Modeling of Photonuclear Reactions & Transmutation of Long-lived Nuclear Waste in High Photon Fluxes M.-L. GIACRI-MAUBORGNE, D. RIDIKAS, J.-C. DAVID DSM/DAPNIA/SPhN, CEA/Saclay, F Gif/Yvette, France M. B. CHADWICK, W. B. WILSON Los Alamos National Laboratory (T-16), Los Alamos, NM 87545, USA

Applications of photonuclear reactions Production of RNB Neutron production Non-destructive characterization of nuclear waste Detection of nuclear materials ( 235 U, 239 Pu) Radioprotection of electron accelerators Transmutation of nuclear waste

Contents 1.Development of a photonuclear cross section library for CINDER’90 evolution code : –use of the IAEA photonuclear evaluation library –use of HMS-ALICE and GNASH to complete the library –use of GSI fission model for photofission-yields 2.Example: transmutation in photon fluxes for 90 Sr, 237 Np and comparison with neutron fluxes 9/5/03

CINDER’90 CINDER’90 (LANL) – material evolution in neutron fluxes Photonuclear activation data library is needed to extend it for photon fluxes Similar efforts for proton induced activation will make CINDER a multi-particle activation code 9/5/03

Cross sections of light nuclides are difficult to reproduce whatever the model In HMS-ALICE model for light nuclides needs to be improved HMS-ALICE : Light nuclides 9/5/03

HMS-ALICE : Heavy nuclides Good agreement for 208 Pb 181 Ta not as good : total absorption cross section has a different shape Calculations for heavy nuclei are good enough to be use in CINDER’90 9/5/03

HMS-ALICE : Absorption cross sections HMS-ALICE model for absorption can not be employed for actinides - sum of two Lorentzians should be used Work is in progress to change the absorption model for actinides in HMS-ALICE 9/5/03

Photoabsorption new model 9/5/03

HMS-ALICE : Conclusion HMS-ALICE should be used with certain precaution for photonuclear reactions Our approach to prepare CINDER’90 library: –Use of the IAEA evaluations when available –Use of GNASH for nuclides of interest to get better accuracy –Complete the library with the HMS-ALICE predictions Next improvements in HMS-ALICE will focus on: –Total absorption cross section model (new parameterization) –Inclusion of photo-fission yields (GSI fission model) 9/5/03

GNASH : 235 U and 239 Pu Input: σ abs from the IAEA evaluations 9/5/03 Good agreement with experimental data for separate channels

GNASH : 237 Np We made a compromise between two experimental data to obtain a integral equal to 3.54 barn.MeV 9/5/03 Data on σ abs are inconsistent We fix this value according to the total integral, using the systematic from the IAEA for neighbor actinides

GNASH : 237 Np 9/5/03 Good agreement for photoneutron production Photo-fission evaluation between the two experimental data

GNASH : Conclusions GNASH is a powerful tool for photonuclear data evaluations Good agreement with experimental data when the total absorption cross section is used as input Might be very time-consuming to use GNASH to build the entire library. However, it can be used to increase the accuracy of cross sections for some elements and actinides in particular 9/5/03

Data on the photofission of 235 U and 238 U with Bremsstrahlung spectra very limited a few mass and charge distributions, some isotopic yields P/V ratios, & Calculation procedure total absorption cross section (GDR parameterization) fission-evaporation in competition (GSI model) calculation of independent fission yields and residual nuclei Photofission Yields 9/5/03

both bremsstrahlung and monoenergetic photons are tried 15 MeV photons are equivalent to 25 MeV bremsstrahlung Example: photofission of 235 U 9/5/03

 n U or n U at 6-8 MeV might be a good combination More careful checks on charge and isotopic distributions to be done! Search for the systematic from (n,fiss) 9/5/03

 we’ve got a working model for photofission (still in validation process) preliminary results are encouraging but sensitivity due to different parameters still to be tested in the near future we will provide for a number of actinides a)fission cross-section predictions b)mass, charge and isotopic distributions of FFs and residual nuclei c)delayed neutron yields and time-dependence; and search for the systematic from neutron induced fission Fission Yield : Conclusion 9/5/03

Example : Transmutation of 90 Sr Irradiation Decay 1 year irradiation in the flux of .cm -2.s -1 7 years decay Results are in agreement with T. Matsumoto NIM A 268 (1988) Total activity decreases by 30% compared to the natural decay of 90 Sr The same result can be obtained with a flux of n th cm -2 s -1 At .cm -2.s -1 activity is decreased ~20 times. 9/5/03

Example : Incineration by fission of 237 Np 9/5/03 5 %/year incineration: - 5x10 16 .cm -2.s x10 14 n th.cm -2.s x10 15 n fast.cm -2.s -1 1 year irradiation as a function of flux intensity

Transmutation : Conclusion Transmutation by photonuclear reaction does not create elements heavier than the initial nuclei It tends to reduce the long term activity Photon fluxes need to be one to two orders of magnitude higher than neutron fluxes

Conclusion and perspectives Thanks to the photonuclear library (by now it includes ~600 isotopes), with CINDER’90 we can do activation analysis in photon fluxes The library will be more precise by improving predictive power of HMS-ALICe Fission yields still have to be added to the library The integrality of the library still needs to be validated-tested by dedicated experiments 9/5/03

HMS-ALICE HMS-ALICE is a multiparticle reaction code Predictions of reaction cross sections for nuclei heavier than 9 Be from a few keV to the pion mass threshold Calculations can be done very quickly for most of the nuclei; it will be our major source for the cross section evaluations 9/5/03

GNASH GNASH is a multi-particle reaction code based on a different model than HMS-ALICE. Often used for neutron and proton data evaluations. Possibility to adjust a number of physical parameters to fit experimental cross sections. Much preparation work is required to start the calculations. Total absorption cross section in input is strongly recommended. 9/5/03

Example : Transmutation of 93 Zr Irradiation Decay 1 year irradiation in a flux of .cm -2.s -1 7 years decay Total activity decreased by 23% compared to the natural decay of 93 Zr. The same result can be obtain with a flux of 3x10 15 n th cm -2.s -1. At higher flux the activity increases. At .cm -2.s -1 major activity is due to 85 Kr (T 1/2 =11 years) at this 55 Fe (T 1/2 < 3 years) 9/5/03

Example : Transmutation of 137 Cs 1 year irradiation in the flux of .cm -2.s -1 7 years decay Total activity decreases 3 times compared to the natural decay of 137 Cs At . cm -2.s -1 the total activity decreases 16 times Irradiation Decay 9/5/03

E e (MeV) P/V Y(Kr) Y(Cs) some major features on photofission of 235 U with bremsstrahlung photons “ good news” from data: little sensitivity to E e 9/5/03