The Nuclear Power Thread

vanesch

The point really is that the risks ARE already really small in the West. The objective risk (as you point out: risk = probability x cost(lives, land...) ) of nuclear activities is about a million times lower than driving cars, and even lower than making shoes (just by comparing the number of yearly dead). The "maximum disaster" is Chernobyl, which is a serious catastrophy, but much less so than many accidents in other branches of human activity (for instance, the Chernobyl disaster is way less terrible than the Bhopal disaster, and a Chernobyl accident in the west is way way way less likely - for fundamental reasons - than another Bhopal).

There are good solutions for the waste. It is not as catastrophic as eco wackos want us to believe. There are in fact 3 timescales in nuclear waste:

- fission products: about harmless after 300 years
- minor actinides: about harmless after 10 000 years
- plutonium: about harmless after 100 000 years.

Now, reprocessing can remove the plutonium (to be re-used as fuel!), and there's a lot of work going on - and prototype processes such as DIAMEX have been set up - to remove also the minor actinides. This leaves us with the main ash from nuclear power: the inevitable fission products. Well, there life time is of the order of 300 years.
That's not the "millions of years" that is usually talked about.

The minor actinides can be considered as waste, but they can also be burned in fast reactors. There are experiments under way to burn them in subcritical accelerator-driven reactors, but I think that this is overkill. Even considering them as waste is not such a problem, because geological storage can be made secure for 10 000 years with high reliability. Also, if there's a leak after, say, 1000 years, that's not a major disaster. There will be a minor polution of a relatively local area, much less of a danger than most waste storages of today.

Most of this is already well-studied. There have been 18 fast breeder reactors active in the world ; only two of them are still working, most of them were closed down for political reasons. So this is not a dream on paper. Prototypes have been build and made working. One just needs to improve a bit on the engineering to optimise the design. There are no known difficulties of principle. This stuff has been working before.

In fact, France has the ambition to put its first Gen-IV reactor, with closed fuel cycle, up and running by about 2020. If the green party didn't ask for drilling a hole in the reactor vessel of super-phenix in 1998 or so, it would probably already be up and running.

Astronuc

Re: Fast Reactors - this would be of interest.

The status of Fast Reactors programme in France in 2005
http://www-ist.cea.fr/publicea/exl-doc/200600003924.pdf

I attended a lecture by the program manager of the US fast reactor program 25 years ago. At the time, he had just dismissed 300 people from the program! He likened a fast reactor to building a supersonic aircraft out of balsa wood. My colleagues and I were rather shocked at the statement.

Fast reactor technology has been rather problematic, not so much from the standpoint of the nuclear physics and fuel design, but from the aspect of balance of plant and operational issues. FR's are complicated because the fuel handling has to be done under liquid sodium. Traditionally, electrical generation has been accomplished by large steam turbines, but the problem there would be the basic incompatibility of water and sodium.

Superphenix was plagued with problems, and the Japanese MONJU had its own set of problems, including some deficiencies in design.

Perhaps the better alternative is a gas-cooled fast reactor.

I'm not arguing that fast reactor technology is impossible, but rather, it is not so easy.

vanesch

This is more kind of emotional rethoric than based upon any technological assessment. I attended a lot of seminars in Karlsruhe a few months ago, and had the opportunity to have a dinner with one of the CEA responsibles for the former Superphenix programme, which seemed to claim exactly the opposite: that liquid sodium cooling is technologically mastered and that the closedown of it was purely political. It is true that Superphenix had a lot of problems in its first years, but in its last years it ran without many troubles, and it was also a prototype: you expect difficulties in a prototype.
Let's not forget that Phenix has been running for over 30 years without problems.
So according to him, one can always improve upon robustness and one can always improve upon engineering, but there wasn't any fundamental objective technological obstacle to building liquid sodium cooled reactors.

