Radioactive Water

Rays of energy from outer space entering the earth's atmosphere cause some hydrogen atoms there to adopt a second neutron. This isotope of hydrogen is called tritium. According to the IATA, 1981, tritium has a radioactive half life of 12.43 years. All three isotopes of hydrogen have a single proton in their nucleus. Atoms of protium (ordinary hydrogen) has no neutron in its nucleus and is stable, deuterium has one neutron in its nucleus and is stable. Tritium with two neutrons in is nucleus is unstable and ejects Beta particles (essentially high-energy electrons). Since the number of protons determines chemical bonding, tritium behaves like ordinary hydrogen and replaces it in water molecules producing radioactive water. Hoffman Tritium Study.

Incorporated in water molecules in precipitation, tritium ultimately reaches the land or sea surface. From where it readily cycles through the hydrologic and biologic components of the environment, including our ground water reservoirs.

There are several sources of tritium in addition to the above. Since the early 1960s, when the atmospheric testing of thermonuclear weapons raised background levels by several orders of magnitude, background levels have receded to twice the level preceding the weapons testing period. All nuclear electric power plant reactors emit tritium into water and the atmosphere.

The standard unit of measure, a tritium unit (TU), is a set ratio of tritium atoms to hydrogen atoms in a substance, for example, water. In terms of radioactivity, one TU is equivalent to 3.19 picocuries per liter (Clark and Fritz, 1997). In SI units, one tritium unit is about 0.118 bequerels per liter (Bq/L), where the bequerel is one unit of disintegration per second. Tritium decays naturally over time to become helium.

Tritium is classified by the EPA as a human cancer causing agent. We can take this agent into our bodies by breathing, though the pores in the skin, and by eating or drinking contaminated fluids or food. EPA sets a fairly tight limit on drinking water under the Safe Drinking Water Act, at 740 becquerels per liter.

All living organisms can be harmed by the beta particles emitted from tritium, which can sever chemical bonds and damage cells, affecting DNA structures and subsequent generations. Effects upon microorganisms are probably not known. By extension, so also are consequences upon dependent ecologic systems and species, on which our marine food web and the livelihood of so many depend. The difficulty in constructing a test environment involving Beta radiation has led to a lack of essential documentation.

Ratios of tritium to helium in ground water can give an accurate measure of age (and possible source) of that water. Both tritium and helium are relatively inert gases. The method separates helium derived from tritium from helium derived from natural sources. The tritium/helium method is based on the radioactive decay of tritium relative to helium. Both tritium and helium are relatively inert gases. Apparent age estimates from the tritium/helium method can be extremely accurate (within months) for ground water containing high tritium concentrations (waters recharged since 1963). Unlike the chlorofluorocarbon dating method, tritium/helium is a valid technique for sites contaminated with organic compounds.

Use of Tritium as an aid to water age assessment — Data on natural tritium concentrations in water in the upper part of the Floridian Aquifer were collected from December 1966 to November 1968 to evaluate tritium as a radioactive tracer. Some useful information on recharge characteristics resulted.

In very general terms, an appreciable concentration of tritium is an indicator of young water.

The natural production rate of tritium in the atmosphere is considered constant, but nuclear weapons tests as late as the early 1960's raised the tritium level to many times the normal level. The level declined after the tests but has not returned to normal, estimated by L. L. Thatcher as about 6 TU along the Atlantic Coast (Stringfield, 1966, p. 150).

During the 2-year sampling period in the Floridian Aquifer study area, one or more samples were collected at each of 26 different observation stations. Bimonthly samples were collected and analyzed from ten of the stations, including Rainbow and Silver Springs, Ocala Caverns, and seven wells. Samples collected irregularly from four wells in the confined part of the aquifer, mostly in the Oklawaha River valley, contained zero to only traces of tritium, indicating complete or nearly complete decay of originally contained tritium. This supports interpretations from other geologic and hydrologic data that the water was old and not subject to direct recharge. On the other hand, all samples collected west of the river valley in the unconfined part of the aquifer had appreciable concentrations of tritium, thus supporting the belief that much of that area is subject to direct recharge. Each of the samples had more than twice the presumed normal concentration of 6 TU in rainfall, but far below peak concentrations measured in rainfall in Ocala in 1963 after the large thermonuclear tests in late 1962, thus suggesting that the high concentrations in the ground water from 1963 recharge had already passed.

The weighted average tritium concentration for 1963 precipitation in Ocala was 620 TU (Stewart and Farnsworth, 1968, p. 281). Concentrations in ground-water samples collected west of the Oklawaha valley during the 1966-1968 sampling period ranged from 13 to 174 TU while rainfall in Ocala ranged from 20 to 158 TU. The concentration in eleven samples collected at Rainbow Springs averaged about 49 TU with a high of 85 TU in May 1967 and a low of 38 TU in March 1968. Silver Springs water during the same period averaged about 47 TU with a high of 150 TU in May 1967 and a low of 25 TU in July 1967. This compares with a count of only 4.2 TU in Silver Springs water in January 1961 (Stringfield, 1966, p.150). The average concentration in the seven wells sampled bi-monthly during 1966-68 was about 80 TU, and that in rainfall at Ocala for the same period was about 60 TU.

Ever since the record highs in precipitation in 1963, there has been a general decline in tritium concentration, although seasonal peaks and troughs continue to occur as they would under normal conditions.

A similar decline apparently occurs at most ground-water observation stations. A correlation between many of the concentration curves for the ground-water stations and the concentration curve for precipitation is suggested. A lag of a month or two is apparent from the rainfall peaks to the peaks in several of the ground-water curves. Correlation of the curves is very much complicated by variable recharge characteristics and by differential rates of ground-water movement in the area. Much remains to be done to properly integrate and fully evaluate the tritium data, but in the meantime the tritium data provide a useful tool for recognition of some differences in recharge conditions from one place to another within the study area.

The amount of tritium estimated for the discharges from the two nuclear plants proposed for Levy County is not known.

Nuclear Energy Electricity Generation — A Progress Energy document avers, "Tritium is a byproduct of generating electricity at nuclear power plants. All nuclear plants release tritium into both the water and air. The U.S. Environmental Protection Agency (EPA) regulates the acceptable level of tritium concentrations in ground water and drinking water".

Other Progress Energy documentation indicates the intention to take between 100 and 130 million gallons of water a day from the Cross Florida Barge Canal. Of that amount 40% (say 50 million gpd) would be emitted to air and 60% (say 60 million gpd), at elevated temperatures, piped alongside the Barge Canal to vent to the Gulf waters using the existing outlet from the Crystal River plants.

Both sources of discharge could carry radioactive tritium. Local precipitation would return tritium to people, soils and ground water cumulatively every day it rains. Ejection to the Gulf waters would pollute water at offshore sea grass meadows, with unpredictable consequences to plants and wildlife. A closed circulation of contaminated water could be the consequence of using the Barge canal route for both inlet and egress.

Citrus County draws its domestic drinking water supplies from wells located in the northeast part of Citrus County. Potentiometric flows from the site proposed for the nuclear plants in Levy County, and concentration of flows within known fracture sets would appear to imperil domestic and drinking water supplies for the population of Citrus County.

See also the "Braidwood and Dresden Nuclear Power Plants" News Item (March 2, 2009).