Thorium as nuclear fuel
AlexLoll
reactor fuelled by thorium?I found these conversion ratios in German Pebble
bed reactor : 0,76 for HEU/thorium and 0,97 for thorium/uranium-233 used as
make - up extracted from the first step.Have you got some numbers about
Hwr/Candu reactor in the same conditions.What about plutonium/thorium cycle
or thorium in fast reactors vs thermal spectrum?
oyo
core and reprocess it to get the fissile material out. Considering the
political impications of enrichment (Iran) and reprocessing (North
Korea) along with the economical burden of these processes I doubt that
thermal breeders will be economical and feasible. On the other hand
PBMR can use "in situ breeding" and utilize more fuel without the need
for reprocessing. It will be rather easy to use any fuel cycle with a
PBMR may it be Pu/Th or others.
AlexLoll
"oyo" <okkad...@gmail.com> ha scritto nel messaggio
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Thanx.Have you got any info about conversio ratios I asked,i.e. Candu
reactors vs PBMR or thermal vs fast reactors.I'm just curious...
Osman Kemal Kadiroglu
> Thanx.Have you got any info about conversio ratios I asked,i.e. Candu
> reactors vs PBMR or thermal vs fast reactors.I'm just curious...
the conversion ratios would be high and close to the upper limit of 1.0
(0.8)
Fast reactors if designed as breeders they have breeding ratios (same as
conversion ratio but always equal or larger than 1.0) such that their
doubling time (time needed to double the amount of fuel in the core) is
around 20 years. Again it is an economical criteria. Presently LMFBR's
are not economical with the price of cheep and abundant uranium.
Osman Kemal Kadiroglu
> Thanx.Have you got any info about conversio ratios I asked,i.e. Candu
> reactors vs PBMR or thermal vs fast reactors.I'm just curious...
AlexLoll
"Osman Kemal Kadiroglu" <okkad...@gmail.com> ha scritto nel messaggio
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> AlexLoll wrote:
>> Thanx.Have you got any info about conversio ratios I asked,i.e. Candu
>> reactors vs PBMR or thermal vs fast reactors.I'm just curious...
> I do not have the numbers right now. I would say that for CANDU and PBMR
> the conversion ratios would be high and close to the upper limit of 1.0
> (0.8)
Yes,I found 0,76 for HEU/thorium and 0,97 for thorium/uranium-233 in this
document " Near breeding thorium fuel cycle in Pebble Bed Htr " (HEU is >
90% uranium enriched with some proliferation issues).I'd like to understand
if Candu reactors could have better neutron economy and better thorium
utilisation than PBMR's,according to German past years data experience.To my
knowledge,no one never used thorium in heavy water moderated
reactors,neither in a lab scale
> Fast reactors if designed as breeders they have breeding ratios (same as
> conversion ratio but always equal or larger than 1.0) such that their
> doubling time (time needed to double the amount of fuel in the core) is
> around 20 years. Again it is an economical criteria. Presently LMFBR's are
> not economical with the price of cheep and abundant uranium.
Of course,I meant thorium exploitation in fast reactors vs thermal spectrum
(see India experience),not plutonium fast breeder reactors
dez...@usa.net
Bah, no one seems to know about molten salt reactors apparently.
The molten salt breeder reactor is ideal for thorium fuel cycles
because of its online reprocessing. The fuel never leaves the reactor,
only the fission products, the reactor is never taken offline, and the
reactor is far safer than light water reactors.
http://en.wikipedia.org/wiki/Molten_salt_reactor
http://www.ornl.gov/~webworks/cppr/y2001/pres/119930.pdf
In fact economic studies indicate molten salt reactors would produce
electricity more cheaply than coal or light water reactors... in
addition to producing only 1/100th the waste and requireing 1/100th the
fuel as unenriched thorium while providing light actinide incineration.
But everyone thinks only of fast breeder reactors or light water
reactors.
ks...@yahoo.com
The next generation of reactors will of the integral fast breeder
reactor (IFBR) variety. Their prototype was EBR-II
(http://www.anlw.anl.gov/anlw_history/reactors/ebr_ii.html ). When
Chernobyl was spewing radiactivity over Europe and Asia, the Loss of
Flow Test (LOFT) was conducted on EBR-II whereby they discontinued main
coolant flow to the reactor. EBR-II shut is itself down because of the
negative k(eff) temperature coefficient.
When I watched the documentary on the LOFT at EBR-II, the comment was
made "Now with accident at Chernobyl, we won't be able to give this
technology away."
There is no reason for anyone to be enriching uranium these days except
for the construction of simple nuclear devices, ie. bombs.
dez...@usa.net
And still has a positive void coefficient. IFBR wont ever take off
because its an inherently useless design except for producing plutonium
really fast. The fuel cycle is more expensive than light water
reactors, and far more expensive than molten salt reactors. The
reactivity flux for fast reactors in general is far higher than for
light water reactors, and far higher than molten salt reactors (which
have significantly lower because the xenon poisoning is removed online
and so no excess reactivity is required)
IFR is junk, allways will be junk. The only good thing about IFR is the
molten salt processing, which by the way is done online in a molten
salt reactor anyways.
> When I watched the documentary on the LOFT at EBR-II, the comment was
> made "Now with accident at Chernobyl, we won't be able to give this
> technology away."
And all fast reactors are prone to accidents, especially involving
criticality excursions due to high reactivity flux. They still have
positive void coefficients, as all solid fuel reactors due; They still
suffer the problems of a 'meltdown' if the fuel gets too hot. Really
please read the links on molten salt reactors rather than posting some
reactionary response on why IFR is better just because its gotten more
press.
