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
(No Transcript)
15
(No Transcript)
16
(No Transcript)
17
Plume Dispersion
18
(No Transcript)
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
(No Transcript)
52
Fukushima
Chiba
53
(No Transcript)
54
(No Transcript)
55
IAEA ACCIDENT SCALE
56
(No Transcript)