Chapter 1 Flashcards
1
Q
Describe broadly the once-through fuel cycles with heavy water reactor?
A
Natural Uranium Concentrates (U3O8) -> Uranium Conversion -> HWR -> Spent Fuel
2
Q
What is the yield of uranium conversion in the HWR fuel cycle?
A
99.5%
3
Q
What is the enrichment of U-235 in HWR fuel?
A
0.711%
4
Q
How many MT of U is fed to a 1 GWe HWR?
A
143 MTU
5
Q
What is the U-235 fraction in HWR spent fuel?
A
0.3% U235
6
Q
Why can HWR work with natural uranium rather than enriched uranium?
A
Because it works with heavy water which has a lower cross-section than natural water.
7
Q
What is the heat generation of 1 GWe HWR?
A
6800 MWd/MTU
8
Q
What is the potential heat generation of 1 MTU? 1 gram?
A
950,000 MWd | 0.95 MWd
9
Q
What is the uranium utilization of a HWR?
A
6800/950,000 = 0.7%
10
Q
What is the typical capacity factor for a Nuclear Power Plant?
A
0.8
11
Q
What is a normal range for thermal efficiency of NPP?
A
0.3-0.4
12
Q
What is the NU consumption in MT/year for a 1GWe HWR?
A
144
13
Q
What is the NU consumption in MT/year for a 1GWe PWR?
A
201
14
Q
What is the uranium utilization of a PWR
A
0.47
15
Q
Name the first 5 steps in the nuclear front-end fuel cycle?
A
Uranium Ore -> Uranium Ore -> Uranium Mill -> Uranium Concentrates -> Uranium Purification and Conversion Plant
16
Q
What are the three minerals containing uranium?
A
- Zeunerite associated with lavendulan
- Uraninite
- Pitchblende, quarry-faced uranium ore
17
Q
What is the uranium concentration of high grade uranium ore?
A
200,000 ppm
18
Q
What is the uranium concentration of average-grade uranium ore?
A
1,000 ppm
19
Q
What is the uranium concentration of granite?
A
4 ppm
20
Q
What is the uranium concentration of aqueous rock?
A
2 ppm
21
Q
What is the uranium concentration of the earths crust?
A
2.8 ppm
22
Q
What is the uranium concentration of seawater?
A
0.003 ppm
23
Q
What are the three types of uranium mining?
A
Open-cast mining, underground mining, and in-situ leach (ISL) mining
24
Q
What is the purpose of uranium mills?
A
- separate uranium from non-uraniferous diluents that accompany uranium in nature.
- increase uranium oxide content from few tenths of a percent to 85-95%
25
What are the two types of leaching in uranium mills?
acid and carbonate leaching
26
What are the five steps in carbonate leaching?
```
1 - Crushing and Grinding
2 - Leaching
3 - Filtration
4 - Precipitation
5 - Purification
```
27
What are the radioactive effluents from uranium mills?
- Airborne (mainly Rn-222 gas and radioactive dust particles)
- Liquid (water-soluble radionuclides)
- Yellowcake: contains decays daughters of U isotopes as impurities
- Mill tailings
28
What happens to liquid effluents of uranium mills?
Held in a storage pond with mill tailings and eventually evaporated to a solid
29
How much wt% uranium normally in uranium ore?
0.2 wt%
30
How many tons of NU is required for 1 GWyear
200 tons of NU
31
Approximate how many tons of mill tailings are generated per ton of uranium ore?
1 ton of tailings per ton of ore
32
What is uranium refining/uranium purification? What step is it in the nuclear fuel cycle?
Removing the rest of non-uraniferous contaminants and producing pure uranium compounds. 5
33
What method is used for uranium purification?
Solvent extraction
34
What is the feed and product of uranium mills?
Uranium Ore U3O8 and produces enriched U3O8 yellowcake
35
What is the composition of yellowcake?
85% U3O8
7. 5% Na2O
0. 2-0.8% V2O5
36
Describe the purification process in uranium refining?
Uranium concentrates from uranium mills are dissolved in nitric acid (HNO3) and forms UNH. Solvent extraction is performed using TBP. Uranium transfers from A to O and impurities from O to A. Purified U in O is then transferred to A. Portion of A is washed to remove remaining TBP with hexane resulting in purified UNH.
37
What is the concentration of uranium in purified UNH?
115 gU/L
38
What is the purpose of uranium conversion?
changing the chemical form of uranium from UNH to that finally wanted of UF6
39
Name the four steps in uranium conversion and what chemicals are used and what is the product of each step?
Reduction (UNH + H2 -> UO2), Hydro-fluorination (UO2 + HF -> UF4), Fluorination (UF4 + F2 -> UF6), Fractional Distillation (Pure UF6)
40
What is the yield of uranium conversion?
99.5%
41
What are two main radioisotopes in waste from uranium refining?
Th-230 and Ra-226
42
Uranium in aqueous raffinate in solvent extraction has what composition?
Sames as NU
43
What are other wastes from uranium purification and conversion excluding uranium and radioactive effluents?
filters, sludges, paper, and polyethylene.
44
What is the product of uranium conversion/
UF6
45
What is the next step after uranium purification and conversion?
Uranium Enrichment
46
What are the two main methods for uranium enrichment?
