Nuclear Power and Public Health Measures in Nuclear Plant Emergencies


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  • Present the objectives of this lesson to the students, and note that two accidents will be discussed, one with minor consequences, and one with major consequences.
  • Take the students through this simple schematic of a power reactor. Note that the essential difference between a nuclear plant and a fossil fuel plant is the method of producing heat to boil water.
  • Take the students through this simple schematic of a power reactor. Note that the essential difference between a nuclear plant and a fossil fuel plant is the method of producing heat to boil water.
  • Describe the worst case LOCA for a power reactor, and discuss the popular conception of a meltdown.
  • Note that U.S. reactors using metal-oxide fuels have a built-in safety mechanism. Briefly describe the ECCS, core catcher, and containment systems.
  • Briefly discuss each possible exposure pathway, and identify the principal radionuclides of concern for each.
  • Discuss atmospheric releases, and the extensive modelling effort that goes into calculating the actual plume dispersion. Mention DOE’s ARAC capability for this effort.
  • Briefly discuss each exposure pathway; ask the students to identify some radionuclides that might be involved in each.
  • Describe the concept of emergency planning zone; identify the two zones for the two different exposure pathways.
  • Define the exclusion area; note that it does not have a set distance from the plant; rather local terrain and meteorological conditions are taken into account to identify the approximate locations of the boundary.
  • Briefly describe the standard classification scheme for emergencies at a power reactor. Mention that the IAEA has a seven-point classification scheme, on which TMI was a 5 and Chornobyl was a 7.
  • Note that the plant site staff is initially responsible for implementing appropriate actions. In the case of a commercial nuclear power plant, federal authorities are quickly involved.
  • Briefly review the appropriate response actions for any accident; emphasize the need to weigh risks to responders against possible life-saving actions to be undertaken.
  • Discuss these figures, emphasizing that they are guidelines, not regulations.
  • Note other planning considerations; ask the class if it seems more reasonable to discuss the application of these guidelines in advance of a hypothetical incident, or during an actual incident.
  • Ask the class for possible reasons for the age preference, and what health effects might be expected at 1 Sv (100 rem)
  • Ask the class to identify the most likely origin of population doses of this magnitude, and the appropriate protective measure(s).
  • Discuss delayed health effects. Again ask the class to identify the possible origins of these doses and available protective measures.
  • Ask the class to identify some of the risks or other considerations that may affect the net benefit of a proposed protective action,
  • Identify the primary protective actions available to the public; have the class suggest some of the other actions that would avoid dose.
  • Discuss these actions in the context of a large release of radioactivity in the plume; ask the class how the potential doses could be estimated.
  • Discuss the logistical requirements for these actions; ask the class for examples of where and how such actions have been undertaken.
  • Note the definition of the intermediate phase, and point out the exposure conditions that would be ameliorated by the proposed actions.
  • Note the late phase/long-term actions; ask the class what sort of health effects might be expected from these exposure levels.
  • Identify the logistical requirements and discuss the implications for medical care and planning.
  • Briefly discuss the various food chain pathways
  • Note that these action levels have been proposed by the IAEA; US levels are quite similar.
  • Point out that the levels for infants are more restrictive only for the transuranics; ask the class why this might be so.
  • List the logistical requirements for alternate food sources; ask students to describe public health measures that would have to implemented concurrently.
  • Bottom Left, TMI-2 Top right Dick Thornburgh (foreground), Pennsylvania's governor at the time of the Three Mile Island reactor accident, and Harold Denton , from the NRC and President Carter 's personal representative on the site, talk to the press about the situation. Bottom Right Jimmy Carter, touring the reactor's control room, calmed public fears with his visit.
  • Describe the initial circumstances of the TMI accident
  • Continue the description of the accident; ask the students what their recommendations would be at this point
  • Continue the description of the accident; ask the students what the medical planning requirements would be for these actions
  • Conclude the description; emphasize that although the accident was a financial disaster, there were no detectable health consequences to the general public.
  • Bottom left: Memorial for the firemen Right: With sarcophagus
  • Briefly review the circumstances of the Chornobyl accident and describe the protective actions implemented in response.
