(Based on a Technical lecture on Nuclear plant explosions and disaster management by Prof.T.Shivaji Rao, Director, Environmental Studies, GITAM University, Visakhapatnam with reference to the publication Accidents Will Happen: Enquiry into the Social and Economic Consequences of a Nuclear Accident at Sizewell B Nuclear plant (UK) (1100 MW) Friends of The Earth ,London (April 1984)
http://www.bt.cdc.gov/radiation/glossary.asp#terrestrialradiation [Definitions of radio-activity]
http://www.radiation-scott.org/radsource/index.htm [Exposure and dosages of radio-activity]
http://www.bt.cdc.gov/radiation/glossary.asp#terrestrialradiation [Definitions of radio-activity]
http://www.radiation-scott.org/radsource/index.htm [Exposure and dosages of radio-activity]
http://tshivajirao.blogspot.com/2010/04/nuclear-plant-risks-srikakulam-district.html
http://bhujangam.blogspot.com/2011/08/economic-costs-of-nuclear-reactor_05.html [Economic costs]
http://en.wikipedia.org/wiki/Uranium-235
http://www.whatisnuclear.com/articles/nucreactor.html
http://bhujangam.blogspot.com/2011/08/economic-costs-of-nuclear-reactor_05.html [Economic costs]
http://en.wikipedia.org/wiki/Uranium-235
http://www.whatisnuclear.com/articles/nucreactor.html
(Working of Nuclear Plant)
http://www.greenpeace.org/international/Global/international/publications/climate/2011/battle%20of%20the%20grids.pdf [Alternate Renewable Energy Sources available]
http://www.greenpeace.org/international/Global/international/publications/climate/2011/battle%20of%20the%20grids.pdf [Alternate Renewable Energy Sources available]
Nuclear power stations produce unusual amount of heat by means of nuclear reactions of Uranium fuel particles bundled in packets and placed in reactor core where neutrons bombard the fuel and thereby abnormal heat and new radioactive particles which damage living tissues emanate. If the nuclear fuel gets overheated and the packed radioactive particles are blown into the air the surrounding areas including the air, water, soil get highly contaminated and the cost of such an accident will be very high. Firstly the local population would be exposed to radiation from the radioactive plume from the reactor and the local soils and buildings also will be contaminated causing deaths including cancer even for future generations, crops and agriculture products will be contaminated and people and animals have to be evacuated from the local areas to safer places for some years. This report attempts to evaluate some of the consequences due to accidents in nuclear power plants. For this purpose the size-well Reactor-B an 100MW pressurized water reactors is taken as model from United Kingdom. This reactor produces 3411 MW of heat at full power the nuclear reaction is driven in 100 tonnes of Uranium Oxide fuel in 50,000 packed fuel rods are tubes of Zirconium alloy, ½ inch in diameter. The reactor core sits in a thick steel pressure vessel, through which 18 tonnes of is pumped every second to carryaway the heat which is used for generation of high pressure steam that drives the turbine that is linked with the generator that produces electricity. During operations fuel rods are kept at 340oC by circulating cooling water that removes heat from the rods and if this flow of cooling water is blocked for any reason fuel temperature rises to 1200oC and the Zirconium tubes began to melt and with the core getting melted the fuel along with massive quantities radioactivity breaches all the barriers and forces its way into the atmosphere. Reactor systems will be provided with means to flood the reactor core in emergencies to avoid core meltdown and to maintain the integrity of the containment. If the emergency core cooling system fails a cloud of radioactivity will enter the atmosphere and will carried by the wind, depositing fission products of the core in a ribbon downwind of the reactor in decreased concentration for hundreds of miles from the reactor. Health hazards occur due to this radioactive contamination of air, water and soil causing physical, economic and social damages in the zone of influence. The dosages of radioactivity in the environment are estimated and necessary steps are taken as preventive and curative measures in sheltering the people administering medicines and evacuating people to safe zones within specified time schedules. Similarly the damage to agricultural crops, milk products are also assessed for taking public health protection measures. Some of the details of this emergency response system of size-well B reactor are presented in the following paragraphs.
If radiation changes DNA molecules enough, cells can’t replicate and begin to die, which causes the immediate effects of radiation sickness -- nausea, swelling, hair loss. Cells that are damaged less severely may survive and replicate, but the structural changes in their DNA can disrupt normal cell processes -- like the mechanisms that control how and when cells divide. Cells that can’t control their division grow out of control, becoming cancerous.
HOW RADIATION DAMAGES THE LIFE SYSTEMS
http://www.popsci.com/science/article/2011-03/fyi-how-does-nuclear-radiation-do-its-damage
Ionizing radiation—the kind that minerals, atom bombs and nuclear reactors emit—does one main thing to the human body: it weakens and breaks up DNA, either damaging cells enough to kill them or causing them to mutate in ways that may eventually lead to cancer.