Gaseous Diffusion and Gas Centrifuge
47
What type of wastes are produced during uranium enrichment?
filter, paper, gloves, laundry waste water
48
What is the yield of uranium enrichment
99.5%
49
How does gaseous diffusion work?
High pressure feed of UF6 into container where lighter isotopes diffuse faster through the barriers/filters producing an enriched and depleted stream.
50
How does gas centrifuges work?
UF6 gas placed in cylinder and rotated at high speeds Rotation creates centrifugal force so that heavier gas molecules (UF6 containing U238 atoms) moves towards the outside of the cylinder
51
Described uranium fuel fabrication from uranium converison?
Hydrolize UF6 to UO2F2 by solution in water, filtration, drying. (2) Ammonia added to precipitate ammonium diuranate (ADU). (3) Reduction by hydrogen at 820C to UO2 powder. (4) Fabrication of assemblies by pressing, sintering, assembling.
52
How many drums of waste generated per MT of U?
3 Drums (200 Liters)
53
What waste is generated in uranium fuel fabrication?
solids including paper, cloth, wood, polyethylene, ashes, sludges, metal, glass, filters
54
What is the average energy release per fission?
196-205 MeV
55
Approximatly how many MeV are lost in gamma rays? Why?
5 MeV, it escapes from a typical reactor
56
What are the three main fissile isotopes? Where do they come from?
U-235 (natural), Pu-239 (capture of U-238), and U-233 (capture of Th-232).
57
What happens to cross section if velocity of neutrons increases?
The loss of neutrons by leakage increases while cross section decreases.
58
What is necessary to do in terms of neutron velocity if fissile concentration is low?
We need to decrease neutron speed to increase cross section and mantain neutron chain reaction.
59
How are neutrons slow down in reactor?
By the use of a moderator by elastically colliding with light nuclei (moderators) such as H, D, Be, and C.
60
How are neutrons slow down in reactor?
By the use of a moderator by elastically colliding with light nuclei (moderators) such as H, D, Be, and C.
61
Name 7 of the most important FP radionuclides?
H3, Kr, Sr, Mo, Tc, I, Cs
62
What is the half life of Cs137 and Sr90? Why are they important?
30 years, they are the major radioactive source for the first thousand years
63
What is the half life of tc99? Is it soluble or not in reducing environment?
2.1E5 years, very low solubility in reducing environment
64
What are two important iodine gaseous FP and their half-life? How is it released? How much activity per year of operation at what power?
- I-131 (8.05 days) and I-129(1.7E7 years)
- Release from cladding to coolant
- 1 Ci/yr of 1 GWe operation
65
What are two important gaseous FP of Kr and Xe? What are there half-life?
Kr-85 (10.76 yr)
| Xe-133 (5.27 days)
66
What is an actinide?
any of the series of elements with increasing atomic numbers that begin with actinium (A=89) or thorium and ends with lawrencium
67
What are five important actinides?
Np-237, Pu-238, Pu-241, Am-241, Cm-242
68
What is the half-life of Np-237?
2.14E6 year
69
half life of Pu-238?
86 years
70
half life of Pu-241
13.2 years
71
Half life of Am-241
458 year
72
half life of Cm242
163 days
73
What are the five tritium production reactions in a reactor?
- 10B(n,alpha)7Li
- 7Li(n,5He)3H
- 7Li(n,n+alpha)3H
- 6Li(n,He-4)3H
- 10B(n,8Be)3H
- H2(n,)3H
74
Where is boron in PWR and BWR?
Solid control absorber (BWR)
| Dissolved in coolant water (PWR)
75
Where is Lithium in LWR?
```
Formed by (n,alpha) reactions in boron (10B(n,alpha)7Li)
LiOH is added to coolant for corrosion control in PWR
```
76
What is breeding and what is necessary?
When the number of neutrons produced per neutron absorbe in fissile material is more than 2 then one neutron is use for chain reaction and the other for production of fissile material from fertile material.
77
What is the isotope that allows breeding in thermal reactors?
U233
78
How is Pu-239 produced in a reactor?
n+U238 -> Np239 + e- -> Pu239 + e-
79
How is U233 produced in a reactor?
n+Th232 -> Th233 -> Pa233 + e- -> U233 + e-
80
Is breeding possible in thermal reactors with U233? Pu239? Why?
Not possible with Pu239 but yes for U233 because the number of neutrons produced per neutron absorb is greater than 2.0
81
Why dont we use water as coolant ina fast reactor?
It is too effective at moderating neutrons
82
What are the two most commonc oolants for fast reactors/
liquid sodium and helium gas
83
What isotope of boron is most responsible for mdoeration and what its is natural abundance?
B-10 with a 20% natural abundance
84
What isotope of lithium is wanted in MSR? Why?
Li-7 because Li-6 is to absorbant and therefore makes breeding imposible.
85
How much heat is generated per gram of U235
0.95MWd
86
What is the resource utilization for HWR?
0.71%
87
Why is it attractive to reprocess spent fuel?
(1) recover U to be recycled (2) recover plutonium (3) reduce radioactive wastes to more compact form.
88
What are the first 6 steps in the fuel-cycle operations for LWRs?
- Uranium Mine,
- U Mill,
- U Purification and Conversion Plant,
- Enrichment,
- Fuel Element Factor
89
What is the extracted product in Uranium Mine?
Uranium Ore
90
What product comes from uranium mills? What are the proccesses?
Uranium Ore concentrates (yellow cake).
