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The Department of Energy Office of Enforcement conducted an independent review of the Los Alamos National Laboratory Weapons Engineering Tritium Facility Safety Significant Tritium Gas Containment System recently.
The Los Alamos Site Office made the assessment and it evaluated the functionality and operability of the TGCS (a vital safety system) and to ensure that the system complied with DOE orders and standards.
Tritium is a radioactive form of hydrogen, used in research, fusion reactors and neutron generators. The radioactive properties of tritium can be useful. By mixing tritium with a chemical that emits light in the presence of radiation, a phosphor, a continuous light source is made and it is commonly used in exit signs or gun sights, for instance. However, as with any radioactive substance, limiting exposure is recommended.
After the two-week assessment, which took place last year, LASO and the Independent Oversight committee came away with nine findings.
• TGCS interfacing and supporting SSC (Structures, Systems and Components) are not fully identified in the WETF documented safety analysis. The analysis does not identify the TGCS bubbler exhaust connection to the fume hoods, the fume hoods themselves and the direct supporting interface with the building’s ventilation exhaust system exhausting the fume hoods to the stack and the environment.
The report stated that LASO and HSS considered the first four findings listed above to be the most significant. These four findings, in the SFD and SST areas, have the potential to challenge the ability of the TGCS to perform its credited safety functions, as documented in the safety basis.
The other five findings identified by the LASO assessment team and HSS are considered to be of lesser significance.
Eight of the nine findings arose from the review of finding closure from the 2007 HSS assessment. The remaining finding (the last in the list above) was identified by LASO and HSS based on its review of other findings (i.e., not the 2007 HSS review)
The oversight review board also made four points for improvement.
• Consider reanalyzing all potential pressure/vacuum source threats to the TGCS glove boxes, including those related to common-event failures of multiple internal sources and common-mode failures in multiple glove boxes and their effects on bubbler tailpipe relief capabilities and threats related to systems interaction failure modes, such as those that may be associated with the facility’s HVAC supply and exhaust systems.
• Based on the results of reanalysis of the potential source threats, where necessary, redesign the glove box bubbler pressure/vacuum relief system to ensure that it can provide the required protection, with particular attention to ensuring that the bubbler tailpipes reflect good engineering practice, as described in ASME and ANSI codes and standards.
• Ensure that the final design of the TGCS does not make it dependent on non-safety SSC for the performance of its safety functions, as the current TGCS depends on the HVAC exhaust system. Also, ensure that it is protected from potential system interactions due to failure modes of non-safety systems (e.g., the HVAC systems) and that any existing or future features in such non-safety systems that provide such protection, such as supply/exhaust fan control interlocks, are upgraded to safety significant.
• Ensure that the safety bases fully, completely and consistently identify and describe all of the TGCS safety functions, its boundaries, and its supporting and interfacing systems, such as the HVAC exhaust system’s supporting function and the HVAC supply and exhaust systems’ indirect interfaces with respect to glove box.