Nuclear radiation, unlike the radiation from a light bulb or a microwave, is energetic enough to ionize atoms by knocking off their electrons. This ionizing radiation can damage DNA molecules directly, by breaking the bonds between atoms, or it can ionize water molecules and form free radicals, which are highly reactive and also disrupt the bonds of surrounding molecules, including DNA.
Peter Dedon, a member of the Radiation Protection Committee at MIT, explains: “What happens is that the nucleus of radioactive elements undergoes decay and emits high-energy particles. If you stand in the way of those particles, they are going to interact with the cells of your body. You literally get a particle, an energy packet, moving through your cells and tissues.” If radiation changes DNA molecules enough, cells can’t replicate and begin to die, which causes the immediate effects of radiation sickness -- nausea, swelling, hair loss. Cells that are damaged less severely may survive and replicate, but the structural changes in their DNA can disrupt normal cell processes -- like the mechanisms that control how and when cells divide. Cells that can’t control their division grow out of control, becoming cancerous.
Radiation exposure risk is measured in units called sieverts. In a typical year, a person might receive a total dose of two or three millisieverts from things like ambient radioactivity, plane flights and medical procedures. In the U.S. the annual exposure limit for nuclear plant workers is 0.05 sieverts per year. At or below these levels, the enzymes that repair DNA keep up with damage enough to keep the risk of cancer low. Above them, the body’s systems of repair can’t keep pace. 100 millisieverts a year is the threshold above which cancer risk starts to increase, according to the World Nuclear Association.
Radiation levels have fluctuated at Fukushima, rising at one reading to 400 millisieverts per hour. At that level, Dedon says, seven minutes would bring you to the U.S. yearly limit. Over an hour could be a lethal dose. The 400 millisieverts level was not a sustained measurement and levels continue to fluctuate much lower. Dedon stresses that because radiation dissipates, like light, by the square of its distance, even if levels are high in the plant, just a few miles away, they would be miniscule. The greater danger for people living in the area is the release of radioactive particles into the air, which can accumulate in the body, damaging tissue over time and causing cancer
Receiving a one-sievert dose of radiation in a day is enough to make you feel ill, according to Dedon. “At one to three, you have damaged bone marrow and organs, and you’ll really be sick. At three to six you add hemorrhaging, and more infection,” he says. “From six to ten, at that level death is something like 90 percent. And above ten, they just call that incapacitation and death.”
usa says 20 km is not enough. us military personal is not allowed within 50 miles of the reactor. the thing is this stuff gets in ground, in the grass and water that animals eat and drink then we eat them.
EXPOSURE PATHWAYS:
Contact with radioactivity can lead to exposure to radiation through a number of exposure pathways for instance direct exposure ingestion or inhalation. Direct exposure refers to a situation where exposure occurs from radiation emitted by radioactive substances outside the body. After a nuclear accident, for example, this may result from radioactivity which is suspended in the air, from radioactive contamination of the ground or the surface of buildings. Ingestion of radioactivity will occur if contaminated foodstuffs are eaten or drunk, and will result in the incorporation of radioactivity into the body. Inhalation will result in radioactive particles lodging in the lungs, causing radiation exposure to the lungs, and certain radioactive elements passing through the lungs into the blood.
When radioactive elements are inhaled or ingested, the body will treat them in the same way as normal elements. Since particular elements tend to be concentrated in particular organs, the same increased concentration will occur if these elements are radioactive. Normal iodine, for example, is concentrated in the thyroid gland, and if radioactive iodine is ingested or inhaled, this causes a high concentration of radioactive iodine in the thyroid, and a correspondingly high chance of contracting thyroid cancer.
The amount of iodine ingested is of particular importance to the calculation of the consequences of nuclear accidents, since a large amount of radioactive iodine is produced in nuclear reactors, and it is very volatile which means it will be released in large quantities. Similar effects will result from ingestion of other radioactive elements; for instance plutonium, if ingested, tends to concentrate in the bones.
HARMFUL EFFECTS OF RDIATION
Effects
|
Dose/Effect Relationship
|
Early effects
-Death
 - Lung damage(fibrosis)
- Radiation sickness (prodomal vomiting)
-Sterility
- Cataracts
- Skin damage, hair loss
|
High dose (> 200 rads) to bone marrow (or lungs, etc.); depends on dose and dose rate
Depends on dose and dose rate
|
Late Effects
-Malignant diseases (fatal cancers, leukemia, non-fatal cancers to organs such as breast, thyroid, etc.
