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Fast neutron activation dosimetry with TLDS

Description: Fast neutron activation using threshold reactions is the only neutron dosimetry method which offers complete discrimination against gamma-rays and preserves some information about the neutron energy. Conventional activation foil technique requires sensitive radiation detectors to count the decay of the neutron induced activity. For extensive measurements at low neutron fluences, vast outlays of counting equipment are required. TL dosimeters are inexpensive, extremely sensitive radiation detectors. The work of Mayhugh et al. (Proc. Third Int. Conf. on Luminescence Dosimetry, Riso Report 249, 1040, (1971)) showed that CaSO/sub 4/: DyTLDs could be used to measure the integrated dose from the decay of the radioactivity produced in the dosimeters by exposure to thermal neutrons. This neatly combines the activation detector and counter functions in one solid state device. This work has been expanded to fast neutron exposures and other TL phosphors. The reactions /sup 19/F(n, 2n)/sup 18/F, /sup 32/S(n,p)/sup 32/P, /sup 24/Mg(n,p)/sup 24/, and /sup 64/Zn(n,p)/sup 64/Cu were found useful for fast neutron activation in commercial TLDs. As each TLD is its own integrating decay particle counter, many activation measurements can be made at the same time. The subsequent readings of the TL signals can be done serially after the induced radioactivity has decayed, using only one TL reader. The neutron detection sensitivity is limited mainly by the number statistics of the neutron activations. The precision of the neutron measurement is within a factor of two of conventional foil activation for comparable mass detectors. Commercially available TLDs can measure neutron fluences of 10/sup 9/n/cm/sup 2/ with 10 percent precision.
Date: January 1, 1975
Creator: Pearson, D. W. & Moran, P. R.
Partner: UNT Libraries Government Documents Department

Hot cell studies of light water reactor fuel reprocessing. [Radioactivity distribution; dissolution; extraction; waste evaporation]

Description: Experiments were run using all-glass equipment with irradiated fuel in a hot cell, in order to study possible problems in LWR fuel reprocessing (radioactivity distribution during dissolution, stability of extraction raffinate, waste partitioning). Behavior of /sup 129/I, tritium, and /sup 14/C in the off-gas was studied, as were the radioisotopes in the dissolver solution; results are compared with ORIGEN calculations. Actinide mass analyses were also made and compared with ORIGEN. Residues and cladding problems were studied. Solvent extraction is next considered, and the beneficial effect of radiation on the Pu and Ru extraction is pointed out. Synthetic waste evaporations were carried out and the composition of the solid analyzed.
Date: January 1, 1976
Creator: Campbell, D. O. & Buxton, S. R.
Partner: UNT Libraries Government Documents Department

Behavior of highly radioactive iodine on charcoal in moist air

Description: The behavior of highly radioactive iodine adsorbed on charcoal exposed to moist air (110 torr water vapor partial pressure) was investigated in a series of six experiments. The amount of radioactive /sup 130/I on the well-insulated 28-cm/sup 3/ bed ranged from 50 to 570 Ci, and the relative humidity was 47 percent at the bed inlet temperature of 70/sup 0/C. Radioactive iodine was released from the test beds at a continuous fractional release rate of approximately 7 x 10/sup -6//hr for all types of charcoal tested. The chemical form of the released iodine was such that it was very highly penetrating with respect to the nine different types of commercial impregnated charcoals tested in backup collection beds. Two types of silver-nitrate-coated adsorption materials behaved similarly to the charcoals. Silver-exchanged type 13-X molecular sieve adsorbers were 20 to 50 times more efficient for adsorbing the highly penetrating iodine, but not as efficient as normally found for collecting methyl iodide. The chemical form of the highly penetrating iodine was not determined. When the moist air velocity was decreased from 28.5 fpm (25/sup 0/C) to as low as 0.71 fpm (25/sup 0/C), the charcoal bed temperature rose slowly and reached the ignition temperature in three of the experiments. At 0.71 fpm (25/sup 0/C) the ignited charcoal beds reached maximum temperatures of 430 to 470/sup 0/C because of the limited oxygen supply. The charcoal exposed for four years at Oak Ridge ignited at 283/sup 0/C compared with 368/sup 0/C for unused charcoal from the same batch. Two of the experiments used charcoal containing 1 or 2 percent TEDA (triethylene-diamine) and a proprietary flame retardant. The oxidation and ignition behavior of these charcoals did not appear to be affected adversely by the presence of the TEDA.
Date: January 1, 1976
Creator: Lorenz, R. A.; Manning, S. R. & Martin, W. J.
Partner: UNT Libraries Government Documents Department

