Deck Flashcards
(200 cards)
1
Q
What is the average energy release in fission of a U-235 atom?
A
200 MeV
2
Q
What type of fuel does the CANDU reactor use?
A
Natural Uranium
3
Q
What type of fuel does the LWR use?
A
Enriched Uranium Oxide 3-5%
4
Q
What are the three radioactive effluents from uranium mills?
A
Airborne: Rn-222 gas and radioactive dust particles
Liquid: water-soluble radionuclides
Yellow Cake: contains decay daughters of U isotopes as impurities
5
Q
Describe secular equilibrium?
A
After several half-lives the activity of the daughter converges to the activity of the parent (since daughter half life is much shorter than parents).
6
Q
What is transient equilibrium? When does it happen?
A
When decay constant of daughter is much much larger than that of the parent, Daughter builds up to a concentration such that its decay rate is identical to that of the parent.
7
Q
What does uranium refining consist of?
A
removing the rest of non-uraniferous contaminants from the uranium to produce a pure uranium compound
8
Q
What is UNH? What is chemical formula?
A
Uranyl Nitrate Hexahydrate, UO2(NO3)2*6H20
9
Q
Describe the process of Uranium refining?
A
Recieve Uranium ore concentrate U3O8, dissolved in HNO resulting in UNH and solvent extraction by TBP
10
Q
What does TBP stand for?
A
Tributyl Phosphate
11
Q
What is conversion
A
Changing the chemical form of UNH to UF6, or from UF6 to UO2
12
Q
What are the steps in conversion?
A
Reduction, Hydro-fluorination, Fluorination, Fractional Distillation
13
Q
What are the two main uranium enrichment processes?
A
Gaseous diffusion and gas centrifuge
14
Q
What are the steps of reconversion?
A
Hydrolyzed UF6 to UO2F2 by solution in water, filtration, drying. Add ammonia (6NH4OH) to precipitate ammonium duranate (ADU) (NH4)2U207, reduction by H at 820C to UO2
15
Q
What are the two sources of C-14 in a thermal reactor and their reactions?
A
Residual nitrogen impurity in fuel dissovled in coolant water: 14N + n -> 14C + 1H
Oxygen in Water: 17O + n -> 14C + alpha
16
Q
How is boron present in a PWR?
A
control rods as absorbers (bwr) OR dissolved in coolant water (PWR)
17
Q
How is lithium present in PWR?
A
Formed by (n,alpha) reaction in boron, also LiOH added to coolant for corrosion control.
18
Q
What two elements are responsible for the appearance of tritium?
A
Boron, Deuterium, and Lithium
19
Q
What are the major radioactivity sources for the first thousand of years, what is the half life?
A
137Cs and 90Sr with half life of 30 years
20
Q
How much activity of Iodine is produced per 1GWe?
A
1 Ci/yr
21
Q
What radioactive wastes due to reactor operation
A
In spent fuel: FPs, Actinides, Activated Material (gaseous and non-volatile)
There are also FP leaking out from fuel to coolant and activated material in the coolant.
Decommissioning waste
22
Q
Why is boron added to reactor?
A
as burnable poison
23
Q
Why is lithium added to reactor?
A
pH adjustment
24
Q
Define decomissioning.
A
all of the activities that must take place at the end of a plant’s life to ensure that the site where the plant is located does not pose any hazard to the public and can, therefore, be considered property suitable for unrestricted use (10 CFR 50).
25
Name three important radionuclides in decomissioning waste?
60-Co, 59-Ni, 94-Nb
26
What compounds are considered radioactive waste?
All compounds with a radioactive level above a defined background threshold level (exemption threshold)
27
What are the three radioactive materials management?
Exemption, Clearence and Exclusion (NORM)
28
What does the EXEMPTION regulation states?
waste with so little radioact. that it cannot be considered radioactive and might be exempted by nuclear regulatory control.
29
What is the max specific activity to be considered EXEMPTION? The individual dose? Collective dose?
70 Bq/g, 10 microSv/year, 1 man Sv
30
What does the CLEARANCE regulation states?
the removal of radioactive materials or radioactive objects within authorized practices from any further regulatory control by the regulatory body. Concerns sources that should not continiu to be under regulatory control
31
What is the max dose to be considered CLEARANCE? Collective dose?
