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The Ottensmeyer Plan, which is named after its lead proponent Peter Ottensmeyer, is a method of using liquid sodium cooled Fast Neutron Reactors (FNRs) to dispose of spent CANDU reactor fuel and other high atomic weight radio toxic nuclear waste with only a relatively small requirement for 300 year radio isotope storage and only a tiny requirement for long term (> 300 year) radio isotope storage.
In addition to solving the problem of disposal of spent nuclear reactor fuel the Ottensmeyer Plan maximizes the amount of energy that can be realized from the finite world wide supplies of uranium and thorium.
A liquid sodium cooled Fast Neutron Reactor (FNR) consists of a horizontal pancake shaped layer of vertical reactor core fuel rods that is sandwitched between two thicker layers of vertical reactor blanket fuel rods. The fuel rods are centrally located in a liquid sodium pool. Fission reactions take place in the core rods. The blanket rods capture excess neutrons from the fission reaction and breed more fissile fuel. Periodic reprocessing of the fuel rods extracts fission products from the core fuel rods and transfers new fissile material from the blanket fuel rods to the core fuel rods. This process will operate as long as there is a supply of replacement blanket rod material (U-238).
The Ottensmeyer Plan operates by fissioning the transuranium actinides, which are high atomic weight isotopes with long half lives, into low atomic weight isotopes that, with a few exceptions, have relatively short half lives. The low atomic weight fission products, which typically constitute about 15% of the FNR spent core rod fuel mass, are electrochemically extracted from the spent core rods. The remaining core rod fuel mass along with 15% new core rod mass obtained by reprocessing blanket rods, is recycled through a FNR. The consumed blanket rod mass is replaced with depleted uranium (U-238).
Repetition of this fuel recycling methodology reduces the natural uranium consumption and interim spent fuel storage requirements per kWh generated by about 100 fold as compared to a CANDU reactor. The small remaining stream of long lived radio isotopes is interim stored in engineered porcelain-stainless steel containers.
The fission products are kept in isolated interim dry storage for about 300 years during which period their radio toxicity naturally decays below the radio toxicity level of natural uranium. After 300 year interim storage the contained elements with long lived radio active isotopes, such as selenium (Se) and tin (Sn), are selectively extracted before the fission products are released to the environment. This selective extraction reduces the spent fuel mass requiring long term storage by a further 10 fold. The selectively extracted elements such as Se and Sn that have long lived radio isotopes are sent to long term (~ 1 million year) storage in a Deep Geologic Repository (DGR).
The location and structure of the DGR is chosen so that the DGR will remain naturally dry, will naturally drain, naturally ventilate and will remain accessible far into the future.
The combined 100 X 10 = 1000 fold reduction in spent fuel mass per kWh requiring long term storage enables economic use of engineered containers to hold the small spent fuel fraction that actually requires long term storage. This arrangement, which allows periodic inspection of the stored waste and future repair or replacement of the engineered containers, protects ground water purity and provides public safety certainty for future generations.
The FNRs used for implementation of the Ottensmeyer Plan are designed to minimize production of long lived radio toxic low atomic weight istopes such as Be-10, C-14, Cl-36, Ca-41, Ni-59, Se-79 and Sn-126. These long lived low atomic weight isotopes, if they form, must be extracted from the waste stream and kept isolated from the environment for periods ranging from 60 thousand to 3 million years. To minimize or avoid production of long lived low atomic weight isotopes the FNR fuel tube assembly should be fabricated out of high purity materials containing minimal amounts of the elements beryllium, carbon, chlorine, calcium, nickel, selenium and tin. Isolation of long lived radio isotopes from the environment for 1 million years requires the use of engineered porcelain encased stainless steel containers stored in a permanently accessible, naturally ventilated and naturally dry (gravity drained) deep geologic repository formed in stable granite.
As a result of the exclusion of these problem elements, especially carbon and nickel, the FNR fuel tubes have constraints on: maximum operating temperature, maximum internal pressure and maximum thermal stress.
In order to prevent leakage neutrons from the reactor blanket impinging on: surrounding intermediate heat exchange tubes, stainless steel pool liner and lava rock insulating walls there is a 2.8 m thickness of liquid sodium between the reactor fuel tube assembly and the nearest heat exchange tube or primary sodium pool containment wall. This sodium thickness requirement sets a minimum on the primary sodium pool size and implies that it is impractical to fully assemble the sodium pool in a factory. Instead FNRs should be site assembled from factory built and tested modules, each of which is sufficiently small to be readily transported by road and/or rail.
