William A. Jester

Cesium-134 and Cesium-137 in Honey Bees and Cheese Samples Collected in the U.S. After the Chernobyl Accident

Abstract As a result of the Chernobyl accident on April 25, 1986, possible radioactive contamination of honey bees and cheese sampled in several areas of the United States were measured. Of bees collected in May and June of 1986 in both Oregon and New York, only those from Oregon showed detectable levels of cesium-134 ( T 1 2 = 2.05 years ), a radionuclide which would have originated from the Chernobyl incident. Cheese produced in Oregon and New York before the accident showed only cesium-137 ( T 1 2 = 30.23 years ) but cheese produced afterwards (May and September, 1986) in Oregon contained cesium-134. Cheese produced in Ohio and California at the time of the accident and thereafter contained only cesium-137. In general, the levels of radioactivity were higher in the West coast samples as compared to those taken in the East. The levels of radioactivity detected were considered to be toxicologically of no consequence.

Radioiodine speciation in the hot cell effluent gases of a radiopharmaceutical production facility.

In order to characterize the various chemical forms of airborne radioiodine species, grab-sampling measurements were conducted at the hot cell laboratory of a radiopharmaceutical production facility, using a selective-adsorbent-iodine filter system. Volatile radioiodine species were produced in the hot cell process which extracted the fission product 99Mo from the irradiated uranium target. The effluent gases were then released through the hot cell filter bank and the main filter bank. Two samplings were made, one at the inlet and one at the outlet of the hot cell filter bank. In comparison with other radioiodine isotopes detected, higher than expected concentrations of 132I were found, primarily in the form of organic iodide--an observation that could be explained by the beta decay of 132Te, the precursor of 132I, in the hot cell waste solution. The relative distribution of airborne 132I was considerably different from that of other iodine radioisotopes. An unexpected component of these distributions was radioiodine penetrating the silver zeolite filter and adsorbed on a triethylenediamine (TEDA) impregnated charcoal filter.

Individual quantification of 89Sr and 90Sr in nuclear reactor effluent.

An analytical method utilizing ion chromatography, a non-radioactive strontium carrier, and liquid scintillation spectroscopy to individually quantify 89Sr and 90Sr in nuclear reactor effluent is presented. It is observed that this method is less time consuming than traditional procedures for quantifying radio-strontium, deals comprehensively with separation and subsequent isotopic quantification of strontium, and avoids difficulties reported in previous research. The equipment, solutions and operating conditions for the chromatographic separation of strontium in aqueous solution are identified, and the strontium fraction is shown to elute between 7 and 7.5 min after injection. The beta spectra of 90Sr, 89Sr and 90Y are obtained using liquid scintillation spectroscopy, and the effects of quenching are shown to be negligible. The positions of the liquid scintillation windows within the combined beta spectra facilitating isotopic analysis of 89Sr and 90Sr are identified, followed by the system of equations to quantify 89Sr and 90Sr within a sample. The performance of the method is evaluated using five solutions representing effluent containing radio-strontium at known concentrations. It is observed that when the 89Sr and 90Sr concentrations each are approximately 37 Bq mL(-1) or more, the method over-estimates the 89Sr activity by 15-20% and under-estimates the 90Sr activity by 10-30%, while yielding the total radio-strontium activity to within 1-4% of expected. The lower limit of detection of the system for either 89Sr or 90Sr is shown to be approximately 0.8 Bq mL(-1) of effluent.

Development of a beta skin dose monitor using a silicon detector

A prototype skin dose monitor has been constructed and tested successfully. The monitor uses an ion-implanted silicon detector available commercially. The detector was selected since it has a lower leakage current than the other type of silicon detectors. It operates on both a pulse mode and current mode, and there is an overlap in the measurable beat dose rate ranges of these two modes. The prototype device includes an 8-b A/D converter and an 8-b microprocessor to display the skin dose directly. The device presently covers more than five orders of magnitude in the measurable beta skin dose rate ranges. The device has been calibrated using an extrapolation chamber and has been used to measure the dose rates produced by several different beta and beta/gamma sources. >

Monte Carlo calculation and silicon detector measurement of the hot particle dose

In our study, we quantitatively compared the hot particle dose calculated by our microcomputer Monte Carlo electron transport code, Eltran3, with the values calculated by the VARSKIN code. For a weightless source, the VARSKIN code overestimated the skin dose by 14% to 37% because the VARSKIN code is based on the data table for point sources in an unbounded medium. Five 60Co hot particles were measured in the current and pulse mode operations of an ion-implanted silicon detector. The measurements were converted to skin dose rates and compared by use of Eltran3 and VARSKIN calculations. Measured values of the skin dose rates for four of the five hot particles agreed well with expected values. The skin dose rate per kBq of the four hot particles ranged from 0.70 to 0.85 mGy h-1 kBq-1. One of the five hot particles showed the presence of a pure beta-emitting radionuclide, which was not detected through gamma-ray measurements.

