Investigating the Feasibility of a Small Scale Transmuter

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Investigating the Feasibility of a Small Scale
Transmuter Part II

• Roger Sit
• NCHPS Meeting
• March 4-5, 2010

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Outline

• Quick Review of Part I
• Preliminary Transmuter Design
• Base Cases for Transmutation
• Radionuclides to be studied
• Activation analyses methodology
• Summary of transmutation results for the
  different radionuclides
• Shielding calculations
• Heatload calculations
• Conclusions

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Preliminary Transmuter Design

• Basic source term
• Evaluate material type for best
  multiplication/reflection to optimize neutron
  flux
• Evaluate optimum thickness of material
• Evaluate optimum size of sphere
• Evaluate mesh tally results inside the sphere
• Evaluate neutron energy spectrum inside
  transmuter by using different moderators and
  target sizes
• Select transmuter base cases to carry out the
  transmutation calculations

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Neutron Source
RF-driven plasma ion source
Geometry 26 cm diameter, 28 cm length
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(No Transcript)
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Transmuter Design Base Cases

• D-T generator, unmoderated sphere (DT-Unmod)
  lead sphere, 25 cm thick, 50 cm inner radius,
  neutron source strength of 3E14 n/s
• D-T generator, moderated sphere (DT-Mod) Lead
  sphere, 25 cm thick, 5cm thick teflon, 45 cm
  inner radius, neutron source strength of 3E14 n/s
• D-T generator, themalized sphere
  (DT-Thermalized) lead sphere, 25 cm thick, 50 cm
  inner radius filled with heavy water, neutron
  source strength of 3E14 n/s
• D-D generator, moderated sphere Lead sphere, 25
  cm thick, 5cm thick teflon, 45 cm inner radius,
  neutron source strength of 1E12 n/s

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DT-therm
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Radionuclides Studied
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Requirements for Activation Calculations

• Neutron flux
• Neutron energy spectrum
• Dominant reactions and the energy thresholds for
  these reactions
• Nuclear reaction cross sections
• EASY-2003, European Activation System, a software
  package utilizing FISPACT

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Activation Analysis Fission Products

• Starting activity (1 Ci except for I-129 0.032
  Ci)
• Ending activity NRC 10 CFR 20 Appendix C values
  (quantities requiring labeling)
• Using the base cases, calculate fluence required
  to reduce the target radionuclides to the ending
  activity level
• Iterate on the base cases by increasing the
  source strengths by factors of 10 to reach the
  ending activity in a reasonable period of time
  (lt 100 years)
• Evaluate effective half-lives for each flux level
• Evaluate activation products (number of
  radionuclides and total activity)
• Evaluate dose rate of activation products
• Evaluate radiotoxicity of activation products
  (based on ICRP 72 DCFs)
• Evaluate cooling of activation products (decay
  down to 1 mR/hr surface dose rate)

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Iodine-129 T1/2 1.57E7 yearsStarting 1.2E9
Bq Ending 3.7E4 Bq
  DT-Unmod DT-Mod DT-Thermalized   DD-mod
           
Initial neutron Flux (n/cm2-s) N/A 1.55E11 1.83E11   5.14E08
Neutron Flux (n/cm2-s) N/A 1.55E16 1.83E14   5.14E15
Irradiation effective T1/2 (yrs) N/A 1.67E00 4.03E00   2.19E00
OM flux increase required N/A 5 3   7
Number of radionuclides generated N/A 541 103   200
Activation Products (Bq) N/A 2.29E15 6.76E10   7.12E14
Dose rate (Sv/hr) N/A 2.15E06 8.71E04   7.52E05
Ingestion dose (Sv) N/A 4.23E06 4.43E05   2.64E06
Inhalation Dose (Sv) N/A 6.50E06 6.08E05   3.37E06
Time to decay to 1 mR/hr (yrs) N/A 900 500   750
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Technetium-99 T1/2 2.13E5 yearsStarting
3.7E10 Bq Ending 3.7E6 Bq
  DT-Unmod DT-Mod DT-Thermalized   DD-mod
           
Initial neutron Flux (n/cm2-s) N/A 1.55E11 1.83E11   5.14E08
Neutron Flux (n/cm2-s) N/A 1.55E15 1.83E14   5.14E14
Irradiation effective T1/2 (yrs) N/A 2.25E00 6.86E00   6.44E00
OM flux increase required N/A 4 3   6
Number of radionuclides generated N/A 227 62   84
Activation Products (Bq) N/A 1.64E14 9.72E13   4.62E13
Dose rate (Sv/hr) N/A 8.71E04 5.33E04   2.55E04
Ingestion dose (Sv) N/A 3.82E04 2.34E04   1.12E04
Inhalation Dose (Sv) N/A 1.53E05 9.54E04   4.55E04
Time to decay to 1 mR/hr (yrs) N/A 1.1 E7 11 yrs   20 yrs
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Strontium 90 T1/2 28.8 yearsStarting 3.7E10
Bq Ending 3.7E3 Bq
  DT-Unmod DT-Mod DT-Thermalized   DD-mod
           