- leaching,
- precipitation,
- solvent extraction,
- ion exchange
91
Why are uranium ore concentrates (yellow cake) yellow?
Sodium DiUranate or Ammonium DiUranate is bright yellow solid
92
What happens at the uranium purifcation and conversion plant?
The chemical impurities are removed and the purified uranium is converted into uranium hexafluoride (UF6)
93
What process takes plcae at the gaseous diffusion plant?
Uranium enrichment using gaesous diffusion stages connected in series.
94
How does the gaseous diffusion plant work?
Each stage contains many porous tubes made of membranes with very fine holes (diffusion barriers). UF6 flows at high pressures along inner wall. Outer wall at low pressure causes lighter U235 to cross the wall and therefore enrichment happens.
95
One gaseous diffision stage increases the ration of U235 to U238 by ??
1.0043
96
What process takes place at the fuel fabrication plant?
UF6 converted to UO2, pressed into pelletes, sintered and loaded into zircaloy tubing (which is filled with helium).
97
What is the typical fuel lifetime?
3 years
98
What happens to the fuel after irradiation?
It is placed at the cooling pool for 150 days and then sent to the fuel reprocessing plant.
99
Describe the fuel reprocessing plant process
fuel cladding removed chemically or mechanically, the fuel material is dissolved in acid and fissile and fertile materials are separated from FP and from each other.
100
What are the resulting products of fuel reprocessing and their form?
Plutonium (concetrated aqueous solution of plutonium nitrate) and UF6
101
wHAT IS A DIFFICULTY WHEN REPROCESSING FUEL?
The chemical similarity between uranium and plutonium
102
What is the most common process for fuel reprocessing? What does it consists on?
PUREX: Solvent Extraction by using TBP and nitric acid. (Refer to book)
103
How do you separate Pu(NO3)4 + UO2(NO3)2?
Use strong enough reducing agent to reduce Pu to tetravalent form but not U (from hexavalent). Tetravalent is more soluble in water and therefore Pu transfers to aqueous phase while U stays in TBP solvent phase.
104
Name the three important U and Pu isotopes in irradiated uranium?0
235, 236, and 238 for U,
| 239, 240, and 241 for Pu
105
Name some important neutron absorbing fission products.
Xe131, 133, 135
Tc99, Gd155, Rh103,
Nd143, Nd145
etc.
106
Name the two most imoprtant Iodine isotopes (long-lived)?
I-129 and I-131
107
What are the three common methods for light element isotope separation
distillation, electrolysis and chemical exchange
108
What are the six principal ways for radioactive nuclides to break down spontaneously?
Alpha decay, beta decay, gamma emission, poistron emission, electron capture, and spontaneous fission.
109
What happens in beta decay?
a neutron is converted into a proton and energy is release in the form of an electron?
110
What happensin electron capture?
a proton is converted into a neutron and a positive charge electron is released
111
What does the decay constant represent?
The probability that a single nuclei will decay in that time. The rate of radioactive decay in 1/s.
112
What is the energy per alpha particle?
4 to 5 MeV
113
What is the energy range for beta particle in decay?
0-1.5 MeV
114
What is the usual average energy for a beta particle?
1/3 its maximum
115
Are alpha particles a hazard to the body? Why? What about beta particles?
If in the outside, no. Alpha particles get stopped by the skin but if ingested it is toxic. Beta particles causes burning if exposed on the outside.
116
What are gamma rays?
photon electromagnetic radiation
117
What is gamma decay?
When a nuclide transitions from a state of higher energy to one with a lower energy.
118
What is the typical wavelength of a gamma ray?
10^-9 which means they are hard, high frequency, x rays.
119
How hazardous are gamma rays?
Very since they can penetrate large distances therefore being the most serious external hazard of all threee. In humans this can cause deep-seated organizers damage.
120
What happens to the positron in positron decay?
undergo strong electrostatic attraction to atomic electrons. positron + electron -> 2 gamma rays with 0.511 MeV each.
121
What is electron capture?
The nuclei captures one of its own electrons from the K or L shell which results in a proton to neutron transformation + neutrino + x-ray (from filling vacancy from outer electrons).
122
What is the competing mechanism for electron capture? Why?
Positron emission because the net change in radionuclide species is from atomic number Z to Z-1
123
What happens when energetic neutrons passes through animal tissue?
protons recoiling from neutron collision causes ionization within the tissue and can result in biological damage.
124
What is a popular isotope that undergoes spontaneous fission?
Cf-252
125
Name examples of positron emitters?
C-11, N-13, O-16, F-18, Cu-64
126
Name examples of spontaneous fission nuclides?
U-235, U-238, Pu-239, Cm-244, Cf-252
127
Name some long lived gamma emitting radioactive nuclides?
Co60m, Br80m, Y91m, Tc99m, Xe135m
128
What are the 4 available long lived nuclides that can undergo fission with thermal neutrons?
U-233, U-235, Pu-239, and Pu-241
129
What is the cross section fundamentally?
fraction of the reacting nuclei consumed by the nuclear reaction per unit time per unit flux.
130
What is the absorption cross section?
the sum of the cross sections for all reactions in which a neutorn is absorbed
131
How much energy do neutrons on average have after fission?
