At the Santa Susana Field Laboratory, approximately twenty facilities were designed and built in Area IV to manage radioactive materials in support of the nuclear reactor programs. These operations included fuel fabrication, storage and reprocessing, radioactive measurement and calibration and radioactive waste management and disposal preparation. As of January 2010, only the Radioactive Materials Handling Facility remains in operation in support of the DOE's cleanup effort. The Energy Technology Engineering Center (ETEC) specialized in the non-nuclear testing of components which were primarily designed to transfer heat from a nuclear reactor using liquid metals instead of water or gas. Atomics International operated the ETEC as a separate division at SSFL under contract to the U.S. Department of Energy. The ETEC operated from 1966 to 1998. Atomics International was a division of a private company which engaged in the commercial enterprise of selling products and services to other companies, Universities and foreign governments. Atomics International also conducted research and development for the United States Government. Operating both as a contractor the U.S. Government and as a commercial company, Atomics International maintained authorizations allowing for the use of radioactive materials in either situation. Activities using radioactive materials owned by the Department of Energy were supervised by that government agency and no licensing was required. For facilities such as the DeSoto, Vanowen operated under a permit to operate granted and monitored by the Nuclear Regulatory Commission or the California State Department of Health Services, Radiological Health Branch. Four buildings at SSFL were licensed by the NRC: Rockwell International Hot Lab (4020), The L-85 reactor building (4093), Nuclear Materials Development Facility (4055), and the Fast Critical Experiment Laboratory (4100). Personnel radiation exposure limitations were generally lower for those working in facilities licensed by the NRC as opposed to sites overseen by the DOE and operating personnel frequently rotated between the facilities.