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2012年10月の6件の記事

2012年10月27日 (土)

PE Day 8: Nuclear Measurements and Instruments

Last section.

Determination of which type of detector to use for a particular application.
Counting statistics
Operation of detectors and associated electronics
Instrumentation electronics

I will have the exam two days later. I don't believe I can pass it however it was nice to go through major nuclear subjects. I will come back sometime in the future.

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2012年10月21日 (日)

PE Day 7:Nuclear Criticality, Kinetics, Neutronics

This theme covers much wide area. For example,
- Neutron transport and diffusion
- Reactor kinetics and control
- Macroscopic cross sections
- Burn-up and depletion
- Multigroup diffusion calculations
- Reactor criticality

Boron Carbide, B4C, can be employed in certain shielding applications.
10-B has a large (n,a) cross section fro thermal neutrons

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2012年10月16日 (火)

PE Day 6: Radiation Protection/Shielding/Interaction of Radiation with matter

Radiation attenuation primary due to scattering
Photons attenuation coefficient
Neutron cross section
Energy deposition involves absorption
Photons Compton electrons, Photoelectronics
Neutrons (n,a) reactions
Sources (usually isotropic) and Fluxes
Point isotropic sources results in inverse square law
Dose rate = (DRCF) S / 4 pi r^2 * exp(- mu x)

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2012年10月14日 (日)

PE Day 5: Nuclear waste management part 2

Secular equilibrium: Ax = Ay
Radiation units:
Exposure [Roentgen, R] X-, gamma ray
Absorbed Dose [Gray, Gy or Rad] 1 Rad = 100 ergs/gram, 1 Gray = 1 J/kg = 100 Rads
Equivalent Dose [Sievert, Sv or Rem] Absorbed dose * Quality factor
1 Rem = 1 Rad * QF
1 Sievert = 1 Gray * QF
QF = 1 for x-, gamma-ray, QF = 10 for Alpha, QF = 2-10 for neutron depending on neutron energy

TRU: Transuranic Waste (z>92), by-products of fuel assembly
Mill tailings: Residue from physical and chemical processing of uranium ore, main concern is radon-222

LLW from NPP: C14 from the activation of N14 in reactor coolant, H3 from boron, Fe55, Co60, Ni59, Ni63, Tc00 from cooling system corrosion products

US government is responsible for final disposal of spent fuel discharged from US commercial NPPs. The utilities are responsible for paying 1 mill per kWh to cover final disposal. (1 mill = 1/1000 dollar)

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2012年10月10日 (水)

PE Day 4: Nuclear Waste Management

Type of wastes; HLW, LLW, Class A, B, C, GTCC(Greater than class C), TRU
Radioactive decay law; probability that a given nucleus will decay per unit time is called the decay constant, ramda (time^-1). It is independent of the age of the nuclei.
The number of nuclei in the mass is given by: N = m * Na / A
The number of nuclei decreases with time due to decay as given by: -dN(t)/dt = ramda * N(t)
The number of nuclei present at any time is: N(t) = N(0) exp(-ramda * t)
Half time = 0.693 / ramda
The number of nuclei decaying per unit time is the activity, A(t): A(t) = ramda * N(t) = ramda * N(0) * exp(-ramda * t) = A(0) * exp(-ramda * t)
Units of activity are: Becquerel (Bq) = 1 decay / sec or 1 dps
Curie (Ci) = 3.7e10 decay/sec
Specific Activity (SA)
Solid: SA = Activity / Mass [Bq/kg or Ci/kg]
Gases: SA = Activity / Volume [Bq/m3 or Ci/cc]
SA of Radium 226 is 3.7e10 Bq/g = 1 Ci/g

To be continued...

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2012年10月 9日 (火)

PE Day 3 Nuclear Fuels

あれっ? 前回から3,4週間開いていますが、気を取り直して再開。
今日はNuclear fuels.

U3O8: Yellow cake
Ore cost: $22.50 / kg (2009)
Ore grade: 0.2% U3O8
Conversion: U3O8 -> UF6 (gas)
Enrichment: 0.71 wt% U235 to 3-5 wt% U235
by Gaseous diffusion and centrifuge, Laser isotopic separation, Atomic vapor laser isotopic separation (AVLIS, Lawrence Livermore National Laboratory, US Enrichment Corporation), SILEX(Global Laser Enrichment)
Enrichment mass balance
Separative Work Units (SWU): kind of energy used for enrichment, kg-SWU
Value function
Cost $146/kg-SWU (2009), 120 t-SWU equal 1 GWe plant
Fabrication: Convert from UF6 to UO2
Total cost about $220/kgU

Burnup: Energy - MWD/kg
Normally 3 cycles of 1.5 to 2 years each
100% burnup = 938 GWd/t
Conversion ratio 0.6
1% wt U235 -> 10 GWD/MTU
10 GWD/MTU -> 1 year
1 GWD/MTU = 1% in keff
1% keff = 100 ppm Boron

Waste: owned by DOE

Time value of Money:
F = P * (1+i)^n



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