10 microSv/a, 1 manSv/a collective dose
32
What does the EXCLUSION regulation states?
determines what waste shall and what shall not be subject to radiation safety
33
Define High Level Waste according to the Nuclear Waste Policy Act?
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 fission products in sufficient concentrations
34
What are the objectives of reprocessing?
to recover U and Pu for reuse as nuclear fuel, remove radioactive and neutron-absorbing FP from SNF, cconvert the radioactive constituents of SNF into forms suitable for safe, long term storage, and recover useful FP.
35
When decladding what gasses emerge and what is done to them?
Kr, Xe, I, Tritium, 14-C which are routed to off-gas treatment system
36
Describe the process of recovering 3H in fuel reprocessing/
Chopped fuel UO2 dissolved in N2O4 for zircaloy converts UO2 to U3O8. Tritium is oxidized to tritiated water HTO
37
What is the objective of dissolution in fuel reprosessing?
To bring U and Pu in the fuel completely into aqueous solution, complete separation of fuel from cladding, convert U, Pu, and FP into the chemical states most favorable for their subsequent separation
38
What compound is used to reduce Pu to tetravalent Pu4+? Does it work with U?
Dinitrogen tetroxide N2O4, it does not reduce U(VI)
39
In once through fuel cycle, is spent fuel considered HLW?
the spent fuel is considered to be HLW.
40
What type of emitters are in HLW?
Alpha, beta, gamma emitters
41
Do HLW requires cooling and shielding
Yes
42
Are fission products and TRU considered HLW or LLW?
HLW mostly
43
Define Transuranic (TRU) Wastes according to the NRC?
wastes containing alpha-emitting isotopes with atomic number > 92, with half-lives longer than 5 years, and concentrations greater than 100 nCi/g-waste
44
Define TRU wastes according to EPA/DOE?
half-lives longer than 20 years
45
Define LLW according to NWPA. When are they generated?
not HLW, spent fuel, or trans-uranic waste. Generated in all activities involving radioactive materials.
46
Name some examples of LLW?
Clothing, tools, syringes, cotton swipes, paper, rags, etc
47
How many classes of LLW are?
Class A, B, C, and GTCC
48
How many tons of CO2 per 1 GWe are produced by crude oil?
5 million
49
How many tons of CO2 per 1 GWe are produced by coal?
6 million
50
How many tons of CO2 per 1 GWe are produced by LNG?
3 million
51
What are two pros of HWR? Three cons?
no enrichment, non proliferation (no U enrichment)
| cons: frequent refueling (low energy density), high volume of spent fuel, non proliferation (pu separation)
52
Why does heavy water reactors work with natural uranium?
since absorption cross section is 0.001 barns, and that of water is 0.66 barns
53
What is the burnup of HWR? Why so low or high?
6800 MWd/MTU, low due to depletion of fissile material and an increase in neutron-absorbing FP
54
What is the full burnup of uranium oxide?
950,000 MWd/MTU
55
What is the potential energy in MWd of 1g of U235?
0.95 MWd
56
What is the fuel enrichment of LWR fuel cycle?
3.3% U-235
57
What is the burnup of U in LWR?
33,000 MWd/MTU
58
What is the average enrichment of U-235 and the content of fissile Pu in LWR spent fuel?
0. 83% of U-235,
| 0. 6% of fissile Pu
59
What is the average heat efficiency of a LWR AND HWR?
0.325 and 0.3
60
What is the uranium utilization factor for HWR?
0.7%
61
What is the uranium utilization factor for LWR?
0.47%
62
What is the input fuel for Pu cycle with LWR?
U and Pu in spent fuel of LWR recovered in reprocessing
63
What is the enrichment in Pu cycle in LWR of U?
3.3%
64
What is the chemical compound of Pu cycle with LWR cycle?
U and Pu oxides
65
What is the utilization factor of Pu cycle with LWR?
0.76%
66
What is the average burnup of HWR?
6800 MWd/MT
67
What is the average burnup of once through PWR?
33,000 MWd/MT
68
What is the average burnup of recycled PWR?
33,000 MWd/MT
69
What is the average burnup of FBR?
