XYLENE POWER LTD.

FNR FUEL

By Charles Rhodes, P.Eng., Ph.D.

INTRODUCTION:
This web page addresses the issues of the start fuels and sustaining fuel required by Fast Neutron Reactors (FNRs).
 

PREREQUISITE STUDY:
Students are encouraged to first study the web pages titled:
FNR POLITICS
FNR CONCEPT
FNR DESCRIPTION
FNR FEATURES
FNR OPERATION
FNR FUEL CYCLE
so that they have a good understanding of what a Fast Neutron Reactor (FNR) is, how it works and its purpose.
 

NATURAL URANIUM:
The Front End of the Nuclear Fuel Cycle
 

WATER MODERATED REACTOR:
A CANDU reactor usually operates with natural uranium oxide fuel in which the initial uranium fractions are 0.7% U-235 and 99.3% U-238. The purpose of the heavy water moderator is to immediately lower the average neutron kinetic energies from about 2 MeV to thermal energies (.05 eV) with minimal neutron absorption. At thermal neutron energies the U-235 fission capture cross-section for neutrons is very high, which provides reactor criticality in spite of the low U-235 concentration.

A water moderated reactor obtains its energy first by fissioning the U-235 in its fuel and then by forming and partially fissioning transuranic actinides (TRU). The fission products include isotopes with large thermal neutron absorption cross sections. Typically, due to fission product accumulation, the fuel has to be replaced about every 18 months. This requirement for ongoing fuel replacement results in very poor energy harvesting from natural uranium. This is a major issue in use of water moderated reactors to displace fossil fuels.

The energy efficiency of a CANDU reqacctor is only about 1.0% and the energy efficiency of a Light Water Reactor (LWR) is only about 0.5%.

A matter common to all nuclear reactors that fission with thermal neutrons is that a fraction of the thermal neutrons are captured by U-238 and by its neutron capture products and their decay daughters which together form a class of isotopes known as transuranic actinides (TRUs). A well known example of a TRU is Pu-239. It is highly toxic and has a half life of about 25,000 years. There are other highly toxic TRU components with atomic weights comparable to uranium and with half lives of the order of 10,000 years.
 

THE FAST NEUTRON REACTOR ADVANTAGE:
A fuel sustainable FNR provides 200X the natural uranium fuel utilization efficiency of a Light Water Reactor (LWR) and 100X the natural uranium fuel utilization efficiency of a heavy water moderated (CANDU) reactor. A fuel sustainable FNR obtains its energy by continuously converting the abundant isotope U-238 into TRU and then later fissioning the TRU. During each fission step sufficient excess neutrons are released to convert more U-238 into more TRU. A FNR should be designed so that there is net production of TRU. Then the cumulative net energy output is limited only by the supply of U-238.

An important property of TRU is that for fast neutrons the fission cross sections are larger than the neutron capture cross sections whereas for thermal neutrons the fission cross sections are smaller than the neutron capture cross sections. Thus, in a fast neutron flux the TRU concentration will gradually decrease whereas in a thermal neutron flux the TRU concentration will gradually increase. Hence, to prevent net formation of TRU in the FNR core zone, the core zone operates with fast neutrons. Similarly, to cause net formation of TRU in the blanket zone the blanket zone operates with thermal neutrons.

However, with 2 MeV fast neutrons, such as are emitted by nuclear fission, the fission capture cross section is only about 3% of the fission capture cross section for thermal neutrons. Hence, to achieve sustained reactor criticality in the core zone the initial TRU concentration fraction must be increased from about 0.7% to about 20%. The core fuel bundles are surrounded by blanket fuel bundles where the fuel rods are a 90% U-238 - 10% Zr alloy and where the U-235 concentration is typiically < 0.3%.
 

FNR FUEL:
A major constraint on the rate of implementation of liquid sodium cooled FNRs is the available supply of FNR core rod start fuel containing about 20% TRU. This fuel supply should gradually increase as FNRs are deployed and their blanket fuels are reprocessed.

At the commencement of each fuel cycle the FNRs contemplated herein initially operate with metallic 20%TRU-70%U-10%Zr alloy core fuel rods and blanket fuel rods which are 90%U-10%Zr. At the time of fuel extraction the core fuel rod concentertion is approximately 12%TRU-63%U-10% Zr-15%fp. Note that the drop in TRU fraction is 8%.
 

