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 Post subject: PRISM
PostPosted: Jul 15, 2010 10:47 am 
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NUCLEAR NEWS FLASHES - Wednesday, July 14, 2010
US:
--GE HITACHI NUCLEAR ENERGY WILL DECIDE BY EARLY 2012 WHETHER TO BUILD its sodium-cooled fast reactor with commercial partners, GE Hitachi Nuclear Energy Chairman John Fuller said at a July 14 press briefing in Washington. The company said in a fact sheet distributed at the briefing that its Prism (Power Reactor Innovative Small Module) design is a 622-MW modular reactor that can recycle spent fuel using electrometallurgical technology rather than conventional aqueous reprocessing. Using this approach, up to 99% of spent fuel from Prism and the current LWR fleet could be recycled, GEH said. Fuller said GEH "hopes to convey" the advantages of the Prism fuel cycle to the blue ribbon commission appointed by Energy Secretary Steven Chu to review US spent fuel and nuclear waste policy. Fuller declined to provide cost estimates for the reactor system, saying they are proprietary.


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 Post subject: Re: PRISM
PostPosted: Oct 31, 2010 12:34 pm 
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I have been reading stories based on GE Hitachi PRISM reactor press release. It looks like they want to use as a burner / converter for spent LWR fuel. I can't find many details about UH3 reactors, because they Google returns mostly references Hyperion's earlier design.

Would a thorium U233 breeder version of a UH3 reactor be practical? Could the neutronics work? Would the Xe and Rn off-gas with the H2. (Probably a good thing for neutronics.) Is there any introductory material for the non-nuclear engineer?


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 Post subject: Re: PRISM
PostPosted: Oct 31, 2010 6:08 pm 
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NUCLEAR NEWS FLASHES - Wednesday, October 27, 2010
US:
--GE HITACHI WILL SEEK DOE APPROVAL TO BUILD A PROTOTYPE PRISM REACTOR at the department's Savannah River Site in South Carolina. GEH said in an October 27 statement that it has signed a memorandum of understanding with Savannah River Nuclear Solutions, a government contractor that manages the site. GEH said the two parties will explore the potential of deploying a Prism reactor as part of a proposed demonstration of small modular reactor technologies at the site. The deal still needs DOE's approval. Prism is a 299-MW fast neutron reactor design that will use recycled spent fuel and liquid sodium as coolant. The parties said schedule and funding for the project are subjects of future discussion.


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 Post subject: Re: PRISM
PostPosted: Oct 31, 2010 6:12 pm 
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Savannah River takes on PRISM
29 October 2010
Savannah River Nuclear Solutions has signed a memorandum of understanding with GE Hitachi Nuclear Energy to explore the potential of deploying a prototype of GEH’s Generation IV PRISM reactor
The deal would aim to determine the suitability of deploying a 299MW PRISM reactor at the Department of Energy's Savannah River site, which is run by SRNS, a private-sector consortium lead by Fluor Daniel, Northrup Grumman and Honeywell.
Last month, Savannah River Nuclear Solutions signed a similar research alliance with Hyperion Power to work on research to develop its 25MW small modular reactor.
The site seems to be focusing particularly on R&D of small modular reactors. "I envisage a clean energy campus, where we will work together with the private sector," said the new director of the Savannah River National Laboratory, Terry Michalske, during a press conference.
The PRISM reactor design, which completed U.S. Nuclear Regulatory Commission pre-application reviews in 1994, is an advanced, Generation IV sodium-cooled reactor technology. A key attribute of PRISM technology is that it generates additional electricity from recycling used nuclear fuel.
PRISM R&D stalled after US federal funding for the GNEP programme was wound down in 2009. Kevin Walsh, GE's senior vice president for nuclear fuel cycle, told Nuclear Engineering International in September 2010 that no PRISM research was then taking place, but that research was mostly complete.
"If we could get government funding to go forward with an experimental installation of the PRISM reactor, then the detailed design would be done at that point. The early design and testing [in GNEP] was to further work done on the EBR at Argonne National Laboratory, which is what the PRISM concept was based on."
He also explained that GE-Hitachi leans away from reprocessing, and towards recycling, as a potential future fuel cycle in the USA: "Our vision is recycling—you burn the actinides in a fast reactor, such as PRISM, and you don't separate plutonium. That alleviates some of the proliferation concerns, and you get as close to closing the fuel cycle as practical. You also reduce waste, and reduce the half-life of radioisotopes that are disposed."