Nobody will deny that a FR is a bit more complicated than a LWR, but that's more because a LWR is *extremely simple*. The problem with steam turbines - in as much as that is a problem - is the low Carnot efficiency, because you cannot use steam much above 400 degrees Celcius (critical point of water). It would of course be dangerous to have a direct Sodium/water heat exchanger, but nothing stops you from having an intermediate fluid which is compatible with both.

Sure, but these are prototypes, exactly to learn from. If one would have built a few tens of prototypes, the experience gathered would make this technology probably just as robust as LWR are now.

There are essentially 4 types of fast reactors:
- liquid sodium
- liquid lead
- gas
- salt

Sodium makes people nervous because of its reactivity with water, but all the other properties of sodium are OK, which makes it less of a problem than people think. For instance, a liquid sodium reactor is NOT under pressure, which relieves a lot of safety, materials and mechanics issues. In that respect, a liquid sodium reactor is "easier" than a LWR which is under high pressure. Also, one can, as with the IFR, use a "buffer bath" of sodium to make the reactor entirely passively safe. The only true engineering challenge is to keep the water out in all circumstances.

Liquid lead seems to address this, but is actually worse. Yes, liquid lead is less reactive towards water, but: 1) it is very corrosive, which puts a strong materials engineering challenge - which isn't the case for sodium and 2) you generate radioisotopes such as polonium.

Gas cooled reactors seem better in this respect, but, again, they are under pressure, and they are difficult to make passively safe. A loss of pressure for instance means a big challenge to restore the cooling.

Salt cooled reactors seem to address many issues, and are very promising. Only difficulty: almost no experience with it!

So, everything in a row, technologically, sodium cooled reactors are "closest to operational commercially". If we are serious in installing MANY production FR by 2030, we better start with a technology where experience exists.

Astronuc

With respect to fast reactor technology, this might be of interest -

Fast Reactors and Accelerator Driven Systems Knowledge Base
Working Materials of the Technical Working Group on Fast Reactors
http://www.iaea.org/inisnkm/nkm/aws/...materials.html

and - http://www.iaea.org/inisnkm/nkm/aws/frdb/index.html


Phenix has had its problems - e.g. shutdown between 1998 to 2003, which is similar to long shutdowns seen at some US LWRs. I think the problems with Superphenix were related to scaling up the technology. The fact that Phenix was shutdown for upgrades didn't help the cause.

Last year, I attended a conference on Gen VI materials, and I'll be involved with the next one coming up next year. While there has been much research with a broad range of materials, and there are some promising ones, none of the presentations and literature addressed the performance of these materials in a radiation environment nor for any time close to intended service life. I'm not cynical (except in a few cases such as molten lead systems), just very cautious when it comes to claims regarding nuclear energy and technology.

BTW, there is a concept for a superheated water reactor.

daveb

In our reactor design class ( a team based design course) we continued work that the previous classes had done with regards to the lquid fluoride reactor (using a 2 salt FLiBe material) originally developed by ORNL. I imagine the next several years' classes will build upon our work, so maybe in several years' time there may be some experience.

Astronuc

One of the former ANS presidents recommended this site for topics on Nuclear Energy and Power Systems.

http://www.atomicinsights.com/AEI_Topics.html

gdsandkes

The Duke Energy plant near Charlotte NC was in trouble during the recent drought due to unprecedented low water levels, and came very close to shutting down because of a lack of cooling water from the intake pipe. The sun is available with no lingering waste or pollution. Thermal solar http://www.youtube.com/watch?v=J_IMRLi8HdY
can be scaled to work with current mature technology large scale turbine generators and water can be split effeciently with this MIT catalyst.

http://web.mit.edu/newsoffice/2008/oxygen-0731.html

If we are to go nuclear we need to have a plan to deal with the 55,000 tons of radioactive material already on hand. We currently use only 5 percent of the energy available in the stored material. Let's reproccess the available material, as the French do, and use 95 percent of the available energy.

vanesch

Every thermal-to-electricity conversion will need external cooling, that's Carnot who dictates that. So there's no point in pointing out "lack of cooling" with a nuclear power plant, and propose any other thermal process in its place (thermal solar, biofuels, coal, gas,....) They all need a heat sink in the environment. It's elementary thermodynamics.

