1. Study on Neutronics of plutonium and Minor Actinides Transmutation in Accelerator Driven System Reactor By
Amer Ahmed Abdullah Al-Qaaod
Ph.D student
Physics Department, Faculty of Science,
Ain Shams University,
Cairo, Egypt

2. Outline Introduction Aim of the work Core Descriptions and Modeling
Spent nuclear fuel
Accelerator driven system
Aim of the work
Core Descriptions and Modeling
Results
Homogenous and heterogeneous distribution for Pu and MA
Burnup calculations for Pu and MA
Conclusion

3. Spent nuclear fuel is the source of nuclear waste

4. Partitioning and Transmutation (P&T)
Spent fuel
Reprocessing
U、Pu
Recycle
Geological disposal (Glass waste form)
FP、MA
Conventional scheme
P&T technology
MA (Np, Am, Cm)
Transmutation by ADS and/or FR
Partitioning (Example)
PGM (Ru, Rh, Pd)
Utilization and/or disposal
Geological disposal after cooling and/or utilization
Heat generator (Sr, Cs)
Geological disposal (high-density glass waste form)
Remaining elements
MA: Minor Actinides
FP: Fission Products
PGM: Platinum Group Metal
FR: Fast Reactor
ADS: Accelerator Driven System

5. Reduction of Radiological Toxicity by P&T
Radiological Toxicity: Amount of radioactivity weighted by dose coefficient of each nuclide.
Normalized by 1t of spent fuel.
9t of natural uranium (NU) is raw material of 1t of low-enriched uranium including daughter nuclides.
Spent fuel (1t)
High-level waste
MA transmutation
Natural uranium (9t)
Radiological toxicity (Sv)
Reduction
Time period to decay below the NU level:
Spent fuel 100,000y 　　↓
High-level waste 5,000y 　　↓
MA transmutation 300y　
Time after reprocessing (Year) 5

6. Short-lived or stable nuclides Long-lived nuclides (MA)
Accelerator Driven System (ADS) for MA Transmutation
Proton beam
Max.30MW
Super-conducting LINAC
100MW
To accelerator
800MW
170MW
Fission energy
To grid
Spallation target (LBE)
MA: Minor Actinides
LBE: Lead-Bismuth Eutectic
270MW
Power generation
Transmutation by ADS
MA-fueled LBE-cooled subcritical core
Utilizing chain reactions in subcritical state
Proton
Spallation target
Fission neutrons
Fast neutrons
Characteristics of ADS:
Chain reactions stop when the accelerator is turned off.
LBE is chemically stable.
 High safety can be expected.
High MA-bearing fuel can be used. 　MA from 10 LWRs can be transmuted.
Short-lived or stable nuclides
Long-lived nuclides (MA)

7. Aim of the work
Investigate the best distribution of a sample of Pu and MA inside the core, which maximize fission rate and efficiency.
find a better distribution to burning the plutonium and minor actinides sample

8. Core Descriptions and Modeling
The UT- TRIGA Mark II research reactor is licensed to at a nominal full power 1 MW
construction completed in 1992
The hexagonal-spaced grid plates are surrounded by an aluminum-canned graphite reflector assembly with an effective inside diameter of cm and a radial thickness of cm
The fully operational reactor core consists of up to 116 reactor fuel elements and four control rods for a total of 120 grid locations
Klystron and power Supplies
Power Supplies
Covered Shield Area
Not to Scale
Fence

10. TRIGA Fuel
The nuclear fuel in TRIGA reactor is uranium zirconium hydride (U-ZrH) content (enriched to 19.7 % U-235)
fuel length 38.1 cm, and 3.63 cm in diameter.
clad in stainless steel, with graphite reflector above and below the fuel “meat” The U-ZrH provides the moderation for the core
Fuel Zr
AISI-304 Gr
Air

11. Fig. 4.1: Effective multiplication factor versus control rod position
Results and discussions
Model validation
Fig. 4.1: Effective multiplication factor versus control rod position

12. Homogenous and heterogeneous distribution for Pu and MA
The present section aims to compare between two models core configuration by distributing the plutonium and minor actinides inside the core in two different ways (homogenous and heterogeneous). Neutron flux, neutron spectrum, fission rate (FR) and subcritical multiplication parameters are analyzed for two core configurations, proton and electron in energy range from 20 to 100 MeV are used also as an incident beam to produce the neutrons inside the reactor core.
a) Heterogeneous
b) Homogenous

13. 1. Neutron flux
Fig.4.5, shows the MCNPX calculated total flux distribution in the two core configurations with Pu and MA sample. The maximum flux, i.e, the peak is in the core center and the axial profile is generally symmetrical about this peak in both configuration, but there are disparity between them, where heterogeneous distribution has little peak than homogenous.
Fig. 4.5: Neutron flux distribution in the core with two different configuration contents Pu and MA sample.