/sup 57/Fe impurity atom lattice dynamics and systematics in group V and VI host metals

Description: The Moessbauer recoil-free fraction f and thermal shift have been measured for very dilute /sup 57/Fe impurities in body-centered cubic V, Nb, Mo, Ta, and W host metals in the range 4 to 860/sup 0/K. These experimental quantities have been interpreted in terms of an impurity-atom lattice-dynamical model of Mannheim where the important parameter ..gamma../sub ih//..gamma../sub hh/ is a measure of the coupling of the impurity atom to the host lattice relative to the corresponding coupling in the pure host lattice. Values of ..gamma../sub ih//..gamma../sub hh/ for each host from the f-value data were obtained and, independently, from the shift data, and for each host rather good agreement is obtained. The general trend of the data shows that for neighboring hosts of the same row of the periodic table, the relative /sup 57/Fe impurity binding is stronger for the Group V host than for the Group VI host. The results also support a previous conjecture that the nearest-neighbor binding between the impurity and the host should be proportional to a geometric mean of the nearest-neighbor couplings for a lattice consisting entirely of impurity atoms and for a lattice of host atoms only.
Date: January 1, 1976
Creator: Taylor, R. D.; Kitchens, T. A. Jr. & Erickson, D. J.
Partner: UNT Libraries Government Documents Department

Beta attenuation transmission system (BATS)

Description: The beta attenuation transmission system (BATS) is an automated radiation gauge designed for quantitative measurement of component thickness in explosive detonators. The BATS was designed and built by Group M-1, the Nondestructive Testing Group, of the Los Alamos Scientific Laboratory to measure the areal thickness, in mg/cm/sup 2/, of a cylinder of high explosive (HE) enclosed within a plastic holder. The problem is to determine the density of the HE. A /sup 90/Sr source is collimated by a 0.25 x 1.59-mm slit, and the transmitted beta-particle flux is detected by a plastic scintillator, coupled to a photomultiplier tube. The detonator is transported through the radiation beam by a leadscrew, ballnut, stepping-motor combination. Continuous analog position data are available, derived from the output from a linear-actuated potentiometer attached to the scanner. A linear electrometer amplifies the detected signal, which is then integrated for a preselected time, to obtain the desired statistical accuracy. A microprocessor (..mu..P) is used to control the scanner position and to make the data readings at the assigned positions. The data are stored, and, at the completion of the scan, are processed into the desired format. The final answer is displayed to the operator or output to a peripheral device for permanent record. The characteristics of the radiation source, the collimator, the signal detection and conditioning, and the final results are described in detail. The scanner and the microprocessor control system are briefly outlined.
Date: January 1, 1977
Creator: Hagan, R. C. & Fullbright, H. J.
Partner: UNT Libraries Government Documents Department

Nondestructive determination of burnup and cooling times of irradiated fuel assemblies

Description: The applicability of nondestructive gamma-ray and neutron techniques for the characterization of irradiated fuel assemblies has been investigated. Consistency of relative cooling times can be verified using specific isotopic ratios. The axial activity profiles of assemblies have been measured using a variety of detectors. Declared burnup values for MTR, BWR, and PWR assemblies have been correlated with the /sup 134/Cs//sup 137/Cs and /sup 154/EU//sup 137/Cs isotopic ratios.
Date: January 1, 1979
Creator: Phillips, J.R.; Hsue, S.T.; Kaieda, K.; Lee, D.M.; Halbig, J.K.; Medina, E.G. et al.
Partner: UNT Libraries Government Documents Department