FNR FUEL REPROCESSING:
After used fuel extraction the fuel is reprocessed to:
1) Reject fission products from the core fuel to be recycled;
2) Extract TRU atoms from the blanket fuel to be recycled;
3) Form new core fuel using recycled core fuel atoms, extracted TRU atoms and new U-238 atoms;
4) Form new blanket fuel using recycled blanket fuel atoms and new U-238 atoms.
 

BLANKET SIZE:
Assume that the blanket fuel rod length is (1 / 2) the core fuel rod length.

At the end of each fuel cycle ideally the average concentration of TRU in the interior layer of blanket fuel rods should be 8%, the average concentration of TRU in the next layer of blanket rods should be 4%, the average concentration of TRU in the next layer of blanket rods should be 2%, the average concentration of TRU in the next layer of blanket rode should be 1%, and so on.

A practical issue is that all of the fuel rods in a single fuel bundle should be nearly identical. Otherwise there could easiy be local over heating of one or a small group of fuel rods that is not easily detectable. It is desired that all the fuel rods in a particular fuel bundle behave in the same way.

At the end of each fuel cycle both core fuel rods and the interior blanket fuel rods are reprocessed. During reprocessing the TRU contained in the inner blanket rods is transferred to the core fuel rods and the 15%fp (fission products) are discarded and are replaced by depleted uranium harvested from the interior blanket fuel rods. At the end of each fuel cycle all the blanket fuel rods move inward one fuel bundle width.

Thus, the optimum length of a blanket fuel rod is the length over which the radial neutron flux emitted by the core decreases by about a factor of two. Note that this length is a function of the properties of U, Zr, Na, HT-9 and their geometry. Thus, with this design which has six blanket rod bundle layers around the core zone, about 1 / 64 of the neutrons radially emitted by the core zone are lost to absorption in the Na guard band around the fuel assembly.

Since about half the fission neutrons flow from the core zone to the blanket zone, the fraction of fission neutrons that are lost to absorption in the Na guard band is about (1 / 128).

The U used in a FNR is depleted uranium, typically containing < 0.3% U-235. The TRU is typically 50% Pu-239 + 16% Pu-240 + 33% other(neptunium, americium, curium,berkelium, californium, einsteinium, etc.). The fuel rods are thermally connected to the fuel tube inner wall by liquid metallic liquid sodium. A practical advantage of this fuel design is extreme safety.
 

POSSIBLE FUTURE FNR FUEL:
Possible future FNR fuel is a mixture of U-238-Pu-239 and Th-232 fuel rods as described in A Symbiotic System of Large Fast Breeder Reactor And Small-Sized, Long Life, Thorium Satellite Reactors - General Introduction -

A problem with thorium (Th-232) is that it forms the element protactinium (Pa-233) which has a large neutron absorption cross section. The protactinium should be removed from the neutron flux until after the protactinium decays into U-233. This ongoing selective protactinium removal is best accomplished using a molten salt reactor,
 

FUEL THERMAL EXPANSION:
a) In normal FNR operation as the fuel temperature increases thermal expansion of the fuel alloy reduces the fissile atom concentration which reduces the reactivity, stopping the nuclear reaction;
b) Fuel melting might allow the fissile fuel alloy to flow downwards by gravity, displacing lower density liquid sodium inside the fuel tube, thus reducing the average fissile atom concentration which stops the nuclear reaction;
c) If the fuel rapidly gets too hot as might occur if prompt neutron criticality occurs the liquid sodium within the core zone of the fuel tube will vaporize which will tend to blow fissile fuel in the fixed fuel bundles toward the fuel tube plenums, stopping the nuclear reaction.
 

TEMPERATURE CONSTRAINT:
The disadvantage of this metallic fuel is that the maximum reactor design liquid sodium discharge temperature is only 460 degrees C. This choice of liquid sodium discharge temperature allows the worst case core fuel rod centerline temperature to reach about 560 degrees C, which is still well below the ~ 602 degree C core fuel rod center line melting point. The 460 degree C discharge temperature of this sodium cooled reactor is still much higher than the 320 degree C maximum temperature of most water cooled reactors but is much less than the 650 degree C discharge temperature anticipated from molten salt reactors.

This author anticipates that due to use of very expensive materials molten salt reactors will only be economic in applications that truly require high temperatures such as synthesis of high energy density liquid hydrocarbons.
 

