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Waste Management > Deck 2 > Flashcards

Deck 2 Flashcards

(90 cards)

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1
Q

What is the objective of LLW treatment?

A

volume reduction

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2
Q

What techniques are carried out for liquid waste and solid waste

A

For liquid: evaporation and/or ion exchange

For solids: Incinartion, surface decontamination, compaction

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3
Q

What are the two main technies for solidifcation of LLW and TRU?

A

Hydraulic cement (portland cement) and bitumen (asphalt)

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4
Q

What are the pros and cons of using hydraulic cement for solidification of LLW and TRU?

A

Pros: Easy handeling, simple equip., no heating (fire safety), no phase separation, small rad. damage, can include solutions to solid
Cons: low volume reduction, high leakability of alkaline metal

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5
Q

What are the pros and cons of using bitumen (asphalt) for solidification of LLW and TRU?

A

Pros: highly leach resistant, plasticity, good volume reduction

Cons: potential fire hazard, large facility, radiation damage (swelling due to H2 generation)

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6
Q

What does reracking consist of? Pros and Cons

A

fuel rods are taken out of the fuel assembly and placed in new rack closer to each other
Pros: maximum fuel rod packing density, number of spent fuel shipping cask halved, volume saving of 2:1 consolidation
Cons: Produces scrap of structured parts, that are radioactive

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7
Q

What is dry cask storage?

A

storing the fuel in a properly shielded canister that is cooled by air

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8
Q

The dose rate at the boundary of a site used to store spent fuel must not exceed ….

A

0.25 mSv/h

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9
Q

What is the objective of vitrification of REPROCESSING HLW?

A

Immobilization of waste so that it can be safely transported from reprocessing plant to waste management facility, retain radioactivity while in repository for > 1000 yr

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10
Q

What is the borosilicate glass FP loading limit to stay in a solid phase?

A

20 wt%

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11
Q

What factors reduce leach time?

A
  • If glass is fractured
  • Temperature effect (if rises accelerates dissolution)
  • flowing water around the glass log
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12
Q

What are the engineered barriers that prevent leaching?

A

chemical conditions, hydrodynamic conditions, mass transport condition

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13
Q

Name some of the waste constraints of the US DOE?

A
  • Waste form temperature < 400C
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14
Q

How does cold induction melting works?

A

uses a high frequency energy field to directly couple with a material where eddy currents produce a joule-heating effect

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15
Q

What are the advatanges of cold walls in cold induction melting?

A
  • eliminates the need for refractory,
  • forms a skull that isolates the material of construction from the high temperature molten product
  • allows for processing at much higher temp. than operational limits of the material of construction
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16
Q

What is the main difference between yellowcake by acid leaching and by carbonate leaching?

A

Th230 is at 5% in acid leaching and 0% in carbonate leaching

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17
Q

As v increases, loss of neutrons by leakage …. while fission cross section ……

A

increases, decreases

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18
Q

How are neutron slowed down?

A

by elastic collisions with light nuclei (moderators) such as H, D, Be, and C.

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19
Q

What is the limit of dose rate at the boundary of a site where SNF is stored?

A

0.25 mSv/h

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20
Q

What is hot isostatic pressing (HIP)?

A

is a manufacturing process, used to reduce the porosity of metals and increase the density of many ceramic materials.

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21
Q

How much percentage does HIP reudces waste volume?

A

mor than 50%

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22
Q

What is the softening temperature of borosilicate glass?

A

600 C

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23
Q

What is waste conditioning?

A

Is a model to determine initial mass loading in a waste package

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24
Q

What are the five main conditions for waste canister conditioning?

A

Materials, radiation, repository, storage conditioning and canister dimensions.