Giuseppe
<dez...@usa.net> ha scritto nel messaggio
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>
> oyo wrote:
>> In all these fuel cycles one has to get the fuel out of the reactor
>> core and reprocess it to get the fissile material out. Considering the
>> political impications of enrichment (Iran) and reprocessing (North
>> Korea) along with the economical burden of these processes I doubt that
>> thermal breeders will be economical and feasible. On the other hand
>> PBMR can use "in situ breeding" and utilize more fuel without the need
>> for reprocessing. It will be rather easy to use any fuel cycle with a
>> PBMR may it be Pu/Th or others.
>
> Bah, no one seems to know about molten salt reactors apparently.
As far I know,no one molten salt reactor is never nuilt,neither in a lab
scale.Definitively,it's not a proven tecnology,unlike HTGR or HWR reactors
dez...@usa.net
Guess the one at oak ridge that ran for five years didn't exist then?
daestrom
<ks...@yahoo.com> wrote in message
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That's right. Any reactor with a positive void coefficient (power rises
when the coolant is removed) is too much like Chernobyl. A significant
contributer to Chernobyl was its positive void coefficient that accelerated
the power excursion. Bad idea, very bad.
daestrom
Paul Studier
>
>
> And still has a positive void coefficient. IFBR wont ever take off
> because its an inherently useless design except for producing plutonium
> really fast. The fuel cycle is more expensive than light water
> reactors, and far more expensive than molten salt reactors. The
> reactivity flux for fast reactors in general is far higher than for
> light water reactors, and far higher than molten salt reactors (which
> have significantly lower because the xenon poisoning is removed online
> and so no excess reactivity is required)
>
> IFR is junk, allways will be junk. The only good thing about IFR is the
> molten salt processing, which by the way is done online in a molten
> salt reactor anyways.
>
>
>>When I watched the documentary on the LOFT at EBR-II, the comment was
>>made "Now with accident at Chernobyl, we won't be able to give this
>>technology away."
>
>
> And all fast reactors are prone to accidents, especially involving
> criticality excursions due to high reactivity flux. They still have
> positive void coefficients, as all solid fuel reactors due; They still
> suffer the problems of a 'meltdown' if the fuel gets too hot. Really
> please read the links on molten salt reactors rather than posting some
> reactionary response on why IFR is better just because its gotten more
> press.
>
Not true. According to
http://nucleartimes.jrc.nl/Doc/ICONE8-8729.pdf
"The sodium void worth was slightly negative for EBR-II owing to the
very small core size."
So it depends on design. And as for all solid fuel reactors, both PWR
and BWR have negative void coefficients.
--
Paul Studier <Stu...@pleasenospamtoPaulStudier.com>
When you work, you create.
When you win, you just take from the loser.
For an explanation, see http://paulstudier.com/win
dez...@usa.net
Sorry, was referring to fast reactors with solid fuel.
In any case, a utility scale IFR design would have a positive void
coefficient then, because its core would no longer be very small. All
the coolant does is absorb neutrons at best, unless the reaction is
accelerated by the very slight moderation of sodium, so I'm not sure
how it can have a negative void coefficient, even with a 'very small
core.'
Whereas the molten salt design, the fuel is the salt, if theres a void
theres no fuel, and it still leaves all these fast reactors with the
problem of high reactivity flux because of the delayed neutron
component being so low. Sure you can make them suck not as much, but
they're still really a box made for making weapons material when
compared against the MSR.
Paul Studier
>> criticality excursions due to high reactivity flux. They still have
>> positive void coefficients, as all solid fuel reactors due;
Another example of a sodium cooled reactor with a negative void
coefficient is the Toshiba 4S. From
http://www.uic.com.au/nip60.htm
The Super-Safe, Small & Simple - 4S 'nuclear battery' system is being
developed by Toshiba and CRIEPI in Japan in collaboration with STAR work
in USA. It uses sodium as coolant (with electromagnetic pumps) and has
passive safety features, notably negative temperature and void
reactivity. The whole unit would be factory-built, transported to site,
installed below ground level, and would drive a steam cycle. It is
capable of three decades of continuous operation without refuelling.
Metallic fuel (169 pins 10mm diameter) is uranium-zirconium or U-Pu-Zr
alloy enriched to less than 20%. Steady power output over the core
lifetime is achieved by progressively moving upwards an annular
reflector around the slender core (0.68m diameter, 2m high). After 14
years a neutron absorber at the centre of the core is removed and the
reflector repeats its slow movement up the core for 16 more years. In
the event of power loss the reflector falls to the bottom of the reactor
vessel, slowing the reaction, and external air circulation gives decay
heat removal.
dez...@usa.net
Sounds very dubious to me. I'm sure they supposedly have done their
homework, but fission products accumulate in the fuel and become
sterile neutron absorbers. How do you control reactivity swings in this
box one might wonder, as all the swings in a fast reactor are going to
be big and fast. And I still dont see how you can have a fast reactor
with a negative void coefficient. You take away the coolant and you
only take away neutron absorbtion. Maybe the coolant does some
reflection of some sort in a small reactor I suppose.
But you still have to cart it away and process the waste and deal with
the accumulated actinides, and one might imagine that such a design
would work just as well using light water reactors with a neutron
reflector/absorber configuration.
The worst sins of these devices is they are all inferior to molten salt
power reactors for doing actinide incineration and electric power but
they continue to get more funding. Why is that?
Billy H
"Osman Kemal Kadiroglu" <okkad...@gmail.com> wrote in message
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In this situation do you allow the material to process or do you store it
away from the 'active' world?
When you say economical, is it not most economical to allow maximum use of
the potential of the materials, all the way down to a non-energy emmiting
material (in terms of our applications)?