The Ottensmeyer Plan, as originally conceived by Peter Ottensmeyer, is described in the following papers:
|LINK NAME||PAPER TITLE|
|Ottensmeyer 16-09||The Travesty of Discarding Used CANDU Fuel|
|Ottensmeyer 15-05-31||Productive Elimination of Nuclear Waste (PENW): A Complementary Boon for CANDUs and the Canadian Nuclear Industry|
|Ottensmeyer 14-05-25||Synergy Between CANDU and Fast-Neutron Reactor Technologies|
|Ottensmeyer 13-05-21||Nuclear Fuel Waste Consumed and Eliminated: Environmentally Responsible, Economically Sound, Energetically Enormous|
|Ottensmeyer 13-03-18||Accelerated Reduction of Used CANDU Fuel Waste with Fast-Neutron Reactors: Fuel Cycle Strategy Cuts TRU Waste Lifetime from 400,000 Years to Less than 80 Years|
|Ottensmeyer 12-07-xx||ENGINEERING DIMENSIONS - CANDU FUEL WASTE RE-USED, RECYCLED, ELIMINATED: $45 TRILLION OF CARBON-FREE ELECTRICITY VIA FAST-NEUTRON REACTORS|
|Ottensmeyer 12-06-10||Used CANDU Fuel Waste Consumed and Eliminated: Environmentally Responsible, Economically Sound, Energetically Enormous|
|Pyroprocessing Slides||Pyroprocessing System|
The practical realization of the required fast neutron spectrum with a liquid sodium cooled fast neutron reactor is the subject of two books. The book titled: Plentiful Energy - The Story of the Integral Fast Reactor by Charles E. Till and Yoon Il Chang provides a good introduction to the subject. The book titled EBR-II Experimental Breeder Reactor-II by Leonard J. Koch provides more in depth technical detail.
A commercial fast neutron reactor known as the GEH PRISM, which is a design evolution of the EBR-2, is available from GE-Hitchi. Technical details about this reactor are available at: GEH PRISM.
The approximate design of 300 MWe fast neutron reactor suitable for implementation of the Ottensmeyer Plan is developed at FNR DESIGN. Issues related to reactor tube selection are set out at FNR FUEL TUBES and at FNR FUEL TUBE WEAR. The details of the fuel reprocessing are set out at FNR MATERIAL RECYCLING and at OTTENSMEYER PLAN DETAIL.
EFFECT OF GOVERNMENTAL INCOMPETENCE/CORRUPTION:
In April 2016 the Canadian Nuclear Laboratories released a report titled A Feasibility Study on the Recycling of Used CANDU Fuel. CNL Research and Development Report # 153-124900-REPT-002 Revision 0. Unfortuantely the authors of this report relied on blatently false information provided by the Nuclear Waste Management Organization (NWMO). The NWMO has been subject to high level government corruption.
The information provided by the NWMO to CNL in 2016 indicates that the cost of a DGR for 3.6 million CANDU Used Nuclear Fuel bundles is $19,360 million. In 2013 parties in the Canadian mining industry offered the NWMO, OPG and the Ontario Ministry of Energy an existing fully formed 5,000,000 ft^2 DGR complete with both mineral and surface rights to 50 km^2 of surroundinng property for $67.5 million. Even if the cost of upgrading this existing DGR to include improved natural drainage, improved natural ventilation, new utility services and engineered spent fuel storage containers is as much as $900 million there is still a price discrepency of about 20:1. This price discrepency can only be explained by very deep seated incompetence/corruption within both the Canadian federal government department controlling the NWMO and the Ontario Ministry of Energy controlling OPG. The failure of the NWMO and OPG to purchase the existing DGR when it was available at a bargain price will likely go down in history as one of the worst ever decisions by the Canadian and Ontario governments. Today key parts of the existing DGR facility are controlled by Chinese investors.
In addition to incorrect conclusions contained in the CNL report flowing from the incorrect DGR cost there are also major technical problems, some of which are highlighted in a document titled Critique of Feasability Study on Recycling by Peter Ottensmeyer.
BENEFITS OF THE OTTENSMEYER PLAN:
As compared to the CANDU fuel cycle the Ottensmeyer Plan reduces the required long term spent nuclear fuel Deep Geologic Repository (DGR) mass storage capacity by about 1000 fold per kWh and increases the energy yield per unit of natural uranium consumed by over 100 fold by transmuting otherwise unused U-238 into Pu-239, Pu-240 and other transuranic actinides and then fissioning the transuranic actinides.
The Ottensmeyer Plan also provides major material cost saving via recycling of expensive materials. Under the Ottensmeyer Plan recycling of the existing spent nuclear fuel inventory would reduce natural uranium requirements per kW energy output about 100 fold. In addition to providing much more energy per unit of mined natural uranium the Ottensmeyer Plan also potentially makes very low concentration uranium ore bodies economic. This issue will become increasingly important in the future as nuclear power displaces fossil fuels.
The Ottensmeyer Plan is highly proliferation resistant. During implementation of the Ottensmeyer Plan U-238 is gradually transformed into a Pu-239 / Pu-240 mixture which is then fissioned to produce energy. With the contemplated first-in first-out fuel cycle the ratio of Pu-240 / Pu-239 is sufficiently high to prevent chemically extracted plutonium from being suitable for weapons production. The effect of addition of Pu-240 to the Pu-239 in a plutonium type atom bomb is to cause premature ignition so that the bomb blows itself apart before most of the Pu-239 can react. To produce a practical atom bomb from a Pu-239 / Pu-240 mixture the Pu-240 must be separated from the Pu-239. That isotope separation process is extremely difficult.