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25
What is WIPP and a short description
WIPP, the Waste Isolation Pilot Plant, it's the world first underground repository licences to permanetly store TRU from research and weapons
26
What are the four disposal methods for HLW?
Outer space disposal, partitiong and transmutation, seabed disposal, ice bed disposal and deep geological repository
27
What are the characteristics of outer space disposal?
Cost, risk of an aborted mission, separation of problematic isotopes may be necessary but will then generate more waste that will need to be place din the repository
28
What are the three types of rocks in deep geologic repository?
Crystalline rock, Sedimentary rock, Salt
29
What are the two main medium types?
unsaturated and saturated
30
What are the two disposal geometries?
tunnel and pit
31
In what presentation is HLW presented for deep geologic repository?
Spent Fuel and Vitrified HLW
32
Why is YMR good choice?
Low precipitation, low infiltration, low percolation flux, slow transport in drift shadows, radionuclide inmobilization in rock layers.
33
What are the three types of waste packages?
Commercial SNF Waste Package, Codisposal Waste Package, Naval Waste Package
34
What is inside the commercial SNF Waste Package?
BWR and PWR fuel
35
What is inside the codisposal waste package
HLW like hanfrod, west valley, savanah river, idaho national laboratory plutonium waste
36
What is in the naval waste package?
250+ types of fuel in naval canisters
37
What are the two main barriers in the multibarrier concept?
natural barrier and engineered barriers
38
What are the natural barriers?
those barriers surrounding geologic formations to prevent waste forms contacting a human by intrusion like excavation and by crustal movements (stratum and erosion). It also has very slow movment of groundwater which makes radionuclides difficult to dissolve in water and to move and also delays corrosion (unsaturated)
39
What are the trhee types of engineered barriers?
Waste Solid, Metal Canister and overpack, and Buffer material
40
What is the waste solid role as an engineered barrier?
to limit leaching of radionuclides to groundwater
41
What is the metal canister/overpack rol as an engineered barriers?
To prevent waste forms contacting groundwater - In oxygen-depleted env. (reducing env.), some metal canister generates hydrogen by corrosion, and keeps the environment reducing constricting mobility - By corrosion, canisters swell, and groundwater movement through EBS becomes more difficult.
42
What is the buffer material role as an engineered barrier?
- To make sure that water movement is negligible slow - To settle and mantain the position of the waste form - To retard radionuclide release from WF - To fill gaps between WF and surrounding host rock - To seal cracks in the host rock (self-sealing) - To control temp. increases in EBS caused by DH - To mantain proper pH and redox potential in pore water - To buffer the stress due to deformation of surrounding host rock as well as the accumulation of corrosion products of metal canister (stress buffering effects).
43
What is burnup?
the amount of thermal energy liberated by fission reactions
44
What is the ingestion toxicity of mill tailings dominated by?
Decay daughters of uranium isotopes such as Th-230 and Ra-226
45
When does the toxicity of mill tailings start to decrease? Why?
around 10,000 years sinec decay half life of Th-230 is 80,000 years which is the most dominant contributro to toxicity
46
How do the constraint lines change if the burnup of nuclea fuel is increased?
Only the fuel composition dependent constraints are affected: - Heat emission line will decrease since more burnup means more heat emission by FP - The mass loading of Mw of Mo will decrease also since Mo is a FP and mrore FP are present at higher burnups
47
I furanium ore deposit that has existed for 100 million years at the same location in a geolgoical formation, we observe several decay daughters of uranium isotopes, which are considered to be in secular equilibrium. By carefully measuring the composition of those decay daughters currently observed, we can tell if there was throium included at one time in the past. True or False Why?
False, all U isotopes have a thorium isotope in their decay chain. Also half life of U is in the order of 10^7 to 10^9 which means some thorium must still be present.
48
True or False and why?For a radionuclide with low solubitliy in groundwater, the release rate from failed packages in a geological repository si determined primarly by the dissolution rate of the waste matrix.
False, low solubility nuclides precipitate outside of the waste package. Congruently released (high solubility) nuclides hav ea release rate determined by waste form disolution.
49
True or False and why? With stron sorption with the host rock, radionuclides are retained in the host rock, which is considered to be unfavorable to performance of a gelogical repository.
False, this is favorable as it is a part of the geolgical barrier
50
True or false why? Because TRU wastes contain low TRU elements at low concentrations, they can be disposed of in a shallow-land repository with LLW?
False, defense TRU waste go to WIPP and have toxicities that do not enalbe them to be on LLW classification (GTCC).
51
True or False? Why? By intense research and development, complete recover( 100% efficiency) of plutonium from SNF by reprocessing can be achieved.
False, There is no such thing as 100% recovery for any chemical separation.
52
How is C14 generated in a PWR?
From 14-N(n,1-H)14-C
53
Why is C14 a concern in the waste management?
Because of its relativeley long half life (5000 years) and the fact that it stays in the env. for long time and substitutes regular carbon in living organism.