Initial neutron Flux (n/cm2-s) 1.23E11 1.55E11 1.83E11   5.14E08
Neutron Flux (n/cm2-s) 1.23E17 1.55E18 1.83E16   5.14E16
Irradiation effective T1/2 (yrs) 6.1 26.4 23.9   20.7
OM flux increase required 6 7 5   8
Number of radionuclides generated 535 750 315   353
Activation Products (Bq) 4.40E11 3.15E12 4.93E10   1.20E10
Dose rate (Sv/hr) 3.38E06 8.06E07 5.68E05   1.18E05
Ingestion dose (Sv) 1.54E02 4.88E02 2.27E02   7.49E02
Inhalation Dose (Sv) 1.58E02 7.38E02 7.61E02   2.72E03
Time to decay to 1 mR/hr (yrs) 1.6E7 1E8 3E7   5E7 yrs
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Cesium-137 T1/2 30.2 yearsStarting 3.7E10
Bq Ending 3.7E5 Bq
  DT-Unmod DT-Mod DT-Thermalized   DD-mod
           
Initial neutron Flux (n/cm2-s) 1.23E11 1.55E11 1.83E11   5.14E08
Neutron Flux (n/cm2-s) 1.23E15 1.55E15 1.83E15   5.14E14
Irradiation effective T1/2 (yrs) 193 422 23   29.4
OM flux increase required 4 4 4   6
Number of radionuclides generated 386 426 180   161
Activation Products (Bq) 9.36E09 8.30E09 2.46E10   8.60E08
Dose rate (Sv/hr) 3.59E04 7.78E04 3.55E04   1.90E04
Ingestion dose (Sv) 3.31E01 4.59E00 1.69E01   6.41E-01
Inhalation Dose (Sv) 7.36E01 4.80E00 2.18E01   4.49E-01
Time to decay to 1 mR/hr (yrs) 1.2E5 7.5E7 7.0E7   2400
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Activation Analysis Actinides

• Starting activity (1 Ci )
• Ending activity NRC 10 CFR 20 Appendix C values
  (quantities requiring labeling)
• Run MCNPX for each base case to calculate
  on-target flux which includes fission neutrons
  added to the spectrum
• Using these fission-modified neutron spectra,
  calculate fluence required to reduce the target
  radionuclides to the target activity level
• Iterate on the base cases by increasing the
  source strengths by factors of 10 to reach a
  reasonable time frame of transmutation (lt 100
  years)
• Evaluate effective half-life as a function of
  flux
• Evaluate activation products (number of
  radionuclides and total activity)
• Evaluate dose rate of activation products
• Evaluate radiotoxicity of activation products
  (based on ICRP 72 DCFs)
• Evaluate cooling of activation products (decay
  down to 1 mR/hr surface dose rate)
• Evaluate amount of other actinides generated

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Amercium-241 T1/2 432 yearsStarting 3.7E10
Bq Ending 37 Bq
  DT-Unmod DT-Mod DT-Thermalized   DD-mod
           
Initial neutron Flux (n/cm2-s) 1.26E11 1.62E11 1.34E11   4.37E08
Neutron Flux (n/cm2-s) 1.26E16 1.62E15 1.34E15   4.37E15
Irradiation effective T1/2 (yrs) 2.89 0.966 0.418   0.304
OM flux increase required 5 4 4   7
Number of radionuclides generated 1066 1012 738   770
Activation Products (Bq) 3.22E12 1.88E12 2.85E12   4.76E12
Dose rate (Sv/hr) 4.59E05 3.18E05 4.79E05   8.58E05
Ingestion dose (Sv) 3.46E03 1.87E03 2.83E03   4.20E03
Inhalation Dose (Sv) 8.57E03 1.38E04 4.78E04   4.15E04
Time to decay to 1 mR/hr (yrs) 1E9 2E8 1E10   5E8
Actinides Created (Bq) 2.55E05 5.83E09 1.53E10   3.11E10
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Plutonium-238 T1/2 87.8 yearsStarting
3.7E10 Bq Ending 37 Bq
  DT-Unmod DT-Mod DT-Thermalized   DD-mod
           
