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Fallout strontium-90 and cesium-137 in northern Alaskan ecosystems during 1959--1970

Description: Thesis. Cycling routes, rates of transport, and resultant concentrations of the fallout radionuclides /sup 90/Sr and /sup 137/Cs in northern Alaskan ecosystems were defined during the period 1959 to 1970. Radiochemical analysis of extensive samples of biota and whole-body counting of / sup 137/Cs in Eskimo and Indian ethnic groups were related to ecological principles, especially the concept of trophic niche, which elucidated the observed patterns of radionuclide concentrations. Experiments involving Sr and Cs radioisotopes applied to natural Cladonia-- Cetraria lichen carpets yielded effective half-times of 1.O to 1.6 years for Sr and more than 10 years for Cs. Direct and indirect estimates of /sup 131/Cs half-times in Eskimos on a caribou meat diet were made by dietary manipulation and by relating dietary /sup 137/Cs intake and resultant change between periodic whole body counts. Effective half- times of 70 days for adults (more than 21 years old) and minors (14 to 20 years old) and of 45 days for children (less than 14 years old) were found. Suitable mathematical models were used to compute lichen forage ingestion rates of free- ranging adult caribou (4.5 to 5.0 kg dry weight per day), caribou meat ingestion rates of Anaktuvuk Pass residents (up to 2 kg wet weight per day for men), and / sup 90/Sr body burdens of Anaktuvuk Pass residents during the period 1952 to 1968 (maximum value of 8 nCi in adult males during late 1966 to early 1967). Special emphasis was made of cultural influences upon the food-gathering patterns of the native peoples studied. Culture change, especially in the form of food stamps, welfare payments, acquisition of snowmobiles, and improved housing was documented throughout the study and noticeably reduced the radionuclide accumulations. Total radiation dose rates to the Anaktuvuk Pass adult population were estimated to be about 100 mrad/year ...
Date: May 1, 1973
Creator: Hanson, W.C.
Partner: UNT Libraries Government Documents Department

Afterheat calculations for the HTGR

Description: Afterheat rates were calculated for the HTGR utilizing new input information. The new afterheat results are a few percent higher than the HTGR afterheat results previously obtained in the 100-to 10,000-sec time range and are 11 to 15% higher than the previous results in the one-day to ten-days time range. The uncertainties were studied in the time region from 100 sec to ten days. The new results were also compared with calculations at other laboratories. The gamma-ray spectra were computed at several shutdown times for future applications in shielding studies. Previous afterheat calculations for the HTGR are completely replaced and updated. (auth)
Date: November 1, 1973
Creator: Sund, R.E.
Partner: UNT Libraries Government Documents Department

High-resolution studies of beta-delayed proton emission in light nuclei

Description: Thesis. Identified protons were observed following beta decay of the precursor nuclei /sup 21/Mg, /sup 25/Si, /sup 37/Ca, /sup 40/Sc, /sup 41/Ti, and / sup 23/Al. These measurements spanned a proton energy range from 600 keV to 8.5 MeV, and included all significant particle decays of these nuclei. A helium-jet transport system was developed and used with various DELTA E - E counter telescopes to obtain high-resolution, lowbackground spectra. These data perrmitted accurate location of proton unbound levels in the beta-decay daughters, and absolute branching ratios and ft values for these allowed decays were determined. The half-lives of these nuclei were measured, and all except that for /sup 41/Ti are consistent with the previous values. For /sup 41/Ti, the half-life is 80 plus or minus 2 msec, which differs from the old value of 88 plus or minus 1 msec. This latter value is thought to have been affected by the presence of /sup 37/Ca activity produced in a competing reaction. The ft values for /sup 21/Mg and /sup 25/Si are compared to the negatron decay rates in their respective mirrors. For mass 21, s 1.17 plus or minus 0.04. A comparison of predicted and observed beta-decay rates for the superalloyed decay to the T = 3/2 state in /sup 41/Sc indicates that this level has an isospin impurity of ~8%. The observed beta-decay rates in /sup 21/Mg and /sup 37/Ca are also contrasted with theoretical predictions for decay rates to their respective daughters. The calculated values agree well for /sup 21/Mg, while for /sup 37/Ca the calculations appear to be limited by the basis space used. Delayed protons from / sup 23/Al, the first member of the A =4 n + 3 series of T/sub z/ = 3/2 nuclei, were observed, and the half-life of /sup 23/Al was measured ...
Date: December 1, 1973
Creator: Sextro, R.G.
Partner: UNT Libraries Government Documents Department

Transmutation of massive loadings of $sup 137$Cs in the blanket of a controlled thermonuclear reactor

Description: From joint meeting of the American Nuclear Society and the Atomic lndustrial Forum and Nuclear Energy Exhibition; San Francisco, California, USA (11 Nov 1973). Calculations have been performed that indicate the possibility of reducing below ten years the effective half-life for transmutation of massive loadings of /sup 137/Cs placed in a CTR blanket. The blanket studied is a modification of the cylindrical standard blanket'' calculational benchmark, having 1 cm of Nb wall material followed by a 20 cm target zone, 70 cm of moderator and a 6 cm absorber of Li. The standard blanket'' source yielding a wall loading of 10 MW/m/sup 2/ of 14 MeV neutrons is assumed. Neutron production by (n,2n) reactions in a Be moderator is used to increase the thermal flux. For an 80% target zone loading of /sup 137/Cs, a transmutation rate of 290 kg per year per meter of CTR length is obtained, with a half-life (including radioactive decay) of 9.9 years. At this loading, the transmutation rate is roughly one percent of the length of a CTR blanket would balance the production rate in a fission reactor of the same power. (auth)
Date: January 1, 1973
Creator: Gore, B. F. & Leonard, B. R., Jr.
Partner: UNT Libraries Government Documents Department