Nuclear islands, which are integrated power production sites, could effectively sequester and safeguard the US stockpile of plutonium. A nuclear island, an evolution of the integral fast reactor, utilizes all the Transuranics (Pu plus minor actinides) produced in power production, and it eliminates all spent fuel shipments to and from the site. This latter attribute requires that fuel reprocessing occur on each site and that fast reactors be built on-site to utilize the TRU. All commercial spent fuel shipments could be eliminated by converting all LWR nuclear power sites to nuclear islands. Existing LWR sites have the added advantage of already possessing a license to produce nuclear power. Each could contribute to an increase in the nuclear power production by adding one or more fast reactors. Both the TRU and the depleted uranium obtained in reprocessing would be used on-site for fast fuel manufacture. Only fission products would be shipped to a repository for storage. The nuclear island concept could be used to alleviate the strain of LWR plant sites currently approaching or exceeding their spent fuel pool storage capacity. Fast reactor breeding ratio could be designed to convert existing sites to all fast reactors, or keep the majority thermal.
Nuclear islands, which are integrated power production sites, could effectively sequester and safeguard the US stockpile of plutonium. A nuclear island, an evolution of the integral fast reactor [
These existing sites have the added advantage of already having a license to produce nuclear power which should allow easier licensing of added on-site nuclear plants. Assuming that nuclear power would increase with at least the same rate as the increase in electrical power in the US, these sites could contribute to this increase in the nuclear power production by adding two or more fast reactors to each site. Doubling the electrical power over the next 40 years could easily occur [
The number of power plants that can be built and powered by reprocessed fuel obtained from the spent fuel resulting from 40 years of operation at a site depends upon the breeding ratios of the fast reactors, the throughput of the reprocessing plant added to the site, and how long the thermal reactors continue to operate with license extensions. Both the TRU and the depleted uranium obtained from reprocessing would be used on site for fast fuel manufacture. Only fission products would be shipped to Yucca Mountain for storage and only depleted uranium would have to be shipped to the site to make up for the uranium that is converted to TRU. Both the thermal spent fuel and the fast reactor spent fuel will be processed.
To minimize the nuclear proliferation threat, the model here assumes that reprocessing of oxide spent fuel from the thermal reactors will be reduced to metal and then the Argonne developed electrochemical process [
The nuclear island concept could be used to alleviate the strain of those LWR plant sites currently approaching their spent fuel storage limit or which have exceeded it and are now installing dry storage racks. Five scenarios are presented, each starts with a light water reactor (LWR) plant site with two 1000 MWe LWRs nearing their 40-year license with spent fuel pools reaching saturation. A reprocessing plant of 100 MTHM/yr would be added to the site. The site would have sufficient spent fuel to supply plutonium for the initial loading of two fast reactors, the first of which would be built in four years. The fast reactors would be designed with a specified breeding ratio. Three different breeding ratios are studied in these scenarios, 0.5, 1.0, and 1.3. The objective of using a breeding ratio of 0.5 would be to convert all the spent fuel from the thermal spectrum plants but not increase the power output. Designing a fast reactor with a higher breeding ratio would increase the number of reactors and thus the power at the site. Reactors with breeding ratios of 0.5 would not use blanket assemblies and would be designed to lose neutrons. Enough DU exists in the fuel rods themselves for a 0.5 breeding ratio. The higher breeding ratio reactors would include blanket assemblies and more efficient geometries to capture more neutrons.
The purpose of this paper is to investigate different scenarios for the nuclear island development in terms of increasing power with breeding ratio, size of reprocessing plant on each site, and length of operation of the thermal plants. The following section discusses the benefits of the nuclear island concept. This is followed by a section which briefly describes the model used to estimate these scenarios. Then a results section follows which investigates these scenarios. Within 40 years from now, all nuclear power plant sites in the US could be on their way to becoming nuclear islands and to doubling or tripling their power output.
