TWRS hydrogen mitigation portable standard hydrogen monitoring system platform design and fabrication engineering task plan

Abstract

The primary function of portable gas monitoring is to quickly determine tank vapor space gas composition and gas release rate, and to detect gas release events. Characterization of the gas composition is needed for safety analysis. The lower flammability limit, as well as the peak burn temperature and pressure, are dependent upon the gas composition. If there is little or no knowledge about the gas composition, safety analysis utilize compositions that yield the worst case in a deflagration or detonation. This conservative approach to unknowns necessitates a significant increase in administrative and engineering costs. Knowledge of the true composition could lead to reductions in the assumptions and therefore contribute to a reduction in controls and work restrictions. Also, knowledge of the actual composition will be required information for the analysis that is needed to remove tanks from the Watch List. Similarly, the rate of generation and release of gases is required information for performing safety analysis, developing controls, designing equipment, and closing safety issues. To determine release rate, both the gas concentrations and the dome space ventilation rates (exhauster flow rate or passive dome/atmosphere exchange rate) are needed. Therefore, to quickly verify waste tank categorization or to provide additional characterization for tanks with installed gas monitoring, a temporary, portable standard hydrogen monitoring system is needed that can be used to measure gas compositions at both high and low sensitivities.