On neutron consumption requirements for long lived fission products (LLFP) transmutation and lanthanides (LA)
- CE Cadarache, CEA, 13108 St Paul lez Durance Cedex (France)
Long Lived Fission Product (LLFP) incineration is important because of long toxicity and mobility of LLFP, which can influence the acceptability of Nuclear Power (NP) in future The potential of LLFP transmutation is based on the neutron availability in the neutron balance of a transmuter. Fission is the only source of these nuclides while stable isotopes and short-lived nuclides can be regularly extracted from the fuel cycle (stream sink). However, LLFP transmutation is a process consuming neutrons during fuel burn up (i.e. when these isotopes are under neutron flux). It was established earlier that the parameter: D* - number of neutrons required to transmute (incinerate) completely any particular nuclide (from LLFP list) and all its family members (measured in neutrons per transmutation) are among one of the main parameters which defines the LLFP transmutation potential of a transmuter at equilibrium state. The D* depends on the neutron flux level, burn up, neutron spectrum in the place of LLFP irradiation (due to a concurrence between neutron processes and radioactive decays). The D* data can be considered as properties of a LLFP nuclides valuable in a given neutron flux and spectrum. A separate problem is represented by the fact that Lanthanide's Fission Products concentration can be significant in cores where Minor Actinides should be transmuted, since the Lanthanide/ Minor Actinide separation ratio will not exceed some limit (e.g. ≅ 0.1). The number of neutrons per fission D (neutron/fission) which is required for complete incineration of a LLFP or Lanthanide, is another decisive parameter of the transmutation potential of a transmuter. The D defines a fraction of transmuters in NP needed to support an acceptable level of LLFPs and can be assessed as the product: - of the D*{sub LLFP} and of the LLFP-yield (for the case of LLFP incineration) and - of the D*{sub LA} and of the LA-yield (Y{sub LA}) and of the separation coefficient K{sub sep}= (1-LOSS{sub LA}) (for the case of a presence of LA in the fuel, where LOSS{sub LA} is the fraction of LA per fission being removed from fuel stream after reprocessing). This paper presents: - D* calculation scheme for most important LLFPs and LAs; - D* data for all toxic LLFPs and some Lanthanides in two types of neutron spectra: fast (FBR) and thermal (LWR) for different flux levels. Analysis of these data leads to following conclusions: - The neutron consumption of Sm-151, required for its incineration, is most significant among LLFP and sensitive to flux, burn up and spectrum: D* changes its value by the factor of two for the flux range 10{sup 14}- 10{sup 17} n/cm{sup 2}s and D* increases significantly (50%) if burn up increases from O to 30%; - Cs-135 neutron consumption is the less (among LLFP) sensitive to neutron flux and to burn up; - D* values for all lanthanides and some combinations of LA-nuclides for two types of spectra and for different neutron fluxes are also presented. Due to absence of a significant decay in the LA-group and due to an significant LA-chain length, there is an enormous consumption of neutrons by LAs: about 34 neutron /transmutation for both fast and thermal spectra. Taking into account real potential of a fuel, it makes impossible to keep all LA's under neutron flux for their incineration. To reduce neutron consumption for transmutation, a separation of LA from fuel has to be sufficiently effective. This work gives the background for a special study. Meanwhile, a presence of a part of LAs such as La, Ce and Pr with relatively modest neutron consumption can be acceptable in some cases. For example, the D*{sub La+Ce+Pr} was estimated as 1.16 neutron/transmutation. Knowledge of neutron consumption of LA allows to create an optimal policy of LA-separation to define appropriate decontamination ratios regarding the role of different Lanthanide isotopes.
- Research Organization:
- American Nuclear Society - ANS, 555 North Kensington Avenue, La Grange Park, IL 60526 (United States)
- OSTI ID:
- 23142085
- Resource Relation:
- Conference: Global'99: International Conference on Future Nuclear Systems - Nuclear Technology - Bridging the Millennia, Las Vegas, NV (United States), 29 Aug - 3 Sep 1999; Other Information: Country of input: France; 3 refs.; available from American Nuclear Society - ANS, 555 North Kensington Avenue, La Grange Park, IL 60526 (US)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
ACTINIDES
BURNUP
CESIUM 135
COMBUSTION
DECONTAMINATION
FISSION
FISSION PRODUCTS
FUEL CYCLE
IRRADIATION
NEUTRON FLUX
NEUTRON SPECTRA
NEUTRONS
NUCLEAR DECAY
NUCLEAR FUELS
NUCLEAR POWER
RARE EARTHS
REPROCESSING
SAMARIUM 151
STABLE ISOTOPES
TRANSMUTATION