65,000 TO 100,000 MWd/MT
70
What is the average capacity factor for all types of fuel cycles?
0.8
71
What is the thermal efficiency of a 1 GW HWR?
0.3
72
What is the thermal efficiency of a 1 GW PWR and recycled PWR?
0.325
73
What is the thermal efficiency of a 1 GW FBR?
0.4
74
What is the natural unraium consumption in 1 GW HWR (MT/year)?
144 MT/year
75
What is the natural unraium consumption of 1 GW once-through PWR (MT/year)?
201
76
What is the natural unraium consumption of recycle PWR (MT/year)?
123 MT/year
77
What is the natural unraium consumption of FBR (MT/year)?
1.5
78
What is the uranium utilization of 1GW HWR?
0.72%
79
What is the uranium utilization of 1GW once through PWR
0.47
80
What is the uranium utilization of 1GW RECYCLE PWR?
0.76
81
What is the uranium utilization of 1GW FBR?
60%
82
What fuel cycle facilities are necessary for a 1 GW HWR cycle?
U Conversion and Fuel Fabrication
83
What fuel cycle facilities are necessary for a 1 GW once through PWR cycle?
U enrichment, U conversion, Fuel Fabrication
84
What fuel cycle facilities are necessary for a 1 GW recycle PWR cycle?
U enrichment, U conversion, Fuel Fabrication (for U and Pu), Reprocessing
85
What fuel cycle facilities are necessary for a 1 GW FBR cycle?
Fuel Fabrication (core and blanket), reprocessing
86
What are three uranium containing minerals?
- Zeunerite associated with lavendulan
- Uraninite
- Pitchblende
87
How many ppm of uranium are in hi grade uranium ore
200,000
88
How many ppm of uranium are in average grade uranium ore
1,000
89
How many ppm of uranium are in granite?
4 ppm
90
How many ppm of uranium are in aqueous rock (sedimentary rock)
2 ppm
91
How many ppm of uranium are in average concentration in the earths crust
2.8 ppm
92
How many ppm of uranium are in average concentration in sea water?
0.003 ppm
93
What are the two types of uranium extraction methods?
underground mining and insitu leaching
94
What do uranium mills do?
Separate uranium from most of the non-uraniferous diluents that accompany uranium in nature. It increases the uranium oxide content from a few tenths to 85-95% in the ore
95
What are the two types of leaching?
acid and carbonate leaching
96
What are the five steps in carbonate leaching?
Crushing and Grinding, Leaching, Filtration, Precipitation, and Purification
97
What are the three main radioactive effluents from uranium mills?
Airborne Effluents, Liquid Effluents and Yellow Cake, and mill tailings
98
What isotope is airbonre effluent fromuranium millos mainly?
Rn-222 GAS and radioactive dust particles
99
What are the liquid effluents from uranium mills and how do we process them?
Water-soluble radionuclides, which are held in storage ponds with mill tailings and eventually evaporated to a solid.
100
What does yellow cake contains?
decay daughters of U isotopes as impurities
101
What are tailings?
Tailings are the byproducts left over from mining and extracting resources
102
In acid leaching tailings where does most of the radioactivity comes from
Th-230 followed by Ra-226
103
In carbonate leaching tailings where does most of the radioactivity comes from
Th-230 followed by Ra-226
104
Explain what is secular equilibrium?
When a radionuclide decays to a daughter of half life much shorter that the parent (t1/2p>>t1/2d), the daughter builds up until a constant ratio of parent to daughter is achieved and aftewards the daughter concentration starts to decrease at a rate controlled by the parent half life
105
What does uranium refining do?
removes the rest of the non-uranifereous contaminants and produce a pure uranium compound
106
How does solvent extraction works in uranium refining?
- recieves uranium ore concentrates (about 85% U3O8)
- dissolves in nitric acid
- solvent extraction by tbp
107
Solvent extraction by TBP removes? What is the final product?
Th-230, 226-Ra, nonuranium metallic impurities. The final product is Uranyl Nitrate Hexahydrate UNH
108
What is the chemical formula of UNH?
UO2(NO3)2 * 6H2O
109
What are the five main steps for the production of yellowcake?
