Test and Evaluation Process for Proposed Double Shell Tank Bottom Inspection Technologies

摘要

The U.S. Department of Energy (DOE) and the Hanford Site Tank Operations Contractor Washington River Protection Solutions, LLC (WRPS) with support from Pacific Northwest National Laboratory (PNNL) are leading a non-destructive evaluation (NDE) technology development program to identify and mature volumetric (non-visual) NDE technology that will enable the examination of Hanford double-shell tank (DST) bottoms. NDE technology for Hanford under-tank inspection will be made possible through testing and evaluation to identify suitable volumetric NDE methods, adaptation of NDE sensor technology to overcome access challenges presented by tank risers and refractory pad air-slots, integration with robotic delivery systems, and finally qualification and deployment in the annular region of the tanks. The flaw detection performance of four ultrasonic guided-wave NDE volumetric inspection technologies was evaluated under two test campaigns at PNNL in 2017 using two mock-ups that represent full-scale swaths of Hanford primary tanks. The mock-ups were constructed with representative carbon steel materials, bottom plate geometries, weld types/patterns, and surface conditions. Surrogate flaws that represent three flaw types of highest concern in the tanks (pitting corrosion, wall thinning, and weld seam openings) were inserted in the mock-up welds and bottom plates at depths that bounded the reportable level and actionable level flaw sizes established for high-level waste tanks. This paper presents the testing and evaluation performed under the NDE program and will describe the test design and evaluation process used to assess proposed sensor technology for use in inspecting the bottom of Hanford DSTs.