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37-550: The plant began in 1949 with the purpose of on-site production of plutonium metal in a form suitable for weapons at Hanford. It also participated in programs to recycle plutonium. One of the projects was the use of mixed plutonium-oxide uranium-oxide (MOX) fuel in the Fast Flux Test Facility (FFTF). For that project, one of the PFP's tasks was to perform quality assurance for the fuel pins that had been constructed for

74-436: A press and converted into pellets. The pellets can then be sintered into mixed uranium and plutonium oxide. Plutonium from reprocessed fuel is usually fabricated into MOX within less than five years of its production to avoid problems resulting from impurities produced by the decay of short-lived isotopes of plutonium. In particular, plutonium-241 decays to americium-241 with a 14-year half-life. Because americium-241

111-534: A Hanford contractor and deemed clean, but rechecked by an independent lab and were found to have small amounts of radioactive contamination. All demolition and cleanup work was completed in November 2021. MOX Mixed oxide fuel , commonly referred to as MOX fuel , is nuclear fuel that contains more than one oxide of fissile material , usually consisting of plutonium blended with natural uranium , reprocessed uranium , or depleted uranium . MOX fuel

148-407: A Norwegian study, "the coolant void reactivity of the thorium-plutonium fuel is negative for plutonium contents up to 21%, whereas the transition lies at 16% for MOX fuel." The authors concluded, "Thorium-plutonium fuel seems to offer some advantages over MOX fuel with regards to control rod and boron worths, CVR and plutonium consumption." Nuclear reactor core A nuclear reactor core

185-646: A lesser extent in Russia , India and Japan . In the UK THORP operated from 1994 to 2018. China plans to develop fast breeder reactors and reprocessing. Reprocessing of spent commercial-reactor nuclear fuel is not permitted in the United States due to nonproliferation considerations. Germany had plans for a reprocessing plant at Wackersdorf but as this failed to materialize, it instead relied on French nuclear reprocessing capabilities until legally outlawing

222-410: A new reactor with a complete fuel loading of MOX. As 2011, of the total nuclear fuel used, MOX provides about 2%. Licensing and safety issues of using MOX fuel include: About 30% of the plutonium originally loaded into MOX fuel is consumed by use in a thermal reactor. In theory, if one third of the core fuel load is MOX and two-thirds uranium fuel, there is zero net change in the mass of plutonium in

259-508: A spent fuel would be difficult to reprocess for further reuse (burning) of plutonium. Regular reprocessing of biphasic spent MOX is difficult because of the low solubility of PuO 2 in nitric acid. As of 2015, the only demonstration of twice-recycled, high-burnup fuel occurred in the Phénix fast reactor. Reprocessing of commercial nuclear fuel to make MOX is performed in France and to

296-438: Is a gamma ray emitter, its presence is a potential occupational health hazard. It is possible, however, to remove the americium from the plutonium by a chemical separation process. Even under the worst conditions, the americium/plutonium mixture is less radioactive than a spent-fuel dissolution liquor, so it should be relatively straightforward to recover the plutonium by PUREX or another aqueous reprocessing method. It

333-476: Is an alternative to the low-enriched uranium fuel used in the light-water reactors that predominate nuclear power generation. For example, a mixture of 7% plutonium and 93% natural uranium reacts similarly, although not identically, to low-enriched uranium fuel (3 to 5% uranium-235). MOX usually consists of two phases, UO 2 and PuO 2 , and/or a single phase solid solution (U,Pu)O 2 . The content of PuO 2 may vary from 1.5 wt.% to 25–30 wt.% depending on

370-458: Is possible that both americium and curium could be added to a U/Pu MOX fuel before it is loaded into a fast reactor or a subcritical reactor run in "Actinide burner mode". This is one means of transmutation. Work with curium is much harder than americium because curium is a neutron emitter, the MOX production line would need to be shielded with both lead and water to protect the workers. Also,

407-434: Is significant – greater than 50% of the initial plutonium loading. However, during the burning of MOX the ratio of fissile (odd numbered) isotopes to non-fissile (even) drops from around 65% to 20%, depending on burn up. This makes any attempt to recover the fissile isotopes difficult and any bulk Pu recovered would require such a high fraction of Pu in any second generation MOX that it would be impractical. This means that such

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444-406: Is the portion of a nuclear reactor containing the nuclear fuel components where the nuclear reactions take place and the heat is generated . Typically, the fuel will be low- enriched uranium contained in thousands of individual fuel pins. The core also contains structural components, the means to both moderate the neutrons and control the reaction, and the means to transfer the heat from

481-460: The actinides , including 92 U , fast reactors could use all of them for fuel. All actinides can undergo neutron induced fission with unmoderated or fast neutrons. A fast reactor is therefore more efficient than a thermal reactor for using plutonium and higher actinides as fuel. These fast reactors are better suited for the transmutation of other actinides than thermal reactors. Because thermal reactors use slow or moderated neutrons,