The Development and Testing of a Prototype On-line Radioiodine Monitor for Nuclear Power Stations

A prototype on-line monitor has been developed which is capable of detecting radioiodine in the presence of as much as 1 X 10(6) higher concentration of noble gases. The system contains two identical radiation monitoring chambers through which the monitored air and a purging gas alternately cycle. Each chamber contains a silver zeolite filter which has a high retention of the various forms of airborne radioiodine but low retention of noble gases. During the purging cycle the radioactive noble gases are quickly purged from the filter and chamber and the lower levels of radioiodine accumulated on the filter are detected. This system has been successfully tested using short-lived radionuclides simulating vented reactor gases resulting from an abnormal condition.

Monitoring Krypton-85 During Three Mile Island Unit 2 Purging

The Penn State noble gas monitor played an important role in measuring environmental levels of /sup 85/Kr during the purging of the Three Mile Island Unit 2 primary containment. It filled a gap in the U.S. Environmental Protection Agency monitoring program, which existed between their real time monitors and their cryogenic gas chromatographic separation technique. During the 15-day purging period, the system analyzed a total of 124 samples, of which 37 were quantified to contain /sup 85/Kr in concentrations ranging from 3 X 10/sup 4/ to 1.5 X 10/sup 6/ pCi/m/sup 3/. The maximum whole body beta dose rate was found to be 0.28 mrem/h.

Spatially periodic solutions in a 1D model of phase transitions with order parameter

Abstract A model of phase transitions with convex strain energy is investigated within the limits of 1D nonlinear bar theory. The model is a special case of a coupled field theory using an order parameter that has been developed by Fried and Gurtin to study the nucleation and propagation of phase boundaries. The system of governing equations studied here consists of a wave equation coupled to a nonlinear reaction-diffusion equation. Using phase plane methods, the equilibria of the system have been constructed in order to obtain the macroscopic response of the bar. It is demonstrated that a large number of coexisting spatially periodic, inhomogeneous solutions can occur, with the number of these solutions being inversely proportional to the diffusion coefficient in the reaction-diffusion subsystem. A stability analysis of the equilibria is presented, and the bifurcation diagram is discussed in the context of quasistatic loading. It is shown that, though solutions with more than one interface are unstable, they are only weakly so, and can thus persist for a long time. The nucleation and propagation of phase boundaries are illustrated via a numerical study, which shows how nucleation relates to the loss of stability of the homogeneous equilibria.

On-line radioiodine measurement using hot cell effluent gases of a radiopharmaceutical production facility

In this paper an on-line radioiodine monitoring system designed to operate under nuclear accident conditions is tested at the hot cell laboratory of a radiopharmaceutical production facility. The purpose of the work is to demonstrate that the patented Pennsylvania State University radioiodine monitor, using stabilized NaI(Tl + {sup 241}Am) detectors, can generate information about concentration of airborne radioiodine in real time. In the test of continuous iodine monitoring, the real-time {sub 132}I activities agree with those obtained by a high-purity germanium detector within a factor of {approximately}4. From the simultaneous operation of two monitors, one at the inlet and one at the outlet of the hot cell filter band, the hot cell filter bank efficiency for the removal of airborne radioiodine is estimated to be at least 99.88%.

Microcomputer Monte Carlo electron transport codes for beta skin dose calculations

The adaptation of a one-dimensional Monte Carlo election transport program (called ZEBRA) for use on microcomputers in a program called Eltran2 is described. The purpose of this adaptation was to reduce the cost of the Monte Carlo calculations. Eltran2 has, in turn, been modified into a two-dimensional program called Eltran3 for computing the dose from a point or a disk source to a cylindrical target. For Monte Carlo calculations, theoretical beta energy spectra are calculated based on the Fermi beta decay theory. The calculated average energies of spectra agree with the values in related publications to within 6%. An extended study has been done using Eltran2 and Eltran3 to facilitate the design of, a beta/gamma skin dose monitor. The programs calculate the effects of angular distribution of source electrons and the radial distribution of the hot particle dose. It is found that the hot particle dose averaged over a live skin area of 1 cm/sup 2/ significantly underestimates the real dose value at the very small area just under the hot particle by a factor of about 1000. >