NH COMPARATIVE RISK PROJECT            ECOLOGICAL INTEGRITY,
May 1998
NUCLEAR REACTORS AND ASSOCIATED RADIOACTIVE WASTE
(Seabrook & VT Yankee Nuclear Power Plants & Portsmouth Naval Shipyard)

DEFINITION: Nuclear reactors are facilities in which controlled nuclear fission reactions are maintained for the purpose of generating electricity or producing nuclear materials for defense or biomedical use.  Most electricity-generating reactors in the United States are light-water reactors (LWR), which include boiling water reactors (BWR) and pressurized water reactors (PWR).  Nuclear reactors generate both high and low level radioactive wastes.  High level radioactive wastes (HLRW) consist of the spent fuel elements, which contain both fission products generated directly by nuclear reactions within the core, and activation products formed by neutron bombardment of impurities and corrosion products in the water that passes through the core (Eisenbud and Gesell 1997).  These include 543 different nuclides, many but not all of which are radioactive (Lipschutz 1980).  Radionuclides in spent fuel have half-lives ranging from minutes (e.g., I-134, Ba-137, Pr-144) to millions of years (e.g., U-235, U-236, U238).  Table 1 presents radionuclides produced by nuclear reactors that are of potential environmental concern and other radionuclides in spent reactor fuel that have long half-lives or are present in large quantities.  Low-level wastes include a variety of types of materials contaminated with radioactivity (see Non-reactor Sources of Radiation). 

DATA QUALITY AND QUANTITY
Sources/Availability: The NRC collects data on radioactive effluent releases from nuclear power plants; and, until 31 December 1997, maintained a Direct Radiation Environmental Monitoring program (DREM) in cooperation with the states.  The NH Bureau of Radiological Health (NHBRH) monitored the >30 DREM sensors in the vicinity of the Seabrook Station plant.  NHBHR conducts an environmental monitoring program including several different sampling media in the vicinity of the Seabrook and Vermont Yankee nuclear power plants, and maintains a database of New Hampshire Radiological Incident Events.  The Sandia National Laboratory maintains a Radioactive Materials Incident Reporting System.  The EPA monitors public health and environmental impacts of radiation from all sources. 

Significant gaps: Cumulative risks associated with commercial power plant decommissioning and long-term (i.e., over centuries) storage of high level radioactive wastes are unknown.  Understanding of long-term effects of environmental contamination from nuclear reactor accidents is limited to what has been learned to date from the Chernobyl accident in 1986.  Risks associated with gradual deterioration of safety components in nuclear power plants are unknown.  Synergistic effects of radiation with other hazardous materials (e.g., mercury) are unknown.

HISTORY: The first nuclear reactor (University of Chicago) was operational (briefly) in 1942.  Additional reactors developed in the U.S. through 1954 were used primarily for military applications.  The first nuclear powered submarine (Nautilus) was launched in 1954.  Amendments to the Atomic Energy Act in 1954 and the First United Nations International Conference on the Peaceful Uses of Atomic Energy in 1955 led to civilian applications, and New Jersey Central Power Company purchased the first nuclear reactor for civilian power generation in 1963 (Eisenbud and Gesell 1997).  By the end of 1992, 419 nuclear reactors in 30 countries were producing approximately 16% of the world's electricity (Tykva and Sabol 1995), and by 1994 civilian reactors had accumulated a total of 5500 operating years (Eisenbud and Gesell 1997).

Nationwide, nuclear fuel shipments experienced 6 accidents and 47 incidents during 1971-1991; none involved release of radioactive materials (Reed 1996).  Spent fuel and other HLRW are transported by truck and rail and are shipped as dry solids in specially designed, NRC- certified metal casks to facilities in Washington, Idaho, and South Carolina.  The DOT and the NRC regulate transportation of nuclear waste, and  New Hampshire requires a transportation permit for shipment of spent fuel and other HLRW.  During 1972-1992, 1237 shipments of spent fuel occurred in the U.S. (Reed 1996).

Minor accidents and "unusual occurrences" are frequent in all complex technologies.  Major accidents are extremely rare.  Of 14 reactor accidents involving core damage that have occurred worldwide since the advent of nuclear technology, three involved commercial power plants (see Table 2).  Four of these accidents (Windscale, 1957; Idaho Falls, 1961; Three Mile Island, 1979); and Chernobyl, 1986) involved releases of radioactivity to the environment (Tykva and Sabol 1995)(see Table 3).

During 1971-1993, 100-149 nuclear-powered ships were in operation by the U.S. Navy in any given year (Mangeno et al. 1994).  Operation of nuclear-powered vessels by the United States and United Kingdom navies has never involved an accident with significant radiation release to the environment (SCNP 1992).  No radioactivity above normal background levels has been detected in harbors where nuclear-powered vessels are based, overhauled, or constructed.  As of 1994, the Navy had decommissioned 35 nuclear submarines and transported their reactor compartments to a disposal trench at the DOE Hanford site in Washington (Mangeno et al. 1994). 

