Savannah River Site Health Effects Subcommittee (SRSHES) Meeting

Meeting Minutes
March 13, 2003

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Mr. Cliff Blackman announced that GDNR’s Environmental Radiation Monitoring Program was established in 1976 through the Georgia Radiation Control Act and was initiated the following year. GDNR’s Environmental Radiation Laboratory (ERL) was established in 1977 at Georgia Tech through a cooperative agreement. GDNR is also responsible for radiological safe drinking water testing and emergency response. In addition to SRS, GDNR monitors Plant Vogtle and other facilities once or twice per month. Matrices tested around SRS include direct radiation samples from thermoluminescent dosimeters (TLDs); air samples from filters, charcoal cartridges for iodine-131 and silica-gel cartridges for tritium; water samples from river water, ground water and precipitation; soil and river sediment; vegetation, crops, milk and game; and fish and seafood.

ERL tests several radionuclide groups, including alpha/beta, gamma, iodine-131, iodine-129 at Four Mile Creek only, tritium, strontium-89/90, plutonium-238/239, americium-241 and TLD dose. For the air pathway, GDNR collects rainfall samples to determine the amount of materials deposited. Air monitoring data showed the following results. Alpha/ beta was found at normal background levels from naturally occurring lead-210, bismuth-210 and polonium-210. Gamma was primarily non-detectable, while strontium-89/90 and plutonium-238/239 have not been found since GDNR was established. Tritium has been routinely sampled since 1996 and was not found at significant doses. Exceptions to the air results are Chernobyl, peaks in cesium-137 releases and nuclear weapons tests in China.

Some periodic spikes in gross beta concentrations may be related to incidents, but the majority of increases were associated with changes in atmospheric conditions. One peak in manmade gamma concentrations was attributed to Chernobyl, but GDNR could not determine whether another spike involving xenon-133 was from the SRS area or other sources. GDNR believes that a cesium-137 spike was from a source within a 25-radius of SRS, but the increase was not determined to be significant. The maximum tritium dose calculated at the highest location was 0.003 mRem. The calculation was based on EPA data of dose factors multiplied by the average breathing rate of an individual.

For the rainfall pathway, precipitation is collected each month. While SRS uses a no-ion exchange column to concentrate rainfall, GDNR runs the sample without pre-treatment. Precipitation monitoring data showed the following results. Alpha/beta was routinely detected in samples, but these concentrations varied with rainfall dilution and were primarily associated with naturally occurring lead-210, bismuth-210 and polonium-210 in the air. No strontium-89/90, plutonium-238/239 or manmade gamma concentrations were found. Tritium was routinely detected, but these levels are declining on an annual basis as SRS effluents decrease. Tritium concentrations in precipitation were not found to be dose-significant at < or equal to 0.5 mRem per year if consumed.

For the soil pathway, cesium-137 was detected in most samples and was primarily assumed to be from nuclear weapons testing. However, concentrations in soil from sources within a 25-mile radius of SRS were not easily determined because no correlation was made with distance. Cesium-137 levels are declining with time at a much faster rate than radioactive decay. Soil sample data show that cesium-137 contributes <0.05% of the soil-related direct radiation dose. Plutonium-238 was not detected in any samples, but plutonium-239 was found in a few samples with higher cesium-137 levels. These concentrations do not appear to be associated with SRS or decrease with distance. The strong correlation between plutonium-239 and cesium-137 may indicate a common origin and relationship with fallout from weapons testing.

Strontium-90 was below detection limits in most soil samples. Shorter-lived gamma seen in the 1970s and early 1980s were primarily from weapons testing. For naturally occurring long-lived radionuclides, parent or daughters were detected in all soil samples, including potassium-40, radium-226 from the uranium-238 chain, and radium-228 from the thorium-232 chain. These radionuclides in soil are important because of contributions to most direct radiation doses under normal conditions. The materials result in a 0.4% dose from cesium and >99% dose from natural origins.

For direct radiation testing, TLDs are placed on telephone pools, trees and other inconspicuous locations for one-quarter periods. Upon heating, TLDs emit light in proportion to cumulative doses and measures both natural and manmade doses. GDNR has used two TLD systems over its 26-year monitoring period with slightly different field responses and calibration. The old system was calibrated with radium-226 and showed an average of 55 mRem/year of radiation, while the new instrument measures with cesium-137 and shows an average of 58 mRem/year. Several minor elevated readings of unknown origin were detected in one quarter, but these results may be due to tampering. A TLD that showed elevated radiation levels near a medical center may be attributed to x-rays or a nuclear medicine patient. No long-term concentrations were seen at SRS or Plant Vogtle.

For the vegetation/grass pathway, cesium-137 detected in ~25% of samples was primarily assumed to be from weapons testing. Some portion may be due to SRS releases, but this result does not appear to be correlated to the site. Cesium-137 concentrations in grass are declining with time at a rate equal to natural radioactive decay. If grass was consumed as a leafy vegetable, the cesium-137 dose would be < or equal to 0.2 mRem/year. A solid correlation was seen with tritium at a distance indicating an origination from SRS. Tritium concentrations in grass are declining with time at a rate equal to airborne effluents and have not been detected over the past four years. If grass was consumed as a leafy vegetable, the tritium dose would be < or equal to 0.01 mRem/year.