  • Note the massive logistical requirements for this effort; ask the students if they think such actions could be accomplished easily in the U.S.
  • Review the health effects; note that the expected increase in leukemia/lymphoma among liquidators has not appeared, but a tremendous increase in childhood thyroid cancer resulted.
  • Nuclear Power and Public Health Measures in Nuclear Plant Emergencies

    1. 1. Nuclear Power and Public Health Measures in Nuclear Plant Emergencies R. E. Toohey, Ph.D., CHP
    2. 2. Lesson Objectives <ul><li>Familiarize students with the basic characteristics of nuclear power plant accidents </li></ul><ul><li>Describe planning guidelines and considerations for accident response </li></ul><ul><li>Apply considerations to the accidents at Three Mile Island and Chornobyl </li></ul>
    3. 3. The Fission Process Fissile nuclide neutron neutrons Fission products
    4. 4. Fission Product Yield by Mass
    5. 5. Approximate Distribution of Fission Energy <ul><li>MeV </li></ul><ul><li>Kinetic energy of fission fragments 165 </li></ul><ul><li>Instantaneous gamma-ray energy 7 </li></ul><ul><li>Kinetic energy of fission neutrons 5 </li></ul><ul><li>Beta particles form fission products 7 </li></ul><ul><li>Gamma rays from fission products 6 </li></ul><ul><li>Neutrinos 10 </li></ul><ul><li>Total fission energy  200 </li></ul>
    6. 6. Neutron Balance <ul><li>Neutrons released in fission may be lost by escaping the container, or by being absorbed by non-fissile materials </li></ul><ul><li>If more neutrons are lost than are produced, the reaction is subcritical and dies out (“safe”) </li></ul><ul><li>If the number lost equals the number produced, the reaction is critical (steady state, e.g., a reactor) </li></ul><ul><li>If the fewer neutrons are lost than are produced, the reaction is supercritical and energy release increases exponentially (e.g., a nuclear weapon) </li></ul>
    7. 7. Nuclear Reactor Schematics Pressurized Water Nuclear Reactor
    8. 8. Nuclear Reactor Schematics Boiling Water Nuclear Reactor
    9. 9. Reactor Accidents <ul><li>Loss of Coolant Accident (LOCA) </li></ul><ul><li>Pipe breaks in the primary loop remove cooling water from the core, leading to an increase in core temperature </li></ul><ul><li>Fuel rods fail, releasing volatile radionuclides (iodine, cesium, etc.) </li></ul><ul><li>Core meltdown—all the way to China? </li></ul>
    10. 10. What Really Happens <ul><li>Fuel expands, reducing reaction rate </li></ul><ul><li>Reactor scrams with gravity-induced lowering of control rods </li></ul><ul><li>Emergency core cooling system activates and floods core </li></ul><ul><li>Even if core does melt, containment systems works, as at TMI </li></ul>
    11. 11. Reactor Accidents <ul><li>Most likely route of exposure to the public would be a release to the air. </li></ul><ul><li>Plume materials could consist of particulates, vapors, mists, or gases. </li></ul><ul><li>Plume could be short duration (puff) or continuous. </li></ul><ul><li>Particulates will tend to settle to the ground as the plume drifts from the plant. </li></ul>
    12. 12. Atmospheric Releases <ul><li>Volatile radionuclides may be released from containment </li></ul><ul><li>Principal radionuclide of concern is 131 I </li></ul><ul><li>Releases are monitored by sensors placed around plant </li></ul><ul><li>Plume dispersal is mathematically modeled, taking local terrain into account </li></ul>