CURRENT CONDITION: One nuclear power generator, Seabrook Station, is located in Seabrook, New Hampshire.  This 1150 megawatt pressurized water reactor began operation in 1990 and is licensed to operate until 2026.  Vermont's only nuclear power generator, Vermont Yankee, is located in Vernon, immediately across the Connecticut River from Hinsdale, N.H.  This 540-megawatt boiling water reactor (BWR) began operation in 1972.  Spent fuel from these reactors is stored onsite.  Wet storage facilities at Seabrook Station will reach capacity in 2010.

Of 13 incident reports from Vermont Yankee in the NH Radiological Incident Event database, one includes increased releases of airborne radioactivity for about 3 hours; the increased releases remained within technically acceptable limits.  The remaining incidents involved no releases.  Of 4 incident reports from Seabrook Station, one involved a slight increase (from 180 to 210 mCi) in radiation in reactor coolant; none involved radiation releases off-site.

The Portsmouth Naval Shipyard conducts maintenance and refueling of nuclear submarines at its facilities on the Piscataqua River.  Depot modernization maintenance requires less than a year in port, and an engineered refueling overhaul is a 2-year operation (A. Robinson, Public Affairs, Portsmouth Naval Shipyard, pers. comm.).  The shipyard currently services up to 4 submarines at a time.  No radiation above natural background levels has been detected in water, sediments, or biota in the vicinity of the Portsmouth Naval Shipyard (Semler 1991).  All spent fuel removed from submarines is transported to the DOE Idaho National Engineering and Environmental Laboratory.  Table 4 summarizes disposal amounts of radioactive solid waste from the Portsmouth Naval Shipyard during 1989-1992.

ECOLOGICAL RECEPTORS OF CONCERN: Normal operations: Aquatic organisms in the immediate vicinity of nuclear power plants.  Normal operations of nuclear submarines discharge no radioactive materials to the environment.  Normal operations of reactors at nuclear power plants in the United States have resulted in no appreciable radiation exposures to natural populations of terrestrial animals (NRC 1991). 

Accidents: Terrestrial and aquatic organisms throughout the contaminated area.  High acute doses of ionizing radiation adversely affect all organizational levels of life, from molecules, cells, tissues, and organs to individuals, populations, communities, and ecosystems (Eisler 1994).  Embryonic and young, rapidly growing tissues are the most vulnerable to damage.  Advanced, complex organisms, such as birds and mammals, are the most radiosensitive; primitive organisms are the most radioresistant.  Table 5 presents the range of lethal radiation doses for organisms of different taxonomic groups.  Table 6 presents sensitivities of different vegetation types to ionizing radiation.

EXPOSURES AND IMPACTS

Severity: Normal operations: Routine releases of radioactive materials from nuclear power plants are closely controlled to limit human exposures, and are unlikely to adversely affect native organisms or natural ecosystems (ICRP 1991, NCRPM 1991, IAEA 1992).  These releases include fission noble gases (krypton and xenon), activation gases (¹⁴C,

¹⁴N, ³⁵S, ⁴¹Ar), tritium, iodine, and particulates released to the air, and tritium, fission products, and activated corrosion products released to the aquatic environment (Kathren 1984, Tykva and Sabol 1995).  Regulatory limits for human doses from routine emissions from nuclear

power plants are 10 mrem/year for airborne emissions (40 CFR 61) and 5 mrem/year for liquid discharges (10 CFR 50) (Eisenbud and Gesell 1997). 

Accidents: The chemical characteristics of radionuclides, and thus their behavior in food webs, are much more variable than those of other categories of contaminants, such as heavy metals or PAHs.  However, the number of radionuclides that are important environmental contaminants is relatively small, and includes tritium, iodine-131, cesium-137, calcium-45, strontium-90, cobalt-60, zinc-65, and plutonium-239.

Environmentally important radionuclides include those that are frequently encountered in releases from weapons testing or nuclear accidents, those that are readily taken up by organisms and incorporated into living tissues, and those that persist for long periods of time in organisms or the environment (Brisbin 1993).   Severity of exposures and impacts depend on the amount and characteristics (particularly half-life and biological activity) of radionuclides released during an accident, on exposure pathways, and on the degree to which they concentrate in organisms.  The inventory of radionuclides in reactor fuel changes in composition and proportions throughout operational life, during temporary shutdowns, and throughout the decay period of spent fuel (Kathren 1984).  Some radionuclides, such as radiocesium, radioiodine, and radiostrontium, replace stable isotopes in tissues and continue to expose organisms to radiation until they decay completely.  

Distribution/Extent: Normal operations: The small quantities of radioactive materials routinely released during normal operations of nuclear power plants are rapidly dispersed in the environment.