UNSUITABILITY OF U-235 FOR USE IN FNRs:
Note that U-235 is NOT a good FNR fissile fuel. Its TCE (Thermal Coefficient of Expansion) is much less than the TCE of both pure plutonium and mixed TRU. The importance of this issue is not obvious until one is involved in the detail of FNR fuel assembly design. Over the course of a fuel bundle's working life it will swell in the core region due to fast neutron impingement, in spite of being made from a swelling resistant alloy (HT-9) and in spite of a mechanical design that is resistant to core zone swelling. To achieve long term reactor control certainty it is necessary to provide sufficient space between adjacent fuel bundles to allow core zone fuel bundle swelling to occur without the movable fuel bundle vertical movement becoming jammed. That clearance space is occupied by liquid sodium. However, additional liquid sodium in the core region introduces a positive component to the reactor reactivity coefficient with temperature. In order to ensure that the net reactor reactivity coefficient with temperature is negative, the more negative term introduced by the higher TCE of TRU as compared to uranium is required.

This author is aware of work by Terrapower to eliminate the sodium inside the fuel tube, which reduces the ratio of sodium to fuel in the core region and hence theoretically allows use of U-235 fissile instead of Pu-239. However, a serious problem with that approach is that it also eliminates the fuel melting safety shutdown mechanism otherwise provided by displacement of liquid sodium internal to the fuel tube by liquid plutonium if the fuel gradually gets too hot.
 

FNR FISSILE FUEL SOURCES:
Note that the main fissile isotope in the core fuel alloy is Pu-239. Pu-239 does not occur naturally. It is obtained by converting U-238 into Pu-239 in a nuclear reactor. The Pu-239 of the core fuel alloy can be obtained via seven possible routes:
1) Reprocessing of used CANDU fuel initially made from natural uranium;
2) Reprocessing of used CANDU fuel initially made from used LWR fuel;
3) Reprocessing of used LWR fuel;
4) Down blending of military plutonium;
5) Reprocessing of used FNR Core Fuel;
6) Reprocessing of used FNR Blanket Fuel.
7) Purchase of foreign supplied Pu alloy of uncertain origin.
 

FNR BLANKET FUEL SOURCES:
The FNR blanket fuel rods are formed from an alloy of zirconium and depleted uranium. The practical sources of depleted uranium are:
1) Concentration of used CANDU fuel initially made from natural uranium;
2) Concentration of used CANDU fuel initially made from used LWR fuel;
3) Concentration of used LWR fuel;
4) Reprocessing of used FNR Blanket Fuel.
5) Purchase of foreign made depleted uranium that is rejected from uranium enrichment processes.
 

FUEL SOURCING PROCESSES:
For practical safety reasons each of the aforementioned fuel sourcing processes is different and requires its own well defined safety procedures. However, in general the sourcing processes break down as follows:

Used Water Cooled Reactor Oxide Fuels:
1) Most existing CANDU and LWR fuels consist primarily of uranium oxide sealed inside zirconium tubes.

2) For these fuels the first step is to concentrate the fuel by using a nitric acid recrystalization process to separate uranium oxide and zirconium from everything else. During this initial fuel concentration process inert gases are rejected, cesium is captured and zirconium is recycled. During this concentration process and during subsequent transport of both pure uranium and fuel concentrates the radiation safety issues related to U-232 are greater for fuels that have been in a LWR as compared to natural uranium based CANDU fuels.

3) This uranium oxide which is depleted in U-235 is stored and is then reduced to metallic uranium as needed to produce FNR blanket fuel rods.

4) The fuel concentrates are transported to the fuel reprocessing site, reduced to metallic form and then electrolytically separated into their major components.

5) The fission products are rejected and sent to 300 year storage.

6) The remaining components are mixed together in the appropriate ratios and then formed into fuel rods.
%nbsp;

Recycling Used FNR Fuel:
1) The fuel tube reprocessing sequence involves:
a) Venting the compressed inert gases;
b) Removal of sodium and sodium salts;
c) Recycling of the fuel tube alloy;
d) Mechanical sorting of blanket fuel rods from core fuel rods;
e) Electronic assessment of the Pu concentration in each blanket fuel rod;
f) Reuse of most blanket rods.

Downblended Military Plutonium:
Military plutonium differs from commercial reactor plutonium in two important respects:

1) Military plutonium contains a smaller fraction of Pu-240. As long as this fraction is small the plutonium is a potential security risk because with appropriat chemistry it could be made into a bomb. Thus from a securityperspective, if military plutonium is to be used for power generation the first step is to blend it with a sufficient fraction of Pu-240 to make it unsuitable for military use. Once so blended this plutonium no longer has significant military value.

