Review of ALARA plan for activities at the 105 K-East fuel storage basin

Abstract

This report was .prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, make any warranty, express or implied, or assumes a n y legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by t h e United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. DISCLAIMER Portions of this document may be illegible in electronic image products. Images are produced from the best available original document. Summary As part of its ongoing efforts to reduce doses to workers to levels as low as reasonably achievable (ALARA), Westinghouse Hanford Company (WHC) tasked the Health Protection Department of the Pacific Northwest Laboratory (PNL) to review operations at the 105 K-East Fuel Storage Basin (105 K-East). This review included both routine operations and a proposed campaign to encapsulate N-Reactor fuel stored there. This report summarizes the results of PNL's reviews of policy, procedures, and practices for operations at 105 K-East as well as an evaluation of the major sources of occupational radiation exposures. Where possible, data previously collected by WHC and its predecessors were used. In addition, PNL staff developed a threedimensional model of the radiological environment within 105 K-East to assess the relative contributions of different radiation sources to worker dose and to provide a decision tool for use in evaluating alternative methods of dose rate reduction. The model developed by PNL indicates that for most areas in the basin the primary source of occupational radiation exposure is the contaminated concrete surfaces of the basin near the waterline. Basin cooling water piping represents a significant source in a number of areas, particularly the Technical Viewing Pit. This report contains specific recommendations to reduce the impact of these sources of occupational radiation exposure in 105 K-East. Other recommendations to reduce doses to workers during activities such as filter changes and filter sampling are also included. .

Dose-Reduction Improvements in Storage Basins of Spent Nuclear Fuel

“…The estimated dose rate in the bays of the KE Baain is high (about 16 mrern/h) [4]; therefore, the occupational dose must be reduced for completion of the SNF project. However, accurate analysis for design optimization is dlftlcult mainfy because the sources of the dose rate include the existing K Baain source terms as well aa those from removal of SNF, sludge, and debris, and from water treatment activities.…”

Functions and requirements for the 105 K-East Base Dose Reduction Project

“…A-6400-073 (11/91) CEF) WEF124 (Vargo, 1994). From this dose level, approximately 20 person rem collective dose is accumulated annually by personnel at this facility performing normal operation and security functions (Kaviani , 1994).…”

“…Radiation dose has already become an issue and will potentially be the limiting factor in the time to resolve the K-Basin fuel removal task. Several sources of radiation are presentz2 however, the overwhelming majority of personnel dose comes from cesium-137 ( Cs) contamination in the 1) concrete walls o f the pool, 2) recirculation piping and equipment, and 3) pool water (Vargo, 1994). dose in the fuel storage area and the surrounding pits As Low As Reasonably Achievable (ALARA).…”

“…Examples of this technique include mocking up or eliminating activities . Estimated dose for fuel removal is based on conversations with K-Basin operations staff (Hoefer, 1994) and on time motion studies for encapsulation (Vargo, 1994). Primary considerations are that the fuel movement will take roughly 30 minutes per can, decontaminating the transportation cask roughly 60 minutes and health physics activities will take roughly 60 minutes.…”

“…4.2.9 All decontamination shall be accomplished in a manner such that the air quality remains below the Derived Air Contamination (DAC) limit for the facility. This level provides an 80% reduction in gamma radiation from the concrete at chest level (Vargo, 1994…”