NEUTRONIC ANALYSIS OF HE-EFIT EFIT ADS - SOME RESULTS -

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1 NEUTRONIC ANALYSIS OF HE-EFIT EFIT ADS - SOME RESULTS - Alan Takibayev & Danas Ridikas CEA Saclay / DSM / IRFU Atelier GEDEPEON 'Accelerator Driven System' Aix-en-Provence

2 HE-EFIT MAIN CHARACTERISTICS Accelerator 24 ma current 800 MeV proton beam Spallation module Primary target made of tungsten Core 400 MW power (Pu+MA)O 2 -MgO fuelled core with Keff = 0.97 CALCULATION TOOLS EMPLOYED Computer code MCNPX Version Nuclear interaction models used BERTINI ISABEL CEM Nuclear data libraries used JEFF3.1 JENDL-3.3 ENDF/B-VII

3 RADIATION DAMAGE & LIFETIME CHARACTERISTICS OF HE-EFIT EFIT SPALLATION MODULE

4 BARE SPALLATION MODULE GEOMETRY MODEL PROTON BEAM 26.6 cm HELIUM 69 cm STEEL OUTER TARGET MATERIAL TUNGSTEN

5 OUTER TARGET MATERIAL SURVEY Outer Target Material Spallation Production [n/p] (n,xn) Total Total Leakage [n/p] Leakage Production [%] Steel Be W V Zr Ta SiC He Pb U

6 NEUTRON SPECTRA NEUTRON FLUX OVER INNER TARGET BE Current / Ln(E) [1] 1x10-4 STEEL HE Flux / Ln(E) [1] 1x10-4 NEUTRON LEAKAGE FROM SIDE SURFACE W

7 NEUTRON PRODUCTION & LEAKAGE Calculation Option Production [n/p] Total Leakage [n/p] Leakage Production [%] Spallation (n,xn) Total BERTINI JENDL BERTINI JEFF ISABEL JEFF CEM JEFF

8 PARTICLE SPECTRA PROTON PARTICLE FLUX OVER INNER TARGET Current / Ln(E) [1] 1x10-4 BERTINI ISABEL CEM Flux / Ln(E) [1] 1x10-4 NEUTRON NEUTRON LEAKAGE FROM SIDE SURFACE

9 BARE SPALLATION MODULE ENERGY DEPOSITION Particle Energy Deposition [MeV/p] Power density averaged over inner target is 320 W/cm 3 for 24 ma beam current Inner Outer Structure Leakage Total p n γ Other Total

10 POWER DENSITY AXIAL & RADIAL DISTRIBUTIONS 10 2 Peak power density is observed in the top cm under the beam spot 10 2 PROTON Power Density [W/cm 3 /ma] AXIAL DISTRIBUTION BERTINI ISABEL CEM Target Depth (69 cm - Target Base) [cm] Power Density [W/cm 3 /ma] RADIAL DISTRIBUTION NEUTRON Distance from Target Axis [cm]

11 METHODOLOGY OF DISPLACEMENT XS ESTIMATION 10 7 BERTINI RUTHERFORD 10 7 SCATTERING Displacement Cross Section [dpabarn] JENDL-3.3 Displacement Cross Section [dpabarn] Neutrons Protons BERTINI

12 W DISPLACEMENT XS ESTIMATION & VALIDATION Displacement Cross Section [dpabarn] THIS STUDY 10 1 LANL PROTON INDUCED Displacement Cross Section [dpabarn] NEUTRON INDUCED ORNL FZK

13 FLUX & DISPLACEMENT AXIAL DISTRIBUTIONS NEUTRON 10 1 Flux [1/cm 2 /s/ma] BERTINI ISABEL CEM PROTON Target Depth (69 cm - Target Base) [cm] Displacement [dpa/yr/ma] TOTAL Target Depth (69 cm - Target Base) [cm]

14 FLUX & DISPLACEMENT RADIAL DISTRIBUTIONS NEUTRON Flux [1/cm 2 /s/ma] PROTON BERTINI ISABEL CEM Distance from Target Axis [cm] Displacement [dpa/yr/ma] TOTAL Distance from Target Axis [cm] 10-1