This paper recommends that existing two-reactor LWR nuclear sites be converted to nuclear islands which starts by adding a 100 MTHM/yr reprocessing plant to the site. This is instead of building a single centralized reprocessing facility to reprocess fuel. A centralized plant would require the shipment of radioactive spent nuclear fuel from all operating reactors in the country to the reprocessing facility and the transport of the reprocessed fuel back to the reactor sites. The nuclear island concept eliminates this transport and the possible accidents and diversion potential associated with it. The 100 MTHM/yr reprocessing plant has been under design for many years at Argonne and hence could be built faster than a large 3500 MT/yr plant. Prototype equipment in 100 MTHM/yr size range has been in operation for several years [
Combining a power production plant with a fuel reprocessing plant could increase the risk of environment contamination in case of a major accident because more is being done but the increase is very small. The increase would be much smaller than adding another reactor plant to the site. The facilities would act independently in an accident because the facilities are not connected except for fuel transfers. The common mode failure would be loss of power. Reprocessing is done behind 5-foot-thick walls of concrete in an inert argon atmosphere to prevent reaction of the metal fuel with oxygen during production. The design base accident is an earthquake that ruptures the cell boundary and lets air in which reacts with exposed metal fuel. The amount of exposed metal fuel is small and the fuel is kept in earthquake-proof and leak- proof containers until needed. In the prototype fuel cycle facility being operated at the Idaho National Laboratory, the only boundary rupture possible is from small penetrations that go through the five foot thick concrete wall. The design of the commercial facility will make the boundary earthquake proof so that this accident will not be possible. Also, there is no possibility of criticality caused by any natural disaster such as earthquake because of the separation of all the fuel. The cooling requirements are small, and in the event of a loss of cooling incident where cooling cannot be reinitiated, the cell temperature would increase so that the heat generated would be lost through the walls. Other minor incidents are possible and have been analyzed and shown to be benign.
The public perception of nuclear power risks has increased due to the Fukushima plants that were damage by the Japan tsunami. But this is only a temporary setback since nuclear power must be eventually embraced as the major power source. It is the only significant power source with low risk and minimal environmental damage. Incidents like Fukashima can only delay what must eventually occur, which is the conversion to nuclear power as the major power source. The reality is that no one was killed or received significant doses of radiation as a result of the damage to the Fukushima nuclear facilities. But 25,000 people were killed by the tsunami and that is where the focus should be, not the blow-by-blow description of what is going on to shut down the nuclear facilities. It is a financial disaster, not a disaster to humans.
Nuclear energy is an 80 to 90 percent solution to the energy problem. The other renewables, which should be used as much as practical, are each, at most, a 5 to 8 percent solution. Wind and Solar are the most promising. Solar power which has the most potential, is being implemented incorrectly with central station paneling of large land areas, or large arrays of mirrors for thermal plants. Instead, the roofs of all existing homes and building should be used to obtain the needed areas with little eye pollution or excessive waste of land. Wind generators, dotting hills, mountain ridges, and oceans often end up becoming the object of protests when they ruin the view and produce power which is not available locally but exported to states that require their utilities to supply 15% green energy but do not want wind farms themselves. Both wind and solar energy are marketed in terms of maximum capacity when in fact they operate only 30 percent of the time. Utilities don’t want to build solar or wind plants because they still must provide full backup power facilities for the times that solar or wind are not providing power. All the reasonable water power sites have been built in the US and any further capacity is extremely expensive and subject to large protests because of the use of large land areas, some of which are populated. The dam failure risk to large population centers downstream of dams is accepted or usually not recognized. Dam failures occur every year.
Besides the continuing thermal pollution from fossil fuel plants, they consistently produce real disasters. Natural gas produces pipeline explosions, house explosions, asphiations, explosions caused by penetrating buried pipelines during construction, and so forth. These accidents are barely covered by the press. Coal mining, oil disasters, and all of these deaths and destruction from these disasters are covered by the press as expected (and acceptable). But nuclear incidents are treated in an irrational manner and serve to delay the eventual construction of needed electrical production. Nuclear plants plus the plug-in hybrid car are the best hope the US has for energy independence and reduction of CO2 emissions.
Each site is assumed to start out with two 1000 MWe thermal spectrum plants. All the results can be applied to any other site by scaling the results by the ratio of actual to the 2000 MWe assumed here.
