lecture 16 mod radioactive waste disposal

8/3/2019 Lecture 16 Mod Radioactive Waste Disposal

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Radioactive WasteDisposal

Lecture 16

Fundamentals of Earth Resources

Environmental Considerations

L. Cathles2011

How is U burned and how is itdisposed?

The Uranium Cycle


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Uranium Cycle

Fuel rods:

Fuel rods (pins)

3 yr in reactor 5 years cooling pond

yrs dry storage

Craig et al. (2001, fig 6.5)

Rods are ore

0 years 3 years

Hypothetical 3.3% 235U rod (pin)

1 g 235U = 13.7 bbl oil= 4.6 t coal

967 kg 238U 946 kg 238U(21 kg burned)

33 kg 235U 10 kg 235U

9 kg Pu

1500 kg metal oxides and reactorcladding so waste ~66% U

Natural ores 0.1 to 15% U

U 235/238 ratio is 10/946= 0.01Natural ratio 235/238 = 0.0071Including Pu, reactor waste 2.8 x richer

Breeder(fastneutron)

reactorsincreaseconversion

34 kg fission prods

2 kg transuranics

Know exact locationno exploration cost

Contain as much 235U as ore


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By current law*, US plantscannot recycle and must

place 1st-cycle U-wastesafely in repositories for

10 yrs

, years

1

talRadiation

~3% initial* This may have changed now, but weare not reprocessing in the US.

10,0

00

Craig et al. (2001, fig 4.30)

T

Waste to be stored each year1. Mass loss in fission of 235U ~0.2 g/mole

E/kg-235U = mc2/ 235 = {(0.2 g/ 235 g)(1 kg)} (3x108m/s)2

= 76.5 x 1012 J/kg-235U

2. Nuclear ower lant 1000 MW = 3.15 x 1016 J / r

J of electricity

(3.15 x 1016 Je/yr )/ {(76.5 x 10

12)(0.3*)(0.75**)}

= 1.8 t 235U/yr = 52# tenr-U = 257## t U/yr

3. 3.5 m x 0.8 cm ID pin+ contains 3.34 kgenr-Ureactor consumes ~15,600 pins =313++ assemblies = 78 canisters/yr

4. Rod life 3 yrs waste canister=52 tenr-U/ 3.34x10

-3 tenr-U per pin

reactor conta ns ~ , p ns = can sters* 30% electrical conversion efficiency** 75% of 235U in rods used# enriched to 3.5% 235U## 0.0071 kg 235U per kg U in ore+ density 19 t m-2 (e.g., 3.34 kg = r2 L, pin is 100% U )++ assembly has ~50 pins, 1 transport/moving canister has 4 assemblies

0.67 t U / canister


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Cross-checking

760 x 1012 W-hr / yr= 8.7 x 1010 W ~ 87 1 GW plants

87 1 GW plants @ 257 tU y-1= 22,400 t U/yr

22,397 t U3O8 = what US consumes per year

* 257 t U-ore/yr/1 GW power plant

www.infoimagination.org/.../global_change.html

Hypothetical High Level WasteRepository

Dispose 70,000 t U

~100,000 canisters

~78 canisters per year per 1 GW plant

~87 1000 MW plants in US today( = 6800 canisters/yr)

~waste (=100,000 can/6800 can/yr) from 100 nuclear plants

Yucca mountain baseline capacity = 70,000 t UBut performance-based capacity is likely much greater than 200,000 tThus capacity is ~50 years of current US waste production

http://neinuclearnotes.blogspot.com/2006/04/per-peterson-on-yucca-mountains.html


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Yucca Mt RepositoryYucca Mt

70,000 t U (15 years of waste)18 burial panels each 450 x 900 m in plan 200 to 500 m deepTunnels hold 0.7 m diameter 3 m long canisters 5 m apart18 panels cover area 3 x 3 km

3x3 km

http://www.ymp.gov/uploads/images/

Water flows around tunnels

Pilot tunnel

Tunnel machine breaking surface

High LevelRepository

,

18 burial panels each 450 x 900 m in plan

200 to 500 m below surface

0.7 m diameter 3 m long canisters 5 m apart

18 anels cover area 3 x 3 km

Initial heat generation, Jo = 0.014 kW m-2

( )32.0 5.05.0

tt

o

eeJ

tJ += ,where t is in ka


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Heating and fluid circulation

3 km


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Maximum hot circulation


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Is this good? Is this bad?

Look to Geology:

What has nature done?

Oklo ReactorCigar LakeOsamu Utsumi mine Brazil

Pocos de Caldas Caldera

30 km diameter

Osamu Utsumi Uranium Mine

Study to see howwaste might migrate

Uranium leaching in equatoriallocation with high rainfall


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Simplified Evolution of Pocos de Caldas Alkaline Complex

time

Mine inbrecciapipe

Failed Waste

RepositoryAnalogue

time

Mining mineralized breccia pipe

Oxidized and ation

leached protore

30 ppm 500mmigr

40+ U ppm protore


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Moles Transported

The altered band

Needed


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Calculated ~ observed chemical changein 500 m layer for 105 kg cm-1

500

a

Calculated ~ Observed(at chlorinity of 5000 to 10,000 ppm)

Al+3

SiO

0

-5002addedtobrecci

K+

-1000

-1500

Mole

s/cm

Na+30 wt% alteration

Calculated ~ observed mineralogic

change at 105 kg cm-2

ObservedCalculated

e

ineralogicchang

Wt%m


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How much can an intrusion convect?

Intusion

Cross sectional area ofintrusion = 2.12 km2

2,000 yrs


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5,000 yrs

7,500 yrs


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10,000 yrs

~ 500 kg cm-2 circulatedthou h i e at 10 ka

500 kg cm-2

fluid volume ~ 1.3 x intrusion


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Hot circulationended by~10,000 yrs

12 km diameter intrusion can circulate 10

5

kg cm-2 through 3, 500m diameter pipes

12 km diameterintrusion


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Complete failure of containment produces1/1000th alteration of natural system

0.03 Wt% (not 30 wt%)

(not 40 ppm)

1/1000th POCOS

Geology provides insight when assisted by quantitative analysis


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References

1. Cathles, L. M., and Shea, M. E., 1992, Near-field hightemperature transport: evidence for the genesis of the Osamu

Utsumi uranium mine, Pocos de Caldas alkaline complex, Brazil,Journal of Geochemical Exploration, 45, 565-603.

2. G. J. Suppes and T. S. Storvick, Sustainable nuclear power,

Elsevier, Amsterdam, Chapter 11, Recycling and waste handlingfor spent nuclear fuel, p. 283-317.

3. http://www.phyast.pitt.edu/~blc/book/chapter11.htmp

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