Mayak Dosimetric Studies
Through the Joint Coordinating Committee for Radiation Effect Research (JCCRER) with Project 2.4: Development of an Improved Dosimetry System for the Workers at the Mayak Production FAcility to “establish a computerized database of individual internal and external radiation doses for Mayak PA personnel. As a result, improved doses for risk assessment analysis of causes of health effects from radiation exposure will be available.” Our faculty and students have been involved in the ongoing project of computer program development for Dose analysis such as Doses 99 and Does 2000. Our research focuses on the uncertainty and error analysis of these models as well as current models in development. The Mayak Production Association is located south of Ozersk along the Ural Mountain Range (see left).
Radiation Hardening of Electronic Components
The University of Utah has a well0characterized irradiator for unbiased and real-time irradiation of electronic components. Neutron fluence delivered is determined using either sulfur pellets (ASTM E265) or nickel foils (ASTM E264). Range of Fluences calibrated are from 1E10 to 2.5E14 (15-30,000 W hours). Power level is used to minimize errors due to ramp rate. Neutron Energy Spectrum fluence is reported in terms of 1 MeV equivalent for Si (ASTM E 722). The electrostatic discharge control program follows ANSI/ESD S20.20-1999 and MIL-STD 1686. Isofluence contours are determined yearly and after any core loading changes. The gamma component of the exposure is kept to a minimum by a lead shield located in the stand, and low burn-up fuel. To the right is the Neutron Fluence Map of the Fast Neutron Irradiator Facility (FNIF), shown is the core-facing map of the FNIF with a sample placement area of 6″x11″. Locations are marked for common neutron and gamma dosimetry positions.
Fission Track Analysis for Ultra-Sensitive Detection of Radionuclides
Fission Track Analysis (FTA) at our facility is a refined, non-invasive method to quantify the levels of Pu-239 in an individual. Urine samples are collected and chemically processed to reduce the volume and contaminants. The samples are placed on LexanÂ© slides or electrodeposited onto stainless steel planchets prior to irradiation in our reactor facility. Neutrons from our reactor induce fission and the fission fragments then create small tracks in the LexanÂ© detectors that can be optically viewed and quantified. THe FTA process has been modified and tested in other sample types and can be used to measure levels of activity for other fissionable isotopes. The current procedure has a Pu detection limit of 2.8 microBq/L (76 aCi/L), much lower than typical alpha spectroscopy equipment. To the left is the typical fission tracks shown at 200x magnification.