The heavy metal in the annual spent fuel product from a 1000 MWe thermal spectrum plant is 20.7 MT/Yr,
Transuranics approximately make up 1% of the spent reactor fuel. Transuranics are made up of 90% plutonium and 10% of the minor actinides americium, curium, and neptonium. Therefore the TRU harvested annually from 100 MT/Yr reprocessing plant is 0.01 * 100. When enough TRU has been harvested in reprocessing to fabricate fuel for a fast reactor core, a fast reactor is loaded and started up. It is assumed that plant construction was started five years before that time and is now complete. The amount of TRU fuel needed to fuel a fast reactor core is 4 MT. Two reloads are needed in addition to the initial core load before new TRU fuel can be assigned to the second fast reactor. A core reload is 1/3rd of an initial core. One-third of the core is replaced every 1.5 years so that a complete core changeout occurs every 4.5 years. The 1/3rd of the core taken out and replaced by the reload is referred to as an xload. The first xload must decay for at least one year after being taken out of the reactor before it can be processed. To simulate the above in a model with year-to-year increments of time, it is assumed that the 4 MT/4.5 Yr = 0.889 MT/Yr spent fuel is removed from a fast reactor. Then a two-year delay is assumed before it can be processed.
The net amount of TRU which must be supplied annually to fuel a fast reactor is 0.889 * (1 – BR). In this model, 0.889 MT of TRU is taken from the TRU fuel reservoir as input to the reactor and the 0.889 * BR MT is added to the TRU reservoir after the fast fuel is processed (two years after). The TRU which is fissioned in a year can also be estimated by
Reprocessing of fast fuel takes precedence over processing thermal fuel because less fast fuel needs to be processed to produce a unit of TRU fuel than thermal fuel. So 9.3 tonnes of spent fuel from the fast plant must be processed to produce 0.889 * BR MT of TRU. For BR = 0.5, 20.9 tonnes of this spent fuel must be processed to produce one tonne of TRU fuel. For BR = 1.0, 10.46 tonnes of this spent fuel must be processed to produce 1 tonne of TRU fuel. From a thermal plant 100 tonnes must be processed to produce one tonne. In addition, the front end oxide reduction process is not performed to process the metallic spent fuel from the fast reactors. Thus, it is less expensive to reprocess the fast fuel.
The change in the amount of nonprocessed spent thermal fuel NPF (i.e, the thermal fuel left to process) is equal to the amount added from the number of thermal reactors (GWT) that year minus the amount of thermal fuel processed last year, THMP,
The annual change in TRU fuel in the reservoir is equal to 0.01 times the thermal fuel reprocessed each year minus the amount used to fuel a fast reactor core minus the amount used in core reloads plus the amount harvested from reprocessing fast reactor fuel. In mathematical notation, this change is represented in the following equation. Each term mentioned above corresponds to each of the terms below
Fast reactors can be designed to produce the breeding ratio most conducive to either reducing plutonium or to producing power, to convert existing sites to all fast reactors or to keep the majority thermal. Three scenarios are described using BR = 0.5, BR = 1.0, and BR = 1.3 to convert 2 thermal plant sites to nuclear islands resulting, respectively, in 2, 4, or 6 fast reactors. In addition, two scenarios are presented where sites are converted to two thermal reactors, two fast reactor nuclear islands or to four thermal reactors, and two fast reactor nuclear islands. The scenario chosen in the US will depend upon the future power increase needed from nuclear reactors and what percentage of fast reactors will be allowed. It must be a minimum of 33%. Without the fast reactors, there can be no nuclear island.
