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Title: Nuclear Power and Public Health Measures in Nuclear Plant Emergencies


1
Nuclear Power and Public Health Measures in
Nuclear Plant Emergencies
R. E. Toohey, Ph.D., CHP
2
Lesson Objectives
  • Familiarize students with the basic
    characteristics of nuclear power plant accidents
  • Describe planning guidelines and considerations
    for accident response
  • Apply considerations to the accidents at Three
    Mile Island and Chornobyl

3
The Fission Process
neutron
Fissile nuclide
neutrons
Fission products
4
Fission Product Yield by Mass
5
Approximate Distribution of Fission Energy
  • MeV
  • Kinetic energy of fission fragments 165
  • Instantaneous gamma-ray energy 7
  • Kinetic energy of fission neutrons
    5
  • Beta particles form fission products 7
  • Gamma rays from fission products 6
  • Neutrinos
    10
  • Total fission energy
    ?200

6
Neutron Balance
  • Neutrons released in fission may be lost by
    escaping the container, or by being absorbed by
    non-fissile materials
  • If more neutrons are lost than are produced, the
    reaction is subcritical and dies out (safe)
  • If the number lost equals the number produced,
    the reaction is critical (steady state, e.g., a
    reactor)
  • If the fewer neutrons are lost than are produced,
    the reaction is supercritical and energy release
    increases exponentially (e.g., a nuclear weapon)

7
Nuclear Reactor Schematics
Pressurized Water Nuclear Reactor
8
Nuclear Reactor Schematics
Boiling Water Nuclear Reactor
9
Reactor Accidents
  • Loss of Coolant Accident (LOCA)
  • Pipe breaks in the primary loop remove cooling
    water from the core, leading to an increase in
    core temperature
  • Fuel rods fail, releasing volatile radionuclides
    (iodine, cesium, etc.)
  • Core meltdownall the way to China?

10
What Really Happens
  • Fuel expands, reducing reaction rate
  • Reactor scrams with gravity-induced lowering of
    control rods
  • Emergency core cooling system activates and
    floods core
  • Even if core does melt, containment systems
    works, as at TMI

11
Reactor Accidents
  • Most likely route of exposure to the public would
    be a release to the air.
  • Plume materials could consist of particulates,
    vapors, mists, or gases.
  • Plume could be short duration (puff) or
    continuous.
  • Particulates will tend to settle to the ground as
    the plume drifts from the plant.

12
Atmospheric Releases
  • Volatile radionuclides may be released from
    containment
  • Principal radionuclide of concern is 131I
  • Releases are monitored by sensors placed around
    plant
  • Plume dispersal is mathematically modeled, taking
    local terrain into account

13
Airborne Radioactivity
  • Source term - source of the exposure
  • examples - stack effluent, burning aircraft, etc.
  • complex function of the material (quantity and
    type), flow rate,distribution,etc.
  • units - activity/unit of time (e.g., Ci/sec
    Bq/sec)
  • Population/personnel exposure
  • airborne (radioactivity) concentration
    µCi/ml Bq/m3
  • resuspended (ground/surface) contamination
    µCi/ft2 Bq/m2 ?µCi/ml Bq/m3

14
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15
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16
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17
Plume Dispersion
18
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19
Exposure Pathways
  • External dose from plume overhead (cloud shine)
    or material on ground (ground shine).
  • Internal dose due to inhaling materials directly
    from plume or from stirred dust.
  • Ingestion of contaminated materials in the form
    of food or water.

20
Emergency Planning Zone
  • Areas for which planning is needed to assure that
    prompt and effective actions can be taken to
    protect the public
  • Plume EPZ radius of approximately 10 miles
  • Ingestion EPZ radius of approximately 50 miles

21
Exclusion Area
  • An area surrounding the plant such that an
    individual located at any point on its boundary
    will not receive a dose to the whole body
    exceeding 250 mSv (25 rem) nor a dose to the
    thyroid exceeding 3 Sv (300 rem) within 2 hours
    of the postulated incident

22
Classification of Emergencies
  • Unusual Event a potential degradation of the
    level of safety of the plant
  • Alert readiness of on-site and off-site
    response organizations increased.
  • Site Area Emergency event resulting in major
    decrease in protection of public or on-site
    personnel.
  • General Emergency event resulting in risk
    requiring implementation of urgent off-site
    actions.