OTTENSMEYER PLAN IMPACT:
The Ottensmeyer Plan will fundamentally change the direction of the nuclear power industry. The Ottensmeyer plan is financially enabled by recognition that one of the major cost components of nuclear energy is long term nuclear waste disposal. The true cost of nuclear fuel is not just the cost of mining new uranium and chemically purifying it. The true cost includes the cost of safely disposing of spent nuclear reactor fuel and other neutron activated nuclear waste. When nuclear electricity generators are forced to pay the full cost of nuclear waste disposal the nuclear reactor technologies employed will change to favor technologies that minimize production of low atomic weight long half life radio isotopes and that transmute high atomic weight long half life isotopes into low atomic weight short half life isotopes.
One of the blunt realities that electric power utilities must ultimately face is phase out of water moderated power reactors in order to achieve the superior uranium utilization efficiency and spent fuel disposal benefits provided by the Ottensmeyer Plan. The liquid sodium cooled FNRs used to implement the Ottensmeyer Plan could also provide the start fuel required by thorium reactors.
During the early 1960s personnel at Atomic Energy of Canada Ltd. (AECL) measured interaction properties between elements and fast neutrons. An important finding was that generally for the transuranium actinides the fast neutron fission cross section is larger than the fast neutron capture cross section. Hence exposure of a material containing transuranium actinides to a fast neutron flux causes a gradual decrease in the transuranium actinide concentration.
An important related issue is that when a fast neutron emitted by a fission reaction impacts a U-238 atom there may be a n > 2 n reaction that increases the number of free neutrons present.
During the period 1964 to 1994 a highly successful 20 MWe liquid sodium cooled fast neutron reactor technology was developed and demonstrated at the Argonne Labs in Idaho, USA with a reactor known as EBR-2 (Experimental Breeder Reactor #2). In 1994 the EBR-2 program was defunded by US president Bill Clinton. That defunding decision set back the US nuclear energy program by at least 30 years as compared to other major industrialized countries such as Russia, China, India, UK, France, Japan and South Korea. In the context of climate change that defunding decision was one of the worst decisions ever made by a US president.
FAST NEUTRON PHYSICS:
Fast neutrons have the property that when they interact with the transuranic actinides (atoms heavier than uranium) they preferentially trigger fission reactions instead of alpha or beta decays. Each Pu-239 fission reaction releases about 3.1 fast neutrons that sustain the fast neutron process. A fission reaction typically causes about a 50% change in atomic number as compared to a less than 2% change in atomic number for an alpha or beta decay. Hence low atomic weight fission product atoms can be physically separated from high atomic weight transuranic actinide atoms by a separation process that sorts atoms by atomic weight.
In a Fast Neutron Reactor (FNR) fast neutron chain reactions are controlled by relative positioning of fuel bundles such that at the desired liquid sodium discharge temperature thermal expansion reliably reduces the fuel bundles' reactivity below the critical point for sustaining a chain reaction.
DEVELOPMENT OF THE OTTENSMEYER PLAN:
In the year 2012 a retired university professor named Peter Ottensmeyer used AECL measured neutron interaction parameters to conclude that spent CANDU fuel should be placed in accessible dry storage, sorted, reprocessed and recycled rather than being buried in an inaccessible wet location as contemplated by the Nuclear Waste Management Organization (NWMO). The details of Ottensmeyer's conclusions and the related nuclear waste handling process are collectively known as the Ottensmeyer Plan. Professor Peter Ottensmeyer, in an article published in the Ontario Professional Engineers publication ENGINEERING DIMENSIONS, pointed out that the toxic lifetime of CANDU spent fuel bundles can be reduced more than 1,000 fold by repeated exposure of the recycled spent CANDU fuel to a fast neutron spectrum together with repeated extraction of fission products.
The extracted fission products must be kept in interim isolated dry storage for about 300 years while the radio toxicity of the short lived fission products naturally decays to the level of natural uranium. After 300 years in storage selective chemical extraction of selected elements can be used to further reduce the mass that must be long term stored by at least 10 fold. This interim storage requires a safe, accessible and secure naturally ventilated dry storage facility and engineered containers with a reliable multi-century working life.
The technical viability of the Ottensmeyer Plan was quickly confirmed by others with relevant scientific and engineering knowledge. During the period 2013-2017 implementation details of the Ottensmeyer Plan were further refined.
The Ottensmeyer Plan is based on a number of straight forward scientific observations made by Peter Ottensmeyer. These observations are summarized below.
OTTENSMEYER'S 1ST OBSERVATION:
Ottensmeyer's first observation was that nuclear waste is radio active because it contains unextracted potential energy. If all of the available potential energy is extracted the nuclear waste will no longer be radio active. Hence, one of the objectives of the Ottensmeyer Plan is to capture and harness all of the available potential energy contained in nuclear fuel.