518-473: The spent fuel and the cycle could be repeated; however, there remains multiple difficulties in reprocessing spent MOX fuel. As of 2010, plutonium is only recycled once in thermal reactors, and spent MOX fuel is separated from the rest of the spent fuel to be stored as waste. All plutonium isotopes are either fissile or fertile, although plutonium-242 needs to absorb 3 neutrons before becoming fissile curium -245; in thermal reactors isotopic degradation limits

555-621: The FFTF by outside vendors, such as Kerr-McGee , NUMEC , and Babcock & Wilcox . The major activities at PFP generally included: Plutonium Conversion Facility Plutonium Reclamation Facility Waste Treatment Facility Incinerator Other Before the last four major facilities at the plant could be demolished, approximately 20 years of work was completed to stabilize approximately 20 tons (nearly 18 metric tons) of plutonium-bearing material by 2004; remove legacy plutonium from plant systems by 2005; ship all weapons-grade plutonium out of

592-494: The actinides that are not fissionable with thermal neutrons tend to absorb the neutrons instead of fissioning. This leads to buildup of heavier actinides and lowers the number of thermal neutrons available to continue the chain reaction. A subcritical reactor with an external neutron source could either be run in the fast neutron spectrum (without the need for highly enriched fuels as otherwise common in fast reactors) or use thermal neutrons to breed fissile materials, compensating

629-416: The control rods are lowered into the core, they absorb neutrons, which thus cannot take part in the chain reaction . Conversely, when the control rods are lifted out of the way, more neutrons strike the fissile uranium-235 (U-235) or plutonium-239 (Pu-239) nuclei in nearby fuel rods, and the chain reaction intensifies. The core shroud , also located inside of the reactor, directs the water flow to cool

666-424: The disadvantage of forming much radioactive dust. A mixture of uranyl nitrate and plutonium nitrate in nitric acid is converted by treatment with a base such as ammonia to form a mixture of ammonium diuranate and plutonium hydroxide. After heating in a mixture of 5% hydrogen and 95% argon will form a mixture of uranium dioxide and plutonium dioxide . Using a base , the resulting powder can be run through

703-583: The entire facility cleaned and destroyed down to a concrete slab in 2017, with all contaminated materials moved to other sites. Open-air demolition of the plant's last four remaining major facilities began in November 2016 on the plant's Plutonium Reclamation Facility. Demolition of the second major facility, the Americium Recovery Facility, also known as the "McCluskey Room" because of a facility accident in 1976 , began in January 2017 and

740-513: The first time. According to Atomic Energy of Canada Limited (AECL), CANDU reactors could use 100% MOX cores without physical modification. AECL reported to the United States National Academy of Sciences committee on plutonium disposition that it has extensive experience in testing the use of MOX fuel containing from 0.5 to 3% plutonium. The content of un-burnt plutonium in spent MOX fuel from thermal reactors

777-538: The fuel to where it is required, outside the core. Inside the core of a typical pressurized water reactor or boiling water reactor are fuel rods with a diameter of a large gel-type ink pen, each about 4 m long, which are grouped by the hundreds in bundles called "fuel assemblies". Inside each fuel rod, pellets of uranium, or more commonly uranium oxide, are stacked end to end. Also inside the core are control rods , filled with pellets of substances like boron or hafnium or cadmium that readily capture neutrons . When

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814-694: The life of the core, so adding some plutonium oxide to the fuel at manufacture is not in principle a very radical step. About 30 thermal reactors in Europe (Belgium, the Netherlands, Switzerland, Germany and France) are using MOX and an additional 20 have been licensed to do so. Most reactors use it as about one third of their core, but some will accept up to 50% MOX assemblies. In France, EDF aims to have all its 900 MWe series of reactors running with at least one-third MOX. Japan aimed to have one third of its reactors using MOX by 2010, and has approved construction of

851-479: The loss of neutrons by increasing the flux from the neutron source. The first step is separating the plutonium from the remaining uranium (about 96% of the spent fuel) and the fission products with other wastes (together about 3%) using the PUREX process. MOX fuel can be made by grinding together uranium oxide (UO 2 ) and plutonium oxide (PuO 2 ) before the mixed oxide is pressed into pellets, but this process has

888-487: The neutron irradiation of curium generates the higher actinides , such as californium , which increase the neutron dose associated with the used nuclear fuel ; this has the potential to pollute the fuel cycle with strong neutron emitters. As a result, it is likely that curium will be excluded from most MOX fuels. A subcritical reactor such as the Accelerator Driven System could "burn" such fuels if

925-517: The nuclear accident at Fukushima Daiichi . In May 2018, the Department of Energy reported that the plant would require another $ 48 billion to complete, on top of the $ 7.6 billion already spent. Construction was cancelled. Most modern thermal reactors using high burn up uranium oxide fuel produce a quite significant proportion of their output towards the end of core life from fission of plutonium produced by neutron capture in uranium 238 earlier in

