i%e KESRAD-BUILD and RESRAD computer waste (LLW) disposal facility. This method is costly and may not be the best approach. The RESRAD-BUILD and RESRAD computer codes (Yu et al., 1993,19941 can calculate a dose estimate to a hypothetical human receptor from residual radioactivity in the structural material or soil for a variety of scenarios and radioiiuclides. These codes can be applied to evaluate dose estimates of alternative actions. This article presents the results of such analysis for contaminated process water tunnels at the Hanford Site.The Hanford Site, acquired in 1943, is a 1,450-km' reservation owned by the U.S. government and administered by the DOE, Richland Operations Office. The major operational areas on the site include (1) the 100 Areas on the south shore of the Columbia River; (2) the 200-West and 200-East Areas on a plateau; (3:) the 300 Area located just north of the city of Richland; (4) the 400 Area northwest of the 300 Area; and (5) the 600 Area, which includes all the Hanford Site not occupied by the 100, 200,300, and 400 Areas (see Exhibit 1).The structures considered for analysis, the 105-C process water tunnels, are located in the 100 Area. The 100 Area includes nine nuclear reactors and associated facilities and structures. These nuclear production reactors were graphite moderated and water cooled and had a once-through coolant water design. The Columbia River was used as a source of water. For once-through cooling, the 190-C pumphouse was used. Two (south and north) underground tunnels connect the 190-C pumphouse to the 10 5-C reactor. The water tunnels are constructed of reinforced concrete floors, walls, and roofs.The tunnels (--152 m length) vary in width and height but average about 3 m by 3.7 m. Each tunnel contained three water lines and one steam line. The tunnels were sloped toward the 190-C pumphouse to allow any water leaks from the piping to flow to the main sump. 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. For the average source term assessment, the average radionuclide concentration and removal rate were used. For the bounding dose assessment, the maximum observed radionuclide concentration and removal rate were used. Three scenarios were selected for calculating the dose from the residual activity in the concrete tunnels. Two scenarios,...
