IN-SITU, LONG-TERM MONITORING SYSTEM FOR RADIOACTIVE CONTAMINANTS

Abstract

This report presents the results of the first phase of the project entitled ''In-situ, Long-term Monitoring System for Radioactive Contaminants.'' Phase one of this effort included four objectives, each with specific success criteria. The first objective was to produce dosimetry grade fibers and rods of aluminum oxide. The success criterion for this milestone was the production of aluminum oxide rods and fibers that have a minimum measurable dose (MMD) of 100 mrem or less. This milestone was completed and the MMD for the rods was measured to be 1.53 mrem. Based on the MMD, the ability of the sensor to measure {sup 137}Cs, {sup 90}Sr/{sup 90}Y, and {sup 99}Tc was evaluated. It was determined that the sensor can measure the release limit of these radionuclides (50 pCi/cm{sup 3}) in 150 h, 200 h, and 54,000 h, respectively. The monitor is adequate for measuring {sup 137}Cs and {sup 90}Sr/{sup 90}Y but is unsuitable for measuring {sup 99}Tc in soil. The second objective was to construct a prototype sensor (dosimeter and fiber optic channel). There were three success criteria for this milestone: (1) Perform measurements with the sensor for both gamma and beta radiation with a standard deviation of 10% or less; (2) Demonstrate the ability of the sensor to discriminate between gamma and beta radiation; and (3) Obtain similar or relatable results for differing lengths of fiber optic cable. These milestones were met. The sensor was able to measure gamma radiation repeatedly with a standard deviation of 3.15% and beta radiation with a standard deviation of 2.85%. Data is presented that demonstrates that an end cap can be used to discriminate between beta plus gamma radiation using beta radiation from a {sup 90}Sr/{sup 90}Y source, and gamma radiation alone. It is shown that some amount of attenuation occurs in longer fiber optic cables, but it is unclear if the attenuation is due to poor alignment of the dosimeter and the cable. This issue will be investigated further when more dosimeters are available so that the dosimeters can be permanently attached to the longer cables. The third objective was to identify a demonstration site. The success criterion for this milestone was to obtain a written agreement from a DOE site to host the demonstration of the monitor during the third phase. Because of uncertainties in funding of the second and third phases of this effort, a written agreement was not obtained. Instead, verbal agreements were reached with both Hanford and the Nevada Test Site. It is believed that the verbal agreements meet the intent of the objective. The final objective was to prepare the Draft Phase I Topical Report. The success criterion for this milestone was to have the report accepted by NETL. It is anticipated that this objective will be met.