Initial neutron Flux (n/cm2-s) 1.26E11 1.55E11 1.59E11   4.22E08
Neutron Flux (n/cm2-s) 1.26E16 1.55E15 1.59E15   4.22E15
Irradiation effective T1/2 (yrs) 1.95 1.36 0.768   0.508
OM flux increase required 5 4 4   7
Number of radionuclides generated 1013 983 717   728
Activation Products (Bq) 6.55E11 3.56E11 3.99E11   8.91E11
Dose rate (Sv/hr) 5.93E05 3.01E05 3.00E05   7.33E05
Ingestion dose (Sv) 7.46E02 3.39E02 3.60E02   7.37E02
Inhalation Dose (Sv) 1.82E03 9.67E02 1.19E03   1.97E03
Time to decay to 1 mR/hr (yrs) 2E9 6E7 1E09   7E7
Actinides Created (Bq) 7.25E03 8.58E07 8.17E08   4.70E11
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Plutonium-239 T1/2 2.4E4 yearsStarting
3.7E10 Bq Ending 37 Bq
  DT-Unmod DT-Mod DT-Thermalized   DD-mod
           
Initial neutron Flux (n/cm2-s) 1.34E11 1.71E11 2.40E11   4.75E08
Neutron Flux (n/cm2-s) 1.34E16 1.71E15 2.40E15   4.75E15
Irradiation effective T1/2 (yrs) 1.39 0.869 0.268   0.296
OM flux increase required 5 4 4   7
Number of radionuclides generated 1101 1041 744   771
Activation Products (Bq) 2.03E14 1.34E14 1.18E15   2.99E14
Dose rate (Sv/hr) 6.14E05 4.20E05 3.17E06   9.37E05
Ingestion dose (Sv) 2.31E05 1.32E05 9.98E05   2.53E05
Inhalation Dose (Sv) 5.53E05 5.37E05 2.41E06   1.03E06
Time to decay to 1 mR/hr (yrs) 1E9 9E7 3E9   1E8
Actinides Created (Bq) 9.73E06 1.37E11 4.31E11   4.70E11
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Calculate Shielding

• Use ANSI/ANS 6.6.1 concrete composition with a
  density of 2.3 g/cc.
• Use two variance reduction techniques
• Geometry (splitting and Russian roulette)
• Source biasing
• Use ICRP 51 photon DCFs
• Use NCRP 38 neutron DCFs
• Result need about 7 ft concrete to reduce dose
  rate to about 5 mrem/hr at 1 foot

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Calculate Heat Load

• Calculate heat load from neutron and photon
  energy deposition (collision heating)in material
  using MCNPX (0.305 kW)
• Calculate heat load from activation products in
  material using MCNP coupled with FISPACT (0.0453
  kW)
• Convert kW to J/hr and then using specific heat
  capacity of lead, the resulting heat rise is 0.69
  C/ hr.
• In the absence of any type of cooling, the
  transmuter can operate 474 hours before reaching
  lead melting point. So will require cooling.

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Conclusions

• A rigorous calculation methodology for
  transmutation analyses was developed by coupling
  the MCNPX radiation transport code with the
  FISPACT activation code
• The present neutron source strength of the D-T
  and D-D neutron generators is not sufficient to
  perform transmutation in a reasonable period of
  time as defined in this investigation
• One single transmuter design is not sufficient to
  transmute all radionuclides (ie, fast neutrons
  are preferable for actinides, slow neutrons are
  preferable for LLFP)
• There is no major benefit from using the D-D
  generator as the neutron source for a
  transmutation device
• The long-lived fission product radionuclides,
  Tc-99 and I-129, behave similarly with regards to
  transmutation characteristics due to the fact
  that they have very similar neutron reaction
  cross sections

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Conclusions

• The short-lived fission products, Cs-137 and
  Sr-90, behave similarly with regards to
  transmutation characteristics due to the fact
  that they have very similar neutron reaction
  cross sections.
• This investigation confirms industry opinion that
  it is not beneficial to treat short-lived fission
  products by transmutation
• The actinides have behaviors that are very
  radionuclide specific because of their complex
  neutron reaction cross sections.
• Transmutation of actinides create more actinides
  higher energy neutron spectrum is advantageous
  because it creates less activation products.
• Thin targets are more beneficial for long-lived
  fission products thick targets for actinides.

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Conclusions

• Radiation protection issues
• Activation products are extremely hot,
  thousands of Sv/h
• Activation products are more radiotoxic for LLFP,
  less for SFP, and different for actinides
• Significant shielding is required for the
  transmuter (but not unreasonable)
• Cooling is required for the transmuter
• The methodology used in this investigation can be
  applied to other radionuclides specifically
  other long-lived fission products of interest
  such as Pd-107, Cs-135, Zr-93, and Se-79
• The methodology used in this investigation can be
  used to analyze the production of a radionuclide
  of interest from irradiating a target radionuclide

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Thank You

• Questions?