23
Who is Responsible for Actions?
  • Staff at the facility at the time of the
    accident.
  • Local officials.
  • National and regional officials.

24
Accident response
  • Independent of the type of accident
  • determine and control hazards to responders
    victims
  • assess, treat, evacuate victims
  • implement further control procedures
  • assess personnel exposures
  • monitor clean-up
  • verify clean-up effectiveness

25
Exposure Guidance for Responders
  • All activities
  • 5 rem TEDE, 15 rem eye, 50 rem organ
  • Protecting major/valuable property
  • 10 rem TEDE, 30 rem eye, 100 rem organ
  • Life saving or protecting large populations
  • 25 rem TEDE, 75 rem eye, 250 rem organ
  • Exceed latter only on a voluntary basis by
    persons fully aware of risks involved

26
Additional Guidance for Responders
  • Risk of injury in rescue and recovery operations
    shall be minimized
  • Risks to responders shall be weighed against
    benefits to be gained
  • Rescue actions involving substantial personal
    risk shall be performed by volunteers
  • Each individual subjected to emergency dose
    limits shall be thoroughly briefed

27
Some More Guidance for Responders
  • Volunteers above age of 45 preferred
  • TEDE shall not exceed 1 Sv (100 rem)
  • Internal exposure should be minimized
  • Exposure under such conditions should be limited
    to once in a lifetime
  • Persons receiving exposures above 250 mSv (25
    rem) should avoid procreation for several months

28
Guidance for Population Protection 1st Principle
  • Intervention to avoid serious prompt health
    effects should be carried out as a first priority
  • serious prompt health effects may be expected in
    susceptible populations at doses gt 1 Gy (100
    rad), and in all at doses gt 2 Gy (200 rad)
    (whole-body)
  • evacuation is usually the only effective
    intervention measure in high dose situations

29
Guidance for Population Protection 2nd Principle
  • Protective actions to avoid delayed health
    effects should be initiated when they will
    produce more good than harm in the affected
    population
  • iodine prophylaxis in case of radioiodine
    releases
  • sheltering in place, evacuation, or temporary
    relocation

30
Guidance for Population Protection 3rd Principle
  • These actions should be introduced and withdrawn
    at levels that produce a maximum net benefit to
    the population
  • guidelines available from USEPA, IAEA, and IRPA
  • may well be driven primarily by logistical
    considerations (e.g., availability of transport,
    availability of temporary shelters, etc.)

31
Protective Actions Available to the Public
  • Sheltering
  • Evacuation
  • Stable Iodine Prophylaxis
  • Other actions to reduce dose

32
Guidelines for Protective Actions
  • Early phase initiation of release to about 4
    days
  • Evacuate to avoid TEDE of 1 - 5 rem
  • Shelter in place if equal or greater protection
    afforded by doing so
  • Administer KI to prevent thyroid dose of 25 rem

33
Logistical Requirements for Early Protective
Actions
  • Sheltering
  • Normal emergency services additional police
  • Evacuation
  • Transportation
  • Temporary housing (schools, tentage, etc.)
  • Food and water
  • Sanitation
  • Iodine prophylaxis
  • KI tablets (or tincture of iodine on skin)

34
Intermediate Phase PAGs
  • Intermediate phase source or release is under
    control, and additional protective actions are
    being implemented weeks to months
  • Relocate to avoid 2 rem TEDE or 100 rem to skin
    in first year
  • Apply dose reduction techniques (e.g.,
    decontamination, hot spot removal) if less than 2
    rem TEDE anticipated in 1st year

35
Late Phase PAGs
  • Late phase recovery phase site remediation and
    long-term mitigation months to years
  • TEDE not to exceed 0.5 rem in any year after the
    first
  • Cumulative dose (TEDE) from all years not to
    exceed 5 rem