OTTENSMEYER'S 2ND OBSERVATION:
Ottensmeyer's 2nd observation was that spent CANDU fuel contains over 97% uranium oxide (UO2). Pure uranium oxide is only very weakly radioactive. Uranium oxide has unique chemical and physical properties that allow it to be selectively extracted from the spent CANDU fuel with an actinide separation ratio per step of the order of 100. Thus, in two simple steps about ~ 90% of the mass of the spent CANDU fuel can be safely extracted. The remaining ~ 10% of the spent CANDU fuel mass can then be economically processed via more sophisticated means. The initial process steps also concentrate the transuranium actinides which increases the rate at which the transuranium actinides are fissioned in a fast neutron reactor.
OTTEMSMEYER'S 3RD OBSERVATION:
Ottensmeyer's 3rd observation was that the radio toxicity of the remaining spent CANDU fuel bundles primarily consists of two components, the transuranic actinides which decay via sequential alpha particle and beta particle emission and fission products which decay via only beta particle emission. He noted that the transuranic actinides take about 400,000 years to spontaneously decay to the radio toxicity of natural uranium whereas the fission products decay to the radio toxicity of natural uranium in less than 300 years. Ottensmeyer's depicition of the relative radiotoxicity decay rates is shown in the diagram below.
On this graph it is important to note that the ordinate axis is relative radio toxicity, not relative energy emission. To obtain relative energy emission the fission product data values must be increased by a factor of 20 because the fission products are beta emitters whereas the actinides are alpha emitters. On a per unit of energy basis the beta emitters are about 20 fold less radio toxic than the alpha emitters.
At ten years after CANDU fuel bundle removal from a CANDU reactor the fission product decay heat is about 20X the actinide decay heat but the radio toxicity of the fission products is similar to the radio toxicity of the actinides.
Note that the quantity of contained fission products and actinides is not the same in all spent CANDU fuel bundles. The decay heat thermal output calculated from this Ottesnsmeyer graph, relative to the decay heat from natural uranium, at 1 year, 10 years and 100 years after removal from the reactor, varies from 26% to 66% of the thermal output values indicated by the NWMO. The likely explanation for this data discrepency is that the NWMO and Ottensmeyer used different assumptions as to the various isotope concentrations at the instant of spent fuel bundle removal from the CANDU reactor.
OTTEMSMEYER'S 4TH OBSERVATION:
Ottensmeyer's 4th observation was that an essential aspect of fast neutron reactor fuel treatment is to completely convert the transuranic actinides into fission products, because the fission products have much shorter half lives.
OTTENSMEYER'S 5TH OBSERVATION:
Ottensmeyer's 5th observation was that the transuranic actinide fission products are almost entirely rare earth atoms that potentially have a high economic value. Currently there are about 50,000 tonnes of spent CANDU fuel. If this spent fuel is fully converted into transuranic fission products and then stored for 300 years to reduce its radio toxicity the amounts of the various fission products and their current values are shown on Ottensmeyer's graph below. The potential financial value of this material is impressive.
OTTENSMEYER'S 6TH OBSERVATION:
Ottensmeyer's 6th observation was that in a fast neutron nuclear reactor only 10% to 20% of the core rod fuel is consumed before accumulation of high neutron cross section fission products and fuel tube swelling forces removal and reprocessing of the fuel rods. Hence, to fully consume the transuranic actinides, it is necessary to selectively extract the low atomic weight fission products from the high atomic weight actinides and then to recycle these high atomic weight actinides through the reactor. This fission product extraction and fuel recycling process must be repeated many times.
In this respect Ottensmeyer and some engineering students investigated mechanical-chemical processes that would allow achievement of a high separation ratio between uranium oxide (UO2), transuranium actinides and fission products.
OTTENSMEYER'S 7TH OBSERVATION:
Ottensmeyer's 7th observation was that a practical way of separating fission products from actinides is to sort the atoms based on their atomic weight. Most fission product atoms have an atomic weight less than cadmium (atomic weight = 112.41). Hence to a first order fission products will float in liquid cadmium whereas the actinides will sink. More precise atomic weight selection can be achieved by taking advantage of different atomic electrochemical properties.
Drawing on his observations Peter Ottensmeyer developed the initial version of the Ottensmeyer Plan for processing spent CANDU fuel bundles. A few implementation aspects of the Ottensmeyer Plan have since been refined by Charles Rhodes.
RHODES 1st OBSERVATION:
Rhodes examined practical issues with respect to implementation of the Ottensmeyer Plan. He concluded that due to the shipping weight of the required biosafety shielding it is economically impractical to transport fully assembled spent CANDU fuel bundles off a CANDU reactor site as contemplated by the NWMO. To reduce the transportation cost it is essential to first selectively extract 90% of the spent CANDU fuel bundle weight and volume in the form of low radioactivity uranium oxide. Hence the first step of the Ottensmeyer Plan, selective uranium oxide extraction, must be implemented at each CANDU reactor site.