15 FLUX & DISPLACEMENT SPECTRA WITH CORE Flux / Ln(E) [1] 1x10-4 +CORE Displacement / Ln(E) [1] 1x10-4 Neutrons Protons 10-6 BARE MODULE

16 ISOTOPE & GAS PRODUCTION DUE TO W BURNUP Isotope Production [100appm/Yr/mA] < 20 MeV Neutron Reactions Gas Production [appm/yr/ma] H He La-Lu Hf Ta Re Other 10 0 p D T He-3 α Product Product

17 MAIN CHARACTERISTICS OF SPALLATION MODULE Peak Value Tungsten Rod Pattern Averaged Bare Module BERTINI JENDL-3.3 Bare Module BERTINI JEFF3.1 Bare Module ISABEL JEFF3.1 Bare Module CEM JEFF3.1 + Core CEM JEFF3.1 Neutron Flux [1/cm 2 /s/ma] Proton Flux [1/cm 2 /s/ma] Power Density [W/cm 3 /ma] Neutron Displacement [dpa/yr/ma] Proton Displacement [dpa/yr/ma] Total Displacement [dpa/yr/ma] Isotope Production [appm/yr/ma] 1200 H+He Gas Production [appm/yr/ma]

18 W RADIATION DAMAGE PERFORMANCE LIMITS M. Wechsler et al. J. Nucl. Mater (1997): The results of our calculations concerning the displacement production indicate <total rate> of about 1.1 dpa/d. A rough indication of the consequences of this radiation exposure may be obtained by considering the effect of fission reactor irradiation on the ductility of tungsten. Krautwasser et al. [33] studied the effect of irradiations at about C in the FRJ2 reactor at Jülich and the HFR reactor at Petten on the ductile-brittle properties of pure W < > for the pure W, exposure to 1.1 dpa produced an increase in the ductile-brittle transition temperature of 485 C. < > this suggests that after only one day in the SNS, the W target rods would be operating well into the brittle domain. 1 dpa M. Cappiello & E. Pitcher. Mater. Charact (1999): The highest radiation damage rates occur in the front ladders of the tungsten neutron source. < > Due to radiation damage, the window and the front neutron source module are expected to require replacement on an annual basis. ~ 3-5 dpa M. Übeyli. J. Fusion Energ (2003): At present there is no consensus on a DPA limit backed up by experimental data due to the lack of an intense fusion neutron source. While an earlier work [44] has assumed higher limits for fusion reactors, namely DPA = , more recent studies [45,46] suggested a lower damage limit as DPA = 165. Technologically admissible damage limit for DPA can be significantly higher than those values. In the present work, a very conservative limit of DPA= 100 is assumed. < > Refs. [45,46] propose a helium limit of 500 appm (atomic parts per million) that is used in the present work. 100 dpa 500 appm He

19 CONCLUSIONS Bare spallation module produces about escaped neutrons per 1 incident 800 MeV proton. Maximum power density due to energy deposited by nucleons would be about 100 W/cm 3 /ma, while power density averaged over tungsten rod pattern is 25 W/cm 3 /ma. These values rescaled to 24 ma current appear within operation limits set for He-EFIT (~ 3 kw/cm 3 ). Peak displacement is found to be 6 dpa/yr/ma and its value averaged over tungsten rod pattern is 1.5 dpa/yr/ma. Isotope production due to tungsten burnup is 1200 appm/yr/ma including appm/yr/ma of H+He. The core does not affect radiation damage characteristics of the module, since these characteristics are mostly defined by high energy interactions. Lifetime of the module is estimated to be less (and probably much less) than Yr ma. Further experiments are in demand to provide realistic estimation of tungsten radiation damage performance limits.