Crush and Grinding of Ore (U3O8 + impurities),
| Leaching, Filtration, Precipitation which produces impure yellowcake and Purification which produces pure yellowcake
110
What is the chemical formula of yellowcake?
85% U3O8 0.2% V2O5 7.5% Na2O
111
What process follows after yellowcake production? What does it do? What is the final product?
uranium refining, purifies yellowcake by dissolving it in nitric acid and solvent extraction with TBP which produces UNH
112
What process follows uranium refining and what does it do?
Conversion, changes the chemical formula of uranium from UNH to UF6
113
What are the four steps in conversion of UNH to UF6?
Reduction of UNH with H2 which leads to impured UO2, Hydrofluorination with anhydrous HF which produces Impure UF4, Fluorination with F2 which leads to impure UF6, AND THEN Fractional Distillation to purify the UF6
114
What is the overall process yield of conversion?
99.5%, 0.5% is lost to waste
115
What is the enrichment of uranium waste in conversion/
Same as NU
116
What are the three waste forms in the conversion step?
aqueous raffinate (Th230 and Ra226)
Lost uranium
filters, sludges, paper, polyethilene
117
What follows converison?
Uranium Enrichment
118
What are the three main uranium enrichment tequniques?
gaseous diffusion, gas centrifuge, laser siotope separation
119
What are the waste forms in uranium enrichment?
filter, paper, gloves, laundry waste water
120
What is the separation efficiency of gaseous diffusion and gas centrigue?
99.5%
121
Describe gaseouds diffusion. In what principle does gaseous diffusion work
A high pressure feed goes in where the output is depleted gas stream. Ligher isotopes diffuse faster through the barriers to a low pressure zone which is an enriched stream.
122
How does a gas centrifuge works?
UF6 gas placed in gas centrifuge cylinder and rotated at a high speed. The rotation creates a strong centrigural force making heavier gas molecules (UF6 containing U-238) movethe outside of the cylinder
123
What follows after uranium enrichment? what does it do
uranium fuel fabrication, re conversion to UO2
124
Describe the uranium fuel fabrication process
- hydrolyzed uf6 to UO2F2 by solution in water, filtration and drying
- ammonia added to precipitate ammonium diuranate (ADU = (NH4)2U2O7
- reduction by hydrogen at 820 to UO2 powder
- Fabrication (pressing, sintering, assembling)
125
What are the two wastes generated in the uranium fuel fabrication precipitation step?
- U contaminated with NH4F + H2O
| - NH4F recycle as ammonia
126
What type of waste forms are generated in the uranium fuel fabrication step?
solids: paper, cloth, wood, polyethylene, ashes, etc.
| 3 drums of contaminated water per 1 MT U
127
What is the half life of Sr-90?
28.8 years
128
What is the half life of 127 Cs
30.17 years
129
What is the halflife of 99 Tc
2.1E5 years
130
Name two characteristics of Tc99
Very low solubility in reducing environment, weakly sorbing species
131
Name the five main gaseous FPs
I-131, I-129, Kr-85, Xe-133, H-3
132
How is iodine relaese?
radio iodine released to coolant from fuel cladding is absorbed by activated carbon
133
What is the activity of Iodine FP per 1GWe?
1 Ci/yr of 1 GWe operation is generated
134
What is the half life of Kr 85
10.76 yr
135
What is the half life of Xe 133
5.27 days
136
What is the haf life of H3?
12.4 yr
137
Name the five highest radioactive actinides and their activity per year?
```
Np-237 1.44E1
Pu-238 1.01E5
Pu-241 2.81E6
Am-241 4.53E3
Cm-242 4.40E5
All in Ci/yr
```
138
How is Li-7 produced in na reactor?
B-10(n, alpha)Li-7
139
Name the 5 main reactions for tritium generation in a reactor?
```
Li-7(n,5He)H-3
Li-7(n, n+alpha)H-3
Li-6(n, alpha)H-3
B-10(n,Be-8)H-3
H-2 + n -> H-3
```
140
Where does boron come from?
Solid control absorber (BWR) and Dissolved in coolant water (PWR)
141
Where does Lithium come from?
```
Formed by (n,alpha) reaction in boron
LiOH is added to coolant for corrosion contrl (PWR)
```
142
What is the highest tritium source in coolant? How many Ci/yr?