Retention of low-level radioacrive waste material by soil

Description: Beacuse of the wide variations in soil and waste characteristics, the degree of radionuclide retention would be expected to vary; knowledge of that variation may be of value in predicting radionuclde mobility. This report discusses results of investigations of radioactive waste/soil interactions as they relate to radionucldie retention and its variability among soils and radionuclides. In soil column leaching studies, radioactive waste solutions were applied to four different soil types; /sup 241/Am, /sup 88/Y, and /sup 172/Hf were retained in the top four cm of soil with better than 90% retained by a protective surface sand layer. Less than 50% of the /sup 85/Sr, /sup 137/Cs, and /sup 83/Rb was retained by the surface sand. No /sup 88/Y, /sup 172/Hf, /sup 85/Sr, /sup 137/Cs, or /sup 83/Rb was detected by gamma counting in the leachate solutions, however, using a more sensitive analytical technique small amounts of /sup 238/Pu, /sup 239/ /sup 240/Pu and /sup 241/Am were found in leachates from all soils. It appears that release of this small fraction of mobile radionuclide may have a significant long-term impact on the environment. It aslo appears that reliance for attenuation of some radionuclides can not be placed solely on characteristics of the soil matrix.
Date: January 1, 1979
Creator: Essington, E.H.; Fowler, E.B. & Polzer, W.L.
Partner: UNT Libraries Government Documents Department

Summary of thyroid findings in Marshallese 22 years after exposure to radioactive fallout

Description: Inhabitants of several atolls in the Marshall Islands were accidently exposed to fallout radiation following a detonation of a high yield thermonuclear device during experiments at Bikini in the Pacific Proving Grounds in March 1954. The most serious acute effects of the exposure were due to penetrating gamma radiation. Contamination of the skin in the Rongelap group resulted in widespread beta burns and epilation. These lesions healed and hair regrew normally within several months. Radiochemical urine analyses revealed that measurable amounts of radionuclides, including /sup 131/I, were absorbed internally from ingestion of contaminated food and water and from inhalation. No acute effects due to this internal exposure were seen. Late thyroid effects from radioiodine absorption are described. Follow-up examinations have revealed, except for one fatal case of leukemia and extensive thyroid lesions, only a few findings that might be related to radiation exposure. A group of more than 200 Rongelap people who were relatives of exposed people, but had been away from the island at the time of the accident, moved back with the exposed people to their home island in 1957 and have served as an ideal comparison population for the studies. Results of medical examinations carried out on these populations for the past 22 years are reviewed.
Date: January 1, 1976
Creator: Conard, R A
Partner: UNT Libraries Government Documents Department

Health and Safety Laboratory environmental quarterly, September 1, 1976--December 1, 1976. [Monitoring of environment for radioactivity and chemical pollution]

Description: This report presents current data from the HASL environmental programs, The Swedish Defense Research Establishment, The Woods Hole Oceanographic Institution, Argonne National Laboratory and The New Zealand National Radiation Laboratory. The initial section consists of interpretive reports and notes on ground level air radioactivity in Sweden from nuclear explosions, plutonium in air near the Rocky Flats Plant, nitrous oxide concentrations in the stratosphere, lake sediment sampling, plutonium and americium in marine and fresh water biological systems, radium in cat litter, and quality control analyses. Subsequent sections include tabulations of radionuclide and stable lead concentrations in surface air; strontium-90 in deposition, milk, diet, and tapwater; cesium-137 in Chicago foods in October 1976 and environmental radioactivity measurements in New Zealand in 1975. A bibliography of recent publications related to environmental studies is also presented.
Date: January 1, 1977
Creator: Hardy, E. P. Jr.
Partner: UNT Libraries Government Documents Department