    13. 13. Airborne Radioactivity <ul><li>“ Source term” - source of the exposure </li></ul><ul><ul><li>examples - stack effluent, burning aircraft, etc. </li></ul></ul><ul><ul><li>complex function of the material (quantity and type), flow rate,distribution,etc. </li></ul></ul><ul><ul><li>units - activity/unit of time (e.g., Ci/sec; Bq/sec) </li></ul></ul><ul><li>Population/personnel exposure </li></ul><ul><ul><li>airborne (radioactivity) concentration [µCi/ml; Bq/m 3 ] </li></ul></ul><ul><ul><li>resuspended (ground/surface) contamination [µCi/ft 2 ; Bq/m 2  µCi/ml; Bq/m 3 ] </li></ul></ul>
    14. 17. Plume Dispersion
    15. 19. Exposure Pathways <ul><li>External dose from plume overhead (cloud shine) or material on ground (ground shine). </li></ul><ul><li>Internal dose due to inhaling materials directly from plume or from stirred dust. </li></ul><ul><li>Ingestion of contaminated materials in the form of food or water. </li></ul>
    16. 20. Emergency Planning Zone <ul><li>Areas for which planning is needed to assure that prompt and effective actions can be taken to protect the public </li></ul><ul><li>Plume EPZ: radius of approximately 10 miles </li></ul><ul><li>Ingestion EPZ: radius of approximately 50 miles </li></ul>
    17. 21. Exclusion Area <ul><li>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 </li></ul>
    18. 22. Classification of Emergencies <ul><li>Unusual Event: a potential degradation of the level of safety of the plant </li></ul><ul><li>Alert: readiness of on-site and off-site response organizations increased. </li></ul><ul><li>Site Area Emergency: event resulting in major decrease in protection of public or on-site personnel. </li></ul><ul><li>General Emergency: event resulting in risk requiring implementation of urgent off-site actions. </li></ul>
    19. 23. Who is Responsible for Actions? <ul><li>Staff at the facility at the time of the accident. </li></ul><ul><li>Local officials. </li></ul><ul><li>National and regional officials. </li></ul>
    20. 24. Accident response <ul><li>Independent of the type of accident: </li></ul><ul><ul><li>determine and control hazards to responders & victims </li></ul></ul><ul><ul><li>assess, treat, evacuate victims </li></ul></ul><ul><ul><li>implement further control procedures </li></ul></ul><ul><ul><li>assess personnel exposures </li></ul></ul><ul><ul><li>monitor clean-up </li></ul></ul><ul><ul><li>verify clean-up effectiveness </li></ul></ul>
    21. 25. Exposure Guidance for Responders <ul><li>All activities: </li></ul><ul><ul><li>5 rem TEDE, 15 rem eye, 50 rem organ </li></ul></ul><ul><li>Protecting major/valuable property: </li></ul><ul><ul><li>10 rem TEDE, 30 rem eye, 100 rem organ </li></ul></ul><ul><li>Life saving or protecting large populations: </li></ul><ul><ul><li>25 rem TEDE, 75 rem eye, 250 rem organ </li></ul></ul><ul><li>Exceed latter only on a voluntary basis by persons fully aware of risks involved </li></ul>
    22. 26. Additional Guidance for Responders <ul><li>Risk of injury in rescue and recovery operations shall be minimized </li></ul><ul><li>Risks to responders shall be weighed against benefits to be gained </li></ul><ul><li>Rescue actions involving substantial personal risk shall be performed by volunteers </li></ul><ul><li>Each individual subjected to emergency dose limits shall be thoroughly briefed </li></ul>
    23. 27. Some More Guidance for Responders <ul><li>Volunteers above age of 45 preferred </li></ul><ul><li>TEDE shall not exceed 1 Sv (100 rem) </li></ul><ul><li>Internal exposure should be minimized </li></ul><ul><li>Exposure under such conditions should be limited to once in a lifetime </li></ul><ul><li>Persons receiving exposures above 250 mSv (25 rem) should avoid procreation for several months </li></ul>