Strontium-90 was detected in several grass samples at levels roughly equal to cesium-137, but does not appear to be correlated to SRS. Concentrations were most likely related to weapons testing. Grass samples with higher strontium-90 and cesium-137 ratios indicate enhanced plant uptake or increased deposition of strontium-90. If grass was consumed as a leafy vegetable, the strontium dose would be < or equal to 1.1 mRem/year. Plutonium-238/239 and strontium-89 were not detected in grass. Several nuclides detected in the late 1970s and early 1980s were from Chernobyl and weapons testing. Doses from these sources were relatively minor at 0.5 mRem for an effective dose and 3 mRem for a thyroid dose.

For the milk pathway, samples are collected on a monthly basis from up to 10 regional dairies. Tritium was detected in many samples, but levels are declining with tritium emissions from SRS. Tritium is currently non-detectable in the majority of milk samples and was found at a dose of only <0.02 mRem/year. Cesium-137 from weapons testing was routinely detected in milk samples with a low-level counting procedure that provides solid sensitivity. Iodine-131 detected in milk in 1983, 1984 and 1986 from one dairy was possibly from a local source rather than SRS. Low doses were found at <0.25 mRem/episode. Strontium-89 found in one milk sample in 1986 potentially originated in the Girard area instead of the site. Strontium-90 was not detected in any milk sample.

River sediment is typically collected with a Ponar dredge. GDNR prefers high clay-silt content samples over sandy samples because these measurements have better absorption and retention characteristics. Elevated cesium-137 concentrations detected in river sediment samples upstream of Augusta, Georgia and SRS were primarily due to waste operations and problems with a reactor at SRS. Cesium-137 levels in river sediment were found to be a strong predictor of concentrations in fish. Cobalt-60 levels were found in both upstream and downstream locations of Plant Vogtle and were attributed to SRS reactor operations and Plant Vogtle. Cobalt-58 and short-lived manganese-54 concentrations were detected and attributed to Plant Vogtle.

Plutonium-238/239 and americium-241 were found in a few river sediment samples and attributed to SRS or weapons testing. Naturally occurring radionuclides from the uranium, thorium and potassium series were detected as well. River sediment consists of a sand, silt and clay mixture and results in highly variable radionuclide samples. The variability increases the difficulty of establishing trends. For the river water pathway, the following locations are monitored: Augusta, Georgia; upstream and downstream of SRS and Plant Vogtle; Savannah, Georgia; Plant Vogtle at the Georgia Power Company; and the SRS area encompassing Upper Three Runs Creek, Beaver Dam Creek, Four Mile Creek and Lower Three Runs Creek. River water samples are collected weekly.

Tritium was detected in most samples, but levels are generally declining in downstream samples. Increases were recently found at some effluent locations and historical spikes were seen in river water samples as well. Elevated levels of tritium that appear to be approaching the drinking water standard are near the mouth of the creek and do not appear downstream after being diluted by the Savannah River. Water in creeks are not consumed by persons and do not present a risk to the population. Some higher peaks detected in tritium were due to GDNR’s enhanced monitoring program of testing more frequently and over a shorter time period. GDNR, SRS, the state of South Carolina and the city of Savannah are closely tracking any changes in tritium releases in the Savannah River.

Based on annual averages for each year since 1977, the highest historical downstream level at the Savannah ID Water Plant was < or equal to 4,000 pCi/L or 20% of the drinking water limit. Some periodic fluctuations in tritium from Plant Vogtle were related to electrical outages or maintenance work. Alpha/beta was typically found near the detection limit and is not easily correlated with SRS or Plant Vogtle. Strontium-89/90, plutonium-238/239 and gamma concentrations were generally not detected. For the fish and seafood pathway, cesium-137 was detected in most samples with the highest results from Upper Three Runs Creek and Lower Three Runs Creek at SRS. Strontium-90 was found in most samples with the highest results between Beaver Dam Creek and Four Mile Creek at SRS.

Tritium was detected in most samples with the highest results between Four Mile Creek and Steel Creek. Overall, concentrations of radionuclides in fish and seafood were below GDNR’s trigger of > or equal to 10^-5 for an advisory. The level of concern is based on average annual consumption for both radiological and non-radiological substances, but GDNR realizes its methodology may result in slightly lower calculations than other agencies. GDNR, Georgia Power, SCDHEC and SRS share findings twice per year. Data collected by the agencies are generally found to be consistent. Special projects are also conducted in which independent samples are gathered to determine if the agencies will obtain the same results. GDNR expects to publish an updated environmental radiological monitoring report in the next month. The document will contain GDNR’s dose calculations, risk estimates and technical approaches.