A breeding ratio of 0.5 used in the fast reactors added to a reactor site will allow it to be converted from a two thermal reactor site to two fast reactor sites over a 40-year time frame. As in all these examples, the site initially contains two 1000 MWe unit thermal reactors. Construction of a 100 MT/Yr reprocessing plant construction begins 36 years after initial operation of the thermal plants. The reprocessing plant is completed in year 40 and begins reprocessing spent fuel. Simultaneously with the start of reprocessing, construction on a 1000 MWe fast reactor plant is begun. The processing consists of reducing spent oxide fuel to metal and electrorefining the metal to produce TRU, DU, and fission products. The TRU and DU are processed to produce metallic fast reactor fuel of the type developed in EBR-II and the fission product waste form is sent to Yucca Mountain for 300-year storage [
At the end of four years of operation, enough fuel has been processed to fuel a fast reactor. The fast reactor is assumed to be built, to be ready to accept this core, and to begin operation. Another three years are required to produce the two reloads (each 1/3 core) needed for operation. The first reload is needed after 1.5 years of operation, at which time, it is inserted in the core and the first xload is removed from the core to allow it to cool for one to two years before reprocessing can occur. Since an electrochemical process is being used, only one or two years of cooling are required before reprocessing can occur. After another 1.5 years, the second reload is inserted in the core and the second xload is removed. The first xload is now added to the reprocessing line since it has cooled long enough. It produces more TRU/MT of spent fuel processed than the thermal fuel and the amount depends on the breeding ratio designed into the fast reactor. Since the same reprocessing facility is used for both fast and thermal spent fuel, the spent fast reactor fuel processed reduces the amount of thermal fuel which is processed. The fast fuel has an advantage in processing in that it does not have to be reduced to metallic fuel since it is already metallic. Some of the thermal fuel which is processed at this time will be used to fuel the second fast reactor. The rate of TRU production which is allotted to the second reactor is reduced by the amount of TRU needed for reloads in the first reactor, which is high in this case because the breeding ratio is 0.5.
The time history of non-processed spent fuel is shown in Figure
Site conversion from two thermal to two fast spectrum plants (BR = 0.5).
Thermal reactor spent fuel inventory
Time history of TRU reservoir
TRU reservoir with modified increase in breeding ratio
Time history of the reprocessing
Reprocessing rates needed for continued thermal plant operation
Effect of reducing reprocessing plant size
The time history of the TRU fuel reservoir is shown in Figure
Two problems are noted with this scenario. The first is that the total reprocessing rate shown in Figure
Several possibilities exist for resolving these problems. The first would be to extend the license of the thermal plants by another 20 years and change the breeding ratio to 0.6 at year 26. This increased breeding ratio and the extra thermal spent fuel supplies enough TRU until the reservoir of spent fuel drops to just the amount added each year and then the breeding ratio must again be increased, say to 0.75 for the last four years. The reprocessing rate for this case is shown in Figure
Capital costs would be less if the reprocessing plant on each nuclear island were smaller, but this section shows that reprocessing plants on the order of 100 MT/Yr are close to ideal for nuclear islands. Much larger plants are appropriate if the decision is made to use central reprocessing [
It is seen that processing produces sufficient TRU fuel for the first fast reactor to begin operation in year 7 and the second to begin operation in year 26. The breeding ratio is increased to 0.7 at the same time as the second plant starts up to supply sufficient TRU fuel. The spent fuel is completely reprocessed by year 36 and the breeding ratio must be increased to 1.0 at that time. The processing plant is used at full capacity out to year 35. If the plant has reached its end-of-life at this time, it could be replaced by a smaller plant which only reprocesses the fast reactor spent fuel. A problem with this scenario is that when the thermal reactors are shut down in year 21, there is only 1000 MWe being generated at the site until year 26 when the second fast reactor is started. If the thermal plants are extended to run to year 26 to provide more power, the thermal spent fuel will still all be processed by year 39. Thus the smaller reprocessing plant size is practical but tends to delay when the conversion occurs to the fast reactors, so, is dependent upon being able to get a further plant life extension for the thermal plants.
Both this and the previous scenario with breeding ratios of 0.5 do not increase total site power but do convert the site from two thermal reactors to two fast reactors over 36 years. The breeding ratios of the fast reactors must eventually be increased to one toward the end of the first forty years of operation.
This case increases power from two thermal plants to four fast reactor plants and begins with the same assumptions as the previous section; however, the fast reactors utilize a breeding ratio of 1 in their design. Due to the quicker build up of TRU fuel, the fast reactors are brought online more quickly. The nonprocessed spent fuel inventory is shown in Figure
Site conversion from two thermal to four fast spectrum plants (BR = 1.0).
Thermal reactor spent fuel inventory
TRU fuel inventory, thermal plants 60-year service
TRU fuel inventory, thermal plants 60–65-year service
Processing rates, thermal plants 60–65-years service
The TRU fuel inventory is shown in Figure
The reprocessing rates for this constant 4 GWe power profile is shown in Figure
This breeding ratio has the capability of converting two thermal reactor sites to more than six fast reactor sites and would apply to sites with enough room for these additional reactors. The nonprocessed fuel is shown in Figure
Conversion from two thermal to six fast spectrum plants (BR = 1.3).