    24. 28. Guidance for Population Protection: 1st Principle <ul><li>Intervention to avoid serious prompt health effects should be carried out as a first priority </li></ul><ul><ul><li>serious prompt health effects may be expected in susceptible populations at doses > 1 Gy (100 rad), and in all at doses > 2 Gy (200 rad) (whole-body) </li></ul></ul><ul><ul><li>evacuation is usually the only effective intervention measure in high dose situations </li></ul></ul>
    25. 29. Guidance for Population Protection: 2nd Principle <ul><li>Protective actions to avoid delayed health effects should be initiated when they will produce more good than harm in the affected population </li></ul><ul><ul><li>iodine prophylaxis in case of radioiodine releases </li></ul></ul><ul><ul><li>sheltering in place, evacuation, or temporary relocation </li></ul></ul>
    26. 30. Guidance for Population Protection: 3rd Principle <ul><li>These actions should be introduced and withdrawn at levels that produce a maximum net benefit to the population </li></ul><ul><ul><li>guidelines available from USEPA, IAEA, and IRPA </li></ul></ul><ul><ul><li>may well be driven primarily by logistical considerations (e.g., availability of transport, availability of temporary shelters, etc.) </li></ul></ul>
    27. 31. Protective Actions Available to the Public <ul><li>Sheltering </li></ul><ul><li>Evacuation </li></ul><ul><li>Stable Iodine Prophylaxis </li></ul><ul><li>Other actions to reduce dose </li></ul>
    28. 32. Guidelines for Protective Actions <ul><li>Early phase: initiation of release to about 4 days </li></ul><ul><li>Evacuate to avoid TEDE of 1 - 5 rem </li></ul><ul><li>Shelter in place if equal or greater protection afforded by doing so </li></ul><ul><li>Administer KI to prevent thyroid dose of 25 rem </li></ul>
    29. 33. Logistical Requirements for Early Protective Actions <ul><li>Sheltering: </li></ul><ul><ul><li>Normal emergency services; additional police </li></ul></ul><ul><li>Evacuation: </li></ul><ul><ul><li>Transportation </li></ul></ul><ul><ul><li>Temporary housing (schools, tentage, etc.) </li></ul></ul><ul><ul><li>Food and water </li></ul></ul><ul><ul><li>Sanitation </li></ul></ul><ul><li>Iodine prophylaxis: </li></ul><ul><ul><li>KI tablets (or tincture of iodine on skin) </li></ul></ul>
    30. 34. Intermediate Phase PAG’s <ul><li>Intermediate phase: source or release is under control, and additional protective actions are being implemented; weeks to months </li></ul><ul><li>Relocate to avoid 2 rem TEDE or 100 rem to skin in first year </li></ul><ul><li>Apply dose reduction techniques (e.g., decontamination, hot spot removal) if less than 2 rem TEDE anticipated in 1st year </li></ul>
    31. 35. Late Phase PAG’s <ul><li>Late phase: recovery phase; site remediation and long-term mitigation; months to years </li></ul><ul><li>TEDE not to exceed 0.5 rem in any year after the first </li></ul><ul><li>Cumulative dose (TEDE) from all years not to exceed 5 rem </li></ul>
    32. 36. Logistical Requirements for Later Protective Actions <ul><li>Temporary relocation: </li></ul><ul><ul><li>Transportation </li></ul></ul><ul><ul><li>Housing & furnishings </li></ul></ul><ul><ul><li>Security </li></ul></ul><ul><ul><li>Decontamination equipment & waste disposal </li></ul></ul><ul><li>Permanent resettlement: </li></ul><ul><ul><li>Transportation </li></ul></ul><ul><ul><li>Housing & furnishings </li></ul></ul><ul><ul><li>Security </li></ul></ul>
    33. 37. Food Chain Considerations <ul><li>Early times: radioiodine pathway is air to soil to vegetation to cow to milk to man </li></ul><ul><li>Late times: cesium and strontium pathways include </li></ul><ul><ul><li>air to soil to food plants to man </li></ul></ul><ul><ul><li>air to soil to forage plants to food animals to man </li></ul></ul><ul><ul><li>air to water to aquatic vegetation to fish to man </li></ul></ul>