962-470: The nuclear reactions inside of the core. The heat of the fission reaction is removed by the water, which also acts to moderate the neutron reactions. There are also graphite moderated reactors in use. One type uses solid nuclear graphite for the neutron moderator and ordinary water for the coolant. See the Soviet-made RBMK nuclear-power reactor. This was the type of reactor involved in

999-447: The operating characteristics of a reactor, and the plant must be designed or adapted slightly to take it; for example, more control rods are needed. Often only a third to half of the fuel load is switched to MOX, but for more than 50% MOX loading, significant changes are necessary and a reactor needs to be designed accordingly. The System 80 reactor design deployed at the U.S. Palo Verde Nuclear Generating Station near Phoenix, Arizona

1036-660: The plant and to the Savannah River Site by 2009; remove 238 large pieces of contaminated equipment, including glove boxes and fume hoods , and approximately 50 plutonium processing tanks; and demolish numerous plant support facilities, including the vault complex used for secure storage of plutonium by 2012. That preparatory work has been called the most hazardous cleanup work at the Hanford Site and PFP has been called Hanford's most hazardous building. The Department of Energy's PFP Closure Project intended to have

1073-451: The plutonium into usable fuel increases the energy derived from the original uranium by some 12%, and if the uranium-235 is also recycled by re-enrichment, this becomes about 20%. Plutonium is only reprocessed and used once as MOX fuel; spent MOX fuel, with a high proportion of minor actinides and plutonium isotopes, is stored as waste. Existing nuclear reactors must be re-licensed before MOX fuel can be introduced because using it changes

1110-456: The plutonium recycle potential. About 1% of spent nuclear fuel from current LWRs is plutonium, with approximate isotopic composition 52% 94 Pu , 24% 94 Pu , 15% 94 Pu , 6% 94 Pu and 2% 94 Pu when the fuel is first removed from the reactor. Because the fission-to-capture ratio of high energy or fast neutrons changes to favour fission for almost all of

1147-416: The plutonium-239 is "burned" in the reactor. It behaves like uranium-235, with a slightly higher cross section for fission, and its fission releases a similar amount of energy . Typically, about one percent of the spent fuel discharged from a reactor is plutonium , and some two-thirds of the plutonium is plutonium-239. Worldwide, almost 100 tonnes of plutonium in spent fuel arises each year. Reprocessing

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1184-405: The problems associated with their handling and transportation are solved. However, to avoid power excursions due to unintended criticality, the neutronics must be known precisely at any given point in time, including the effect of build-up or consumption of neutron emitting nuclides as well as neutron poisons. MOX fuel containing thorium and plutonium oxides is also being tested. According to

1221-929: The risk of nuclear proliferation , by encouraging increased separation of plutonium from spent fuel in the civil nuclear fuel cycle . In every uranium-based nuclear reactor core there is both fission of uranium isotopes such as uranium-235 , and the formation of new, heavier isotopes due to neutron capture , primarily by uranium-238 . Most of the fuel mass in a reactor is uranium-238. By neutron capture and two successive beta decays , uranium-238 becomes plutonium-239 , which, by successive neutron capture, becomes plutonium-240 , plutonium-241 , plutonium-242 , and (after further beta decays) other transuranic or actinide nuclides. Plutonium-239 and plutonium-241 are fissile , like uranium-235. Small quantities of uranium-236 , neptunium-237 and plutonium-238 are formed similarly from uranium-235. Normally, with low-enriched uranium fuel being changed every five years or so, most of

1258-710: The transport of German spent fuel for reprocessing in 2005. The United States was building a MOX fuel plant at the Savannah River Site in South Carolina. Although the Tennessee Valley Authority (TVA) and Duke Energy expressed interest in using MOX reactor fuel from the conversion of weapons-grade plutonium, TVA (the most likely customer) said in April 2011 that it would delay a decision until it could see how MOX fuel performed in

1295-447: The type of nuclear reactor. One attraction of MOX fuel is that it is a way of utilizing surplus weapons-grade plutonium, an alternative to storage of surplus plutonium, which would need to be secured against the risk of theft for use in nuclear weapons . On the other hand, some studies warned that normalizing the global commercial use of MOX fuel and the associated expansion of nuclear reprocessing would increase, rather than reduce,

1332-606: Was completed in March 2017. Demolition of the third remaining major facility, the ventilation stack and fan house, was completed in July 2017. Demolition of the last of four major remaining facilities, the Main Processing Facility, began in July 2017. As of December 2017, all demolition is on hold, after contamination was found as far away as 10 miles from the site, and found in two car air filters that were checked by

1369-463: Was designed for 100% MOX core compatibility, but so far has always operated on fresh low enriched uranium. In theory, the three Palo Verde reactors could use the MOX arising from seven conventionally fueled reactors each year and would no longer require fresh uranium fuel. Fast neutron BN-600 and BN-800 reactors are designed for 100% MOX loading. In 2022, the BN-800 was fully loaded with MOX fuel for

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