RHODES 2nd OBSERVATION:
Rhodes observed that in practical implementation of the Ottensmeyer Plan over 80% of the fuel mass to be reprocessed is blanket rod material, not core rod material. By making the blanket rods from depleted uranium extracted from the spent CANDU and FNR fuel the blanket rod processing can be simplified and the cost reduced. Since the blanket rods are reactor fuel during reprocessing it is not necessary to highly reduce their radio activity. Since the blanket rods constitute over 80% of the total FNR fuel weight, the resulting cost savings are substantial.
RHODES 3rd OBSERVATION:
Rhodes concluded that after over 90% of the uranium oxide is selectively extracted from the spent CANDU reactor fuel the remaining spent fuel residue can be economically shipped by truck and/or rail to Chalk River for oxide reduction and for sophisticated electrolytic separation by atomic weight and subsequent fuel rod fabrication.
To mitigate transportation accidents the core fuel rods are shipped from Chalk River to the FNR site in containers stabilized with B4C. The fission products are shipped in lead containers from Chalk River to 300 year interim storage by truck and/or rail.
RHODES 4th OBSERVATION:
Rhodes observed that in practical implementation of the Ottensmeyer Plan zirconium, which constitutes about 10% of fast neutron reactor fuel rods, flows along with the low atomic weight fission products. Hence, after fission product extraction but before the fission products are transported to 300 year interim storage, there should be a chemical step that selectively extracts zirconium from the fission product stream and recycles this zirconium back into the FNR fuel.
RHODES 5th OBSERVATION:
Rhodes observed that the plenum space in the fuel tubes must accommodate both spare liquid sodium and inert gas fission products. Due to the high energy neutrons liberating He-4 over time the fuel tube material tends to swell, increasing the volume inside the fuel tube. There must be enough spare sodium to ensure that through out the working life of the fuel tube the gap between the fuel rods and the fuel tube is entirely filled with liquid sodium. During the fuel tube working life the fuel tube material gradually converts from iron to chromium and then to titanium. The yield stress of the fuel tube material may decrease with time. Hence the fuel tube plenum size must be sufficiently large to ensure that the combined fuel tube pressure stress from inert gas fission products and thermal stress due to the heat flux in the core region at full reactor power remain safely below the fuel tube material yield stress.
RHODES 6th OBSERVATION:
Rhodes observed that the fuel tubes should be arranged in a square grid rather than a staggered grid to ensure continued natural circulation of liquid sodium coolant in the presence of moderate fuel tube swelling.
RHODES 7th OBSERVATION:
Rhodes observed that the mass of liquid sodium inside the fuel tube must be much more than sufficient to chemically absorb the fission product gases F, I and Br.
RHODES 8th OBSERVATION:
Rhodes observed that after the fission products have been in storage for 300 years there will still be significant concentrations of the long lived low atomic weight isotopes Se-79 and Sn-126. Selenium (Se) and tin (Sn) should be selectively extracted from the decayed fission products before the fission products are released into the environment.
RHODES 9th OBSERVATION:
Rhodes observed that the activation and fission products include the radio active inert gases Ar-39 (half life = 269 years) and Kr-81 (half life = 210,000 years). There is no practical method of reliably containing these inert gases for anything like 10 half lives. If mankind relies on fission nuclear energy over many years the Ar-39 and Kr-81 concentrations in the atmosphere will gradually increase. There is no practical alternative other than for all life forms on Earth to gradually adapt to the corresponding increase in the background radiation.
OTTENSMEYER PLAN SUMMARY:
According to the NWMO (Choosing A Way Forward 2005, Appendix 3) fresh CANDU fuel consists of 99.28% U-238 and 0.72% U-235 and spent CANDU fuel consists of 98.58% U-238, 0.23% U-235, 0.07% U-236, 0.25% Pu-239, 0.10% Pu-240, 0.02% Pu-241, 0.01% Pu-242 and 0.74% fission products.
The fraction of the spent fuel that is plutonium oxide is:
0.25% + 0.10% + 0.02% + 0.01% = 0.38%.
The fraction of the spent fuel weight that is uranium oxide is:
98.58% + 0.23% + 0.07% = 98.88%.
In order to realize core fuel for a FNR which consists of 70% uranium, 10% zirconium and 20% plutonium it is necessary to retain:
(70 / 20) X 0.38% = 1.33%
of the spent CANDU fuel weight as uranium in the core rod material.
Thus the weight of (uranium + plutonium) in the core rods is:
1.33% + .38% = 1.71% of the spent CANDU fuel weight.
Thus the weight of (uranium + plutonium + fission products) in the core rod material prior to fission product extraction by pyroprocessing is:
1.71% + .74% = 2.45%
of spent CANDU fuel weight
The significance of this issue is that only about 2.45% of the spent CANDU fuel needs to be reduced from oxide to metallic form during initial core rod material processing.
