University of Florida Proliferation Risks and Nuclear Safeguards Concerns HW 1. What are the proliferation risks and nuclear safeguards concerns associated

University of Florida Proliferation Risks and Nuclear Safeguards Concerns HW 1. What are the proliferation risks and nuclear safeguards concerns associated with:

a. Mining and Milling, b. Conversion, c. Enrichment

Discuss the types and quantities of materials typically involved with each aspect of the fuel cycle.

2. Suppose you are to downblend 2 tonnes of HEU (93% U-235) for use as commercial reactor fuel with

enrichment of 4.5% U-235. How much reactor fuel can be produced? The original HEU constitutes

how many SQ? How many for the resultant reactor grade fuel? Show all your work.

3. Compare the SWU requirement for producing 1 kg of HEU (93% U-235) from (a) natural uranium, (b)

19.9% enriched research reactor grade uranium. Compute the energy requirement to produce 1 SQ of

said HEU by the centrifuge method. Reference typical value of energy required per kgSWU.

4. Suppose Iran is operating an enrichment plant with 10,000 IR-1 type machines capable of

1.5kgSWU/year. What would be the breakout time for producing 1 SQ of HEU at 93% U235 from

natural uranium? How does your answer change if you are feeding research reactor grade uranium

(19.9% U235) instead of natural uranium? Define the term “breakout time”. Reprocessing and Recycling
Enriched Uranium*
U234 – 0.035wt%
U235 – 5 wt%
U238 – 95 wt%
Depleted Uranium*
U234 – 0.001wt%
U235 – 0.2 wt%
U238 – 99.8 wt%
U235 is fissile,
will fission with
neutron of any
energy.
Enrichment
necessary for
self-sustaining
chain reaction.
Fissionable U238
requires fast
neutrons and is
more easily
utilized in fast
reactors. U238
can be converted
to Pu239 (fissile).
Natural Uranium
U234 – 0.005 wt%
U235 – 0.711 wt%
U238 – 99.284 wt%
Source: IAEA
Nuclear Fuel Cycle
* varies with enrichment (% U235) or burnup (MWD/MTU)
Used Fuel*
Uranium 93 wt%
U235 0.8 wt%
U236 0.6 wt%
Plutonium 1%
Minor Actinides 0.1wt%
Fission Products 5 wt%
Production of Plutonium
Fission Chain Reaction & Neutron Economy
Duderstadt and Hamilton
Duderstadt 1976
Simple schematic of a fission chain reaction
•
•
Slow down through collisions with medium
Thermal energy (vibration) of atoms of a medium on
order of kT, k is Boltzmann constant 8.617E-05 ev/K,
k=R/Na
– Approximate by Maxwellian distribution
– Most probable energy is (1/2)kT
– Average energy (3/2)kT
– Energy of most probable velocity is kT, at 20˚C
this is 0.0253eV
Born high energy, fission or Chi distribution
Most probably ~0.7 MeV
Average energy ~2 MeV
Very few above ~10MeV
Duderstadt 1976
Production & Transmutation of
Transuranics (TRU)
Transuranics are produced through
nuclear reactions; occurs through
capture of a neutron during reactor
operations.
Through transmutation new elements and
radioisotopes are created. These may decay,
fission, or be transmuted into other isotopes still.
Transmutation-decay chains for U238
(Stacey 2001)
Mass (g/kg HM initial)
Production of Pu
 Spent fuel contains
about 1% Pu
 ~70% fissile
 MOX fuel
 ~9% Pu (RG)

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