Transmutations of Long-Lived and Medium-Lived Fission Products Extracted from CANDU and PWR Spent Fuels in an Accelerator-Driven System (original) (raw)
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Nuclear Technology, 2020
The use of the RSG-GAS research reactor as a transmutation reactor is analyzed to study its effectiveness for transmuting long-lived fission products (LLFPs), particularly 129 I and 99 Tc. Both radionuclides selected are assumed as discharged from of a 1000-MW(electric) pressurized water reactor (PWR) spent fuel. If these radionuclides are stored in sustainable geologic disposal, they will require high-cost handling due to their special shielding. In one cycle of PWR1000 operation, the 99 Tc produced is 43.7 kg and 129 I is 9.5 kg in its spent fuel. Considering reactor safety, the maximum target mass permitted to be transmuted in the RSG-GAS is 3.0 kg for the 99 Tc and 5.0 kg for the 129 I. In 1 year of (five cycles) operation, the 99 Tc and 129 I targets would be reduced by 126 and 290 g, respectively. Although it has the potentiality to safely transmute LLFP targets in its core, RSG-GAS requires longer irradiation time (about 20 years) to entirely transmute the targets.
LWR spent fuel transmutation with fusion-fission hybrid reactors
Progress in Nuclear Energy, 2013
In this paper the transmutation of light water reactors (LWR) spent fuel is analyzed. The system used for this study is the fusion-fission transmutation system (FFTS). It uses a high energy neutron source produced with deuterium-tritium fusion reactions, located in the center of the system, which is surrounded by a fission region composed of nuclear fuel where the fissions take place. In this study, the fuel of the fission region is obtained from the recycling of LWR spent fuel. The MCNPX Monte Carlo code was used to setup a model of the FFTS. Two fuel types were analyzed for the fissile region: the mixed oxide fuel (MOX), and the inert matrix fuel (IMF). Results show that in the case of the MOX fuel, an important Pu-239 breeding is achieved, which can be interesting from the point of view of maximal uranium utilization. On the contrary, in the case of the IMF fuel, high consumption of Pu-239 and Pu-241 is observed, which can be interesting from the point of view of non-proliferation issues. A combination of MOX and IMF fuels was also studied, which shows that the equilibrium of actinides production and consumption can be achieved. These results demonstrate the versatility of the fusion-fission hybrid systems for the transmutation of LWR spent fuel.
Transmutation of high-level nuclear waste by means of accelerator driven system
Wiley Interdisciplinary Reviews: Energy and Environment, 2013
To be able to answer the worlds' increasing demand for energy, nuclear energy must be part of the energy basket. The generation of nuclear energy produces, besides energy, also high-level nuclear waste, which is nowadays for geological storage. Transmutation of the minor actinides and long-lived fission products that arise from the reprocessing of the nuclear waste can reduce the radiological impact of these radioactive elements. Transmutation can be completed in an efficient way in fast neutron spectrum facilities. Both critical fast reactors and subcritical accelerator driven systems are potential candidates as dedicated transmutation systems. Nevertheless, an accelerator driven system operates in a flexible and safer manner even with a core loading containing a high amount of minor actinides leading to a high more-efficient transmutation approach.
LWR spent fuel transmutation in a high power density fusion reactor
Annals of Nuclear Energy, 2004
The prospect of light water reactor (LWR) spent fuel incineration in a high power density fusion reactor has been investigated. The neutron wall load is taken at 10 MW/m 2 and a refractory alloy (W-5Re) is used in the first wall. Neutron transport calculations are conducted over an operation period of 48 months on a simple experimental hybrid blanket in a cylindrical geometry with the help of the SCALE4.3 system by solving the Boltzmann transport equation with the XSDRNPM code in 238 neutron groups and a S 8-P 3 approximation. In the neutron rich environment, the tritium breeding ratio remains > 1.05 so that the tritium self-sufficiency is maintained for the fusion reactor. The presence of fissionable nuclear waste fuel in the investigated blanket causes significant energy amplification. The energy multiplication factor is 4atstartupanditincreasessteadilyupto5.55duringpowerplantoperationsothatevenamodestfusionreactorcansupplyasignificantquantityofelectricity.Inthecourseofnuclearwasteincineration,mostofthefissionablefuelisburntinsitu.Inadditiontothat,excessfissilefuelproductionenhancesthenuclearqualityofthenuclearfuel.Startingwithaninitialcumulativefissilefuelenrichment(CFFE)valueofthespentfuelof2.1724 at startup and it increases steadily up to 5.55 during power plant operation so that even a modest fusion reactor can supply a significant quantity of electricity. In the course of nuclear waste incineration, most of the fissionable fuel is burnt in situ. In addition to that, excess fissile fuel production enhances the nuclear quality of the nuclear fuel. Starting with an initial cumulative fissile fuel enrichment (CFFE) value of the spent fuel of 2.172%, CFFE can reach 4% after an irradiation period of 4atstartupanditincreasessteadilyupto5.55duringpowerplantoperationsothatevenamodestfusionreactorcansupplyasignificantquantityofelectricity.Inthecourseofnuclearwasteincineration,mostofthefissionablefuelisburntinsitu.Inadditiontothat,excessfissilefuelproductionenhancesthenuclearqualityofthenuclearfuel.Startingwithaninitialcumulativefissilefuelenrichment(CFFE)valueofthespentfuelof2.17212 months. Then the spent fuel becomes suitable for a new recharge in an LWR as a regenerated fuel. Further residence in the fusion blanket continues to upgrade the nuclear waste so that after 48 months, CFFE can reach such a high level (9%) that it becomes qualified to be used in a new type of the advanced high temperature reactors for the Generation-IV.