Thus the total weight of extracted UO2 is:
100% - 2.45% = 97.55%
of spent CANDU fuel weight.
The weight of (uranium + plutonium + zirconium) in the core rods is:
(10 / 9) X 1.71% of spent CANDU fuel weight
= 1.90% of spent CANDU fuel weight.
Hence the maximum weight of initial core rod material that can be realized from 50,000 tonnes of spent CANDU fuel is:
.0190 X 50,000 tonnes = 950 tonnes
During the initial core rod material fabrication the amount of fission products that will be extracted via pyroprocessing is:
.0074 X 50,000 tonnes = 370 tonnes
During the initial core rod material fabrication the amount of zirconium required is:
0.1 X 950 tonnes = 95 tonnes.
The web page titled: FNR DESIGN shows that the ratio of blanket rod weight to core rod weight is 4.269__________. Hence the blanket rod weight is:
4.269 X 1.90% = 8.11 %__________
of the spent CANDU fuel weight.
The blanket rods are made from uranium metal and zirconium metal that are extracted from the spent CANDU fuel during the core rod material fabrication process. As shown on the web page titled:
FNR Design the assumed reactor geometry gives the ratio:
(blanket rod weight) / (core rod weight) = 4.269_________
Hence the amount of blanket rod material required to match the available amount of core rod material is:
950 tonnes X 4.269 = 4055.55 tonnes____________
Note that during one fuel cycle the neutron abdorption by the blanket rods should be sufficient to produce twice the amount of plutonium consumed by the reactor core during that same fuel cycle.
Note that the fuel rods contain 10% zirconium. This zirconium is rejected by the pyroprocess. This zirconium is then recovered by the dry chloride zirconium recovery process and forms about 10% of the weight of the new fuel rods.
Note that the mass output from the blanket rod reprocessing flowing toward the core rod reprocessing as a fraction of the input spent CANDU fuel weight nominally consists of:
0.38% Pu, 1.33% U, 0.19% Zr, 0.74% fission products.
The fuel processing steps required in the Ottensmeyer Plan are set out on the web pages titled:
FNR MATERIAL RECYCLING and OTTENSMEYER PLAN DETAILS
During each fuel cycle a FNR converts about 15% of its core fuel weight into fission products. These fission products are extracted and are placed in containers for 300 year dry storage. While it is possible to operate an FNR so that it converts a higher fraction of its core fuel during each fuel cycle the economics are questionable due to reduced fuel bundle thermal power and increased required fuel tube plenum volume.
During each fuel cycle the liquid sodium within the fuel tubes chemically captures the fission products fluorine, chlorine, iodine and bromine. Hence the liquid sodium in the fuel tubes, in additon to providing good thermal contact between the fuel rods and the steel tubes, performs the esential function of chemical absorption of these potentially corrosive fission product gases. Absent the sodium these gases would increase the internal pressure in the fuel tubes and would corrode the steel fuel tube material. During subsequent fuel reprocessing the sodium salts should be extracted because they will contain the long lived isotopes Cl-36 and I-129.
The high atomic weight material left behind after fission product and zirconium extraction via pyroprocessing is a mixture of uranium and transuranium actinides such as Pu-239. The extracted weight of fission products is replaced by an equal weight of new core rod material. The material wihin the blanket rod process is replenished by depleted uranium drawn from the spent CANDU fuel inventory.
In the FNR core the ratio of U-238 to Pu-239 is approximately (70 / 20). The U-238 fast neutron capture cross section is 0.25 b. The Pu-239 fast neutron fission cross section is 1.7 b. Hence in the core region for every Pu-239 fission there is breeding of:
(70 / 20)(0.25 b) / (1.7 b) = 0.514
replacement Pu-239 atoms. These replacement Pu-239 atoms together with Pu-239 atoms bred in the adjacent blanket regions extend the operating life of the fuel until the reactor becomes non-critical due to an unacceptably high fission product accumulation.
IRRADIATED MATERIAL HANDLING:
The core and blanket FNR fuel rods are removed from the FNR and are separately processed. The neutron irradiated blanket rods are an input to the blanket rod process. The residue from the blanket rod process is rich in Pu-239, transuranium actinides and zirconium and is used as an input to the core rod process. The neutron irradiated core rods are a further input to the core rod process.
The FNR blanket rods can never form a critical mass and hence might potentially be safely pre-processed on FNR sites to minimize transportation, storage and handling costs.
The core rod material, if mishandled, could potentially form a dangerous critical mass. Hence, for public safety the core rod reprocessing is conducted at a remote facility such as Chalk River that is far from any urban center. Core rods are transported in B4C filled containers to prevent a critical mass forming if water penetrates the shipping container.
The reactor operation and reprocessing cycle is repeated over and over for both blanket rod material and core rod material until all of the available high atomic weight atoms contained in the spent CANDU fuel are consumed.