2) The electrolytic plutonium-uranium separation process results in pure uranium and a 70% uranium-30% plutonium alloy. This alloy is suitable for making FNR fuel but the parties must be aware that the plutonium could be selectively chemically removed. Hence it is desirable that the Pu-240 be added before the Pu-U aloy is formed.
 

FOREIGN SOURCES OF DEPLETED URANIUM:
Several nations have facilities for converting natural uranium (0.7% U-235) into LWR fuel (5% U-235). These facilities discard large amounts of depleted uranium (~ 0.3% U-235) in the form of the chemical UF6.The process for converting UF6 into metallic uranium is described in Elita
 

IMPORTANT FNR FUEL FEATURES:
In summary, liquid sodium cooled power FNRs can provide sufficient energy to sustainably displace fossil fuels with almost no production of long lived nuclear waste. FNRs can also be used to safely dispose of spent fuel from CANDU and other water moderated nuclear reactors.
 

CHANGE IN CORE FUEL ROD Pu CONCENTRATION WITH TIME:
During each FNR fuel cycle the Pu fraction in the core fuel rods decreases from 20% to 12.5% by weight corresponding to 15% core fuel burnup and 7.5% conversion of U-238 into Pu in the core fuel. With U-238 blanket fuel the fuel recycling process yields excess core fuel rod material which enables ongoing expansion of the FNR fleet.
 

TECHNICAL CONSIDERATION:
A major practical issue with liquid sodium cooled FNRs is the necessity for full automation of fuel rod, fuel tube and fuel bundle production and reprocessing. The required processes have been proven in a laboratory which can process several kg of fuel per day. This processes needs to be scaled up to tonnes per day for supporting a fleet of power FNRs.

Due to neutron activation of the fuel bundle materials the fuel reprocessing is nearly all carried out by robotic equipment. In order to make FNRs economic all aspects of FNR fuel rod, fuel tube and fuel bundle production and reprocessing must be fully automated. This automation requires a major capital commitment.
 

BACKGROUND INFORMATION:
The FNR geometry is chosen so that about (1 / 3) of the fission neutrons are absorbed by plutonium in the core zone to sustain the nuclear chain reaction and the remaining (2 / 3) of the fission neutrons are absorbed by U-238 located in both the core and blanket zones for the purpose of breeding more Pu-239 for future use. A small fraction of the fission neutrons are absorbed by steel in the fuel tube assembly and by liquid sodium.
 

Pu DOUBLING TIME:
1) A CANDU reactor takes about 1.7 years to convert 1% of its fuel weight into fission products.

2) One FNR fuel cycle time is the time period between successive reprocessing of FNR fuel bundles. During one ~ 30 year fuel cycle time a FNR converts about 15% of its core fuel weight or 75% of its plutonium into fission products. With each fission it generates about 0.6 atoms of plutonium in addition to the two atoms of plutonium required to usstain its own operation.

3) The Pu-239 doubling time is the time required to double the total available Pu-239 mass. Since each Pu-239 fission in a FNR produces about 0.6 new Pu-239 atoms in addition to those necessary to sustain the FNR operation in one fuel cycle the amount of net new plutonium produced is:
0.75 (number of original plutonium atoms in core zone)(0.6) = 0.45 (number of original plutonium atoms in core zone)

Hence the Pu-239 doubling time is given by:
(fuel cycle time) / 0.45 = 2.22 fuel cycle times

Since one fuel cycle time is about 30 years the time required to double that amount of available Pu-239 is about:
2.22 X (30 years) = 67 years

A relevant reference is: Effect of TRU fuel loading on core performance and plutonium production
 