2 MeV
132
What is the thermal cross section for U235
582 barns
133
What is the thermal cross section for Li6
940 barns
134
Does neutron leakage increase with neutron spead or decrease/
Increase
135
How does the fission cross section vary with velocity? How does this affect fast reactors?
neutron velocity increase causes fission cross section to decrease. Fast reactors work by having high concentration of fissionable material (high enriched u235 or Pu239)
136
What is the neutron flux physically?
total distance traveled in unit time by all the neurons present in unit volume
137
What are typical values of flux in a reactor?
10^{11} to 10^14 n/cm2*s
138
What is the maxwell boltzmann distribution
Gives the distribution of gas molecules in thermal equilibrium which is representative of the distribution of neutrons in thermal equilibrium with nuclei at an absolute temperature T
139
How is energy distributed in fission?
```
Fission Fragments 167MeV
Neutrons 5 MeV
Gamma Rays 7 MeV
Neutrinos 12 MeV
Other
Total Recoverable ~200 MeV
```
140
How many curies of tritium are produce per year in a 1GWe PWR?
1.9Ci
141
What is the half-life of tritium?
12.3 years
142
What is the half life of c-14?
5730 years
143
How is carbon 14 produced in a reactor
N-14+n -> C-14 + H
| O-17+n -> C-14 + He
144
Where does N-14 and O17 come from in a reactor?
Residual nitrogen from impurity in fuel and also dissolved in coolant water. Oxygen comes from natural abundance in light water.
145
What are two important iodine isotopes and the krypton isotope in fission product leaking from fuel to coolant?
I-131, I-133 and Kr-85
146
What does CRUD stand for and what is it?
Chalk River Unidentified Deposit. It is corrosion of coolant piping, which releases small particles and circulates through coolant. This particles are activated and deposited on cladding surfaces, steam generator and so on. It contains Co-60, Ni-63, Co-58, Cr-51, Mn-54, Fe-59
147
What is decomissioning?
all of the activities that take place at the end of a plant's life to ensure the ist does not pose any hazard to public and can be considered property suitable for unrestricted use (10 CFR 50)
148
What is decomissioning waste?
contamination carried by water coolant circulating through the core
- activation products produced by neutron absorption
149
What are the three of the most important radionuclides in decomissioning wates (include half lifves and emissions)?
Co-60 (5.2yr, gamma and beta rays), Ni-59 (80,000 yr, xrays), Nb-94 (20,000 yr, gamma and beta)
150
What are the three decomissining methods?
DECON, SAFSTOR, ENTOMB
151
Summarize DECON method?
all radioactive material removed soon after final shutdown. site release for unrestritcted use.
152
Describe SAFSTOR method?
liquid and portable solid radioactive removed, remaining structure and equipment secured and controlled. Evenutall dismantling.
153
Describe the ENTOMB method?
Same as SAFSTOR except facility sealed completly by covering with concrete creating a single monolithic structure. Monitored until site able to release for unrestricted use.
154
What are the three low level radioacive materials managemen levels?
Exemption, Clearance and Exclusion (NORM)
155
What does the "Excemption" safety regulation dictate? What is the range of radioactivites considered here?
Exemption refers to materials that contain so little radioactie material that it cannot be considered "radioactive" and might be exempted from regulatory control. 0.1 to 10^4 Bq/g
156
What does an "Exemption" procedure specifies in terms of individual dose and collective dose?
Individual does must not exceed 10 microSv/year.
| Collective dose must not exceed 1 man Sv
157
What does the "Clearance" procedure dictates?
Removal of radioactive materials/objects within authorized practices from any regulatory control. Sources that are under regulatory control but should not continue to be.
158
What does the "Clearence" procedure dictates in terms of invididual dose and collective dose?
Individual dose must not exceed 10 microSv/year
| Collective dose msut be less than 1 man Sv/a
159
What does the "Exclusion" procedure dictates?
determines what waste shall and what shall not be subject to radiation safety
160
What are the 4 objectives of spent fuel reprocessing?
- To recover U and Pu
- Remove FP from SNF
- Convert radioactive constituents of SNF into forms suitable for safe, long-term storage
- Recover useful FP such as 90Sr and 137Cs and TRU elements such as Np, Am, and Cm.
161
What are the 5 main steps in SNF reprocessing?
- Decladding,
- Dissolution
- Conditioning
- Co-decontamination
- Pu/U separation
162
What does decladding consist on?
Chemical and Mechanical separation by traverse chopping of Zr-clad UO2. Send to dissolver.
163
What are some major gases in decladding evolution?
Xe, Kr, Iodine and Tritium, C-14
164
What does dissolution in SNF reprocessing consist on? (4 Objectives)
- Bring U/Pu into aqueous solution
- Complete separation of fuel from cladding
- Determine the amoutns of U/Pu dischared to reprocessing.
- To convert U/PU and FP into the chemical states most favorable for their subsequent separation.
165
Is nitric acid an oxidizing or reducing agent?
oxidizing.
166
Do we want to reduce Uranium or Plutonium?
Plutonium.
167
What agent is used to reduce Plutonium ?
N2O4
168
What are the two main iodine isotopes of concern in off-gas treatment in fuel reprocessing? Half lifes? Why must it be removed as much as possible?
I-129 (1.7E7yr)
I-131 (8.05day)
Iodine reacts with solven to form hard-to-remove compounds.
169
What does codecontamination in fuel reprocessing do? How?
separation of U and Pu from FP and TRU by adjusting HNO3 concentration to give the larges ratio of D(pu)/D(Ru) or D(Pu)/D(Zr) (distribution coefficient)
170
What is D?