    34. 38. Action Levels for Foodstuffs for General Consumption Radionuclide Action Level 89 Sr 103 Ru, 106 Ru 134 Cs, 137 Cs 131 I 1 kBq/kg (30 pCi/g) 90 S 0.1 kBq/kg (3 pCi/g) 238 Pu, 239 Pu 241 Am 0.01 kBq/kg (0.3 pCi/g)
    35. 39. Action Levels for Milk, Infant Foods and Drinking Water Radionuclide Action Level 89 Sr 103 Ru, 106 Ru 134 Cs, 137 Cs 1 kBq/kg (30 pCi/g) 90 S 131 I 0.1 kBq/kg (3 pCi/g) 238 Pu, 239 Pu 241 Am 0.001 kBq/kg (0.03 pCi/g)
    36. 40. Logistical Requirements for Control of Food and Water <ul><li>Monitoring capability </li></ul><ul><li>Centralized distribution </li></ul><ul><li>Alternate (distant) sources </li></ul><ul><li>In case of food shortages, alternate (higher) action levels should be instituted </li></ul>
    37. 41. Three Mile Island Goldsboro, Pennsylvania
    38. 42. Three Mile Island <ul><li>Unit 2 feedwater pump tripped at 4:00 a.m. on March 28, 1979 </li></ul><ul><li>Reactor scrammed 8 seconds later </li></ul><ul><li>Pressure relief valve stuck open, so ECCS water lost </li></ul><ul><li>Pressurizer (only way of controlling water level and pressure in primary loop) filling up, so high pressure injection pumps shut down </li></ul>
    39. 43. TMI, con’t <ul><li>Core partially uncovered by 6:15 a.m. </li></ul><ul><li>Site emergency declared at 7:00 a.m. </li></ul><ul><li>General emergency declared at 7:24 a.m. </li></ul><ul><li>Radiation levels indicated fuel damage around 8:00 a.m. </li></ul><ul><li>Core covered with water by 10:30 a.m. </li></ul>
    40. 44. TMI, con’t <ul><li>State route 441 closed at 12:45 p.m. </li></ul><ul><li>Everything fairly calm the next day </li></ul><ul><li>Because of confusion and concern over the “hydrogen bubble”, evacuation advised for pregnant women and preschool children with 5 miles at 12:30 on March 30 </li></ul><ul><li>Schools closed and further evacuation planned </li></ul><ul><li>Supplies of KI shipped in </li></ul>
    41. 45. TMI, con’t <ul><li>NRC did not share info that hydrogen bubble was really not a threat </li></ul><ul><li>Many families, including health care providers, left on their own </li></ul><ul><li>Schools reopened April 4 </li></ul><ul><li>5-mile evacuation advisory withdrawn on April 9 </li></ul><ul><li>Final clean-up cost was $1E9 </li></ul>
    42. 46. Chernobyl
    43. 47. Chernobyl
    44. 48. The Chernobyl Experience <ul><li>I. Evacuation: </li></ul><ul><ul><li>Accident occurred 26 April 1986 at 1:23 am </li></ul></ul><ul><ul><li>49,000 evacuated from Pripyat (3 km from station) on April 27 </li></ul></ul><ul><ul><li>53,000 evacuated from 30-km exclusion zone over next 10 days </li></ul></ul>
    45. 49. The Chernobyl Experience <ul><li>II. Sheltering: </li></ul><ul><ul><li>270,000 persons remained in controlled area (10,300 sq. km with 137 Cs > 15 Ci/sq. km) </li></ul></ul><ul><ul><li>delivery of non-contaminated meat and dairy products continues </li></ul></ul><ul><ul><li>agricultural products monitored for contamination before release for consumption </li></ul></ul><ul><ul><li>slow decontamination of settlements </li></ul></ul><ul><ul><li>5 year external dose about 5 rem </li></ul></ul>
    46. 50. The Chernobyl Experience <ul><li>III. Health effects: </li></ul><ul><ul><li>2 acute trauma fatalities </li></ul></ul><ul><ul><li>237 suspected cases of acute radiation syndrome </li></ul></ul><ul><ul><li>103 confirmed </li></ul></ul><ul><ul><li>28 prompt fatalities </li></ul></ul><ul><ul><li>10 fatalities during 10-year follow-up </li></ul></ul><ul><ul><li>54 local radiation injuries, 14 severe </li></ul></ul><ul><ul><li>10--50-fold increase in childhood thyroid cancer </li></ul></ul>