Definition of Problem

Nuclear power plants can contribute to exposure of the public by routine releases of radioactivity into the environment.  The annual dose to the public from this source is very low, much less than from natural sources.  The radioactivity is produced as a by-product of the nuclear fission process.  Nearly 100% of this activity remains trapped in the fuel assemblies; that which escapes or is produced outside of the fuel assemblies is trapped by the primary coolant system.

The primary coolant system is continuously filtered to remove trapped radioactivity.  Radioactive gasses are captured and held for 60 days or longer to allow the short half-life radioisotopes to decay.  The remaining gas is then released in a controlled manner to the environment.  The radioactive elements in particulate form are captured on filter media;  filters are then disposed of as radioactive waste.  The filter effluent, water will contain some small amount of radioactivity that was not removed.  The effluent is held in holding tanks, for varying amounts of time, then discharged to the environment.

The main fear among those opposed to further reliance on nuclear power is the remote possibility of a catastrophic release of radioactive materials should a major accident occur.  The nuclear power plant design strategy for preventing accidents and assuaging their potential effects is the “defense in depth” concept that is characterized by repeated layers of thick shielding materials and multiple safeguards designed to ensure safety.  Of course, it is possible that each system in this series of back-ups might fail one after the other, but the probability for that occurrence is exceedingly small.  Probabilistic risk analysis (PRA) suggests that a fuel meltdown might be expected once in 20,000 years of reactor operation. Even in the well-known Three Mile Island accident (1979) when a partial meltdown occurred there was a minimal release of radioactivity from the reactor containment building.  The maximum estimated dose to any neighboring member of the public was estimated as 0.1 rem (1mSv) which equals the average dose in 1 year from natural background radiation in the USA.  (See J. G, Kemeny:  the President’s Commission on the accident at Three Mile Island, Pergamon Press, 1979).

Both high level and low level radioactive waste products from the nuclear industry must be isolated from contact with people for very long periods of time.  Low level wastes are currently disposed of in specially licensed burial sites.  The Nuclear Waste Policy Act of 1982 and the Nuclear Waste Policy Amendments Act of 1987 specify a detailed approach for the disposal of high level radioactive waste.  The Department of Energy (DOE) possesses operational responsibility and the Nuclear Regulatory Commission (NRC) has regulatory responsibility for transportation, storage, and geological disposal of the radioactive waste.

As of this date, however, there is no site for disposal of high-level wastes.  Such wastes must therefore be stored on-site awaiting the operation of the nation’s first permanent repository for high level radioactive waste.
 

Data

The annual effluent report from Seabrook nuclear power station documents the amount of radioactivity released from the facility via monitored liquid and gaseous effluent pathways.  Under the conditions of the license issued by the U.S. Nuclear Regulatory Commission (NRC), Seabrook Station must monitor on a continuous basis all potential liquid and gaseous effluent release pathways and the surrounding environment.  In addition, the NRC has placed monitors at various locations, some of which are co-located with those of the utility.  Also, the State Department of Health and Human Service’s Bureau of Radiological Health conducts off-site independent monitoring of a 10 mile radius surrounding Seabrook Station and Vermont Yankee Nuclear Power stations.  Sample data for air, water, milk, dairy feed, direct gamma, deposition, and plants, sediment, fish and ocean water at the point of discharge are available from the Bureau of Radiological Health.  In general, the sample data to date shows emissions from Seabrook Station and Vermont Yankee to be well within the licensing and regulatory criteria and that exposures to the public as a result of these emissions are ALARA.  (as low as reasonably achievable).
 

Confidence

High among the experts
Low among some lay persons
 

Exposures and Health Impacts

The routine release of radioactive materials and exposure to ionizing radiation from nuclear power plants is regulated by the U.S. Nuclear Regulatory Commission.  In addition to dose limits to members of the public described in 10 CFR part 20, nuclear power plants must meet lower, so called ALARA (As Low As Reasonably Achievable) dose guidelines given in 10 CFR part 50.  ALARA is the implementation of a philosophical goal in radiation protection to keep exposures to a minimum.  It has developed as a result of the continued debate about health effects of low-dose ionizing radiation exposure.  The ALARA guidelines for nuclear power plants were implemented in January of 1971.  Though technically not standards or regulatory limits, the ALARA guidelines are, in effect, de factor exposure limits for nuclear power plants.  In addition, the US EPA has established exposure limits for members of the public from nuclear facilities (40 CFR part 190).

Currently, Seabrook’s license limits the radioactive content of liquid discharges to an equivalent dose of 1.5 mrem per quarter to a member of the public (representing a maximum total dose of 240 mrem for an assumed 40 year operating lifetime).  In addition, Seabrook’s operating license limits the radioactive content of gaseous releases to an equivalent dose of 7.5 mrem per quarter to any organ of a member of the public (representing a maximum total dose of 1,200 mrem for an assumed 40 year operating lifetime).  In a recent report to federal regulators, required by Seabrook’s operating license, the maximum total radiation dose from all liquid and gaseous pathways was estimated to be 0.00568 mrem for 1996.  This is about 6,000 times smaller than the dose allowed under the license and about 0.006% of annual background.