Distribution Coefficient = Organic/Aqueous
171
What is Beta in terms of solvent extraction?
Extraction Factor
172
How do you separate Pu and U in solvent extraction?
Organic Extract from Co-decontamination contains both UO2-TBP + Pu-TBP. Addition of aqueous HNO3 2.9M solution with reductant Fe^2+ LEADS to reduction of Pu which is much slower for U. U remains in organic phase.
173
After U/Pu separation, how is Uranium purified? What are the restrictions?
Uranium is in the organic phase and back extracted to aqueous phase by 0.01M HNO3. Total beta and gamma must be less than twice the natural U radioactivity and alpha must be less than 1500 Bq/g-U
174
After U/Pu separation, how is Plutonium purified? What are the restrictions?
Plutonium in aqueous solution purified by two additional solvent extractions:
- 1 Extraction: TBP extracts Pu and U traces from FP and Np
- 2 Extraction: Pu is stripped from U by reducing Pu(IV) back to Pu^3+
175
What is High Level Wastes according to the NWPA?
highly radioactive material resulting from the reprocessing of spent fuel including liquid waste produced directly in reprocessing and any solid material derived from such liquid waste that contains FP in sufficient concentrations.
176
Is SNF HLW or LLW?
HLW
177
Is the liquid (raffinate of reprcessing) LLW or HLW? What about solid (spent fuel or cladding hull)?
HLW both
178
What are TRU wastes according to the NRC? What are the concentrations limits in terms of activity per gram of waste?
Wastes containing alpha-emitting isotopes with atomic number >92 with half-lives longer than 5 years and concentrations greater than 100 nCi/g-waste
179
What are TRU wastes according to the EPA/DOE?
Wastes with half-lives longer than 20 years
180
Give some example of TRU wastes?
Various forms of solid, heterogeneous generated at a reprocessing plant
181
What is LLW according to the NWPA?
Not HLW, SNF, or TRU wastes generated in all activities involving radioactive materials.
182
Give examples of LLW?
Clothing, tools, syringes, cotton swipes, paper, rags, etc.
183
What are the classes of LLW?
Class A, B, C, and GTCC
184
What are class A LLW?
The waste with least amoutn of radioactivity that becomes non-hazardous during the institutional control period after the site is closed
185
What are class b LLW?
More radioactive than class A and remain hazardous for up to 300 years.
186
What are class C llw?
most radioactive of all three types of LLW thar allowed to be stored in near-surface burial sites. it remains hazardous for more than 300 years. In some cases it may require burial at depths greater than those of class A or B.
187
Where are LLW wastes stored?
A, B, and sometimes C are buried in near-surface burial sites.
188
What are gtcc LLW?
Waste not appropiate for shallow burial that are the responsibility of the federal government. Must be buried in a deep geologic repository.
189
What is one main waste from uranium mills?
Airborn Rn and Ra
190
What is Dose?
Dose [rem] = Absorbed Dose (rad) * Quality Factor * Distribution Factor
191
How much is 1 rem in Sv
1 rem = 0.01 Sv
192
What is absrobed dose?
Absorbed Dose = Energy Absorbed by Material given in rad or Gy
193
How much is 1 rad in J/kg?
0.01 J/KG = 1 rad
194
How much is 1 Gy in J/kg?
1 Gy = 1 J/kg
195
how much is 1 rad in Gy?
0.01 Gy
196
What is the quality factor?
It is determined based on LET [eV/m]
197
What is the quality factor of a 1 MeV neutron?
10
198
What is the quality factor of the recoil nuclei?
20
199
What is the average dose from nautral radioactivity in rem/year and in Sv/year?
100 mrem/yr or 1 mSv/yr
200
What is the average dose from airline crew flying from NYC to Tokyo?
9 mSv/yr
201
What is the limit for nuclear industry emplyees and uraniuim miners?
20 mSv/yr
202
What is the lowest average dose at which an increase in cancer is clearly evident?
100 mSv/yr
203
What is the toxicity index?
is the volume of air or water with which the mixture of radionuclides must be diluted so that breathing the air or drinking the water will result in accumulation of radiation dose at a rate no greater than 0.05 rem/year
204
What is the formula for toxicity index?
Toxicity Index = summation{ lambda*N/C}
205
What is the maximum permissible concentration of radionuclides
MPC is the radioactivity concentration limit of a given radionuclide in the air or in water an individual who obtains his total intake of air or water from this source will receive a radiation dose from this radionuclide at a rate of 0.05 rem/yr.
206
What is the goal of LLW treatment/
Volume reduction
207
What is needed to do for TRU wastes>
(1) recovery of TRU elements from wastes
| (2) effective immobilization
208
How is LLW volume reduction works for liquid wastes?
Evaporation and ion exchange for volume reduction.
209
How is LLW volume reduction accomplish for solid wastes?
Incineration (Burnable solid waste, off-gas treatment, safe handling of ashes), Surface Decontamination, Compaction.
210
What are the two materials used for solidification of LLW and TRU?
Hydraulic Cement and Bitumen (asphalt)
211
What are the pros and cons of hidraulic cement?
Pros: easy handling, no heating, no phase separation, small radiation damage, can include solution to solid.
Cons: low volume reduction, high leachability for alkaline metal
212
What are the pros and cons of asphalt?