Accidents: The area affected by uncontrolled radioactive releases during a serious accident depends on the atmospheric level into which they are dispersed, on direction and speed of prevailing winds, on precipitation events, and on the nature, duration, and extent of the release.  Cases range from contamination limited to the area within a few hundred meters of the reactor (i.e., Idaho Falls 1961) to long-range transport of radionuclides throughout the northern hemisphere (i.e., Chernobyl 1986)(Tykva and Sabol 1995).  Birds and mammals also can distribute radioactive contaminants beyond the original area of deposition (Brisbin et al. 1973, O'Farrell and Gilbert 1975, Halford et al. 1981, Brisbin 1993).

Frequency: Normal operations: Small quantities of radioactive materials are emitted in airborne and liquid effluents during the normal operations of nuclear reactors; fossil fuel power plants also generate radioactive emissions (Tykva and Sabol 1995). 

Accidents: No serious reactor accidents have occurred at Seabrook Station, Vermont Yankee, or the Portsmouth Naval Shipyard.

Variability of exposure: Normal operations: Negligible.

Accidents: Varies with distance from source, position relative to prevailing winds, and nature and duration of contact with contaminated material.  Dose rates for different species of small mammals inhabiting contaminated areas differed with habitat preferences and behavior patterns (Halford and Markham 1978).  Exposure pathways for terrestrial plants include surface deposition and uptake from soil; pathways for animals include inhalation, surface contact, absorption through skin, and ingestion in food or water.  Organisms retain and accumulate some, but not all radionuclides; accumulation levels differ among radionuclides, species, ages, and environments (Kathren 1984). 

Variability of effects: Normal operations: Effects are generally negligible, based on current knowledge.

Accidents: Varies with species, age, life span, position in food chain, amount and types of contaminating radionuclides, duration of exposure.  Effects include cell death, decreased life expectancy, increased frequency of malignant tumors, inhibited reproduction, increased frequency of genetic mutations, altered blood-brain barrier function, reduced growth, and altered behavior (Eisler 1994).   Available information on impacts of the Chernobyl accident indicate

significant mortality and damage in pine forests, mutations in hardwoods, and high mortality, embryonic mortality, and chromosomal damage in various rodent populations in the vicinity of the facility; reindeer in heavily contaminated areas of Norway experienced a decline in calf survival, and rodents in Sweden showed increased chromosome damage 6 months and 1 year after the accident (Hoffman et al. 1995).

Duration/Reversibility of effects: Normal operations: Effects are negligible.

Accidents: Varies with extent of damage.  Some cells can repair limited damage and organisms can replace some dead or damaged cells.  When damage is extensive these processes become overwhelmed.  Damage to embryonic tissues is likely to be lasting and irreversible (Turner 1975).  Plant succession and animal immigration from uncontaminated areas foster recovery of communities and populations where heavy mortality occurs; resistant species and individuals dominate in surviving communities and populations (Turner 1975, Whicker and Fraley 1974).  Normal life spans of small mammals may be short enough to preclude damaging cumulative radiation effects at the population level (Halford and Markham 1978).   

OTHER ISSUES FOR CONSIDERATION: The Nuclear Waste Policy Act of 1982 (NWPA)(Public Law 97-425) directed DOE to provide for the deep, mined geologic repositories for the disposal of HLRW.  The first repository was to be located in basalt, salt, or tuff, and to commence operation in 1998.  The NWPA also required DOE to recommend a site for a second repository, to be located in one of the above formations or in crystalline rock (DOE 1986).  During the early 1980s, DOE evaluated available data for 235 crystalline rock formations in the Northeastern, North Central and Southeastern United States, and subsequently recommended 12 areas as potentially acceptable sites.  One of the recommended sites encompasses portions of Cheshire, Hillsborough, Merrimack, and Sullivan counties in New Hampshire (DOE 1986).  The problem of storing high level radioactive wastes from commercial reactors has yet to be completely solved.  Potential options under consideration, in addition to isolation in deep repositories for long time periods, include disposal in outer space and conversion of radioactive elements into stable elements (Tykva and Sabol 1995).

The probability of a major reactor accident is extremely small, but is larger than zero.  Because of extensive and redundant safety systems, such accidents require the confluence of multiple problems, which can include various combinations of operator errors and equipment failures.    

The sequences of events at Three Mile Island and Chernobyl suggest that once an accident begins, initial disbelief on the part of operators, lack of experience with the abnormal situation, and the extreme complexity of the system may make it extremely difficult to rapidly bring the situation under control.

Table 1. Radionuclides of potential environmental concern produced by nuclear reactors (*) and other radionuclides in spent reactor fuel with long half-lives or present in large quantities.  (Compiled from: Whicker, F.W. and V. Schultz. 1982. Radioecology: Nuclear Energy and the Environment, Vol, CRC Press, Boca Raton, FL; Lipschutz, R. 1980. Radioactive Waste: Politics, Technology and Risk. Ballinger Publishing Company, Cambridge, MA.)