Nuclear Power and Public Health Measures in Nuclear Plant Emergencies R. E. Toohey, Ph.D., CHP

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

The Fission Process Fissile nuclide neutron neutrons Fission products

Fission Product Yield by Mass

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

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)

Nuclear Reactor Schematics Pressurized Water Nuclear Reactor

Nuclear Reactor Schematics Boiling Water Nuclear Reactor

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 meltdown—all the way to China?

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

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.

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

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/m 3 ] – resuspended (ground/surface) contamination [µCi/ft 2 ; Bq/m 2  µCi/ml; Bq/m 3 ]

Plume Dispersion

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.

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

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

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.

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

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

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

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

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

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 > 1 Gy (100 rad), and in all at doses > 2 Gy (200 rad) (whole-body) – evacuation is usually the only effective intervention measure in high dose situations

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

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.)

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

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

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)

Intermediate Phase PAG’s  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

Late Phase PAG’s  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

Logistical Requirements for Later Protective Actions  Temporary relocation: – Transportation – Housing & furnishings – Security – Decontamination equipment & waste disposal  Permanent resettlement: – Transportation – Housing & furnishings – Security

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

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)

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 kBq/kg (0.03 pCi/g)

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

Three Mile Island Goldsboro, Pennsylvania

Three Mile Island  Unit 2 feedwater pump tripped at 4:00 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

TMI, con’t  Core partially uncovered by 6:15 a.m.  Site emergency declared at 7:00 a.m.  General emergency declared at 7:24 a.m.  Radiation levels indicated fuel damage around 8:00 a.m.  Core covered with water by 10:30 a.m.

TMI, con’t  State route 441 closed at 12:45 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 12:30 on March 30  Schools closed and further evacuation planned  Supplies of KI shipped in

TMI, con’t  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

Chernobyl

Chernobyl

The Chernobyl Experience  I. Evacuation: – Accident occurred 26 April 1986 at 1:23 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

The Chernobyl Experience  II. Sheltering: – 270,000 persons remained in controlled area (10,300 sq. km with 137 Cs > 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

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 – fold increase in childhood thyroid cancer

Fukushima Chiba

IAEA ACCIDENT SCALE