20 ABOUT HE-EFIT EFIT CORE NUCLEAR DATA UNCERTAINTIES

21 HE-EFIT EFIT ESSENTIAL NEUTRON MULTIPLICATION DATA Nuclear Data Library He-EFIT Pu+MA Mixture Kinf He-EFIT Keff Fission Multiplication Factor JEFF (1σ = 276 pcm) (1σ = 190 pcm) 41 JENDL (1σ = 353 pcm) (1σ =137 pcm) 19 ENDF/B-VII (1σ = 314 pcm) (1σ = 154 pcm) 22

22 EFFECT OF NUCLEAR DATA LIBRARY SELECTION JENDL-3.3 Effect of structural materials JEFF3.1 Subcriticality [%] ENDF/B-VII Effect of fuel 6.0 SM O Mg Np Pu Am Cm Fuel All Nuclide Group

23 CORE SPECTRUM & FUEL ACTINIDE COMPOSITION 10 0 ENDF/B-VII 0.75 Flux / Ln(E) [1] 1x10-4 Atomic Fraction [1] JENDL (12%) 243 (10%) 241 (50%) 10-6 JEFF (16%) Np Pu Am Cm Actinide

24 CORE SPECTRUM AV CAPTURE XS DISCREPANCIES Outside 0.45 JENDL σ/σ JEFF Outside F Σ-Σ JEFF3.1 Normalized to Fuel Σ-Σ JEFF3.1 [1] ENDF/B-VII -0.5 Uncertainties [JEFDOC/1063] F Np Pu Am Cm Np Pu Am Cm

25 CORE SPECTRUM AV NU FISSION XS DISCREPANCIES νσ/νσ JEFF JENDL F νσ-νσ JEFF3.1 Normalized to Fuel νσ-νσ JEFF3.1 [1] Uncertainties [JEFDOC/1063] ENDF/B-VII F Np Pu Am Cm Np Pu Am Cm

26 CORE SPECTRUM AV FISSION XS DISCREPANCIES Uncertainties [JEFDOC/1063] σ/σ JEFF JENDL F Σ-Σ JEFF3.1 Normalized to Fuel Σ-Σ JEFF3.1 [1] ENDF/B-VII F Np Pu Am Cm Np Pu Am Cm

27 CORE SPECTRUM AV NU DISCREPANCIES Uncertainties [JEFDOC/1063] ENDF/B-VII 0.02 ν/ν JEFF Outside Outside F Np Pu Am Cm JENDL-3.3

28 AM-241 CAPTURE XS DATA & DISCREPANCIES 10 4 JEFF ENDF/B-VII Cross Section [barn] 10 0 σ/σ JEFF Uncertainties [JEFDOC/1063] x x JENDL-3.3

29 AM-241 NU FISSION XS DATA & DISCREPANCIES 10 2 JEFF ENDF/B-VII Cross Section [barn] 10 0 νσ/νσ JEFF Uncertainties [JEFDOC/1063] JENDL x x

30 AM-241 FISSION XS DATA & DISCREPANCIES JEFF ENDF/B-VII Cross Section [barn] 10 0 σ/σ JEFF Uncertainties [JEFDOC/1063] JENDL x x

31 AM-241 NU DATA & DISCREPANCIES Prompt Neutron Multiplicity [1] JEFF3.1 ν/ν JEFF ENDF/B-VII Uncertainties [JEFDOC/1063] JENDL x x

32 KEFF TARGET ACCURACY G. Aliberti et al. Nucl. Sci. Eng (2004): As for target accuracies in integral parameters, we have defined a tentative first set for the multiplication factor keff < >. The target accuracies are < > ±1 < > %. These values are, of course, rather arbitrary, but they are consistent with standard requirements for reactor design in early phases of development. 1% CONCLUSIONS Neutronics of the core is strongly influenced by nuclear data libraries used: the keff discrepancies between JEFF3.1, JENDL-3.3 and ENDF/B-VII are in order of several percents. It is found that discrepancies between JEFF3.1, JENDL-3.3 and ENDF/B-VII are above nuclear data uncertainties proposed in JEFDOC/1063. Therefore, re-examination of nuclear data (especially for 241 Am isotope being the main contributor into total discrepancy) and/or re-examination of nuclear data uncertainties is recommended.