54
Why does Li exist in a PWR?
neutron capture in boron and also dissolved in the coolant as LiOH to prevent corrosion
55
How can nautral uranium requirepement per unit amount of electricity generation be reduced for a PWR with the once-through system? No recycling is assumed. Answer as many different methods as you can and exlain why these can reduce NU requirement?
Increase thermal efficiency - generates same energy with less fuel - Decrease the U235 content in depleted uranium, better separation capabilities - Increase the burnup of the fuel, utilize more fissile material in the same amount of fuel produce more Energy with less fuel
56
Describe the differential equation for population of U-235?
dN/dt = -(absorption x-section)*(N-235)*(Flux)
57
What is the formula for the population of certain fission product (i)? What is being neglected?
Ni(t)=Y(235)N(f235) + Y(239)N(f239) | Assumptions are: constant flux, absorption in FP neglected, for t>tR no fission reactions.
58
What is the differential formula for tritium population?
dN/dt = Ni*(x-section i)*(flux) - L_T*N_T where i is the nuclide responsible for production of Tirtium which could be Boron Lithium, etc.
59
What is the maximum source of Tritium? How much is produced in the coolant for a 1000MWe plant?
10-B(n,8-Be)3-H, with a production of 360 Ci/yr
60
How is N-14 present in a reactor? Why is this a concern?
It is present due to impurities in fuel and is also added to the coolant. It is a concern due to C-14 production by an (n,1-H) reaction.
61
How much N-14 is added to coolant approximatly ?
1 ppm
62
Approximatly how much N-14 is in fuel as an impurity?
25 ppm
63
What are the two main isotopes that leak from fuel to coolant?
85-Kr and I(131 and 133)
64
What is the formula for the total decay heat power P(t,T)? How is this formula modified if we only considered fission by U-235 and U-238?
P(t,T)=Pf * F(t,T)/Q where Q is the thermal energy per fission. We include a correction factor of 1.02
65
What is the degradation tempearture for Bentonite buffer?
100 C
66
What is the toxicity index?
the volume of air or water that mixture must be diluted so that breathing air or drinking water will result in accumulation of radiation dose at a rate no greater than 0.05 rem/year
67
What is MPC?
The maximum permissible concentration of radionuclides is the radioactivity concentration limit of a given radionuclide in air or water so that an individual will recieve a dose rate of 0.05 rem/yr
68
Where is the sweden SFR LLW repository located?
60 m below the seabed in the baltic sea
69
What type of rock is the WIPP facility placed on? How deep?
Salt at around 2000 feet.
70
What are the three types of rock types?
Cyrstalline rock, sedimentary rock, and salt
71
What type of rock is the canadian repository situated? Saturated or unsaturated? Buffer?
Crystalline, saturated, bentonite buffer
72
What type of disposal and rock is the SWISS HLW repository situated? Saturated or unsaturated? Buffer?
Tunnel type disposal, crystalline or sedimentary, saturated, bentonite
73
Is granite crystalline, sedimentary or salt?
crystalline
74
Is Clay sedimentary, crystalline or salt?
sedimentary
75
What is t1, t2 and t3 in terms of performance assessment?
``` t1 = water enters containers (75,000 yrs) t2 = container overflows (radionuclide release) t3 = all of the elements have been disolved ```
76
What formula relates t2 and t1 in terms of perfromance assesmsent?
t2-t1=V/Q where V is the void volume in a package, Q the volumetric water flow rate
77
What is congruent release of radionuclides?
Assuming that the fractional release rate of the nuclide is the same as that for the waste matrix
78
What happens to congruency if radionuclide is solubility limited?
Then congruency dissapears, water will be saturated with radionuclide and the excess will precipitate.
79
What formula gives Q, the volumentric water flow rate?
Q = e*v*a where e is the porosity of the surrounding rock, v is the pore velocity of groudnwater in the surrounding rock, and a is the cross section of the holes on a package
80
What are the three main assumptions in the far field analysis?
- No travel time considered in the unsaturated region - neglect radionuclide transport perpedicular to water flow direction - radionuclides are sorbed by the solid phase of the medium.
81
What is the sorption equilibrium?
S = K*d*N where S is the concentration of radionuclide in the rock-solid phase compartment 1, N is the concentration of radionuclide in the water phase in the pores in compartment 1, Kd is the soprtion distribution coefficient
82
What are the four main YMR regulators?
EPA, NRC, DOE and DOT
83
What is the YMR capacity?
70,000 MT
84
What is performance assessment?
method for evaluation system, subsystem or component performance
85
what is total system performance assessment?
a system-level PA, subsystems and components are linked into a single analysis
86
What are the four main radionuclide that contribute to the ttotal mean dose at 10,000 yrs in YMR?
Tc-99, C-14, Pu-239 and I-129
87
What is the total estimated peak mean annual dose for 10,000 yrs of the YMR analysis?
0.24 mrem/yr
88
What are the major contributors to dose at 1 million years
99Tc, 129I, 239Pu, 242Pu, 226Ra, and 237Np
89
What is the total estimated peak mean annual dose for 1 million yrs of the YMR analysis?
0.96 mrem/yr
90
Does partitioning and transmutation improves repository performance? Why?
No, it has been demonstrated that repository performance is insensitive. Low solubility of actinides prevents them from being a problem in the first place, if recovered uranium is sent to repository then much of the benefits of P&T will be reduced, repository p erformance is already good enough

Waste Management (3 decks)

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