An evaluation of 1957 to 1966 data to assess residual radiation from nuclear weapons sites in the U.S.
- Author(s): Cheng, Chih Jen
- Advisor(s): Stenstrom, Mickael K
- et al.
Between 1950s and 1960s, active bomb tests produced many radionuclides and exposed radiation to the environment. This thesis addresses the radioactivity caused by strontium-90 (90Sr), a beta-only emitter and the health concerns it has caused. Through the bomb detonations, radioactive compounds were carried by atmospheric transport globally. This research is conducted to analyze the pattern of distribution and the inventory of 90Sr. Data from a total of 53 sites were collected from public records and seven, four and eight sites were further analyzed for gross beta in milk, air and raw surface water, respectively. Monthly concentrations of 90Sr and the values of gross beta from 1957 to 1966 are presented in multiple figures, and shows that radionuclides are not transported in predictable directions. By comparing the concentrations of 90Sr to the gross beta detected in the local ecological systems, a relation between gross beta and 90Sr is examined, and eventually concluded to show a weak linkage between them. Distance to the bomb test sites is not proportional to the amount of 90Sr detected at the inspection stations. The results also show a 2-year atmospheric residence time before 90Sr settles down. It is suggested that precipitation (wet deposition) may play a more significant role of enhancing gravity settling of 90Sr in different areas, and more factors should be considered for the analysis.