MAJOR CONCERNS:
1) Presently there is no recognition by either the Canadian or US governments that the Pu-239 shortage threatens the very existence of the human species. Without sufficient Pu-239 there is no sustainable substitute for fossil fuels.
2) Making Pu-239 from U-235 requires consumption of one atom of U-235 for every 1.5 atoms of Pu-239 produced. It takes much more natural uranium to start a FNR than it does to fuel a CANDU reactor of similar thermal output capacity.
3) If we contemplate quadrupling the the world nuclear reactor capacity over the next 40 years using breeder reactors to achieve sustainability we are committing the entire known mineable natural uranium resource. If we fail to do so as fossil fuels are exhausted there will be no economic fuel source left but renewable energy.
4) The only strategy that can mitigate these problems is conservation of Pu-239 and U-235. The present practise of consuming Pu-239 in water moderated reactors or burying spent water moderated reactor fuel containing these isotopes in the ground is worse than stupid.
5) All the new reactor designs that do not net breed new fuel should simply be discarded as a waste of critical resources. The regulatory authorities should do all necessary to to accelerate approval and funding of new breeder reactor designs.
6) From an electricity market perspective all new breeder reactor capacity should have the highest priority for electricity grid access. The existing market mechanisms will just have to be changed to make that happen. The high school core curriculum should have a section that discusses the crucial role of Pu in future energy production and that sufficient Pu will not exist unless breeder reactors are both funded and operated at maximum capacity today irrespective of present natural gas prices.
7) The above observations are dictated by the laws of physics. There are all kinds of claims based on market models that have no foundation in physical reality. The human species as we now know it will live or die in accordance with the natural physical laws.
8) There is a possibility of harvesting natural uranium from the oceans. However, the concentration of uranium in sea water is only about 3 parts per billion so the cost of uranium recovery from the ocean is very high. Possibly there might be some marine life species that naturally concentrates uranium in the ocean which might make harvesting of uranium from the ocean more practical.
 

CORE FUEL SOURCE #1 - UK:
Ask the UK to pay us to use some of their excess Pu, since it is costing them money to store it (that’s why they have tenders out to dispose of it). We could either take it for free, or pay something for it. However, the politicians seemed to be petrified by the thought of transporting such material, fearing blockades by anti-nukes and movements greater than what stopped the rather benign transport of steam generators across the Great Lakes and through the St. Lawrence Seaway to Sweden or Denmark. If the gamma emitting fission products are removed from the Pu it may be practical to transport the Pu from the UK to Ontario using a heavy lift military transport aircraft.

Moving the required fuel from the UK to Canada would likely require several flights. The planes could land at Trenton. From Trenton the fuel could be moved by rail. The shipping container(s) could be fitted with buoyancy modules similar to those used for salvaging sunken ships so that even if the transport plane went down in the ocean the container would float.

This author believes that it would be prudent for Canada and Ontario to obtain a written commitment from the UK with respect to possible supply of pilot FNR startup fuel. In view of the highly technical nature of this matter the government of Ontario should subcontract this task to an organization such as Xylene Power Ltd./ Micro Fusion International Ltd. that has the necessary contacts in both Canada and the UK.
 

CORE FUEL SOURCE #2 - USA:
Import LEU (Low Enriched Uranium) from the US, since one can start a FNR with U-235 at or below 20%. Again, the politicians would not want to go in that direction if they can help it, even though we import that sort of material regularly for reactors such as the one on the McMaster campus.

This is not a good long term solution because in the future US based FNR suppliers would likely move to restrict LEU exports to Canada if they thought that they were losing business due to Canadian FNR competition. There are precedents for such trade restrictions in other sectors such as softwood lumber and agricultural products. The problem in dealing with the USA is that Congress and the Senate can over ride any treaty signed by the US president. This problem is particularly acute when neither the US Democrats nor the US Republicans have a commanding majority. In those circumstances special interest groups in the US frequently over ride US treaty obligations. The bottom line is that the US is not a good single source of a critical material.
 

CORE FUEL SOURCE #3 - SPENT CANDU FUEL:
Selectively extract most of the UO2 from spent CANDU fuel and then take the remainder (much smaller volume) and selectively extract the fission products by pyroprocessing (one does not need an excessively large capacity for that). That leaves a mix of U-238, and transuranic actinides with sufficient concentration to start the FNR. This approach also makes major immediate inroads into reducing the amount of currently stored used CANDU fuel.

If the purity of the selectively extracted uranium oxide is sufficiently high the uranium oxide could be stored in conventional barrels, not high tech containers. That issue alone might save $500 million. Thus the issue of the purity and radioactivity of the selectively extracted uranium oxide needs very careful attention.

An advantage of this approach is that relatively little transport of radio isotopes is required and the amount of stored used fuel is visibly reduced up front even before the FNR starts (even if the trans-uranic actinides don’t get reduced until the reactor is actually operating). The politicians see this methodology as a new source of skilled jobs in addition to maintaining the nuclear plant jobs.