14. Fig. 4.6: Comparison between cross-sections of the 235U(n,γ), 241Am(n,γ), 239Pu(n,γ) and 244Cm(n,γ) reactions 90

15. Subcritical multiplication parameters
Neutron multiplication M
Subcritical multiplication factor ks
External source efficiency

16. Table 4.4: Fission rate FR, neutron multiplication M, Subcritical multiplication factor ks and source efficiency j* for heterogeneous and homogenous cores.
Core Configuration
keff = 0.92
FRa
FRa for MA
ks b Mc
j* d
Heterogeneous
0.261
0.046
0.983
57.28
4.87
Homogenous
0.336
0.045
0.986
72.66
6.18
a Statistical error in FR is less than 2.25E-7
b Statistical error in Ks is less than 6.8E-6
c Statistical error in M is less than 0.036
d Statistical error in j* is less than 0.04
The results shown that the fission rate for Pu and MA in heterogeneous distributions is slightly higher than homogenous this due to the most neutrons emitting from the source are fast, hence the presence of the Pu and MA sample near the source gives a greater opportunity to benefit from them, especially as the most isotopes in the minor actinides sample fission by the fast neutrons.

17. 2. Beam type and energy
Table 4 : Neutron multiplication M Subcritical multiplication factor ks and source efficiency φ* for proton and electron beam at varying incident energies in homogenous distribution.
a Statistical error in Ks is less than 6.8E-6
b Statistical error in M is less than 0.04
c Statistical error in ϕ*is less than 0.043

18. Plutonium and minor actinides burnup
The burnup of plutonium and minor actinides is calculated by MCNPX for heterogeneous and homogenous distribution based on electron-driven ADS. The core is simulated with keff as 0.93 in the two configuration types. The burnup time was set at 720 days, in the first 650 days, the time interval of 50 days was chosen, and from 650 days to 720 days, a time interval of 70 days was chosen.
Fig. 4.10: Burnup of Plutonium and minor actinide material in heterogeneous and homogenous distribution

19. Fig. 4.11: variation of mass of 239Pu in two years operation cycle in heterogeneous and homogenous distribution.

20. Fig. 4.12: variation of mass of 240Pu with two years operation cycle in heterogeneous and homogenous distribution.

21. Fig. 4.14: variation of mass of 241Am in two years operation cycle in heterogeneous and homogenous distribution.

22. Fig. 4.15: variation of mass of 243Am with two years operation cycle in heterogeneous and homogenous distribution.

23. Fig. 4.16: variation of mass of 244Cm in two years operation cycle in heterogeneous and homogenous distribution.

24. Fig. 4.18: variation of mass of 245Cm in two years operation cycle in heterogeneous and homogenous distribution

25. Conclusion
The heterogeneous distributions achieve slightly more fission rate for the Pu and MA due to the fast neutrons contribution.
The external source efficiency is found to be clearly higher for electron beam at energy range from 20 to 60 MeV than proton beam at the same incident energy.
The 239Pu mass is decreased significantly during operation time . At the same time there is no significant deference between the two core configuration, this due to that the 239Pu can be split by both thermal and fast neutrons.
The heterogeneous distributions give a good results for transmuted of both isotopes 241Am and 243Am with decreases in mass ratio by ~ 21% and 17%, respectively. Whereas the homogenous distributions are considered better suited to 245Cm transmutation.

26. Thank you for your ATTENTION

27. What is the minor actinides ?
The minor actinides are the actinide elements in used nuclear fuel other than uranium  and plutonium, which are termed the major actinides. The minor actinides include neptunium, americium, curium, berkelium, californium, einsteinium, and fermium.

28. Computational Tools
MCNP5 can be used for neutron, photon, electron, or coupled neutron/ photon/ electron transport, including the capability to calculate eigenvalues for critical systems.
For neutrons, all reactions given in a particular cross-section evaluation (such as ENDF/B-VI) are accounted for.
MCNPX is a Fortran 90 (f90) Monte Carlo radiation transport computer code that transports 34 particle types, including four light ions, at nearly all energies. MCNPX stands for MCNP eXtended
Newer capabilities and enhancements of MCNPX include the depletion/burnup capability which based on CINDER90.

29. Fig. 4.7: Comparison between calculated neutron spectra in the two configuration, heterogeneous and homogenous.

30. Fig. 4.17: Probability of fission per neutron absorbed in actinides isotopes for thermal and fast spectra (IAEA, 2010)

31. Fig. 4.13: Actinides formation scheme in neutronic simulations (KIT)91