 Federal radiation protection regulations were enacted to protect the public and nuclear workers.  These regulations limit the maximum radiation exposure to a member of the public to 100 mrem per year.  This limit corresponds to a theoretical maximum exposure of 4,000 mrem (4 rem) to any member of the public from the operation of a nuclear power plant over its assumed 40 year lifetime.  The> 

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Populations of Concern

Members of the public, occupationally exposed persons, pregnant workers and fetuses.  The emergency planning zone for Seabrook and Vermont Yankee nuclear power stations for all pathways includes all persons living within a ten mile radius of the plants.  For ingestion pathways, the area is extended to a fifty mile radius.
 

Technical Assessment of Risk
 

 
 

Criterion	Score
Severity	5
Distribution	1
Reversibility	4
Uncertainly - Toxicity	4
Uncertainty - Exposure Data	3-5

 

Data Gaps

The risk to the population of New Hampshire from nuclear power generation at both the Seabrook facility and the Vermont Yankee nuclear power station is dominated by the possibility of a severe nuclear reactor accident.  This event seems to possess a very low probability with a possibility for very high consequences.  Although station personnel receive training on response to these events, are sufficient data available to reduce these uncertainties that are associated with the probability of occurrence, and, what is the estimated impact on the public’s health?

Additional questions surround the risks associated with Seabrook nuclear power station in terms of premature deterioration of vital safety components, such as steam generators, due to increased economic pressure from electric utility deregulation.  What impact does this have on the safety of the employees at the facility, as well as the surrounding public?  Furthermore, what effect does the investigation of Seabrook nuclear power station’s lead owner, Northeast Utilities, have on the safe operation of the nuclear facility?

Overall, more information regarding the risks associated with the deterioration of safety components at the Seabrook nuclear power station, risks associated with nuclear waste and the decommissioning process, utility deregulation, and routine accidental emissions of radioactivity into the surrounding air and water would be extremely useful in ranking the risk of nuclear power generation to the public in New Hampshire.
 

Summary

Under normal operating conditions, radiation exposure to the general population emerging from  nuclear power plants comes primarily from the deliberate release of controlled quantities of radioactive gases to the atmosphere.  Also, small amounts of radioactive materials may be discharged with wastewater into the surrounding water body.  Public exposure to such emissions has been calculated as ranging from a maximum individual dose of less than 100 mrem to an average of 80 mrem for those living a lifetime within a ten mile radius of the nuclear power plant.  The routes of such exposure include inhalation or skin contact with airborne radionuclides and ingestion of radioactive contaminants in food and water.  Overall the radiation hazard to people living in the vicinity of a normally operating nuclear reactor is considerably less than that from natural background sources.

In general, radiation from nuclear power generation and from the management of low-level and high-level radioactive waste currently poses a low risk compared to other environmental risks.  The primary factors in determining this level of risk are based on the historical safety of the day to day operations at Seabrook Station and the high degree of regulation of the nuclear industry.  Seabrook Station in many respects has served as a model plant and through increased public participation and stricter regulation, has brought safety standards for the nuclear industry to a new level.

Seabrook Station began operations in August 1990 and is licensed to operate until the year 2026.  Whether the plant will operate its full life expectancy or even be granted a license extension for another twenty years remains a point for discussion.  When Seabrook ceases operation, it must be decommissioned in accordance with the State law and federal standards.  Such decommissioning will be costly.

As Seabrook approaches the end of its license and through the decommissioning process, there will be a need for continued surveillance and re-evaluation of the risks.  All radiation exposures resulting from routine operation and decommissioning must be monitored and kept ALARA. Also, high-level and low-level wastes must be disposed of in accordance with federal and state regulatory requirements.
 

References 

1. National Council on Radiation Protection and Measurements, Report No. 93.  “Ionizing Radiation Exposure of the Population of the United States.”  September 1, 1987.

2. Maine Environmental Priorities Project.  “Technical Appendix Volume 2:  Background Papers Prepared by Members of the Human Health Technical Working Group.”  July 1995.

3. Maine Environmental Priorities Project.  “Summary of the Reports from the Technical Working Groups to the Steering Committee.”  July 1995 and August 1995.

4. Maine Environmental Priorities Project.  “Technical Appendix Volume 1:  Background Papers Prepared by the Members of the Ecological Health and Quality of Life Technical Working Groups.”  July 1995.

5. Ignatius, Amy, L., and Diane E. Tefft, “Radiation.”  New Hampshire Comparative Risk Project.

6. Maine Environmental Priorities Project.  “Report from the Steering Committee, Consensus Ranking of Environmental Risks Involving Maine.”  January 1996.

7. Caron, Rosemary M., “New Hampshire Comparative Risk Project Technical Report:  Public Health and Radiation.”  January 1998.

8. Cardis E. Gilbert ES et al.  “Effects of Low Doses and Low Dose Rates of External Ionizing Radiation:  Cancer Mortality Among Nuclear Industry Workers in These Countries.”  Radiation Research 142, 117-132 (1995).

9. Jablon, S., Boice J. et al.  “Cancer in Populations Living Near Nuclear Facilities”.  NIH Publication # 90-874 (1990).

10. Doll R. and Wakeford R.  “Risk of Childhood Cancer from Fetal Irradiation”.  Brit. Tour. Rad. 70, 130-139 (1979).