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 Post subject: Re: PRISM
PostPosted: Nov 01, 2010 5:53 am 
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Sodium cooled fast reactor is under construction in India. I have just one problem with it. It is the risk of sodium fires. I wish some other heat transfer medium is used in the reactor. I hesitate in calling the sodium a 'coolant'.
I searched all over the internet. I read out everything on this subject in this forum. I also read about the IFR. I made some pretty wild suggestions. Ultimately I found one possibility that could reduce the fire risk. It is the Al-Mg eutectic. Unfortunately it does not dissolve metallic thorium or uranium. IFR reprocessing system appears to meet the requirement. So the solution, according to my knowledge and belief, is a PRISM/IFR/Solid Fuel Fast Reactor with a eutectic heat transfer agent.
I have extended a suggestion to the Indian BARC.


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 Post subject: Re: PRISM
PostPosted: Nov 01, 2010 7:06 am 
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The sodium fire risk isn't that bad. I've been in a sodium fire training exercise recently and really if you see it with your own eyes, it reduces the worries...

It's basically a risk like the risk of a high pressure reactor...it's quite manageable. You just have to be certain not to do any stupid stuff with it.

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 Post subject: Re: PRISM
PostPosted: Nov 01, 2010 11:58 am 
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STG wrote:
The sodium fire risk isn't that bad. I've been in a sodium fire training exercise recently and really if you see it with your own eyes, it reduces the worries...

It's basically a risk like the risk of a high pressure reactor...it's quite manageable. You just have to be certain not to do any stupid stuff with it.


I'm not buying the manageable part, and its bad PR to have your reactor, any part of it, go on fire. The japanese fast sodium reactor had a sodium fire. Recently it has been put into use again, after it was shut down for 14 years (!) due to the complexity of the damage and safety concerns from the japanese nuclear regulatory agency. Reactive coolants are great if you want to delay nuclear power development. Greenpeace might want to push it.

Sodium is a dumb coolant. There are lots of nuclear engineers trying to look insightful and intelligent with claims that sodium has attractive advantages. That just does't matter. A good coolant, first of all, has no major disadvantages. And then we can talk about its advantages. Water may be a high pressure coolant, but this has proven manageable and thus not a disadvantage. Having opaque low heat capacity reactive coolants like sodium is a big inherent disadvantage.


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 Post subject: Re: PRISM
PostPosted: Nov 01, 2010 12:17 pm 
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jagdish wrote:
Ultimately I found one possibility that could reduce the fire risk. It is the Al-Mg eutectic.


Isn't liquid Al-Mg flammable also? Magnesium burns under water. It seems that the only advantage is that cold Al-Mg is pretty inert.


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 Post subject: Re: PRISM
PostPosted: Nov 01, 2010 1:56 pm 
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Cyril R wrote:
Sodium is a dumb coolant. There are lots of nuclear engineers trying to look insightful and intelligent with claims that sodium has attractive advantages. That just does't matter. A good coolant, first of all, has no major disadvantages. And then we can talk about its advantages. Water may be a high pressure coolant, but this has proven manageable and thus not a disadvantage. Having opaque low heat capacity reactive coolants like sodium is a big inherent disadvantage.


Advantages and disadvantages are regrettably a subjective criteria. So what seems to you a major disadvantage, may seem to someone else a manageable small disadvantage with a manageable risk. And if you look at it, sodium leaks and small fires have been manageable trough history. It is however true that there exist different types of sodium fires, and only good management renders them not that dangerous. This is the same for any type of coolant. FLiBe may seems to have a major disadvantage trough its high melting point, which can cause unacceptable reactor transients. Water has a major disadvantage due to its high pressure, and history has shown that this is also not that good (TMI, Tsjernoby,...). Thus again, it's quite subjective. As what actually went wrong during the Monju fire, I don't know yet...that's still a part of my literature study.