Plutonium and cesium radionuclides in the Hudson River estuary. Annual technical progress report, December 1, 1976--November 30, 1977

Description: We have obtained a large set of sediment cores from the Hudson estuary through much of the ambient salinity range. A number of core sections and samples of suspended particles have been analyzed for /sup 137/Cs, /sup 134/Cs and /sup 60/Co by direct gamma counting, and /sup 239/Pu, /sup 240/Pu, and /sup 238/Pu by alpha spectrometry. The distribution of both /sup 137/Cs and /sup 239/Pu, /sup 240/Pu indicates rapid accumulation in marginal cover areas, and especially in the harbor region adjacent to New York City. The distributions of both /sup 137/Cs and /sup 239/Pu, /sup 240/Pu are similar in surface sediments and with depth in cores, but there are deviations from the fallout ratio due to addition of reactor /sup 137/Cs and loss of /sup 137/Cs from the particle phases at higher salinities. Measureable amounts of reactor-derived /sup 134/Cs and /sup 60/Co are found in nearly all sediment samples containing appreciable /sup 137/Cs, between 15 km upstream of Indian Point and the downstream extent of our sampling, 70 km south of the reactor. Accumulations of /sup 239/Pu, /sup 240/Pu in New York harbor sediments are more than an order of magnitude greater than the fallout delivery rate. The most likely explanation is accumulation of fine particles in the harbor which have been transported from upstream areas of the Hudson. Our evidence so far indicates that Indian Point is probably not a significant source of /sup 239/Pu, /sup 240/Pu or /sup 238/Pu compared with the fallout burden of these nuclides already in the sediments.
Date: January 1, 1977
Creator: Simpson, H. J. & Trier, R. M.
Partner: UNT Libraries Government Documents Department

Locating giant resonances with photoneutrons

Description: Recent studies of collective magnetic dipole resonances in heavy nuclei are reviewed with an emphasis on photoneutron experiments. In particular, the nuclear mass regions of 120, 140, and 208 are discussed in detail. New very-high-resolution photoneutron studies of /sup 208/Pb are presented. Applications of the photoneutron polarization method to the /sup 208/Pb(..gamma..,n/sub 0/)/sup 207/Pb and /sup 119/Sn(..gamma..,n/sub 0/)/sup 118/Sn reactions are reviewed. 12 figures, 2 tables)
Date: January 1, 1978
Creator: Holt, R.J.
Partner: UNT Libraries Government Documents Department

Evaluation of the health hazard from inhaled krypton-85

Description: Evaluation of the degree of internal radiation hazard requires knowledge of the parameters of Kr-85 metabolism in human beings. Data on the rate of saturation and desaturation of the body tissues are required for this estimation. The object of this in vivo study was to characterize the metabolism of inhaled Kr. For this purpose, measurements were made of the distribution and clearance of Kr following inhalation of /sup 79/Kr by the normal subjects. The rate constants determined for /sup 79/Kr were used to calculate the radiation dose associated with exposure to the long-lived /sup 85/Kr. The retention data were obtained with the Brookhaven whole-body counter. The clearance of /sup 79/Kr from the body indicates five components ranging in half-times from 14 sec to 9.6 h. The slowest components, varying between 4.2 and 9.6 h, correlated highly with percent body fat. The long-term retention was localized in regions of high fat content. The stimated radiation dose based on the retention data of this study indicates that doses to body fat and gonads are larger than those estimated by other investigators. This increased estimated dose derives from the increase in retention time of krypton in fat pools.
Date: January 1, 1979
Creator: Cohn, S.H.; Ellis, K.J. & Susskind, H.
Partner: UNT Libraries Government Documents Department

Project Rio Blanco. Environmental surveillance summary report, Part 2, July 1973-December 1976