B-10(n,Be-8)H-3, it produces 360 Ci/yr
143
What is the half life of C-14?
5730 yr
144
How is carbon 14 generated in a reactor
N-14(n,H-1)C-14
| O-17(n,alpha)C-14
145
Where does the nitrogen come from for carbon 14 formation?
Residual nitrogen impurity in fuel which dissolves in coolant water.
146
Name the three main sources of radioactive wastes due to reactor operation?
Spent Fuel, Radioactive wastes from reactor operation, decomissioning waste
147
What does spent fuel contain?
FPs, Actinides, activated materials (gaseous C-14 and H-3, non volatile)
148
What are the radioactive wastes from reactor operation?
FPs leaking from fuel to coolant, activated materials in coolant
149
What are the three main FPs leaking from fuel to coolant AND what do they decay into?
Kr-85 -> Rb-85 , I-131 -> Xe-131, I-133 -> Xe-133 -> Cs-133
150
What does CRUD stand for and what is it?
Chalk River Unidentified Deposit:
- corrosion of coolant piping
- small particles ciruclating with coolant
- small particles activated and deposited on cladding surfaces, steam generator and so on
- contains 60Co (60%), 63Ni (25%), 58Co, 51Cr, 54Mn, 59Fe
151
What is decomissioning?
all of the activities that must take place at EOL to ensure that the site does not pose any hazard to the public and can be considered suitable for unrestricted use
152
What document dictates decomissioning?
10 CFR 50
153
What are the two decomissioning waste?
- contamination carried by the water coolant circulating through the core
- activation products produced by neutron absorption
154
What are three important radionuclides in decommisioning wastes and what type of radiation do they emit?
60Co (gamma and beta)
59Ni (x-rays of 60Co, bremsstrahlung)
94Nb (gamma and beta)
155
What are the three decomissioning methods?
- DECON
- SAFSTOR
- ENTOMB
156
What does the DECON decomissioning method constist of? What are some pros and cons?
All radioactive materials removed SOON after final shutdown.
Good if site has only one reactor and the utility has no plans to build others, this is the best. bad if more than one reactor or plans to build more.
157
What does the SAFSTOR decomissioning method constist of? What are some pros and cons?
All liquid and portable solid radioactive materials are removed. Remaining struc. and equip. secured and controlled by amended nuc. licence. eventually, rest of plant
- If site has more than one reactor, or plans for building more, this is attractive since site will not be released for unrestricted use anyway and monitoring will not incurr too much additional expense
- Occupational doses and amounts of radwastes will be reduced
158
What does the ENTOMB decomissioning method constist of? What are some pros and cons?
Same as SAFTOR except facility sealed completely by covering with conrete, thus creating one monolithic strucutre. Wait until radioactivity decays to a level when site can be returned to unrestricted use
least attractive of all since licensee must demonstrate site could be released for unrestricted use after 100 yrs following shutdown.
159
What is the exemption threshold?
If compounds with a radioactive level are above a defined background level (the eqxemption threshold) then they are considered radioactive waste that are submitted to special regulation and control
160
According to the IAEA Safety Series No. 111-G-1.1, what is the upper activity per gram for a source to not be of regulatory concern?
< 70 Bq/g
161
According to the IAEA Safety Series No. 111-G-1.1, what is the max individual dose?
10 microSv/year
162
According to the IAEA Safety Series No. 111-G-1.1, what is max collective dose?
1 man Sv
163
According to the IAEA Safety Series No. 111-G-1.1, what is it equivalent to compared to the average natural background?
1% of the average natural background
164
What is clearance according to the IAEA RS-G-1.7
defined as the removal of radioactive materials or radioactive objects within authorized practices from any further regulatory control by the regulatory body
165
What does clearance conerns to?
sources that for one reason or another are under reg. control and should not continue to be so
166
What is required for clearance to be granted for a rad. material or object?
show the safety by deteailed assessment
167
What are the safety points for clearance?
- Dose for member of public in the range of 10 microSv/a
- 1 manSv/a collective dose
- single events with low likelihood can be accepted if < 1 mSv/a effective dose and <50 mSv/a skin dose
168
What is exclusion? What does it concern?
determines what waste shall and what shall not be subject to radiation safety and concerns mostly uncontrollable exposures and exposures that are essentially not amenable to control regardless their magnitude
169
What is the objective of reprocessing?
