Executive Summary The Retrieval Process Development and Enhancements Program (RPD&E) is sponsored by the U.S. Department of Energy Tanks Focus Area to investigate existing and emerging retrieval processes suitable for the retrieval of high-level radioactive waste inside underground storage tanks. This program, represented by industry, national laboratories, and academia, seeks to provide a technical and cost basis to support site-remediation decisions. Part of this program has involved the

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... opment of a highpressure waterjet dislodging system and pneumatic conveyance integrated as a scarifier. Industry has used high-pressure waterjet technology for many years to mine, cut, clean, and scarify materials with a broad range of properties. The scarifier was developed as an alternate means of retrieving waste inside Hanford single-shell tanks, particularly hard, stubborn waste. Testing of the scarifier has verified its ability to retrieve a wide range of tank waste ranging from extremely hard waste that is resistant to other dislodging means to soft sludge and even supernatant fluid. Since the scarifier expends water at a low rate and recovers most of the water as it is used, the scarifier is well suited for retrieval of tanks that leak and cannot be safely sluiced or applications where significant waste dilution is not acceptable. Although the original scarifier was effective, it became evident that a lighter, more compact version that would be compatible with light weight deployment systems under development, such as the Light Duty Utility Arm, was needed. At the end of FY 95, the Light Weight Scarifier (LWS) was designed to incorporate the features of the original scarifier in a smaller, lighter end effector. During FY 96, the detailed design of the LWS was completed and two prototypes were fabricated. During FY 96, a thorough testing program was initiated to determine the range of applicability within a matrix of hard and soft simulants, determine appropriate mining strategies, and address integration issues associated with deploying the LWS by a robotic manipulator arm or remote crawler. Long duration tests with materials simulating salt cake, hard pan, and sludge waste forms have been conducted to evaluate the effectiveness of mining strategies, end effector reaction forces, and retrieval rates. This document will describe the testing program, present test results, and provide recommendations for future technology development activities. These tests measured the performance of the LWS and validated its compatibility with existing long reach manipulators. Although there are no planned hot deployments of the LWS at this time, it is believed that the LWS will find application at Hanford for hard heal retrieval and at Oak Ridge National Laboratory (ORNL) for gunite removal. It is hoped that this information will provide a basis for field-able end effectors to meet site remediation requirements.