It is only wind, hydro, photovoltaic, and tidal sources that don't need any thermal dump.

There is a simple plan to deal with the waste. Compare 55 000 tons (world-wide some 170 000 tons I think) of waste accumulated over 30 years or more with the 2.8 MILLION tons of coal a single 1 GWe coal fired plant needs in one year, and you will see the smallness of the actual amount of waste. I'm not talking about its toxicity, I'm talking about its amount. If it is possible to mine tens of millions of tons of coal, then it is also possible to burry 55 000 tons of high level waste, which looses its "high level" status after a few centuries. We can also sit on it for as long as we want to as the total quantity is small. If we need to keep it as of yet some 50 more years to find out whether really there is not any problem with burying it, then that's no big deal. It is a few acres of land storage for the waste of a whole continent, for several decades. To bury it deeply under the surface is very feasible, given the smallness of the quantity compared to what one digs up from deep within the earth. So really, the waste is a non-issue. It is a small amount, and one knows what to do with it, and it is feasible.

Reprocessing is also a good idea as it separates the inert and useful (U and to a lesser extend, Pu) from the radioactive (fission products and minor actinides). The active part only represents 5% of the total spend fuel, so as a matter of volume (but not of activity and toxicity) it is a good idea to reprocess. It diminishes the volume of the waste to be buried and hence optimizes the use of the final repository.

However, it is a misunderstanding that - right at this moment - one can re-use the inert part. In thermal reactors such as light-water reactors, the plutonium can only be re-used once (MOX), because it gets a worse and worse isotopic composition, and the conversion of uranium into plutonium is only marginal. What is really needed, are fast (breeder) reactors, which can use *all* the plutonium, which can convert *all* the uranium and which can even burn all the minor actinides and don't produce many of them.

While it is true that LWR currently burn about 5% of the *enriched* uranium, that corresponds to about 0.5% of the natural uranium from which this enriched uranium was made. So overall, we only use about 0.5% of the energetic potential of natural uranium. With fast reactors, this can be in principle 100% (although in practice probably lower). That means a gain of about 50-100 in fuel efficiency.

Or, put differently: if you have the "waste" of 30 years of LWR operation, you can re-use this for about 1500 - 3000 years of equivalent energy output with fast reactors. Without any new natural uranium. Just by reprocessing the current waste and using the depleted uranium.

But all this is only possible in fast reactors. Not in LWR.

Astronuc

U.S. Decides One Nuclear Dump Is Enough
http://www.nytimes.com/2008/11/07/wa...n/07yucca.html
By MATTHEW L. WALD
It certainly keeps changing.

Astronuc

FYI,

Nuclear Energy Papers/Presentations

EBR-II (link to pdf - use 'save target as')

Astronuc

Can Nuclear Power Compete?
http://www.sciam.com/article.cfm?id=...-power-compete
Newly approved reactor designs could reduce global warming and fossil-fuel dependence, but utilities are grappling with whether better nukes make market sense
By Matthew L. Wald (Science Writer at NYTimes)

Sciam produced several articles on the current and future trends of nuclear power.
http://www.sciam.com/report.cfm?id=nuclear-future

Sriram.S

Is it possible to recreate the happenings on the sun on earth? Well, what is happening in the sun is fusion and there still isn't a solution to controlled fusion, but why not uncontrolled fusion by supplying extremely little fuel(i.e, what is going to fuse, for example hydrogen and helium in the sun).

Sriram

Vals509

i feel that people shoul install breeder nuclear reactors as they can re use fuel instead of the conventional reactors. i know that congress has banned/blocked the building of such a source but believe that it is a viable alternative and that it should be brought up again.

another thing is that the only thing scaring people to death about nuclear reactors are accidents like chernobyl. what needs to be done is informing people of the latest safety features of current reactors and we must remember is that chernobyl occured because of several stupid mistakes. sure stupid mistakes can still happed but we are a lot more educated to respond to such accidents.

finally research into fusion rather than fission reactors must be accelerated. i know that it is still taking place but more attention must be given to it. also reactors need to be built in areas with a cordoned off area of whatever kilometeres needed and people around should be trained to respond in emergency.

or the simplest solution is to invest into other sources of energy like solar and wind???????