And just to clarify, sodium has actually a quite high (specific) heat capacity...the opaqueness, has to be weight against other things. For example a fast reactor with a gas coolant suffers from other difficulties, some less manageable than the opaqueness in liquid metals.

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 Post subject: Re: PRISM
PostPosted: Nov 01, 2010 2:12 pm 
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STG wrote:
FLiBe may seems to have a major disadvantage through its high melting point, which can cause unacceptable reactor transients.

Would you care to clarify the unacceptable reactor transients you are referring to here?


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 Post subject: Re: PRISM
PostPosted: Nov 01, 2010 5:24 pm 
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STG wrote:
Cyril R wrote:
Sodium is a dumb coolant. There are lots of nuclear engineers trying to look insightful and intelligent with claims that sodium has attractive advantages. That just does't matter. A good coolant, first of all, has no major disadvantages. And then we can talk about its advantages. Water may be a high pressure coolant, but this has proven manageable and thus not a disadvantage. Having opaque low heat capacity reactive coolants like sodium is a big inherent disadvantage.


Advantages and disadvantages are regrettably a subjective criteria. So what seems to you a major disadvantage, may seem to someone else a manageable small disadvantage with a manageable risk. And if you look at it, sodium leaks and small fires have been manageable trough history. It is however true that there exist different types of sodium fires, and only good management renders them not that dangerous. This is the same for any type of coolant. FLiBe may seems to have a major disadvantage trough its high melting point, which can cause unacceptable reactor transients. Water has a major disadvantage due to its high pressure, and history has shown that this is also not that good (TMI, Tsjernoby,...). Thus again, it's quite subjective. As what actually went wrong during the Monju fire, I don't know yet...that's still a part of my literature study.

And just to clarify, sodium has actually a quite high (specific) heat capacity...the opaqueness, has to be weight against other things. For example a fast reactor with a gas coolant suffers from other difficulties, some less manageable than the opaqueness in liquid metals.


Manageable? A full delay to commercial maturity of sodium cooled reactors, poor capacity factors and high costs and complexity?

Tell me how the problems of opaqueness and reactivity are manageable if sodium cooled reactors, after decades of development, and various real companies working on it, still do not have major licensed designs? Why would I want to buy a reactor that might have safety issues, is certainly less reliable (look at the capacity factors of those darned things!) and more expensive, plus might fall apart in, oh 10 years perhaps, and even before all that get into all sorts of silly proliferation discussions? No thanks I'll have a water reactor instead, and MSRs as long term innovation.

I recall very well the simi reactor incident. While the dangers where exaggerated, little details like pump coolant leaking into the primary coolant can be major headaches with an opaque reactive coolant.

The heat capacity of sodium is poor. Its not even a quarter of water. Its especially poor compared to FLiBe. The thermal conductivity is also too high leading to heat shock design requirements. So when you try to go for high delta T to make up for the poor heat capacity there are seperate issues that take a lot of money and time to work out. The stuff is violently reactive with steam and that is a big problem with all the proven nice cycles based on steam Rankine. Any fast reactor still has questions relating to fissile requirements and material neutron dislocations reducing structural component lifetime. Solid fuel fast reactors have additional safety questions to be answered in beyond design basis transients and LOCAs. Thermal breeder concepts like CANDU-thorium and LFTR seem much more clever. Chlorides MSR could make sense as fast reactor design, and in a limited R&D world, not funding the fluoride versions would be nuts.

Why do people always want to do things the hard way? TMI didn't kill anyone and valve plus instrument failure was the real technological cause. This depends on valve and instrument design not on coolant choice. Badly designed low pressure valves can fail too. Chernobyl was not a disaster due to water use as coolant, it was the combination water and graphite in such configuration that the reactor had positive coefficients. If Chernobyl was sodium cooled and had the same positive coefficients it would have been just as bad. When you have 100x design power it is not hard to boil all your sodium and even sublime the graphite. Indeed the sodium cooled reactors have at least one less coefficient to help make total coefficients negative (strong moderator) and certain layouts have been found to have positive coefficients. fast reactor designers have had to go to funny geometries to avoid some positive coefficients. With solid fuel you also don't get a lot of easy expansion coefficient to help you out and fuel can't be dumped easily from the core. Talk about Chernobyl. Then there is the messy expensive inefficient reprocessing and fuel extrusion. Lots of problems. What problem were we trying to solve anyway? Water high pressure... big deal, its rediculously well known science and an inherent safety feature that prevents Chernobyls or similar beyond design basis accidents for solid fuelled reactors.