Pros: Highly leach resistant, plasticity, good volume reduction
Cons: potential fire hazard, large facility, radiation damage (swelling due to h2 gas generation).
213
What is wet storage?
storage of spent fuel in water pools by reracking (high density racks) and adding Boral (neutron absorbing composite material consisting of boron carbid evenely dispersed with an aluminium matrix).
214
What is spent fuel rod consodliation and what are its pros and cons?
Fuel rods removed from assembly and paced in a grid with spacing closer than that of intact assembly.
Pros: maximum fuel rod packing density, # of spent fuel shipping casks would be halved.
Cons: produces scrap of structured parts, that are radioactive
215
What is dry cask storage?
storing the fuel in a properly shielded canistar that is cooled by air.
216
What is the dose rate limit at boundary of a site used to store spent fuel?
0.25 mSv/h
217
What type of waste does Hnaford stores?
HLW
218
What is the objective of vitrification of reprocessing HLW? How long does it retain radioactivity?
Inmobilizes waste so that it can be safely transported from the reprocessing plant to the waste management facility. It retains radioactivity while in repository for more than 1000 years.
219
What material is used for vitrification? What is its loadling limit of fission products?
Borosilicate Glass. 20 wt% of FP
220
What is the leach rate of borosilicate glass?
1E-5 g-glass/cm2-day
221
What is the formula for leach time?
t=density*(r/j)
222
What happens if glass is fractured in terms of leach time? How does fracturing affects the leach time in terms of formula?
Leach time becomes smaller. The differential equation is a function of surface area. Example: if fracturing by a factor of 10 then leach time is reduced by a factor of 10 since there is 10 times greater surface area than the original geometrical surface area.
223
What is the effect of temperature in leach time?
Accelerates disolution if temperature rises
224
What are the three type of conditions existing in engineered barriesr?
chemical conditions, hydrodynamic conditions, mass transport conditions.
225
What is cold crucible induction melter?
Inudction melting uses high frequency energy field to directly couple with a material. Eddy currents induced in the material produce a joule-heating effect.
226
What are the benefits of cold crucible induction melting?
System can be tuned to the specific material for optimal heating. eliminates the need for refractory, isolates materials of construction from high temperature molten product, due to cold weals allows for processing at much higher temperatures than operational limits of materials of construction
227
What is the 7 factors affecting repository performance from the radionuclide composition vector from the separation process?
- Waste Composition in Canister
- # of Canisters
- Materials Conditions
- Canister Dimensions
- Radiation Conditions
- Repository Conditions
- Storage Conditions
228
What type of waste is in Sweden-SFR? What city?
LLW in Stockholm
229
The LLW repository in Sweden-SFR is located at the seabed? What sea?
No, it is 60 meters below the Baltic Sea
230
What type of waste is stored in Finland repository? How deep is it? What other charactersitis?
LLW, two rock silos each 20 m in diameter located 30 to 60 meters in depth.
231
What are some charactersitics of the LLW repoisotry pit in Japan?
Pit is lined with porous concrete which allows any water to seep away before reaching the drums.
232
What will happen in the first 15 years in the LLW repository pit in Japan?
Any water entering the pit is drained, radiological monitoring is conducted, if radioactivity measured pit to be repaired.
233
What will happen 15 to 45 years in the LLW repository pit in Japan?
Water entering the pit its stilled monitored. remedial action is taken in the cover soil or elsewhere if necessary.
234
What will happen 45 to 345 years in the LLW repository pit in Japan?
people can enter the area but excavation is restricted, utilization of stream water is prohibited.
235
How is waste categorized in the LLW repository in Belgium?
A = Low Level
B = TRU (mainlly from U/Pu fuel fabrication and reprocessing)
C = High Level
B and C will be dispoes of into a deep geologic repository.
236
What type of fuel is in the Spain repository?
LLW, ILW, and some HLW
237
Where are the only three LLW repositories in the USA?
Barnwell, South Carolina
Beatty, Nevada
Richland, Washington
238
What type of waste does WIPP facility stores?
TRU radioactive waste left from the research and production of nuclear weapons.
239
Where is the WIPP facility located?
Carlsbad, New Mexico
240
What type of rock is the WIPP facility located at?
Bedded Salt Rock
241
How deep is the disposal rooms of the WIPP facility?
650 meters
242
What are the 4 disposal methods considered for HLW?
- Outer Space Disposal
- Partitioning and Transmuation
- Seabed Disposal
- Ice Bed Disposal
243
What is are the cons of outer space disposal of HLW?
- Cost
- Risk of aborted mission
- Separation of problematic radionuclids will genearte secondary waste that will have larger volume raising the question if a repository is a better option
244
What are the three rock types?
Crystalline Rock
Sedimentary Rock
Salt
245
Where is salt rock located?
Only in the US and a part of Germany
246
Where is sedimentary rock located?
Belgium, France, Switzerland, Japan
247
Where is crystalline rock located?
US, Sweden, Finland, Canada, Switzerland, Japan, China
248
What are the two medium types and where can they be found?
Unsaturated (US, China), and Saturated (all others)
249
What are the two types of disposal types? Where are they lcoated?
- Tunnel (US, Belgium, Switzerland, Japan)
| - Pit (Sweden, Finland, Canada, Japan)
250
Is there vitirfied HLW in the US? Any more places?