Nonprocessed fuel inventory (BR = 1.3)
TRU fuel inventory (BR = 1.3)
TRU fuel reservoir (BR = 1.3 then reduced to 0.91)
Reprocessing rates (BR = 1.3 then reduced to 0.91)
The TRU fuel inventory is shown in Figure
In order to decrease the steady state TRU inventory, the breeding ratio may be reduced after the sixth fast reactor has been started. Figure
The reprocessing rate, shown in Figure
Due to the additional expense of fast reactor plants over thermal plants, it may be more desirable to continue to use thermal plants even with no off-site shipments of spent nuclear fuel. The first two thermal plants are shut down after 60 years of operation but are replaced by two new thermal plants or the license extensions. Two fast reactors are added to the site in a similar manner as in the breeding ratio = 0.5 scenario. The resultant TRU inventory is shown in Figure
Conversion to two thermal, two fast spectrum plants (BR = 0.5, then to 0.55 and then 0.75).
TRU fuel reservoir
Reprocessing rates
The reprocessing rates are shown in Figure
The minimum practical breeding ratio is about 0.5 [
The non-processed fuel for this scenario is shown in Figure
Conversion to four thermal, two fast spectrum plants (BR = 0.5, increased to 0.55 and then 0.5).
Nonprocessed fuel
Reprocessing rate
TRU fuel reservoir
Increased processing rate of 103 MT/yr
The reprocessing rate is shown in Figure
The TRU reserve is shown in Figure
Alternatively, the reprocessing plant can be built initially for 103 MT/Yr to yield a reprocessing rate curve that remains constant, as shown in Figure
The conversion of existing plant sites to nuclear islands would eliminate the need for long-term repository storage of plutonium. This conversion would not be done on a rush basis but over decades by beginning now with older sites reaching or having reached spent fuel storage capacity. If the conversion is carried out when each site reaches this stage, over the next 40 to 100 years, all of the existing commercial nuclear sites can be converted to nuclear islands. The conversion would be initiated at any given site with the construction of a 100 MT/Yr reprocessing plant. Fast reactors can be designed to produce the breeding ratio most conducive to either maintaining current power levels or increasing power to match increased electrical demands, and to either convert existing sites to all fast reactors or to keep the majority thermal. Scenarios have been investigated using, BR = 0.5, BR = 1.0, and BR = 1.3 to convert two thermal plant sites to nuclear islands with respectively two, four, or six fast reactors. In addition, scenarios were presented where two thermal reactor sites could be converted to two thermal reactors, two fast reactor nuclear islands or to four thermal reactors, two fast reactor nuclear islands. The latter case yields the 2/3rds thermal, 1/3rd fast reactor ratio, and is close to the maximum thermal to fast reactor ratio possible and still meets the no spent fuel shipping requirement.
Fast reactors must be part of a nuclear island to first sequester the TRU which exists in the spent nuclear fuel on-site and then to fission the annual production of spent fuel from thermal reactors and supply any additional TRU needed to run the fast reactors. Without the fast reactors, there can be no nuclear island. The criteria to select the best nuclear island conversion scenario would depend upon many factors, but primarily economics and how effectively the US intends to use its total uranium supply. In all of these examples, no spent fuel would ever have to be shipped off-site. Only fission products would be disposed of in Yucca Mountain. However, the last scenario, four thermal and two fast reactors, would leave a lot of wasted depleted uranium. The author would like to see the scenario adopted which converts two thermal reactors to six fast reactors since this most fully uses uranium and triples the nuclear power. Hopefully, the additional nuclear plants would be in place of fossil fuel plants. Detailed cost estimates of each scenario are beyond the scope of this paper, but the total cost of each may be similar per GWh. The all fast reactor options offer the advantage of reprocessing much less spent fuel than the two thermal reactor scenarios, but fast reactors are more expensive to build than thermal reactors (25%). Reprocessing also produces cost savings since it decreases the volume which must be stored and the heat load which must be dissipated in Yucca Mountain by a factor of 5.
This paper was supported by the US Department of Energy, Science, and Technology, under Contract W-31-109-eng-38.