Summary: Radiation Dose Estimates from Hanford Radioactive Material Releases to the Air and the Columbia River

Page 1

to the Air and the TheTechnical Steering Panel of the Hanford Environmental Dose Reconstruction Project

Page 2

This material was prepared with the support of the US.Centersfor Disease Control and Prevention (CDC). However, any opinions,findings, conclusions,or recomnzendations expressed herein are those of the Technical Steering Panel of the Hanford Environmental Dose Reconstruction Project, and ab not necessarily reflect the view of CDC.

Page 3

Table of Contents Air Exposure Pathway ............................ 9 Doses from the Air Pathway....................... 17 Columbia River Exposure Pathway ................. 39 Doses from Radioactive Materials Released to the Columbia River .................... 47 Sources of Additional Information ................. 58 Source Term Tables ............................. 59 Technical Steering Panel Members ................. 61

Page 4

For more than 40 years, the U.S. Government made plutonium for nuclear weapons at the Hanford Site in southeastern Washington State. As a result of these operations, radioactive materials were released from Hanford to both the air and the Columbia River. People were exposed to these radioactive materials. Public concern that this exposure could have affected people’s health prompted a study into past radioactive material releases from Hanford. The purpose of the Hanford Environmental Dose Reconstruction Project is to determine how much radioactive material was released from Hanford, how that material may have reached and exposed people, and most importantly, what radiation dose people may have received. An independent Technical Steering Panel (TSP) directs the Project, which is being conducted by Battelle Pacific Northwest Laboratories in Richland, Washington. The Project is funded by the US.Centers for Disease Control and Prevention (CDC). In July 1990, the TSP and Battelle reported preliminary dose estimates for ten counties surrounding Hanford. These estimates covered periods of the largest releases to air and the Columbia River. After analyzing the preliminary estimates and receiving extensive public comment, scientists revised and improved the dose estimating models. They also continued to search for additional data and expanded the study area. The results in this summary reflect this four year effort. This report provides a summary of two reports completed by Battelle in the spring of 1994. These reports explain the dose estimates for representative persons from radioactive materials released to the air and to the Columbia River. These dose estimates are subject to change. Although the TSP considers significant changes unlikely, additional Project work could result in revisions of these dose estimates. Companion Technical Reports are Available This Summary Report is directed to readers who want a general understanding of the representative dose estimates. Other reports are for readers who understand the radiation dose assessment process and want to see more technical detail. Some of these reports are listed in Appendix 1. Technical reports are available in the USDOERichland Public Reading room or from: Technical Steering Panel c/o Nuclear Waste Program Department of Ecology Tribal Dose Estimates Not Included Here Northwest Native American Tribes are now in the process of collecting demographic and lifestyle data for use in Tribal dose estimates. Tribes included are Coeur d’Alene, Colville, Kalispel, Nez Perce, Spokane, Umatilla, Warm Springs and Yakima. Tribal dose estimates will be included in later reports. One important user of the new dose estimation process is the Hanford Thyroid Disease Study, which is being conducted for the CDC by researchers at the Fred Hutchinson Cancer Research Center in Seattle. The purpose of the Thyroid Study is to determine whether thyroid disease has increased among persons exposed to air releases of radioactive iodine- 131 from Hanford between 1944 and 1957. Participants in the Thyroid Study and their close relatives or friends are asked to provide information needcd to estimate the radiation dose to the participants’ thyroid glands. This information is then entered into the computer programs developed in the Dose Reconstruction Project to calculate those estimated doses. For more information about the Hanford Thyroid Disease Study call Hanford Thyroid Disease Study