Nuclear Engineering and Design, 2018
The performance of the fusion-fission hybrid system based on the molten salt (flibe) blanket, driven by a plasma based fusion device, was analyzed by comparing transmutation scenarios of actinides extracted from the LWR (Sweden) and RBMK (Lithuania) spent nuclear fuel in the scope of the EURATOM project BRILLIANT. The IAEA nuclear fuel cycle simulation system (NFCSS) has been applied for the estimation of the approximate amount of heavy metals of the spent nuclear fuel in Sweden reactors and the SCALE 6 code package has been used for the determination of the RBMK-1500 spent nuclear fuel composition. The total amount of trans-uranium elements has been estimated in both countries by 2015. Major parameters of the hybrid system performance (e.g., k scr , k eff , Φ n (E), equilibrium conditions, etc.) have been investigated for LWR and RBMK trans-uranium transmutation cases. Detailed burn-up calculations with continuous feeding to replenish the incinerated trans-uranium material and partial treatment of fission products were done using the Monteburns (MCNP + ORIGEN) code system. About 1.1 tons of spent fuel trans-uranium elements could be burned annually with an output of the 3 GW th fission power, but the equilibrium stage is reached differently depending on the initial trans-uranium composition. The radiotoxicity of the remaining LWR and RBMK transmuted waste after the hybrid system operation time has been estimated.
Nuclear Science and Technology
An investigation on the nuclear transmutation of elemental long-lived fission product (LLFP) in a fast reactor is being conducted focusing on the I-129 LLFP (half-life 15.7 million years) to reduce the environmental burden. The LLFP assembly is loaded into the radial blanket region of a Japanese MONJU class sodium-cooled fast reactor (710 MWth, 148 days/cycle). The iodine element containing I-129 LLFP (without isotope separation) is mixed with YD2 and/or YH2 moderator material to enhance the nuclear transmutation rate. We studied the optimal moderator volume fraction to maximize the transmutation rate (TR, %/year) and the support factor (SF is defined as the ratio of transmuted to produced LLFP). We also investigated the effect of LLFP assembly loading position in the radial blanket and the severe power peak appeared at the fuel assembly adjacent to the LLFP assembly.
Spent Nuclear Fuel and Alternative Methods of Transmutation
Spent Nuclear Fuel and Accelerator-Driven Subcritical Systems
The chapter deals with the status of the spent nuclear fuel and accumulation of unspent nuclear fuel world over. Its fertile, fissile and fission product components are also discussed along with their applications and various methods of reprocessing the SNF. International situation related to reprocessing, security aspects arising from the SNF, and the fissile components along with its handling at individual national level are also summarized. 1.1 Spent and Unspent Nuclear Fuel and the Nuclear Waste Spent nuclear fuel (SNF) is the nuclear fuel that is irradiated in a power reactor. A few percent of this is utilized in power generation, and a very large part is left behind as a radiotoxic material at the time of discharge of a reactor. In the SNF major actinides, U and Pu are 95-96 and 1%, respectively. Minor actinides (Np, Am, and Cm) are 0.1%, short-lived fission products (FP) are 3-4%, and long-lived FPs are 0.1%. Different composition elements pose different challenges for disposition of SNF. In fact, unspent nuclear fuel (UNF) is of high concern because its components can be utilized for nuclear energy or other atomic devices with least efforts.