Application for approval of derived authorized limits for the release of the 190-C trenches and 105-C process water tunnels at the Hanford Site: Volume 2 - source term development

Abstract

TRADEMARKMSCLAMERReference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or o t h e k . does not n e d y constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof or its contractors or subcontractors.This report has been reproduced from the best available copy. Available in paper copy and microfiche. (Volume 2) contains the Source Term Development. This volume contains the radiological characterization data, spreadsheet analyses, and radiological source terms. The source terms characterize the radionuclides and activity concentration levels for the facilities, and serves as input to the various radiation exposure pathways and scenarios used to estimate the individual annual radiation doses that could result from release of these facilities. Based on the results of these evaluations, it is determined that the application of the proposed authorized limits for the 190-C trenches and the 105-C process water tunnels represents a safe and cost-effective approach to their final disposition.iii BH 1-00844Rev.

Dose Assessment for Process Water Tunnels at Hanford Site

“…Bechtel Hanford, Inc. (BHI) provided detailed characterization results for the 105-C process water tunnels. The data were collected after the asbestos removal action (Denham et al, 1997). The contamination levels were not significantly different in the two tunnels, where the average concentration was 162,000 and 159,000 dpm/100 cm2 (1 dpm/100 cmz = 45.045 pCi/m2) at the south and north tunnels, respectively.…”

“…The recreationist was assumed to use a tunnel as an overnight shelter for 8 hours a day (h/d) for one week. The tunnel was modeled as one compartment with a floor area of 456 m2 (length, 152 m; width, 3 m) and a 3.7-m ceiling height (Denham et al, 1997). For dose assessment, it was assumed that the floor surface was uniformly contaminated, with some parts of the contamination fixed and others removable.…”

“…The average removable fraction was 1.4 percent of the total concentration. The radionuclide distribution used in calculating the radionuclide-specific concentration was based on the gamma-ray spectrum analysis (Denham et al, 1997). Exhibit 3 details the average and maximum radionuclide concentrations and removable fractions obtained from BHI survey.…”

“…Both the 190-C pumphouse and the 10 5-C process water tunnels were on the intake side of the water cooling system. During operation of the 105-C reactor, cooling water occasionally entered the tunnels and deposited radioactive contamination on the tunnel floors (Denham et al, 1997).…”

“…The Final Environmental Impact Statement, Decomniissioning of the Eight Surplus Production Reactors at the Hanford Site (DOE 19921, identified safe storage followed by deferred on-piece removal as the preferred alternative for the 105-C reactor. This article presents the dose assessments using the source terms based on survey data presented by Denham et al (1997). Two different source terms were considered in these assessments: the average source term assessment and the bounding dose assessment.…”