No according to the slides. Japan , France, Switzerland, Belgium, Germany
251
Where is HLW Spent Fuel dispose directly?
US, Finland, Sweden, Canada, Germany
252
What type of disposal location is used in the Canadian Repository concept? What type of Rock? Is it saturated or unsaturated? What type of waste? Is overpack used? If so what type? Is buffer used and if so what?
- Pit Type
- Crystalline (granite)
- Water Saturated
- CANDU Spent Fuel
- Copper or Titanium alloy container with glass beads packed around used fuel bundles.
- Bentonite Buffer
253
Wat type of disposal location is used in the Swiss HLW repository concept? What type of rock? is it saturated or unsaturated? What type of waste? Is overpack used? If so what type? Is buffer used? If so What type?
- Tunnel Type
- Crystalline (granite) or clay (sedimentary)
- Water Saturated
- Vitrified waste, spent fuel
- Carbon Steel Overpack
- Bentonite Buffer
254
What type of rock is in the german repository concept? What type of waste?
- Rock Salt
| - Vitrified Waste + LWR spent fuel
255
Is Yucca Mountain repository concept an unsaturated or saturated project? if so what percent?
Saturated (65%)
256
What is the proositoy of the rock in yucca mountain?
0.10
257
Where is yucca mountain located?
Nevada near the nevada test site.
258
How many MTHM are to be stored in Yucca mountain (name their source)?
- 63000 MTHM for Commercial SNF
| - 7000 MTHM from defense waste (4500 HLW and 2500 SNF)
259
What are the five main reasons to put a repository in Yucca Mountain?
- Low Precipitation
- Low Infiltration
- Low Percolation Flux
- Slow Transport in Drift Shadows
- Radionuclide Immobilization in Rock Layers
260
What are the three type of waste packages for yucca mountain?
- CSNF Waste Package
- Co-disposal Waste Package
- Naval Waste Package
261
What type of fuel is in the CSNF Waste package?
BWR and PWR fuel including some mixed oxide fuel from excess weapons from plutonium disposition waste
262
What are the three aspects of a site selection for repository?
- geology
- transportation of wastes from various parts of the country
- national concesus, and local public agreement
263
What are the six aspects of construction, operation, and closure of repository facility?
- Site selection
- Licence application
- Construction
- Transport and Emplacement of HLW (or other)
- Monitoring
- Closure of Tunnels and Shafts
264
What are the two barriers in multibarrier concept?
Natural Barriers
| Engineered Barriers
265
What are the goals of natural barriers in the multibarrier concept?
- Prevents waste form from contacting a man by human intrussion and by crucial movements
- Slow movement of groundwater to make radionuclides difficult to dissolve in water and to move,
- delay corrosion of metal canisters
266
What are the engineered barriers?
- Waste Solid
- Metal Canister, Overpack
- Buffer Material
267
What is the goal of waste solid as an engineered barrier?
To limit leaching of radionuclides to groundwater
268
What is the goal of metal canisters, overpack as an engineered barrier?
- Prevent waste forms from contacting groundwater
- To keep a reducing environment (generation of hydrogen by corrosion keesp environment reducing = oxygen depleted) which makes the canister swells making groundwater movement through EBS becomes more difficult).
269
What is the goal of buffer material as an engineered barrier?
- make sure groundwater movement is neglibily slow
- settle and position waste form
- retard radionuclides release from waste form
- fill gaps between waste form and surrounding host rock
- seal cracks in the host rock
- Control temeprature increase in EBS caused by decay heat
- mantain proper pH and redox potential in pore water
- To buffer the stress due to the deformation of surrounding host rock as the accumulation of corrosion products of metal canisters
270
What are the four sections of the biosphere pathway?
- Water Usage
- Environment Transport Pathways
- Environmental Media Concentrations
- Exposure Pathway
271
What are the four agencies that play a role in Yucca Mountain regulations? What are there roles?
- Environmental Protection Agency (EPA): establishes environmental standards
- Nuclear Regulatory Commission (NRC): issues and enforces regulation meant to protect public and workers health, licencing procedures, and issues dessicions regarding construction and operation
- Department of Energy (DOE): characterizes site, develops repository design, and builds and operates repository
- Department of Transportation (DOT): regulates transportation of waste, enforces requirements on routing and vehicle
272
What are the 4 statues and regulations that apply to the YMR project?
- Nuclear Waste Policy Act of 1982
- Nuclear Waste Policy Amendments Act of 1987
- Energy Policy Act of 1992
- 10 CFR Part 63
273
What did the Nuclear Waste Policy Amendments stated?
- It focused the NWPA to the YMR project
- limits disposal amount to 70,000 MT
- Site characterization for YMR project
274
What did the the Energy Policy Act of 1992 states?
- Directed EPA to develop safety standards following NAS recommendations
- requires continuous monitoring of repository even after closure.
- set standards specific for YMR
275
What are the two type of studies to study safety of repository?
- performance assessment (PA)
| - Total System PA (TSPA)
276
What does performance assesment consist on?
method for evaluating a system, subsystem, or component performance
277
What does TSPA consist on?
system-level PA, subsystems and compoments are linked into a single analysis.
278
What are the 5 steps in the safety PA procedure?
- Develop/screen scenarios
- Develop Models
- Define Values/Uncertainties
- Perform Calculations
- Interpret Results
279
What are the two type of models develo in a PA procedure? Explain each one.