Description: Project RIO BLANCO was a joint venture undertaken by the US Atomic Energy Commission (AEC) representing the federal government, and CER Geonuclear Corporation representing private industry. As originally conceived, Phase I of the project involved the simultaneous detonation of three nuclear devices in a single emplacement well, and was the third event in the AEC's Plowshare program to develop peaceful uses for nuclear devices. The main purpose of the RIO BLANCO experiment, as well as that of the other two Plowshare detonations, was to investigate the feasibility of using nuclear detonations in deep underground formations where the gas was too tightly held to be released under other known techniques. A total of approximately 9000 radiochemical analyses have been done on 4110 environmental samples pertaining to Project RIO BLANCO by the Department during the period July, 1973 through December, 1976. These include: 3186 air particulate filter samples; 54 air moisture samples; 34 sediment and soil samples; 9 compressed air samples; 44 municipal water supply samples; 122 special well samples; 622 river and stream samples; and 39 snow samples. Levels of radioactivity in the environment and salinity in the surface and well waters were determined before the detonation so that any undesirable changes caused by the detonations could be more easily identified. The collected data identify environmental levels of radioactivity for an extensive area of western Colorado. This report is prepared in two parts. Part I covers the period January 1, 1971 through June 30, 1973, including pre-shot activities and results of surveillance for the six weeks following the detonations. Part II contains the results of environmental surveillance during the periods of re-entry and production test flaring of the gas from the cavities produced by the nuclear explosions and during the period at final shutdown and abandonment of the site. 18 figs., ...
Date: January 1, 1976
Partner: UNT Libraries Government Documents Department

BLIP production of Fe-52 and the Mn-52m generator

Description: Fe-52 (t 1/2 = 8.275 h) is the only radioisotope of iron with decay properties suitable for imaging applications (100% 169-keV and 112% annihilation gammas). It can also be used in a Fe-52/Mn-52m generator system as a source of Mn-52m (t 1/2 = 21.1m) which is a short-lived positron emitter (192.54% annihilation gammas). Clinically useful quantities of Fe-52 have been prepared at the Brookhaven Linac Isotope Producer (BLIP) by bombarding manganese or nickel targets with medium-energy protons. After chemical separation, Fe-52 is loaded onto a generator column from which carrier-free Mn-52m is eluted. The Mn-52m generator is potentially useful in positron emission computed tomography.
Date: January 1, 1979
Creator: Ku, T.H.; Richards, P.; Stang, L.G. & Prach, T.
Partner: UNT Libraries Government Documents Department

Removal of radioactive contaminants from aqueous laboratory wastes by chemical treatment

Description: The following conclusions can be drawn from the studies reported. The presence of suspended matter (i.e., clay) in the spiked tapwater solution improved the plutonium removals; however, the addition of clinoptilolite to the plant raw feed did not provide any noticeable improvement for plutonium removal. The addition of powdered clinoptilolite to the regular treatment in the plant significantly improved the removal of /sup 137/Cs, but had little effect on plutonium or /sup 90/Sr removal. Magnesium sulfate-lime-TSP (trisodium phosphate) treatment in the plant performed adequately, but not as well as the regular ferric sulfate-lime-TSP treatment. However, magnesium appears to be an adequate alternate during occasions of non-typical influents. A large portion of the plutonium is associated with the suspended solids matter in the waste. Autoradiographs indicate that the plutonium is generally evenly distributed, with some occasional hot spots.
Date: January 1, 1976
Creator: Drago, J. A. & Buchholz, J. R.
Partner: UNT Libraries Government Documents Department

Thermal/fluid modeling of the response of saturated marine red clays to emplacement of nuclear waste

