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| Fig. 1: 75,276 square mile area including Hanford Nuclear Site and area surrounding involved in environmental study (gray). [4] (Image Source: A. Ganesh, template from Wikimedia Commons) |
The Hanford Site is a large nuclear complex located in southeastern Washington State, USA. The site covers an area of about 580 square miles (1,500 square kilometers) and is situated along the Columbia River. The Hanford site played a significant role in the development of the United States' nuclear weapons program during World War II and the Cold War. Its primary mission during World War II was the production of Plutonium for the Manhattan Project. This led to the development of the atomic bomb. The B Reactor at Hanford produced the Plutonium used in the "Fat Man" bomb dropped on Nagasaki, Japan, in 1945. After the war, Hanford continued to produce Plutonium for the U.S. nuclear arsenal. Over the years, the site housed 9 nuclear reactors, processing facilities, and at its peak 177 waste storage areas containing 56 million gallons of radioactive material. [1,2]
The Hanford site houses two-thirds of the nation's high-level radioactive waste: Originally there was 1,700 waste sites, 450 billion gallons of liquid radioactive waste, 70 billion gallons of contaminated groundwater, 53 million gallons of tank waste stored in 177 tanks, 9 reactors, 5 million cubic yards of contaminated soil, 22 thousand drums of mixed waste, 2.3 tons of spent nuclear fuel, and 17.8 metric tons of plutonium-bearing material. Cleanup entails managing over 50 gallons of liquid waste, 2,300 gallons of spent fuel, 12 tons of plutonium, 25 million cubic feet of solid waste, and addressing 270 billion gallons of contaminated groundwater across 1,700 sites and 500 facilities spanning 586 square miles. Tasks include transferring waste, vitrification, groundwater mitigation, reactor demolition, and burying tons of waste in lined pits. The DOE, EPA, and Washington state have progressed in Hanford's cleanup: 6 of 9 reactors cocooned, 2,300 tons of spent fuel removed, 7.5 million gallons of liquid waste transferred, stabilizing 149 tanks. Additionally, 1.25 million gallons of radioactive waste retrieved, and 8 billion gallons of groundwater treated monthly by 5 Columbia River facilities. [1,2,5]
The final report of the federal governments Hanford Thyroid Disease Study revealed that approximately 3,440 people born between 1940 and 1946 were included in the study. The study cost $18 million and took nearly 13 years to complete. The study found 12 cases of thyroid cancer among 1,747 women and 7 cases among 1,693 men, amounting to less than 1% prevalence. For benign nodules, the Framingham (Mass.) Heart Study found a cumulative incidence over 15 years of 8.1% in women and 2.4% in men. The Hanford study found 9.7% and 4.7%, respectively, but many cases were detected through ultrasound, and if these are excluded, the numbers fall to 4.8% and 2.0%. For hypothyroidism, the authors found that prevalence estimates from several major studies are in reasonable agreement with each other and define a range that encompasses the estimates derived in the Hanford Thyroid Disease Study, 11.7% in females and 3.7% in males. Less than 1% of the participants had radiation doses over 1000 milliGray (mGy), while the mean dose was 186 mGy. [3,4]
The prevalence of thyroid cancer among the study participants was less than 1%, suggesting a relatively low risk compared to general population estimates. However, the prevalence of benign nodules and hypothyroidism appears to be higher than reported rates in other studies, particularly when detected through ultrasound. This discrepancy could indicate a potential association between radiation exposure from the Hanford nuclear site and non-cancerous thyroid abnormalities. Despite intentional oversampling of highly exposed areas, less than 1% of participants had radiation doses exceeding 1000 milliGray (mGy), indicating predominantly low exposure levels. However, the study's statistical power was limited due to the small number of individuals with high radiation doses, potentially impacting the ability to detect a dose-response relationship for thyroid diseases. Further research with larger sample sizes and longer follow-up periods may be necessary to elucidate the true extent of any health effects associated with radiation exposure from Hanford on thyroid health. [4]
The Hanford Site, a pivotal center in the United States' nuclear weapons program, has left a legacy of extensive radioactive contamination spanning over 580 square miles. Cleanup efforts have made significant progress, with accomplishments including the cocooning of six reactors, removal of spent fuel, and treatment of billions of gallons of contaminated groundwater. However, challenges persist in managing vast amounts of radioactive waste and mitigating environmental hazards. The Hanford Thyroid Disease Study, conducted over 13 years at a cost of $18 million, examined the health effects of radiation exposure on residents born between 1940 and 1946. While the prevalence of thyroid cancer among participants was low, rates of benign nodules and hypothyroidism were notably higher, particularly when detected through ultrasound. Limited statistical power due to small sample sizes with high radiation doses underscores the need for further research to fully understand the potential health impacts of Hanford's radioactive legacy on thyroid health. Continued efforts in cleanup and research are essential to mitigate risks and safeguard public health in the aftermath of Hanford's nuclear activities.
© Ananya Ganesh. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] R. E. Gephart, "A Short History of Hanford Waste Generation, Storage, and Release," Pacific Northwest Laboratory, PNNL-13605, October 2003.
[2] "History of Hanford Site Defense Production (Brief)," Fluor Hanford, U.S. Department of Energy, HNF-5041-FP, February 2001.
[3] E. S. Gilbert, "Mortality Studies of Hanford Workers," Pacific Northwest Laboratory, PNL-SA-1390, April 1986.
[4] T. Reynolds, "Final Report of Hanford Thyroid Disease Study Released," J. Natl. Cancer Inst. 94, 1046 (2002).
[5] J. Chenevey, "Hanford Waste Cleanup," Physics 241, Stanford University, Winter 2017.
[6] C. W. Connell, "Tracking Cleanup at Hanford," U.S. Department of Energy, HNF-24532-FP, May 2005.
