Rationale for the closure of the soil density unreviewed safety question and recommended structural analyses improvements for the TWRS underground storage facilities

摘要

The purpose of this report is twofold. First, this report documents the technical evaluation supporting the Project Hanford Management Contract (PHMC) contractor recommendation to close the Unreviewed Safety Question (USQ) as originally evaluated in TF-94-0260, Soil Compaction Test Data Indicates Soil Density in Excess of Density Used in Tank Qualification Analysis for AP Tank Farm. Second, this report describes the status of existing structural analyses for the Tank Waste Remediation System (TWRS) waste storage structures and outlines the associated technical upgrades being considered by the contractor. This second feature of the report serves to communicate the distinction between the soil density issue which is the topic of the open USQ and other technical issues which are important to the contractor from a programmatic standpoint. Contractor actions to address the latter technical issues would support improvements in day-to-day operations (e.g., provide possible relaxations in soil load restrictions) but are not necessary to close the soil density USQ. Section 2.0 of this report documents the rationale for the PHMC contractor recommendation to the Department of Energy (DOE) to close the soil density USQ. Section 3.0 documents the recommended structural analyses improvements for the double-shell tanks (DSTs) which are the structures associated with the soil density USQ. Sections 4.0 and 5.0 provide, for completeness, the same information for single-shell tanks (SSTs), double-contained receiver tanks (DCRTs), catch tanks and inactive miscellaneous underground storage tanks (IMUSTs). Section 6.0 provides the conclusions of this report.