-Hereditary effects
-Developmental effects
|
‘Risk factors’ determined for different organs and for the whole body. Normally assumed risk of fatal cancer ~ 1 per 10,000 rems collective dose (to a population).
Risk factors determined (~ 2 effects per 10,000 rems gonad irradiation).
Results from irradiation of embryo before birth. Effects unknown.
|
REACTOR FAILURE MODES:
Emission factors known as source terms are essential to evaluate moment of poisonous nuclear radioactivity between the core of the reactor and the external environment downwind of the reactor. Figure shows types of barriers in the nuclear plant which must be broken to permit the escape of pollutants in the environment. Fuel matrix is the first barrier and fuel cladding is the second barrier and these fail when heated upto 2000oC or more. The coolant system is the 3rd barrier and the containment building is the 4th barrier. In Light Water Reactor (LWR) and Liquid Metal Fast Breeder Reactor (LMFBR). The reactors are housed in strong buildings. Pollutants sometimes by-pass the containment also. At Chernobyl first 3 barriers failed in the initiating reactivity excursion and as there was no strong containment building flimsy reactor housing was promptly thrown out. At Three Mile Island first 3 barriers were damaged and the containment is the 4th barrier retained most of the pollutants except for a trace of reactivity that escaped from the core. An example of the various stages of failure, grouping together the individual sequences of system failures, plant damage, accident phenomena and similar source terms are presented hereby a containment Event Tree (Fig2) for Sizewell-B Reactor. Core of an 1100MW Reactor contains several thousand million curies of radioactivity at the onset of an accident and many powerful barriers must be breached before the pollutants escape into the atmosphere and establishing the timing and nature of breaches is essential part of source term analysis which is linked to sequence definition. The reactor safety study methodology used by Westinghouse source term analysis for Sizewell-B Reactor includes nil treatment of transport through the reactor coolant system and the Event Tree and categorization deal only with events of the reactor containment and behavior of its safety systems. Five nodes deal how containment response by examining the time and mode of its failure or by-pass. Remaining 3 nodes deal with behavior of the radio-nuclides, questioning whether they release mechanisms of steam explosion or vaporization occur or whether operation of containments sprays is washing radioactivity out of the containment atmosphere. The characteristics of 4 of the 12 release categories are presented in the table, 1)containment by-pass (UK1), or 2) Early failure UK2 3) delayed failure UK5, 4) Intact containment UK11. The accidents are 1)Large Break, LOCA, 2)small break LOCA, 3) Transient initiated accident. Three Mile Island had transient type accident with core cooling being recovered.
Table-1 RELEASE CATEGORIES AND THEIR CHARACTERISTIC PARAMETERS
Timing Characteristic
Release Category
|
Frequency of occurrence (Y-1)1
|
Time before release2 (h)
|
Duration of release3 (h)
|
Warning time 4 (h)
|
UK1
|
2.4 10-9
|
1
|
3
|
0
|
UK1C
|
1.4 10-9
|
1
|
3
|
0
|
UK9
|
5.2 10-9
|
2
|
10
|
1
|
UK11
|
6.2 10-7
|
2
|
Long9
|
1
|
Physical Characteristics
Release Category
|
Energy of release (106 Btu/h)
|
Elevation of release (m)
|
Fraction of core inventory released to environemnt5
| |||||||
Xe-Kr
|
Organic I
|
Inorganic I-Br6
|
Cs-Sb
|
Te-Sb
|
Ba-Sr
|
Ru7
|
La8
| |||
UK1
|
0.3
|
10
|
9 10-1
|
7 10-3
|
7 10-1
|
5 10-1
|
3 10-1
|
6 10-2
|
2 10-2
|
9 10-1
|
UK1C
|
0.3
|
10
|
9 10-1
|
7 10-3
|
1.3 10-1
|
1.3 10-1
|
7.5 10-2
|
1.5 10-2
|
5 10-3
|
1 10-3
|
UK9
|
0
|
0
|
3 10-1
|
2 10-3
|
8 10-4
|
8 10-4
|
1 10-3
|
9 10-5
|
7 10-5
|
1 10-5
|
UK11
|
0
|
10
|
6 10-2
|
3 10-5
|
3 10-5
|
3 10-5
|
3 10-5
|
3 10-6
|
2 10-6
|
4 10-7
|
NOTES FOR TABALE 1:
1. As estimated in studies done / commissioned by, the CEGB (Central Electricity Generation Board)
2. The time between reactor shut-down and the release of radioactivity to the environment
3. For the purposes of this assessment the duration of releases UK1 and UK1C are taken as 1 hour, as over 90% of the activity released occurs within this time
4. The warning time is the time available for the initiation of counter measures before the release of activity to the environment. It has been evaluated conservatively as the time between vessel melt through and the release of activity to the environment.