Description: This report discusses the heat and mass transport in marine red clay sediments being considered as a nuclear waste isolation medium. Development of two computer codes, one to determine temperature and convective velocity fields, the other to analyze the nuclide migration problem, is discussed and preliminary results from the codes reviewed. The calculations indicate that for a maximum allowable sediment/canister temperature range of 200 to 250/sup 0/C, the sediment can absorb about 1.5 kW initial power from waste in a 3 m long by 0.3 m diameter canister. The resulting fluid displacement due to convection is found to be small, less than 1 m. The migration of four nuclides, /sup 239/Pu, /sup 137/Cs, /sup 129/I, and /sup 99/Tc were computed for a canister buried 30 m deep in 60 m thick sediment. It was found that the /sup 239/Pu and /sup 137/Cs, which migrate as cations and have relatively high distribution coefficients, are essentially completely contained in the sediment. The anionic species, /sup 129/I and /sup 99/Tc, which have relatively low distribution coefficients, broke through the sediment in about 5000 years. The resultant peak injection rates which occur at about 15,000 years were extremely small (0.5 ..mu..Ci/year for /sup 129/I and 180 ..mu..Ci/year for /sup 99/Tc).
Date: January 1, 1979
Creator: McVey, D.F.; Gartling, D.K. & Russo, A.J.
Partner: UNT Libraries Government Documents Department

Radionuclide content of an exhumed canyon tank and neighboring soil

Description: To assess the long-term hazard potential associated with the burial of partially decontaminated process equipment, burial emplacements of equipment from an irradiated-fuel separations building (canyon) are being exhumed and examined. One piece of equipment, a Purex feed adjustment tank that was retired in 1957 from service in a hot canyon at the Savannah River Plant, has been exhumed and studied. This paper describes sampling of neighboring soil, tank exhumation, results of assay of soil and tank, and conclusions. Assays of the tank and soil show that only 1 mCi of /sup 137/Cs and 0.4 mCi (7 mg) of /sup 239/Pu remain on the surfaces of the tank; amounts of these radionuclides in neighboring soil are substantially less. Radionuclides from the contaminated surface of the tank migrated into neighboring soil. Of the three nuclides studied, /sup 90/Sr migrated most extensively, as observed previously. /sup 239/Pu contents of the tank and neighboring soil were less than the 10-nCi/g total transuranic nuclide content allowed under ERDA standards for burial of nonretrievable waste. This paper also describes plans for future studies including (1) exhumation of other equipment and (2) in-place lysimeter and laboratory-column tests for studying radionuclidic migration in soil.
Date: January 1, 1977
Creator: Holcomb, H. P.
Partner: UNT Libraries Government Documents Department

Methodology for the determination of environmental /sup 129/I and /sup 99/Tc

Description: The Savannah River Laboratory is using existing techniques and developing new methodology to determine the environmental impact of the Savannah River Plant with regard to /sup 129/I and /sup 99/Tc. /sup 129/I is determined by neutron activation after the method of Brauer. Activation products are quantified by ..gamma..-ray spectroscopy (Ge(Li)) following chemical isolation. /sup 125/I is used as a yield tracer. /sup 129/I amounts as low as 3.8 fCi can be determined with 30-minute counting times. An isotope dilution method for /sup 99/Tc based on a three-stage surface ionization mass spectrometer is being developed. Its chemical isolation scheme ends with the Tc loaded on a single ion-exchange bead for enhanced mass-spectrometric sensitivity. /sup 97/Tc will be used as a yield tracer. A lower limit of 0.2 fCi is sought. A modified method using liquid scintillation counting has determined /sup 99/Tc in some aqueous samples. These methods have confirmed that /sup 129/I and /sup 99/Tc can be highly mobile in the aqueous environment, establishing the need for monitoring.
Date: January 1, 1978
Creator: Anderson, T. J.
Partner: UNT Libraries Government Documents Department

Effects of interstitial solutes on the microstructures of self-ion irradiated vanadium