Page 6

The federal government chose Hanford in 1942 as one of the sites for the Manhattan Projectthe country’s secret program to build an atomic bomb. The Hanford area was selected because of its remote location, arid climate, abundant electricity, and access to river water to cool the In 1943,construction began on the first of what would eventually be nine nuclear production reactors at Hanford. All were built along the banks of the Columbia River. Fuel fabrication facilities were built to prepare the uranium fuel for the reactors. The fuel was irradiated in the reactors to create plutonium. Chemical separation plants were used to separate the plutonium from uranium and from fission products created during irradiation. The first three nuclear reactors-B, D, and F-began operating in 1944 and 1945. Chemical separation plants T and B were started up in December 1944 and April 1945, respectively. After World War I1 ended in 1945, the Cold War prompted a major expansion at Hanford. From 1949 through 1963, six new reactors-H, separation plants were built. In addition to producing plutonium, N Reactor produced steam to generate electricity. This reactor also differed from earlier reactors in that it discharged much smaller amounts of radiation to the river. During the first few years of operations, large amounts of radioactive materials-primasphere from the separation plants. Better filter systems, new knowledge about radiation hazards, and stricter operating procedures all but eliminated these releases by the mid- 1950s. Radioactive material releases to the Columbia River came primarily from the eight charged cooling water directly to the river. Through much of the 1950s and the mid1960s, as many as eight production reactors operated at one time. These eight reactors used water from the Columbia River for cooling. During the cooling process, impurities in the water became radioactive. ment began to shut down the production reactors at the rate of about one per year. By 197 1, all eight reactors that used this once-through cooling system were shut down. N reactor Heath Concerns Prompt Dose ReconstructionWork Public concern about past Hanford operations led the U.S. Department of Energy (USDOE) in 1986 to release thousands of pages of documents. These documents detailed some of Hanford’s operating history and showed that there were past off-site releases of radioactive Washington, Oregon, and regional Native American Tribes gathered an independent panel of experts-called the Hanford Health Effects Review Panel-to evaluate this information. They found that the releases to the air in the 1940s and early 1 9 5 0 ~ ~and releases to the river up until 197 1,exposed people in the region to radioactive materials. Many people in the region fear these releases caused a variety of health problems. In September 1986, the Health Effects Review Panel recommended dose reconstruction and thyroid health effects feasibility studies. In response, USDOE directed Battelle Pacific Northwest Laboratory to conduct the Hanford Environmental Dose Reconstruction Project. The project was to determine how much radioactive material was released, how that material may have reached and exposed people, and most importantly, what radiation dose people may have received. Mistrust of USDOE threatened the credibility of the Project results. After decades of

Page 7

secrecy, some members of the public believed USDOE was to blame for the radioactive material releases, and would be less than forthcoming in investigating them. Some members of the public also lacked confidence in the independence of the Battelle scientists doing the work. As a result, USDOE agreed with the States and Tribes that independent project direction was necessary to provide credible scientific direction. It would also provide a forum for participation and direction by the States, Native American tribes, and the public. A Technical Steering Panel (TSP) of independent scientists and experts was formed in 1988 to direct the work. The TSP consists of experts in the various technical fields relevant to the Project. The TSP includes experts in environmental pathways, epidemiology, and surface and ground water transport. There is expertise in statistics, demography, agriculture, and meteorology. And, the Panel has experts in nuclear engineering, radiation dosimetry, cultural anthropology, health physics and public policy. The technical members on the Panel were selected by Deans of Research at major universities in Washington and Oregon. Washington and Oregon State representatives were selected by the respective governments. Two members were selected by involved Indian tribes. One member represents the public and was chosen by the TSP. At the request of their Governor, Idaho gained a representative on the Panel in 1991. The TSP first met in 1988. USDOE initially asked the TSP to give independent guidance to the project. The Panel concluded that its independence would be credible only if the TSP directed the work. USDOE agreed and committed to distance itself from the study. USDOE has lived up to that promise. There were still some concerns about the TSP’s independence, in large part because USDOE funded the study. The question of the funding source was one which concerned the TSP from the beginning. They recognized that the public perceived a major conflict of interest Independent Project Direction with USDOE controlling the funding. Therefore, funding was transferred to the CDC in 1992 through a memorandum of understanding signed by the Secretary of Health and Human Services and the Secretary of Energy in 1990. But, the TSP develops its own budget and sets Project priorities. Early in the process, the TSP set the tone for strong direction of quality science done in an open public forum. This tone was clearly encouraged and supported by the states, the Northwest Tribes and the public. Public trust and support is an absolute necessity to the success of the Project. If the work is not credible, public questions about exposures from Hanford will remain unanswered. The time and money spent on the study would be wasted. TSP members verify and evaluate project data and computer models. Five subcommittees and two working groups allow scrutiny and meaningful interactions with project staff. The TSP has access to all documents that relate to the Project. Some TSP members have security clearances and review classified documents. The TSP believes it is crucial that the public have access to all documents used in the Project. This allows for an independent check of the TSP’s work. The TSP strongly advocated that USDOE declassify all Projectrelated documents. USDOE agreed. However, the declassification process is expensive and slow. It will take some time before all Projectrelated documents are publicly available. Washington and Oregon State staff provide logistic and communications support to the TSP. These staff also provide technical support and assure TSP coordination and intra-panel communications. Technical staff provide assistance on quality assurance and special technical reviews. Hanford dose reconstruction started by gathering data about the amounts and types of radioactive materials released to the environment The Source Term estimates are based on data found in Hanford records. Battelle and

