Seismic Safety Analysis of Heavy Element Facility at Lawrence Livermore National Laboratory

Conference · Wed Jun 06 00:00:00 EDT 2001

OSTI ID:15005475

O'Connell, W J; S, Hildum J

The Heavy Element Facility is a cold war legacy facility at Livermore National Laboratory. The facility's mission has varied over its lifetime, but operations included the preparation of radioactive heavy element tracers used in underground nuclear weapons testing and the conduct of a heavy element research program. It is a one story concrete masonry structure constructed in several phases between 1955 and 1981. In 1993, a seismic re-evaluation of the facility determined that portions of the building did not meet the PC-2 requirements applicable to it. A seismic upgrade evaluation determined it was not practical to upgrade the facility to support continued programmatic operations. It is now maintained in a storage mode awaiting Department of Energy disposition. In this mode the operations are limited to (1) storage of radioactive material from previous operations, (2) clean-up and decontamination of facility work areas and equipment, (3) removal of contaminated systems and enclosures, (4) facility maintenance, (5) removal of radioactive materials from the facility, (6) characterization of the waste generated by these activities, (7) surveillance activities and (8) security. An important part of the facility's storage function is provided by underground storage vaults. These are embedded in a massive reinforced concrete block whose top is at the building interior's floor level. The inventory in these vaults is limited to solid forms of transuranic isotopes and other radioactive isotopes stored with double or triple containment. The vaults may be accessed infrequently for surveillance or on occasion for removal of inventory to other facilities. As part of maintaining this storage function until final disposition, the safety of the underground storage system was reevaluated using guidance in DOE standard DOE-STD-1027-92. An overview is presented here to highlight important considerations in the evaluation of an older safety system. Special effort is directed to effects of aging when screening for failure modes, energy sources and initiating events. Processes influencing aging include radiation, transmutation of radioactive elements within the solid material forms, and generation of helium gas from alpha decay, Affected objects include the radioactive material solids and the containers, including the O-ring of the outer container. Seismic events were identified as the dominant concern after a screening of potential damage initiators. The vault embedment and cover plate protect the container barriers from major damage during an earthquake. But combined with aging effects, the earthquake may cause some narrow cracks in the barriers. Leakage paths proceed outward through the concentric containers, the vault, and the HEPA filter exhaust system, which itself may be damaged by the earthquake. The prior buildup of He pressure in the containers, as the result of radioactive decay, may provide energy and a motive force to drive fine particles through the leakage paths. The release by this physical process is extremely limited. The analysis takes no account of attenuation by fallout or plateout. The potential off-site consequences remain far below the emergency planning limit for the site. The potential damage and release that can result when an underground storage rack is raised for surveillance or removal of a container is also evaluated. In this case the damage caused by a concurrent earthquake may be more severe and the release path to the environment is reduced. He gas still plays a large part in the release mechanism. The off-site consequences are substantially higher than from an earthquake during storage mode even though the inventory involved is smaller, but they are still below the emergency planning limit for the site, of 5 rem committed effective dose equivalent (CEDE) at the site boundary.

• Research Organization: Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
• Sponsoring Organization: US Department of Energy (US)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 15005475
• Report Number(s): UCRL-JC-141999; TRN: US200322%%462
• Resource Relation: Conference: 111th Annual Workshop, Milwaukee, WI (US), 06/14/2001--06/21/2001; Other Information: PBD: 6 Jun 2001
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEFENSE
99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE
ALPHA DECAY
DOSE EQUIVALENTS
ENERGY SOURCES
EXHAUST SYSTEMS
GASKETS
LAWRENCE LIVERMORE NATIONAL LABORATORY
NUCLEAR WEAPONS
RADIOACTIVE MATERIALS
REINFORCED CONCRETE
RESEARCH PROGRAMS
SAFETY
SAFETY ANALYSIS
SEISMIC EVENTS
UNDERGROUND STORAGE