36
Logistical Requirements forLater Protective
Actions
  • Temporary relocation
  • Transportation
  • Housing furnishings
  • Security
  • Decontamination equipment waste disposal
  • Permanent resettlement
  • Transportation
  • Housing furnishings
  • Security

37
Food Chain Considerations
  • Early times radioiodine pathway is air to soil
    to vegetation to cow to milk to man
  • Late times cesium and strontium pathways
    include
  • air to soil to food plants to man
  • air to soil to forage plants to food animals to
    man
  • air to water to aquatic vegetation to fish to man

38
Action Levels for Foodstuffs for General
Consumption
Radionuclide Action Level
89Sr 103Ru, 106Ru 134Cs,137Cs 131I 1 kBq/kg (30 pCi/g)
90S 0.1 kBq/kg (3 pCi/g)
238Pu, 239Pu 241Am 0.01 kBq/kg (0.3 pCi/g)
39
Action Levels for Milk, Infant Foods and Drinking
Water
Radionuclide Action Level
89Sr 103Ru, 106Ru 134Cs,137Cs 1 kBq/kg (30 pCi/g)
90S 131I 0.1 kBq/kg (3 pCi/g)
238Pu, 239Pu 241Am 0.001 kBq/kg (0.03 pCi/g)
40
Logistical Requirements for Control of Food and
Water
  • Monitoring capability
  • Centralized distribution
  • Alternate (distant) sources
  • In case of food shortages, alternate (higher)
    action levels should be instituted

41
Three Mile Island
42
Three Mile Island
  • Unit 2 feedwater pump tripped at 400 a.m. on
    March 28, 1979
  • Reactor scrammed 8 seconds later
  • Pressure relief valve stuck open, so ECCS water
    lost
  • Pressurizer (only way of controlling water level
    and pressure in primary loop) filling up, so high
    pressure injection pumps shut down

43
TMI, cont
  • Core partially uncovered by 615 a.m.
  • Site emergency declared at 700 a.m.
  • General emergency declared at 724 a.m.
  • Radiation levels indicated fuel damage around
    800 a.m.
  • Core covered with water by 1030 a.m.

44
TMI, cont
  • State route 441 closed at 1245 p.m.
  • Everything fairly calm the next day
  • Because of confusion and concern over the
    hydrogen bubble, evacuation advised for
    pregnant women and preschool children with 5
    miles at 1230 on March 30
  • Schools closed and further evacuation planned
  • Supplies of KI shipped in

45
TMI, cont
  • NRC did not share info that hydrogen bubble was
    really not a threat
  • Many families, including health care providers,
    left on their own
  • Schools reopened April 4
  • 5-mile evacuation advisory withdrawn on April 9
  • Final clean-up cost was 1E9

46
Chernobyl
47
Chernobyl
48
The Chernobyl Experience
  • I. Evacuation
  • Accident occurred 26 April 1986 at 123 am
  • 49,000 evacuated from Pripyat (3 km from station)
    on April 27
  • 53,000 evacuated from 30-km exclusion zone over
    next 10 days

49
The Chernobyl Experience
  • II. Sheltering
  • 270,000 persons remained in controlled area
    (10,300 sq. km with 137Cs gt 15 Ci/sq. km)
  • delivery of non-contaminated meat and dairy
    products continues
  • agricultural products monitored for contamination
    before release for consumption
  • slow decontamination of settlements
  • 5 year external dose about 5 rem

50
The Chernobyl Experience
  • III. Health effects
  • 2 acute trauma fatalities
  • 237 suspected cases of acute radiation syndrome
  • 103 confirmed
  • 28 prompt fatalities
  • 10 fatalities during 10-year follow-up
  • 54 local radiation injuries, 14 severe
  • 10--50-fold increase in childhood thyroid cancer

51
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52
Fukushima
Chiba
53
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54
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55
IAEA ACCIDENT SCALE
56
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