Description: Vanadium and vanadium containing 0.1 percent C, 0.4 percent C, 1.0 percent N, and 1.0 percent O were irradiated with 3-MeV /sup 51/V/sup +/ ions in the temperature range 650 to 880/sup 0/C to a dose level of approximately 20 dpa. The results show that nitrogen is most effective in controlling the void swelling. Carbon and oxygen also suppress the swelling considerably when compared with unalloyed vanadium. Except for V-1.0 percent N, all compositions exhibit a fine platelet precipitate with (012) habit at 650/sup 0/C. In the case of vanadium-carbon alloys, this phase persisted even at higher temperatures. Vanadium and V-1.0 percent O showed fine precipitation on dislocations and void surfaces at 880/sup 0/C. V-0.1 percent C exhibited a metastable (013) carbide precipitate at 880/sup 0/C, whereas V-0.4 percent C showed equilibrium V/sub 2/C phase with some (012) precipitates. This (012) precipitation was irradiation induced and was dependent upon the carbon concentration. V-1.0 percent N did not show any evidence of precipitation over the entire temperature range.
Date: January 1, 1976
Creator: Agarwal, S. C.; Potter, D. I. & Taylor, A.
Partner: UNT Libraries Government Documents Department

Optical theorem for heavy-ion scattering. [Scattering amplitudes, cross sections]

Description: An heuristic derivation is given of an equivalent of the optical theorem stated in the charged situation with the remainder or nuclear elastic scattering amplitude defined as a difference of elastic and Coulomb amplitudes. To test the detailed behavior of this elastic scattering amplitude and the cross section, calculations were performed for elastic scattering of /sup 18/O + /sup 58/Ni, /sup 136/Xe + /sup 209/Bi, /sup 84/Kr + /sup 208/Pb, and /sup 11/B + /sup 26/Mg at 63.42 to 114 MeV. (JFP)
Date: January 1, 1976
Creator: Schwarzschild, A. Z.; Auerbach, E. H.; Fuller, R. C. & Kahana, S.
Partner: UNT Libraries Government Documents Department

Relationship of dose rate and total dose to responses of continuously irradiated beagles

Description: Young-adult beagles were exposed continuously (22 hours/day) to /sup 60/Co ..gamma.. rays in a specially constructed facility. The exposure rates were either 5, 10, 17, or 35 R/day, and the exposures were terminated at either 600, 1400, 2000, or 4000 R. A total of 354 dogs were irradiated; 221 are still alive as long-term survivors, some after more than 2000 days. The data on survival of these dogs, coupled with data from similar preliminary experiments, allow an estimate of the LD/sub 50/ for ..gamma..-ray exposures given at a number of exposure rates. They also allow comparison of the relative importance of dose rate and total dose, and the interaction of these two variables, in the early and late effects after protracted irradiation. The LD/sub 50/ for the beagle increases from 258 rad delivered at 15 R/minute to approximately 3000 rad at 10 R/day. Over this entire range, the LD/sub 50/ is dependent upon hematopoietic damage. At 5 R/day and less, no meaningful LD/sub 50/ can be determined; there is nearly normal continued hematopoietic function, survival is prolonged, and the dogs manifest varied individual responses in other organ systems. Although the experiment is not complete, interim data allow several important conclusions. Terminated exposures, while not as effective as radiation continued until death, can produce myelogenous leukemia at the same exposure rate, 10 R/day. More importantly, at the same total accumulated dose, lower exposure rates are more damaging than higher rates on the basis of the rate and degree of hematological recovery that occurs after termination of irradiation. Thus, the rate of hematologic depression, the nadir of the depression, and the rate of recovery are dependent upon exposure rate; the latter is inversely related and the former two are directly related to exposure rate.
Date: January 1, 1978
Creator: Fritz, T. E.; Norris, W. P.; Tolle, D. V.; Seed, T. M.; Poole, C. M.; Lombard, L. S. et al.
Partner: UNT Libraries Government Documents Department

Nuclear Chemistry Research. Annual progress report, 1 January--31 December 1975. [Summaries of research activities at Pittsburgh University]

Description: Research is summarized on heavy ion fusion reactions, equilibrium charge-state distributions of heavy ions, the statistics of low level counting, and strontium and radiostrontium in marine mollusc shells. A list of publications is included. (JFP)
Date: January 1, 1976
Creator: Wolke, R L
Partner: UNT Libraries Government Documents Department