5. The specified fractions of the core are assumed to be released uniformly over the specified release during (See note3) . The release fractions apply to stable isotopes of the specified elements.
6. The iodine and bromine are assumed to be released in an elemental form
7. Includes Ru, Rh, Co, Mo and Tc
8. Includes Y, La, Zr, Nb, Ce, Pr, Nd, Np, Pu, Am and Cm
9. For this category the releases of Xe-Kr and organic I are protracted and may continue over some tens of days. The assumption is made in this study that the total release occurs in 10 hours.
Source: D.Charles, S.M.Haywood & G.N Kelly, ‘The Radiological Consequences of Postulated Accidental Releases from the Sizewell PWR in Particular Meteorological Conditions’, NRPB-M84, May 1983.
Table 2 METEOROLOGICAL CONDITIONS USED IN ESTABLISHING THE ACCIDENT SCENARIOS
Code Name
|
Atmospheric stability
|
Duration (h)
|
Pasquill category
|
Windspeed1
(m s-1)
|
Mixing layer depth1(m)
|
Rainfall rate (mm h-1)
|
D5
|
Neutral
|
Total
|
D
|
5
|
800
|
0
|
FD
|
Stable
|
t < 4 h
t > 4 h
|
F
D
|
2
5
|
100
800
|
0
0
|
DR
|
Neutral (Rain)
|
Total
|
D
|
5
|
800
|
1.0
|
Note: The Values assigned to the wind speed and mixing layer depth are representatives values for the corresponding Pasquill stability categories and have been taken from: R.H Clarke, ‘The First Report of a Working Group on Atmospheric Dispersion: A model for short and medium range dispersion of radio nuclides released to the atmosphere’, NRPB, Harwell, NRPB-R91, 1979. Pasquill categories are used to classify the degree of stability of weather conditions in order to distinguish the main atmospheric dispersion patterns of clouds emitted from land-based source.
IMPORTANT RADIONUCLIDES AND TYPICAL CORE INVENTORIES
EXAMPLES OF ACCIDENT SOURCE TERMS
Sizewell B PRA Release
Categories
|
Start
|
Duration
|
Fraction of Core Inventory Released
| ||||||
Xe
|
I
|
Cs
|
Te
|
Ba
|
Ru
|
La
| |||
UK1
|
1 hr
|
3 hr
|
0.9
|
0.7
|
0.5
|
0.3
|
6(-2)
|
2(-2)
|
4(-3)
|
UK2
|
1 hr
|
0.5 hr
|
0.9
|
0.7
|
0.4
|
0.35
|
5(-2)
|
0.2
|
3(-3)
|
UK5
|
8 hr
|
0.5 hr
|
1.0
|
0.3*
|
0.3
|
0.5
|
4(-2)
|
3(-2)
|
6(-3)
|
UK11
|
2 hr
|
>24 hr
|
6(-2)
|
6(-5)
|
3(-5)
|
3(-5)
|
3(-6)
|
2(-6)
|
4(-7)
|
*Revised first estimate
| |||||||||
Chernobyl
|
0 hr
|
10 d
|
1.0
|
0.4
|
0.25
|
>0.1
|
4(-2)
|
5(-2)
|
3(-2)
|
TMI-2
|
3 hr
|
1 hr
|
<8(-2)
|
2(-7)
|
0
|
0
|
0
|
0
|
0
|
Note: 3(-3) = 3 x 10-3
| |||||||||
IMPORTANT RADIONUCLIDES AND TYPICAL CORE INVENTORIES
Group
|
Nuclides
|
T ½
|
Core Inventory, 1100MWe Reactor Mega-Curies
| |
Thermal
|
LMFBR
| |||
Xe
|
Xell-113
|
502d
|
185
|
173
|
I
|
I-131
|
8.04d
|
91
|
95
|
I-133
|
20.8h
|
184
|
169
| |
Cs
|
Cs-134
|
2.06y
|
10.4
|
1.7
|
Cs-137
|
30.0y
|
6.2
|
2.6
| |
Te
|
Sb-127
|
3.9d
|
7.9
|
8.9
|
Te-132
|
3.2d
|
131
|
125
| |
Ba
|
Sr-89
|
50.5d
|
91
|
48
|
Sr-90
|
29.1y
|
4.7
|
1.0
| |
Ba-140
|
12.7d
|
166
|
133
| |
Ru
|
Mo-99
|
66h
|
174
|
52
|
Ru-103
|
39.4d
|
142
|
72
| |
Ru-106
|
368d
|
35
|
49
| |
Rh-105
|
1.5d
|
86
|
38
| |
La
|
Y-91
|
58.6d
|
122
|
68
|
Zr-95
|
65.5d
|
159
|
19
| |
Nb-95
|
35.1 d
|
157
|
16
| |
La-140
|
40.3 d