Implementation of the Ottensmeyer Plan yields sufficient plutonium from the existing CANDU spent fuel inventory to start several power FNRs.
Implementation of the Ottensmeyer Plan increases the fraction of CANDU fuel that fissions from less than 1% to almost 100%.
While in interim 300 year storage the fission products naturally decay to become stable elements with potential high economic value. The fission product stream contains a few low atomic weight elements with isotopes that have long half lives. These isotopes should be selectively extracted after 300 years in storage. The selectively extracted radioactive isotopes should be placed in long term storage.
Prior to FNR fuel reprocessing the fuel tube assembly should be disassembled using automated equipment and physically separated into steel, sodium, sodium compounds, blanket rods and core rods. Sodium and sodium compounds adhering to the fuel tube material can be stripped off with water. This physical separation greatly simplifies subsequent fuel reprocessing steps.
OTTENSMEYER PLAN IMPLEMENTATION:
The Ottensmeyer Plan uses technologies that have proven performance in: selective uranium oxide extraction, separation of low and high atomic weight elements, selective extraction of zirconium and long term preservation and water exclusion.
In the Ottensmeyer Plan water exclusion problems are avoided by storing the radioactive material in engineered containers that are kept within a permanently accessible naturally dry (gravity drained) and naturally ventilated Deep Geologic Repository (DGR). This DGR should be at least 300 m above the local water table and should be kept at atmospheric pressure and temperature by natural ventilation. Resistance to DGR damage by glaciation and other events is ensured by forming the DGR inside the stable high density granite core of a mountain that provides over 400 m of overhead rock above the DGR. There is no attempt to find a "receptive community" because at geologically suitable DGR sites there is insufficient fresh water to support a permanent community. In the Ottensmeyer Plan the DGR location is determined by favorable geophysical criteria, not by political criteria.
In the Ottensmeyer Plan double wall storage containers (outer wall porcelain, inner wall stainless steel, oil dielectric in between the inner and outer walls) are used to store the radioactive material while it is in the DGR. While in the DGR the physical integrity of each nuclear waste storage container is remotely monitored by monitoring the container dielectric level and dielectric loss tangent. During the storage period the dielectric will out gas and may need occasional replacement.
OTTENSMEYER PLAN FEATURES AND BENEFITS:
The main features and benefits of the Ottensmeyer Plan are:
1) It provides certain safe disposal of all types of nuclear waste, including: spent light water reactor fuel, spent heavy water (CANDU) reactor fuel, refurbishment waste, decommissioning waste and maintenance waste;
2) The average required storage time for most high level nuclear waste is reduced by about 1000 fold from 400,000 years to about 300 years;
3) The useful energy yield per unit of natural uranium consumed is increased by over 100 fold as compared to a CANDU reactor;
4) The stored nuclear waste is reliably excluded from ground water;
5) If an accessible DGR and suitable nuclear waste containers are also used for interim storage then the interim storage can safely default to becoming a long term storage facility if future changes in human society so dictate;
6) It is not necessary to build large nuclear waste storage facilities that can only be used once and then must remain in isolation for over 400,000 years. Most of the storage space can be recycled;
7) The interim depleted uranium and fission product storage containers need only be engineered to last 300 years. The Ottensmeyer Plan for radio isotope storage can be implemented using suitable existing naturally dry depleted hard rock mine facilities in granite mountain cores;
8) Both the DGR storage space and the porcelain containers can potentially be reused;
9) The integrity status of each nuclear waste container in interim storage is remotely monitored for safety and security;
10) The Ottensmeyer Plan is relatively simple and inexpensive to implement as compared to the present NWMO / OPG nuclear waste disposal plan.
11) The nuclear industry material costs are greatly reduced under the Ottensmeyer Plan due to recycling of about 94% of the neutron activated material. The dry accessible interim storage methodology of the Ottensmeyer Plan allows recovery and reuse of over $200 million worth of existing irradiated zirconium, inconel 600, nickel and helium-3 that are contained in the current inventory of low and intermediate level nuclear waste.
12) Over 50,000 tonnes of existing spent CANDU nuclear fuel are converted via fission into valuble elements with atomic numbers in the range 31 to 65. Note that recovery of elements with atomic numbers in the range 49 to 65 may require a second stage of pyro processing for atomic weight separation.
13) The problem of nuclear waste spent fuel management and disposal is not passed on to numerous future generations. The high level waste stream is almost entirely eliminated. The costs of nuclear waste disposal are largely met by the persons who benefit from the nuclear energy generated.
14) The technology for implementing the Ottensmeyer Plan has been field proven. This technology uses a proven liquid sodium fast neutron reactor coolant and a proven fuel design based on metallic uranium-plutonium-zirconium alloy core rods, metallic uranium-zirconium alloy blanket rods and sodium contained within HT-9 steel fuel tubes.
