modeling of photonuclear reactions & transmutation of long-lived nuclear waste in high photon...

Modeling of Photonuclear Modeling of Photonuclear Reactions & Reactions &

Transmutation of Long-Transmutation of Long-lived Nuclear Waste in lived Nuclear Waste in

High Photon FluxesHigh Photon Fluxes TRAMU@GSI

M.-L. GIACRI-MAUBORGNE, D. RIDIKAS, J.-C. DAVIDDSM/DAPNIA/SPhN, CEA/Saclay, F-91191 Gif/Yvette, France

M. B. CHADWICK, W. B. WILSONLos Alamos National Laboratory (T-16), Los Alamos, NM 87545, USA

[email protected]

Applications of photonuclear Applications of photonuclear reactionsreactions

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

ContentsContents

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 90Sr, 237Np and comparison with neutron fluxes

TRAMU@GSI 9/5/03 [email protected]

CINDER’90CINDER’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


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 : HMS-ALICE : Light nuclidesLight nuclides


HMS-ALICE : HMS-ALICE : Heavy nuclidesHeavy nuclides

Good agreement for 208Pb

181Ta not as good : total absorption cross section has a different shape

Calculations for heavy nuclei are good enough to be use in CINDER’90


HMS-ALICE : HMS-ALICE : Absorption cross Absorption cross sectionssections

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


Photoabsorption new modelPhotoabsorption new model


HMS-ALICE : ConclusionHMS-ALICE : ConclusionHMS-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)


GNASH : GNASH : 235235U andU and 239239Pu Pu Input: σabs from the IAEA evaluations


Good agreement with experimental data for separate channels

GNASH : GNASH : 237237NpNp

We made a compromise between two experimental data to obtain a integral equal to 3.54 barn.MeV


Data on σabs are inconsistent

We fix this value according to the total integral, using the systematic from the IAEA for neighbor actinides

GNASH : GNASH : 237237NpNp


Good agreement for photoneutron production

Photo-fission evaluation between the two experimental data

GNASH : ConclusionsGNASH : 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


Data on the photofission of 235U and 238U with Bremsstrahlung spectra very limited• a few mass and charge distributions, some isotopic yields• P/V ratios, <LM> & <HM>

Calculation procedure

• total absorption cross section (GDR parameterization)• fission-evaporation in competition (GSI model)• calculation of independent fission yields and residual nuclei

PhotofissionPhotofission YieldsYields


• both bremsstrahlung and monoenergetic photons are tried • 15 MeV photons are equivalent to 25 MeV bremsstrahlung

Example: photofission of Example: photofission of 235235UU


n + 234U or n + 235U 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 Search for the systematic from (n,fiss)(n,fiss)


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 actinidesa) fission cross-section predictions b) mass, charge and isotopic distributions of FFs and

residual nucleic) delayed neutron yields and time-dependence; and

search for the systematic from neutron induced fission

Fission Yield : ConclusionFission Yield : Conclusion


Example : Transmutation of Example : Transmutation of 9090SrSr

Irradiation

Decay

1 year irradiation in the flux of 1017.cm-2.s-1

7 years decay

Results are in agreement with T. Matsumoto NIM A 268 (1988) 234-243

Total activity decreases by 30% compared to the natural decay of 90Sr

The same result can be obtained with a flux of 1016 nth cm-2 s-1

At 1018 .cm-2.s-1 activity is decreased ~20 times.TRAMU@GSI 9/5/03 [email protected]

Example : Incineration by Example : Incineration by fission of fission of 237237NpNp


5 %/year incineration:

- 5x1016 .cm-2.s-1

- 7x1014 nth.cm-2.s-1

- 2x1015 nfast.cm-2.s-1

1 year irradiation as a function of flux intensity

Transmutation : ConclusionTransmutation : 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 perspectivesConclusion 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


modeling of photonuclear reactions & transmutation of long-lived nuclear waste in high photon...

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