|
171
|
136
| |
Ce-141
|
32.5 d
|
160
|
143
| |
Ce-143
|
33.0 d
|
147
|
118
| |
Ce-144
|
285 d
|
97
|
41
| |
Pr-143
|
13.6 d
|
146
|
118
| |
Nd-147
|
11.0 d
|
64
|
55
| |
Np-239
|
2.36 d
|
1976
|
1966
| |
Pu-241
|
14.4 d
|
8.6
|
24
| |
Cm-242
|
153 d
|
1.8
|
5.8
| |
Sizewell-B reactor 1100MW released
doses and GLC in Bq per cubic meter (65 Bq = 1mSv)
Wind
Velocity :5m/sec stack height:100m Source term 0.3Btu per hour or 12 million Bq/sec Neutral stability class
Gaussian Plume Model Calculations
Tabular results: - Wind velocities in meters per second Effective Stack heights in meters
- Concentrations in mmg per cubic meter
| Wind Velocity | Effective Stack Height | Concentration at 0 meters | Concentration at 1000 meters | Concentration at 3000 meters | Concentration at 5000 meters | Concentration at 8000 meters | Concentration at 16000 meters | Concentration at 40000 meters | Concentration at 80000 meters | Concentration at 110000 meters | Concentration at 140000 meters | Concentration at 170000 meters |
| 1 | 475 | 0 | 295561 | 101318 | 61125 | 38322 | 19211 | 7697 | 3851 | 2801 | 2201 | 1813 |
| 3 | 225 | 0 | 102180 | 34186 | 20524 | 12832 | 6418 | 2568 | 1284 | 934 | 734 | 604 |
| 5 | 175 | 0 | 61564 | 20540 | 12325 | 7703 | 3852 | 1541 | 771 | 560 | 440 | 363 |
| 7 | 154 | 0 | 44037 | 14678 | 8806 | 5503 | 2752 | 1101 | 550 | 400 | 314 | 259 |
| 9 | 142 | 0 | 34277 | 11419 | 6850 | 4281 | 2140 | 856 | 428 | 311 | 245 | 201 |
| 11 | 134 | 0 | 28058 | 9345 | 5605 | 3503 | 1751 | 700 | 350 | 255 | 200 | 165 |
| 13 | 129 | 0 | 23747 | 7908 | 4743 | 2964 | 1482 | 593 | 296 | 216 | 169 | 139 |
| 15 | 125 | 0 | 20586 | 6854 | 4111 | 2569 | 1284 | 514 | 257 | 187 | 147 | 121 |
| 17 | 122 | 0 | 18166 | 6048 | 3627 | 2267 | 1133 | 453 | 227 | 165 | 130 | 107 |
| 19 | 120 | 0 | 16256 | 5411 | 3246 | 2028 | 1014 | 406 | 203 | 147 | 116 | 95 |
| 21 | 118 | 0 | 14709 | 4896 | 2937 | 1835 | 917 | 367 | 183 | 133 | 105 | 86 |
http://www.shodor.org/Master/environmental/air/plume/index.html
THE CONSEQUENCES OF SPECIFIED RADIOACTIVE RELEASES FROM THE SIZEWELL ‘B’ NUCLEAR STATION ON THE POPULATION: Main results of the countermeasures scenario, using the MARC model
Assumptions:
1) 1 Bq per cubic meter = 0.0156 mJ-hour per cubic meter
2) 1 mJ hour per cubic meter = 1.1 mSv per year
3) 1 Bq per cubic meter = 0.0044 Working Level Month(WLM)
4) 1 WLM = 4 mSv
5) 1 Btu = 1054 Joules
6) 65 Bq per cubic meter = 1 mJ hour per
THE CONSEQUENCES OF SPECIFIED RADIOACTIVE RELEASES FROM THE SIZEWELL ‘B’ NUCLEAR STATION ON THE POPULATION: Main results of the countermeasures scenario, using the MARC model
TABLE -3 TYPE OF ACCIDENT: (UK-1)
Wind direction (North:0o, clockwise)
|
Weather Conditions:D5
|
Weather Conditions: FD
|
Weather Conditions: DR
| |||||||
270o
|
240o
|
210o
|
270o
|
240o
|
210o
|
270o
|
240o
|
210o
| ||
1*.Sheltering1: Surface area2
Maxi. distance from reactor
Population concerned
|
Sq.km
Km
Persons |
2,700
160
450,000 |
2,700
160
245,000 |
1,450
160
115,000 |
820
74
110,000 |
820
74
205,000 |
415
74
130,000 |
4,350
170
725,000 |
4,350
170
4,500,000 |