- to recover U and Pu for reuse as nuclear fuel
- to remove radioactive and neutron absorbing FP
- convert radioactive constituents into forms suitable for safe long term storage
- to recover useful FP such as 80Sr and 137Cs and byproduct TRU elements such as Np, Am, and Cm
170
What are the 5 main steps in reprocessing?
Decladding, dissolution, conditioning, co-decontamination and Uranium Plutonium speration into UF6 and PuO2
171
What is the objective of dissolution?
- bring U and Pu into aqueous solution
- complete sepearation of fuel from cladding
- determine the amounts of U and Pu discharged to reprocessing
- conver U, Pu and FP into chemical states favorable for subsequent separation
172
What compound is used as the first step of dissolution? For what?
nitric acid to dissolve U, Pu, Am, Cm, nearlly all FP
173
What does conditioning in fuel reprocessing consist off?
adjust all Pu to tetravalent Pu4+ by the addition of N2O4 (all Pu is reduced -> Pu(VI)) in the form of PuO2. U is dissolved in H2O or HNO3 to obtain UO2(NO3)2
174
What is the off-gas treatment?
absorption of Iodine compous by aqueous NaOH (removes HI, I2, but not organic I2) and also noble gases (Xe and Kr).
175
Why is the off-gas treatment necessary?
iodine reacts with solvent to form hard to remove compounds therefore they must be removed as much as possible before solvent contacting
176
What does co-decontamination do and consist of?
Separation of U and Pu from FPs and TRUs by adjusting HNO3 concentration
177
What is High Level Waste according to the Nuclear Waste Policy Act?
The 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 fission products in sufficient concentrations
178
In a onec through cycle is spent fuel considered HLW or LLW?
HLW
179
wHAT TYPE OF EMITTERS ARE IN hlw?
alpha, beta and gamma emmiters
180
What care does HLW required?
shielding and cooling
181
What are TRU wastes according to the NRC?
Wastes containing alpha-emitting isotopes with atomic number > 92 with half lives longer than 5 years and concentrations greater than 100 nCi/g waste
182
What are TRU wastes according to the EPA/DOE?
half-lives longer than 20 years
183
Where are TRU wastes generated?
At the reprocessing plant
184
What is LLW according to the NPWA? When are they generated? Give examples of LLW.
Not HLW, spent fuel, or TRU wastes. Generated in all activities involving radioactive materials. Some examples include clothing, tools, syringes, cotton swipes, paper, etc.
185
How many classes of LLW are there? What are their names?
4: Class A, B, C and GTCC (greater than class C)
186
What is in class A of LLW?
Waste that has the least amount of radioactivity, it becomes non-hazardous during the institutional control period after the site is closed.
187
What is class B of LLW?
More radioactive than class A and remains hazardous for up to 300 yrs
188
What is class C of LLW?
It remains hazardous for up to 300 yrs and it may require burials at depth greater than those of class A and B
189
What is GTCC of LLW?
Waste not appropriate for shallow burial and are the responsibility of the federal government and must be stored in a deep geological repository
190
What is DOSE
Dose (REM) = absorbed dose (rad) * quality factor * Distribution factor
191
What is the absorbed dose?
Energy absrobed by thematerial
192
How much is 1 rad in J/kg
0.01 J/kg
193
How much is 1 Gy in J/kg
1
194
How many Gy are in 1 rad?
0.01 Gy
195
What is the typical backgroud radiation?
2 mSv/yr
196
What is the average dose to US nuclear industry employers?
2.4 mSv/yr
197
average dose to airline crew in tokyo to new york?
9 mSv/yr
198
average dose to in several places in Iran, India, and Europe?
50 mSv/yr
199
What is the lowest level (dose) at which any increase in cancer is clearly evident?
100 mSv/yr
200
What is the maximum permissible concentration (MPC) of radionuclides?
Radioactivity concentration limit of a given radionuclide in air or in water an individual who obtains his or her total intake of air or water from this srouce will receive a radiation dose from this radionuclide at a rate of 0.05 rem/year