A major further advantage of this approach is that it eliminates the tens of billions of dollars of future fuel disposal liability identified by the Nuclear Waste Management Organization (NWMO). These dollars are needed for other purposes such as health care, infrastructure and old age care.

Going the route of obtaining the fissile starting material from spent CANDU fuel puts the emphasis on eliminating the radioactive fuel “waste” (which no one could argue against, and for which monies have already accumulated in trust). To do that right one of course will need a FNR once the start fuel has been extracted from the stored spent CANDU fuel.

To minimize implementation delays relating to nuclear licencing, a small amount of the spent CANDU fuel inventory at Pickering should be moved to Chalk River to enable testing and debugging of the selective uranium oxide extraction process, the selective fission product extraction process and the zirconium recovery process in a suitably licenced facility. This small amount of spent CANDU fuel could be moved by rail using existing CNSC approved spent fuel transport containers.
 

EXECUTION AND POLITICS:
The advantage of starting fuel sources #1 and #2 is that Ontario could proceed directly to implementation of a pilot FNR now and could then develop the chemical process necessary for fuel reprocessing after the pilot FNR was in operation. In this respect sources #1 and #2 have a major commercial advantage. The additional revenue from earlier FNR electricity sales would largely offset the pilot FNR and fuel reprocessing development costs.

The electricity output of the pilot FNR would be less than 10% of the generation connected to the Ontario grid, Hence the impact of the pilot FNR on the Ontario Long Term Energy Plan (LTEP) would be insignificant. Moreover, since the pilot FNR can load-follow, one could think of not renewing some of the contracts for gas-fired generation that are up for renewal in a few years. That would reduce Ontario’s CO2 emissions even further.

However, the strong emphasis on eliminating the fuel “waste” meant that using extraneous Pu was negating getting rid of transuranics in used CANDU fuel by importing more transuranics (Pu) instead. Similarly, one “burns” fewer used fuel transuranics if one buys enriched uranium to start the reactor. Therefore from a political perspective the best solution is to concentrate on Source #3 and get the fuel recycling/fabrication going. Then the FNR is merely required for fuel cycle completeness and not primarily for power, which just happens to be a very useful bonus, similar to the fact that avoiding CO2 emissions is just a normal by-product of the whole process.

The contemplated Pickering Advanced Recycling Compex (PARC) is a very useful happening, since conversion of the Pickering facility to recycling the stored used fuel saves jobs politically and also in reality. The Pickering site is licensed at least for nuclear activity, though perhaps not yet for fuel refabrication. It’s inventory of 15,000 tons of used CANDU fuel serve as a useful and easy mathematical example of the fuel recycling process.
 

CANDU SPENT FUEL RECYCLING PROCESS:
The following process is appropriate for fuelling of a 700 MWe pilot FNR.

a) Move 75% of the existing spent CANDU fuel inventory (0.75 X 50000 tonnes = 37,500 tonnes) to safe, secure long term accessible naturally dry off-site storage. This material will be needed to start future FNRs.

b) If after evaluation of the long term risks related to the Pickering location it is decided that these additional FNRs are to be built at Pickering to take advantage of existing electricity transmission facilities, then there is limited merit in use of off-site storage for the spent CANDU fuel inventory.

c) Process the remaining 12,500 tonnes of spent CANDU fuel to selectively remove uranium oxide so as to obtain 1250 tones of fuel precursor and 11,250 tonnes of depleted pure uranium oxide which go to interim storage.

d) Use part of the remaining residue to form blanket rods.

e) Use the remainder of the residue as an FNR blanket rod material.

f) Further extract fission products from the fuel precursor.

g) Place the extracted fission products into naturally dry, safe, secure accessible off-site storage for 300 years to allow most of the fission products to decay into stable elements.

h) Form the remaining fuel material into core fuel rods.

i) Run the FNR. Extract fuel bundles when they reach their design cycle time.

j) While the reactor is running in step (i) draw another 50 tonnes per annum of UO2 from on-site storage to form new blanket rods;

k) When each bundle reaches its design cycle time move the bundle from the reactor and store it in liquid sodium around the liquid sodium pool periphery, out of the neutron flux. This bundle will remain in such storage for several years to allow decay of short lived fission products.

l) Every year remove the fuel bundles that have been in peripheral liquid sodium storage and send them for reprocessing. This reprocessing effectively selectively extracts fission products, transfers Pu-239 from blanket rods to core fuel rods, adds pure UO2 to replace the lost weight of fission products and adjusts the zirconium concentration in the core rods.

m) Move the fuel bundles that have been in the reactor for one fuel cycle time to the now vacated storage positions around the periphery of the liquid sodium pool.

n) Load the reactor with new fuel bundles formed during step (j).

o) Repeat steps (l) to (n) every year.

p) Eventually the reserve of pure UO2 stored will be exhausted and either more spent CANDU fuel must be drawn from off-site storage or new UO2 obtained from other sources will be required to maintain reactor operation.