2,600
170
1,000,000 |
- Evacuation: : Surface area
Maxidistance from reactor
Population concerned
|
Sq.km
Km
Persons |
100
28.5
14,000 |
100
28.5
18,500 |
89
28.5
6,500 |
255
37
22,000 |
255
37
72,000 |
190
37
25,500 |
880
85
115,000 |
880
85
225,000 |
335
62
110,000 |
2.*
- Relocation :
Surface area
Max.distance from reactor
Population concerned
|
Sq.km
Km
Persons
|
200
46
18,500
|
200
46
93,000
|
145
37.5
25,000
|
385
41
28,000
|
385
41
150,000
|
260
38.5
32,000
|
2,700
140
420,000
|
2,700
140
1,500,000
|
1,400
140
545,000
|
3* Decontamination
Surface area
Max. distance from reactor
Population concerned
| Sq.km
Km
Persons
| 75
28.5
13,000
| 75
28.5
11,000
| 73
28.5
4,650
| 330
41
25,000
| 330
41
145,000
| 220
38.5
30,500
| 1,900
115
295,000
| 1,900
115
500,000
| 760
115
235,000
|
4* :Decontamination
Surface area
Max.distance from reactor
Population concerned
|
Sq.km
Km
Persons |
14.5
13
6,200
|
14.5
13
1,700
|
14.5
13
1,950
|
175
31.5
17,500
|
175
31.5
23,500
|
145
31.5
8,500
|
700
76.5
99,000
|
700
76.5
200,000
|
315
62
57,500
|
Time-integral of relocation : Surface area
Population concerned
|
Sq.km-years
Persons years
|
1.45 x 103
2.65 x 105
|
1.45 x 103
3.85 x 105
|
1.4 x 103
1.45 x105
|
6.9 x 103
7.2 x 105
|
6.9 x 103
1.95 x 106
|
5.5 x 103
5.9 x 105
|
3.7 x 104
5.25 x 106
|
3.7 x 104
1.2 x 107
|
1.7 x 104
5.3 x 106
|
5*. Health effects
early deaths
- late deaths (cancer)
|
44
7,050
|
792
20,500
|
23
3,600
|
725
5,650
|
4,610
14,300
|
342
2,920
|
431
9,670
|
2,840
39,700
|
151
8,310
| |
1*Potential Sheltering1: Consequences of emergency counter-measures
2*Consequences of emergency counter-measures:Relocation of population prior to 3*decontamination:Decontaminated area still not re-inhabited after 5 years 4* Decontaminated area still not re-inhabited after 20 years
5*Health effects – as estimated by NRPB3: -
NOTES FOR TABLE 3: 1. This ‘potential sheltering’ corresponds to the application of NRPB countermeasures recommendations in ERL-2. In the calculation of health consequences, sheltering is considered only in the evacuation area, prior to evacuation. 2. ‘Surface areas’ in this Table are land areas only. 3. These health effects have been computed by the NRPB considering only evacuation as a counter-measure. Sheltering is assumed to be required only for evacuated people, prior to evacuation. No specific relocation model is used, but it is assumed that source after evacuation (this implicitly corresponds, relocation).
NOTES FOR TABLE 3: 1. This ‘potential sheltering’ corresponds to the application of NRPB countermeasures recommendations in ERL-2. In the calculation of health consequences, sheltering is considered only in the evacuation area, prior to evacuation. 2. ‘Surface areas’ in this Table are land areas only. 3. These health effects have been computed by the NRPB considering only evacuation as a counter-measure. Sheltering is assumed to be required only for evacuated people, prior to evacuation. No specific relocation model is used, but it is assumed that source after evacuation (this implicitly corresponds, relocation).
