Proliferation Aspects of Plutonium Production in Nuclear Reactors

Dwight L. Williams, Ph.D., P.E.

Martin Luther King Visiting ProfessorDepartment of Nuclear Science and Engineering

Massachusetts Institute of Technology

Overview Introduction Reactor Isotopes of Interest Types of Plutonium Plutonium Production

About the Speaker -- the “New Guy” Education and Registration (Nuclear Engineering)

B.S., North Carolina State University (NCSU)M.S., NCSU, Plasma Physics/FusionPh.D. University of Maryland, Radionuclide DetectionP.E., Commonwealth of Virginia

Professional ExperienceNuclear Analyst, Prototype International Data CentreSenior Nuclear Engineer, Department of Defense (DoD)Chief Engineer/Principal Nuclear Physicist, DoD

Introduction Why knowledge of nuclear proliferation is

useful within peaceful nuclear academic programexpands upon foundational knowledge fosters effective nonproliferation and

counterproliferation efforts facilitates nuclear security planningenables better public relations and perceptions to be

cultivated

Weapons Development Pathways

Weapons Development Pathways

Typical Reactor Isotopes of Interest Plutonium (Pu-239)

product of natural and depleted uranium irradiation

one of many Pu isotopes generated Uranium (U-235)

U-235 abundance customarily of 3 - 5% in reactors

Tritium (H-3)product of heavy water irradiationproduct of Li-6 and Li-7 irradiationpossible fission product

Relevant Plutonium Isotopes Pu-239: U-238 + n → U-239 → Np-239 → Pu-239

most desirable for nuclear weapons use

Pu-240: Pu-239 + n → Pu-240 (if no fission)neutron emitter/spontaneous fission

Pu-241: Pu-240 + n → Pu-241 relatively strong gamma-ray emitter

Pu-238: U-235 or U-238 + n → → → Pu-238 generates heat from rapid decay

Plutonium Isotope PropertiesProperty Pu-238 Pu-239 Pu-240 Pu-241 Pu-242t1/2 (y) 87.74 24,110 6537 14.4 376,000

Spec. Act. (Ci/g)

17.3 .063 .23 104 .004

Decay , SF

Notes,Pu-241 decays into Am-241, an intense emitterMost even Pu isotopes (238, 240, etc.) decay by SF

Production of Weapons Grade Pu At least 94% Pu-239 Typically generated in weeks to months in

reactor frequent refueling required for optimum productionseparating isotopes is nontrivial effort

Typically affects power production

Comparison of Plutonium GradesIsotope Weapons Grade Reactor GradePu-238 0.01 - 0.04% 1 - 2%

Pu-239 94% 56 - 60%

Pu-240 6% 24%

Pu-241 0.1% 6 - 13%

Pu-242 0.02% 5%

In general,Weapons Grade: < 7% Pu-240Reactor Grade: > 18% Pu-240

Pu Isotopes as a Function of Burnup

Pu Production in Various Reactors

Pu in Fuel at 1000 MWd/MTU

Reactor Type Pu (kg/MTU) %Pu-239 in PuHanford B 0.79 90.8

MAGNOX GCR 0.88 93.1

Heavy Water 0.90 93.8

RBMK 0.54 96.2

Advanced GCR 0.28 97.5

PWR 0.51 98.5

FBR Blanket (estimate) 3.77 99.8

Reactor Type Burnup (MWd/MTU)

kg of Pu per MTU

% Pu-239 in Pu

g of Pu per MWd

Hanford B 600 0.51 94.2 0.85

MAGNOX GCR 4000 2.49 76.4 0.62

Heavy Water 7000 3.76 65.9 0.54

RBMK 18000 4.96 51.8 0.28

Advanced GCR 18000 3.38 57.5 0.19

PWR 40000 10.65 53.8 0.27

FBR Blanket (estimate)

8000 22.96 98.7 2.87

Estimated Pu in Fuel at Discharge

Pu Production Rules of Thumb

Conclusions Roles exist for nuclear proliferation knowledge

within peaceful nuclear program Pu-239 is generated prolifically in reactors Pu-239 is most useful isotope for weapons, but

generating weapons grade plutonium (>94% Pu-239) is nontrivial

Typical power reactor operations are not conducive for weapons grade plutonium production