- Detailed Models: contains as much complexity as needed. high fidelity at a fundamental level.
- System Models: fewer details but still relevant. used for probabilistic analysis.
280
What are the engineered barriers of YMR?
- Low Water Infiltration
- Titanium Drip Shield
- Waste Package
- Spent Fuel Cladding
- Waste Form
-
281
What are the four scenario classes for the YMR?
- Nominal
- Early Failure
- Igneous
- Seismic
282
What are the four main radionuclide contributing to the mean dose after 10,000 years?
Tc-99
C-14
Pu-239
I-129
283
What is the probability of damage to co-disposed waste packages withing 10,000 years?
less than 0.2
284
What are the four main radionuclide contributing to the mean dose after 1 million years?
```
Tc-99
I-99
Ra-226
Np-237
Pu-239
Pu-242
```
285
What does Partitioning and Transmutation mean?
Partitioning: conventional PUREX process + additional chemical partitioning process (separation of U/Pu and additional elements for transmutation)
Transmutation: in reactors, accelerator, and fusion reactors
286
What must be taken into account in Partitioning and Transmutation?
- secondary wastes of P&T must be taken into account
287
What is the total estimated peak mean annual dose for 10,000 years in the YMR?
0.24 mrem/yr
288
What is the nuclear regulatory limit of peak mean annual dose after 10,000 years of repository placement?
15 mrem/yr
289
What is the total estimated peak mean annual dose for 1 million years in the YMR?
0.96 mrem/yr
290
What is the nuclear regulatory limit of peak mean annual dose after 1 million years of repository placement?
100 mrem/yr
291
What are the four types of rocks for a repository?
Crystalline Rock
Sedimentary Rock
Salt
292
What is the product, the % of U, % of U-235 and the key waste in Mining?
Product: U ore
%U: 0.2-20%
%U235: 0.72%
Key Waste: General Mining Waste
293
What is the product, the % of U, % of U-235 and the key waste in Milling?
Product: Yellowcake (UO2 impure)
%U: 70-90%
%U235: 0.72%
Key Waste: Mill Tailings, airborne Rn222 and radioactive dust, liquid effluents carrying water soluble radionuclides.
294
What is the product, the % of U, % of U-235 and the key waste in Refining?
Product: UO2
%U: 99%
%U235: 0.72%
Key Waste: Th230 and Ra226 radionuclides.
295
What is the product, the % of U, % of U-235 and the key waste in Conversion?
Product: UF6
%U: 99%
%U235: 0.72%
Key Waste: Th230 and Ra226 radionuclides, U lost in waste, filters, sludges, paper, and polyethylene
296
What is the product, the % of U, % of U-235 and the key waste in Enrichment?
Product: UF6 enriched
%U: 99%
%U235: 3.3%
Key Waste: Depleted Uranium, filters, paper, gloves, laundry waste water
297
What is the product, the % of U, % of U-235 and the key waste in Fuel Fabrication?
Product: UO2 pellets
%U: 99%
%U235: 3.3%
Key Waste: Depleted Uranium, filters, paper, cloth, wood, polyethylene, ashes, sludges, metal, glass, 3 drums of water per MTU
298
T or F. In uranium ore deposit that has existed for 100 million yrs at he same location in a geological formation, we observe several decay daughters of U isotopes, which are considered to be in secular equilibrium. By carefully measuring the comp. of those decay daughters currently observed, we can tell if there was thorium included at one time in the past.
False. Uranium isotope contains the isotope of thorium in their decay chain. The half-life of uranium is on the order of 1E7-1E9 depending on the isotope meaning thorium should be present.
299
T or F. For a radionuclide with low solubility in groundwater, the release rate from failed packages in a geological repository is determined primarily by the dissolution rate of the waste matrix.
False. Low solubility nuclides precipitate outside the waste package. Congruently released (high solubility) nuclides have a release rate determined by waste form dissolution?
300
T or F. With strong sorption with the hots rock, radionuclides are retained in the host rock, which is considered to be unfavorable to the performance of a geologic repository.
False. This is favorable as it is part of the geological barrier
301
T or F. Because TRU wastes contain low TRU elements at low concentrations, they can be disposed of in a shallow-land repository with low-level wastes.
False. Defense TRU wastes go to WIPP.
302
T or F. By intense R&D, complete recovery *100% efficiency* of Pu from SNF by reprocessing can be achieved.
False. There is no such thing as 100% recovery for any chemical separation.
303
How is C-14 generated in a PWR? Why is this nuclide of concern in the waste management?
It is produced mainly by neutron capture in nitrogen: N-14 + n -> C-14 + H-1. It is of concern because of its relative long half-life (5000 years) therefore staying in the env. for a long time. It readily swaps out regular carbon in living organism.
304
One of the sources that produce H-3 by neutron activation in a PWR is Li. Why and where does Li exist in a PWR?
Li exists in a PWR from production through reactions with boron which is a neutron poison dissolved in the coolant. Lithium is also added to the coolant to prevent corrosion and its present as LiOH.
305
How can the natural U requirement per unit amount of electricity generation be reduced for a PWR with the once-through system? No recycling assumed.
- Increase thermal efficiency (generates same energy with less fuel)
- Decrease the U-235 content in depleted uranium output from enrichment (more U resource utilized needing less NU).
- Increase burnup of the fuel (utilize more fissile material)