15) It is contemplated that the new fast neutron reactors would use cooling towers instead of the direct lake water cooling presently used by CANDU reactors. Use of cooling towers allows siting reactors at higher elevations above major water bodies, which reduces risks due to earth quakes, tsunamis and other geophysical events outside human control. The higher primary coolant temperature of a liquid sodium cooled fast neutron reactor as compared to a water cooled reactor increases the plant thermal efficiency. The low primary coolant pressure contributes to plant safety. Unlike a CANDU reactor there is no potential source of radioactive steam. The major plant design issue is isolation of liquid sodium from both air and water. The use of cooling towers greatly reduces the impact of reactor cooling on marine life.
16) The use of liquid sodium cooled FNRs allows rapid reactor power changes which allow the reactor power to track rapid changes in electricity grid load.
REDUNDANT SAFETY MEASURES:
No material exits to the environment from the Ottensmeyer Plan process until its radio toxicity is below the radio toxicity of natural uranium. However, at any instant in time there may be substantial inventories of unprocessed and partially processed radio isotopes. Hence a high, dry and accessible DGR facility is recommended for interim radio isotope storage. All of the radio isotopes in DGR storage are kept in double walled individually monitored engineered containers. Any container wall failure is detected via a liquid dielectric level change long before there is any radioactive material leakage.
The radio isotope containers are stored in an accessible naturally dry gravity drained DGR with sumps such that if there is a radio isotope leakage it is detected at a sump and remedial measures can be implemented long before there is any leak of radio isotopes into the external environment. Since the Ottensmeyer Plan only requires a few hundred years for interim storage, the radio isotope containers initially used for interim containment do not have to reliably function for more than 1000 years. To put that time in perspective Egyptian mummies have lasted 5000 years.
CHOICE OF DGR:
The Ottensmeyer Plan impacts immediate decisions relating to the storage of low and intermediate nuclear waste because it replaces long term storage of nuclear waste in an expensive inaccessible low and wet DGR with relatively short interim storage of most of the nuclear waste in relatively inexpensive and accessible high and dry DGRs.
There is a requirement for safe, secure and accessible isolated dry storage site(s) for the entire inventory of uranium oxide contained in the spent CANDU fuel bundle material which is over 95% of the CANDU spent fuel mass. Jersey Emerald, in British Columbia, is suitable for both interim and long term storage and may be available at a modest price. Other depleted mine sites may be suitable but are unlikely to be as geologically advantageous.
The main issue preventing immediate implementation of the Ottensmeyer Plan is that the present cost of natural uranium to CANDU nuclear reactor owners is so low and the financial amounts required to be set aside for future nuclear waste disposal are so low that recycling spent CANDU fuel does not make financial sense for present CANDU reactor owners. Spent CANDU fuel bundles, after being removed from a CANDU reactor spent fuel cooling bay, are simply placed in on-site concrete dry storage casks. However, the working life of these casks was only intended to be 50 years. The total amount of this dry storage is becoming very large from a future safety, security, operating and maintenance cost perspective.
In order for the nuclear waste issue to be taken seriously by CANDU reactor owners the financial amounts required to be set aside for nuclear waste disposal must be increased at least ten fold so as to be sufficient to finance the DGRs contemplated by OPG and the NWMO. At that point the Ottensmeyer Plan will be a viable economic alternative that is preferred by knowledgable nuclear industry intervenors.
Outside of North America numerous parties have recognized that the future of mankind will rely on nuclear energy. In Russia power FNRs have already been developed and have operated for over 30 years. The US, Canadian and Ontario governments have failed to recognize this fact. The result is that Canada and the USA have moved from being a world leaders in FNR matters in the mid 1960s to being banana republics now 50 years later. The governments of the US, Canada and Ontario are in a state of decision paralysis. These governments have almost zero technical competence with respect to nuclear matters and with respect to reducing products of combustion emissions from fossil fuels.
The Ottensmeyer Plan for handling nuclear waste requires that politicians face the reality that nuclear power is essential to provide reliable power while minimizing emissions of products of combustion to the atmosphere. These politicians must then face NIMBYism relating to safe transport, safe storage and safe processing of nuclear fuel and nuclear waste. These same politicians must also set electricity rates that encourage energy storage and efficient use of the electricity system and must expropriate electricity transmission corridors that are sufficient to allow total displacement of fossil fuels by electricity.
The major issue with Pu-239 is that to prevent atomic weapon proliferation it should never be produced without accompanying Pu-240 and should never be chemically separated from the accompanying actinides so that there is no available inventory of separated Pu-239. Implementation of the Ottensmeyer Plan needs to be 100% transparent and fully open to both Canadian Nuclear Safety Commission and International Atomic Energy Agency inspection to ensure that Pu-239 is never produced without diluting Pu-240 and so that the plutonium contained in the spent CANDU fuel and used FNR fuel is never chemically isolated.
All routes into or out of high level nuclear waste processing and storage facilities, such as Chalk River and Jersey Emerald, should be monitored with helium-3 based neutron detectors to ensure that there is no illicit transport of fissionable material.
This web page last updated November 6, 2017
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