FIGURE-1 BASIC CHARACGTERISTICS OF THE COUNTERMEASURES MODEL
ZONE
|
Criterion for countermeasures
|
Extent of Zone
|
Distance downwind
|
Time taken to execute countermeasure1
| ||
Shelter 2, 5 in evacuated areas
|
Evacuate 3,5
|
Relocate 5
| ||||
A
|
Major release of activity to containment
|
60o sector extending 2km downwind
|
0-2km
|
1h
|
2h
|
-
|
B
|
Major release of activity containment
|
60o sector extending 2 to 5 km downwind
|
2-5km
|
1h
|
5h
|
--
|
C
|
Bone marrow dose from all exposure pathways exceeds 0.25 Sv in 7 days4
|
Determined by area over which criterion exceeded
|
5-25 km
25-75km
> 75 km
|
6h
6h
6h
|
12h
1d
2d
|
-
-
-
|
D
|
Whole body y dose from deposited material exceeds 0.25Sv in first year
|
Determined by area over which criterion exceeded
|
5-50km
>50km
|
--
--
|
--
--
|
2d
2d
|
NOTES FOR FIGURE1:
1. The times specified are the intervals between the inititation of the countermeasures and their completion. For areas A and B the time is measured relative to the beginning of the warning time (the beginning of the warning time is taken as the occurrence of vessel melt-through and the durationof the warning time is the period between vessel melt-through and a significant release of activity to the environment (see Table 1 in Appendix)
For area C the time is measured relative to the release of activity to the environment (i.e. no credit taken for warning time)
2. For areas A, B, and C, 90% of the population are assumed indoors and 10% outdoors at the time of the release. Sheltering considered here (which affects only the population which would be evacuated) is assumed to cover the whole population, at the specified time. However, it is possible that, following the NRPB official recommendations expressed in ERL 2, the extent of shelterisng would be far wider and cover more than the population to be evacuated in the following hours or day. In Table 3 of Appendix 1, for instance figures are presented on the possible extent of sheltering order using an exposure criteria of 15 mSv to the bone marrow in 7 days. (this criteria is in the middle of the range recommended by NRPB in ERL2, as shown in Table3, Chapter2). The extent of sheltering would in this case be obviously far wider than the alternative in which only the population to be vacuated would be asked to take shelter. Note that the health effects calculated by the NRPB do not take into account this possible supplementary cou8ntermeasures, nor the intake of iodine tablets.
3. The exposure during evacuation is taken to be approximately that which would have been received outdoors in the following hour had evacuation not occurred.
4. The dose to be used in conjunction with this criterion is evacuated assuming people to be outdoors during the passage of the plume and subsequently to spend 90% of their time indoors and 10% outdoors.
5. Those evacuated or relocated are returned to the affected area when the annual wholedboy v dose from deposited material is less than 10mSv per year after decontamination (assumed to reduce radioactivity levels by a factor of 3)
Source: G.N.Kelly, L.Ferguson, D.Charles,’the Influence of countermeasures on the Predicted Consequences of Degraded Core Accidents for the Sizewell PWRm NRPB-R163, December 1983, p42 Fig.1
TABLE-3 OFFICIAL NRPB RECOMMENDATIONS FOR THE IMPLEMENTATION OF EMERGENCY MEASURES: EMERGENCY REFERENCE LEVELS (ERLs)
(dose equivalent levels in mSV)(1)
Counter-measures
|
Lower Value to:
|
Upper Value to:
| ||||
Whole body
|
Thyroid, lung or other single organ
|
skin
|
Whole body
|
Thyroid, lung or other single organ
|
skin
| |
Evacuation
|
100
|
300
|
1,000
|
500
|
1,500
|
5,000
|
Sheltering
|
5
|
50
|
50
|
25
|
250
|
250
|
Distribution of stable iodine tablets
|
--
|
50
|
50
|
--
|
250
|
--
|
(1) : 1mSv = 0.1rem; 1Sv=100 rems
[2] http://www.ccohs.ca/oshanswers/phys_agents/ionizing.html
[conversion of Exposure,Bq or Curies into Body Doses,in mSv]
[2] http://www.ccohs.ca/oshanswers/phys_agents/ionizing.html
[conversion of Exposure,Bq or Curies into Body Doses,in mSv]
Source: NRPB, Emergency Reference levels: Criteria for limiting doses to the Public in the Event of Accidental Exposure to Radiation, ERL-2, July 1981, p.4
TABLE4 SHORT TERM EFFECTS OF EXPOSURE ON POPULATION HEALTH AND THE EFFECTS OF EMERGENCY COUNTERMEASURES: FOUR EXAMPLES OF SELECTED SCENARIOS (1)
Release type
|
Weather condi-tions
|
Wind direc-tion
|
No. of early deaths
|
No. of prodomal vomiting
(2)
|
Area evacuated (sq.km)
|
Max. distance (A)
|
people evacua-ted
(B)
|
shelter- Area (3)
(C )
|
persons sheltered (3)
(D)
|
UK1
|
FD
|
270O
|
725
|
2,300
|
255
|
35
|
22,000
|
820
|
205,000
|
Uk1c
|
D5
|
240O
|
0
|
2
|
17.5
|
8.6
|
5,350
|
325
|
155,000
|
Uk9
|
DR
|
210O
|
0
|
0
|
12.5
|
5
|
1,100
|
23
|
3,200
|
UK11
|
D5
|
240O
|
0
|
0
|
13
|
5
|
4,750
|
13
|
4,750
|
A) Max. distance of evacuation(km)
B) No. of people evacuated
C) Area of sheltering using NRPB’s ERL-2 criteria
D) Total No. of persons sheltering using NRPB’s ERL-2 criteria
(1): Results for all 36 scenarios can be found in Appendix1, Tables 3 and 5. Criteria for countermeasures described in Table 4.