Vals509

well fusion reactions can take place and they are controlled but however they are theoretically possible. examples like the TOKAMAK have i believe achieved fusion but are financially bad.

Astronuc

The Westinghouse AP-1000 is one of the modern Gen 3+ plants that are proposed near future NPPs.

http://www.ne.doe.gov/pdfFiles/AP100...escription.pdf

Other plants under consideration:

US APWR - Mitsubishi
AP600 - Westinghouse
System 80+ - Westinghouse
AP600 - Westinghouse
EPR - AREVA

ABWR - GE/Hitachi
ESBWR - GE

GT-MHR - General Atomics
ACR - AECL
PMBR - Westinghouse/ESKOM
4S - Toshiba
IRIS - Westinghouse


EPRI has established the Advanced Nuclear Technology program regarding the new NPP designs.
www.epri.com/ant

Astronuc

The Future of Nuclear Power - An interdisciplinary study by MIT.

http://web.mit.edu/nuclearpower/

The original study was completed in 2003, and the situation has changed. There is a large (~29 MB pdf file).

There is an update for 2009.

sloughter

I met a nuclear physicist/engineer who was the go to guy for Army Intelligcnce when Chernoble went south. He was asked to give his opinion of impending casualties. He told the Army brass, "You are going to lose some firefighers and some of the helicopter pilots who flew through the radioactive plume. That should be about 35-40 people. That's it" A recent World Health Organization Report came out indicating 23 years later that 40 people had died because of Chernoble, just as the nuclear expert predicted.

What is not appreciated in the American public is that equating American Nuclear Plants to Chernoble is comparable to comparing the safety features of a Lexus to a Model T. Chernoble consisted of vertical concrete walls 2-3 feet thick with a tarpaper roof. We have reactor domes over a foot thick with rebar.

When the radioactive cloud took off, the vertical walls acted like a chimney and the cloud rose vertically, traveled about 30 miles and then descended into an unpopulated area. Unfortunately, the Russian Government forgot to tell the peasants not to drink milk from cows eating grass tainted with radioactive iodine (Only the volatiles, radioactive cesium and iodine were released when the reactor burned, and some of the peasants came down with thyroid cancer---they also used graphite as a moderator which also burns).

Don't eat striped bass from the Hudson River unless you like the taste of PCB's. Don't eat predatory fish from the Atlantic three times a day, unless you like mercury-induced insanity. Don't drink milk from cows eating radioactive grass. Duh.

The studies relating low levels of exposure to radiation used to predict thousands of casualites at Chernoble are based on bogus extrapolation of high doses of radiation to low doses (I was exposed to more radiation digging for pyrite nodules in black shales than most Cheronobleites were exposed to from the radioactive cloud.)

If I eat 1000 aspirin at once and die, does this mean if 1,000,000 people eat one aspirin/day for a year that 1000 will die of aspirin poisoning? This is great science if you want to start a new industry getting radon out of the basements of people's homes, but it is low quality science. Greenpeace and the Union of Concerned Scientists are little more than scare mongers. If they wished to do something useful, they should try to get kids not to start smoking or drinking and driving, they'd save a lot more lives, but it is not nearly as exciting as being in an organization going after those big bad nuclear power plants.

As far as nuclear research, check out the websites by George S. Stanford and Charles E. Till on the Integral Fast Reactor. It promises to provide clean, safe, proliferation-resistant, weapons-incompatible fast breeder technology. It was shut down by Senator John Kerry in 1994 presumably because it competed with MIT's hot fusion program (The research was about to be completed within three years; completing the research cost no more than shutting it down. Commercial viability was inevitable and MIT stood to lose billions of dollars in research grants if the program was completed.