Thus four 700 MWe FNRs will efficiently consume all the transuranium actinides presently in storage. In so doing these FNRs will form the Pu-239 that is necessary to maintain future FNR criticality. This Pu-239 is integral to the recycleable FNR fuel that will be required to sustain FNR operation for many centuries into the future. These four FNRs will be sufficient to replace 3000 MWe of output from the Pickering Nuclear Generating Station.

After the extracted fission products have been in off-site storage for 300 years a few longer lived fission products remain. These fission products are removed by selective chemical extraction and are placed in storage for another 300 years.

After all of the spent CANDU fuel has been processed, each reactor requires only about 0.5 tonne per annum of additional depleted UO2 per fuel load to keep going. It uses the U-238 to create and replenish its own fissile material (Pu-239) as fast as that fissile material is used up by being split into 1.0 tonne of fission products. The fission products are the only residue that leaves the system. These fission products naturally decay to stable elements while in engineered containers stored in a secure naturally dry location such as a depleted hardrock mine located within a suitable mountain.

An important facet of a FNR operated using first-in first-out refuelling is that it is imposible to use such a reactor for weapon production because the at the contemplated fuel cycle time the (Pu-240 / Pu-239) ratio is too large for fission bomb purposes.

This same fuel recycle process sequence could potentially be repeated at any nuclear generating station world wide that possess a FNR and a substantial inventory of spent CANDU fuel. This option of adding a FNR to an existing CANDU reactor facility for on-site nuclear waste dispoal may enable additional CANDU reactor sales. This opportunity should be pursued with CANDU Energy Inc.
 

FNR START FUEL ECONOMICS:
We must stop treating spent CANDU fuel as a liability and start treating it as a potential asset. The existing 50,000 tonne inventory of spent CANDU fuel when reprocessed should be used to start 3 to 4 CANDU 6 size FNRs.

From a practical perspective I suggest that we think in terms of MFI charging OPG a disposal fee of:
$16 billion / 50,000 tonnes = $320 / kg
for spent CANDU fuel disposal over a 10 year period.

MFI reprocesses the spent CANDU fuel inventory into sufficient FNR fuel to start about 4 FNRs that can each displace a CANDU 6E.

The high tech storage containers may cost: $20,000 / tonne X 50,000 tonnes = $ 1 billion.

The storage and transportation costs for a facility like Jersey Emerald might cost $1 billion.

Thus for this plan to hang together the radio chemistry must cost less than $ 5 billion / 50,000 tonnes = $100 / kg.

There will be lots of unexpected expenses, so we really need to think in terms of $50 / kg.

Can we selectively extract 90% of the uranium for less than $25 / kg? That would leave about $250 / kg X 5,000,000 kg = $1.25 billion for the rest of the process.

Think in terms of $300 million for salaries and benefits related to the sophisticated part of the process. The balance would be for equipment, materials and expenses.

Over ten years that is $30 million per year for salaries, Which allows an operation with a staff about half the size of the NWMO. Clearly these people have to be workers, not parasites doing primarily public relations. The plant gross input has to be:
50,000 tonnes spent CANDU fuel / 2000 working days = 25 tonnes / day.

The processed FNR core fuel rod output has to be 1 to 2 tonnes / working day.

I think that these are likely workable numbers in the private sector but they do not allow for a lot of costs related to overhead for dealing with government rubber necks.

Thus the plan must envisage the work being done in circumstances where government, CNSC, NWMO erc. cannot easily interfere. Similarly, to raise the required investment capital the investors must have assurance that once their money is invested government and its agencies cannot interfere. We cannot have circumstances like Darlington where part way through construction government agencies changed the safety requirements. Hence the core rod fabrication portion of this work needs to be done in a remote location, not at Pickering. At an urban location it may be impossible to raise the public liability insurance required to avoid government interference, whereas at a remote location public liability insurance would not be a major issue.
 

This web page last updated July 22, 2023