(2) Not estimated by NRPB; evaluated by using the ratio between early deaths and prodomal vomiting in each type of release in NRPB –R137. The number of people suffering from prodomal vomiting includes those who will die. Figures are estimated after taking into account counter-measures implementation.
(3) Includes the number of people or area which will be evacuated some hours afterwards (shown in above columns 8 and 6) as well as those people or areas for which no evacuation will take place but for which the exposure dose is within the range defined in NRPB’s ERLs for sheltering. The latter group taking shelter are not considered in estimating early health effects.
For Chernobyl accident largest releases occurred. All of the noble gas and major fractions of volatile fission products were released on 26th April in Stage-I the initiating in-core transient blew off the pile cap and ejected fragments of hot fuel along with volatile fission products directly into the environment. 5% of core elementary of volatile fission products and 0.3% to 0.4% of the non-volatile nuclides were released to the atmosphere. In second stage from 26th April to 2nd May in-core fires mainly of the moderative graphite promoted continuing releases from 26th to 27th. On 27th dumping of lead, dolomite, clay and sand heaps on to the core debris caused steady reduction in radioactive releases until 2nd May and the fuel temperatures were around 800oC . But in the 3rd stage from 3rd to 5th May core temperatures rose to 2000oC caused by decay heat when a second peak release occurred on May 5th. Revolatalisation of material trapped earlier in the filter bed perhaps caused high releases. During the 4th stage on May 6th radioactive release reduced due to injection of high flows of nitrogen under the core debris and termination of fuel oxidation drastically reduce emissions of 50 mega curies of released radioactivity was present in the environment.
EFFECT OF LOCATION ON THE NUMBER OF FATAL CANCERS: SOME EXAMPLES FROM NRPB SENSITIVITY ANALYSIS(0)
Type of release
|
Weather conditions (wind direction:270o)
|
Relocation limited to evacuation area
|
Relocation extended to areas in which reference dose criteria is reached
| ||||
No. of late cancer
|
Time interval of relocated people (person-years)
|
No.of people relocated (persons)
|
No. of late cancers
|
Time interval of relocated people (person-years)
|
No.of people relocated (persons)
| ||
R1(1)
|
M1(3)
M2(2)
|
4,936(5)
25,450
|
108,000
5,570,000
|
12,900(6)
198,000
|
4,760
12,040
|
150,000(7)
10,200,000 |
22,000
718,000
|
R2(2)
|
M1
M2
|
2,067
14,730
|
36,800
1,470,000
|
4,740
44,000
|
2,045
10,990
|
580,000
5,630,000
|
9,400
360,000
|
Source: NRPB-M103, tables 8,9,10, pp39-41
(0)methodology and parameters comparable to those used in this study
(1)comparable to UK1
(2)of the same type as UK1c,but with different parameters
(3)M1 is the same as D5 used here
(4)M2 is equivalent to M1, but with 1mm x h-1rain after 3 hours
(5)in the NRPB estimate for this study, this figure is 7,050
(6)in our estimates (See Appendix 1, Table 3) the number of people evacuated in 14,000
(7)Our estimate is 265,000 because of slightly different return criterion and different geographical distribution
grid
(8)our estimate is 18,500
For Chernobyl accident largest releases occurred. All of the noble gas and major fractions of volatile fission products were released on 26th April in Stage-I the initiating in-core transient blew off the pile cap and ejected fragments of hot fuel along with volatile fission products directly into the environment. 5% of core elementary of volatile fission products and 0.3% to 0.4% of the non-volatile nuclides were released to the atmosphere. In second stage from 26th April to 2nd May in-core fires mainly of the moderative graphite promoted continuing releases from 26th to 27th. On 27th dumping of lead, dolomite, clay and sand heaps on to the core debris caused steady reduction in radioactive releases until 2nd May and the fuel temperatures were around 800oC . But in the 3rd stage from 3rd to 5th May core temperatures rose to 2000oC caused by decay heat when a second peak release occurred on May 5th. Revolatalisation of material trapped earlier in the filter bed perhaps caused high releases. During the 4th stage on May 6th radioactive release reduced due to injection of high flows of nitrogen under the core debris and termination of fuel oxidation drastically reduce emissions of 50 mega curies of released radioactivity was present in the environment.
No comments:
Post a Comment