Page 8

ments in an effort to locate references to past Hanford releases. The records contain extensive information about radioactive releases to the air and the Columbia River from Hanford operations. Although some daily reactor operation information does exist, it does not cover the entire 1944-197 1 time period. The next step is to determine how and where the radioactive materials traveled in the atmosphere, soil, ground water and river water. Although radionuclide release monitoring data are plentiful, the number of radionuclides covered and the time periods addressed are limited. The data in the Hanford literature are generally reported on a monthly basis. The ways in which people could have been exposed to radioactive materials-such as breathing contaminated air or eating contamilow). These routes of radiation exposure are called environmental pathways. Figure 1. How People CouldHave Been Exposed to Radioactive Materid ffom Hanford

Page 9

Information is also gathered about the number of people that could have been exposed, and where they lived, their age, sex, eating habits, lifestyles, and any other factors that could influence their exposure. All this information is fed into complex computer programs that calculate the radiation dose Much of the historical data that goes into the computer models contains gaps. Some historical records are incomplete, missing, or not sufficiently detailed. Data gaps like these mean that radiation dose estimates can never be totally certain. However, the TSP is confident that the representative doses reported here, and the methods used to calculate them, are as reliable as today’s science can make them. Scientists have been able to reconstruct data that details each load of fuel that went through the reactors and the processing facilities. With this information, scientists can closely estimate the amount of radioactive material that was released. Through the use of monitoring data, weather records, and other information, the Project’s computer models have been able to track the movement of radioactive materials through the environment, through various exposure pathways, and ultimately, to people. The reliability of the computer models, and the uncertainty of the dose estimates, are addressed elsewhere in this report.

Page 10

The information needed to tell us exactly what dose any one person received simply does not exist. Amounts of radioactive contamination that was in the air, on the ground or on plants, or in water at any given place and time can only be estimated, not calculated. Radiation doses also depend on factors unique to each person. Many of these factors-such as location and diet at specific times-cannot be recalled exactly. As a result, there will be some uncertainty about the true dose that each person Doses have been estimated with models in computer programs that were extensively tested for accuracy and for their ability to predict results that compare with historical monitoring data. This was done through validation and uncertainty and sensitivity analyses. These methods were reviewed by the TSP and a CDCRSP convened peer review panel. The uncertainty analyses help to determine the precision with which dose estimates can be made. The sensitivity analyses determine what data contribute most to the uncertainties. Model validation compares model predictions with actual measurements. The TSP is confident that the representative doses reported here, and the methods used to calculate them, are as reliable as science can make them. Project scientists reconstructed, as well as could be done, events that occurred as long as 50 years ago, using fragmented data. Each of the Project’s models has many inputs. Most of these are themselves uncertain. Values for many key factors were estimated by generating a large number of scenarios that fit the known facts, and then measuring how the differences in the scenarios influence the dose estimates. Uncertainty in the dose estimates can becaused by several factors. One is uncertainty resulting from incomplete information such as not being able to measure all the food people actually ate. Another source is the possibility of errors made in past measurements of radioactivity in emissions, the environment, or people. Natural variations also contribute to uncertainty in much of the input information in the dose model. Examples of these variations include differences among individuals in age, sex,lifestyle and geographic location; differences among dairy cows in the amounts of contaminated pasture grass they ate; and differences in milk production of individual cows during the year. These different factors were assessed to determine their level of uncertainty. Researchers could then decide how much work should go into each part of the …