemed to put an undue risk of failure on one system.

The issue with nuclear power always has been that political and commercial pressure to keep operating will always lead to a situation where requirement to keep operating the reactor to produce those MW will at some point clash with safety.

I'm afraid that no amount of statistics about numbers of coal miners killed will ever convice me that nuclear is a good idea. Surely the correct response would be to call for coal mining to be made safer?

Or better still to start to finally accept that our existing energy usage is unsustainable and try to at least start cutting back on consumption?

I disagree Poly. Households could reduce consumption by 75% and renewables could meet that demand within ten years. You simply need the kind of commitment that went into producing weapons for WWII or the cold war.