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 Post subject: Re: PRISM
PostPosted: Nov 01, 2010 6:40 pm 
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If the FLiBe coolant freezes and the coolant flow is heavily reduced, it causes a significant reactivity insertian. With a reduced coolant flow this causes increased temperatures. I know a reactor drain is possible with a MSBR type of installation, but still this can be seen as an unacceptable incident due to the high and fast neutronic feedback in such a situation and the higher time constant of reactor drainage. (It's qualitatively, just to make a point that a disadvantage is subjective).

As for water coolant. The Tjernobyl incident was aggravated due to a positive feedback increasing the water pressure at such high levels that the reactor top was set into motion and destroyed the poor reactor containment (which wasn't really a containment but just a building). This with all the results known nowadays. TMI suffered indeed from bad instrumentation, but this was related to 2-phase critical flow phenomena forming, which is essentially related to the high vapor pressure of the coolant.

The specific heat capacity of sodium is quite good in comparison with other liquid metals. And it's already 1/4th of water, which isn't that bad. The liquid region spans a wide range and therefore a high amount of heat can be removed. The high thermal conductivity is in this regard quite good to offset critical heat flux phenomena. It is indeed so, that the high thermal conductivity is a cause of concern in regards to thermal fatigue. But thermal shocks isn't a problem for SFRs, it's more a problem for PWRs. A SFR is operated at a sufficiently high temperature to remain in the ductile material region. Even the high reactivity with water in steam generators isn't a huge problem. Fermi-I operated with regular leaks for example and there still is the barrier with the primary system, since there is a secondary sodium loop. The ingression of possible contaminants is prevented by a simple cover gas, as is standard practice. Opaqueness is unfortunately a problem for all liquid metal cooled reactors and therefore special imaging techniques are required...

However, the specific heat capacity of water can be seen as to high. For natural circulation, a low specific heat capacity results in higher density differences with the same heat load. Therefore a higher pressure difference and easier flow. To achieve decent natural circulation with water, 2-phases are necessary. For a lot of liquid metal this can be achieved by simple single phase phenomena. It all depends how you look at it.

As for capacity factors, poor choices of design have indeed led to poor performances. Nevertheless, this isn't an inherent Na problem. For example, the Davis-Besse NPP isn't doing such a good job either.

As solid fuels are concerned, metallic fuels (metal clad, metal U-Pu for example) have quite high expansion factors. They are one of the characteristics that make a metallic core with a negative feedback. However, the phenomena is difficult to predict and it leads to reactivity loss during the cycle. This might, however, be acceptable for certain designs...Again, It all depends how you look at it!

In my personal opinion, SFR, MSR, LWR, ADS,... are all excellent designs with each their particular advantages and disadvantages. I do not support or oppose any of these designs. I just happen to work on SFR designs at the moment and having some experience with some of the typical sodium "disadvantages", I find that these are really overrated.

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 Post subject: Re: PRISM
PostPosted: Nov 01, 2010 7:08 pm 
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Cyril R wrote:
.....is certainly less reliable (look at the capacity factors of those darned things!)

In the last years of operation, prior to its politically-imposed shutdown, the Superphenix LMFBR had an excellent capacity factor !
It took them years to work out the bugs with that prototype design, but in the end it was a success -- only to be trashed by the red-green alliance that ruled the country at the time....


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 Post subject: Re: PRISM
PostPosted: Nov 02, 2010 3:31 am 
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SFR has had $100 Billion USD in development money since 1965 and still zero commercial plants built and on the grid. The reasons why will point to what Cyril is talking about.

SFR has had it's chance. I want to see MSR have the same level of support the SFR has had for the last 40 years.


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 Post subject: Re: PRISM
PostPosted: Nov 02, 2010 11:38 am 
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Is there any reason not to use molten salt like LiF or BeF2 instead of sodium for cooling a PRISM type reactor? It gets rig of the liquid sodium and might act as a moderator.


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