STEADY STATE FLAMMABLE GAS RELEASE RATE CALCULATION & LOWER FLAMMABILITY LEVEL EVALUATION FOR HANFORD TANK WASTE [SEC 1 & 2]
Flammable gases such as hydrogen, ammonia, and methane are observed in the tank dome space of the Hanford Site high-level waste tanks. This report assesses the steady-state flammability level under normal and off-normal ventilation conditions in the tank dome space for 177 double-shell tanks and single-shell tanks at the Hanford Site. The steady-state flammability level was estimated from the gas concentration of the mixture in the dome space using estimated gas release rates, Le Chatelier's rule and lower flammability limits of fuels in an air mixture. A time-dependent equation of gas concentration, which is a function of the gas release and ventilation rates in the dome space, has been developed for both soluble and insoluble gases. With this dynamic model, the time required to reach the specified flammability level at a given ventilation condition can be calculated. In the evaluation, hydrogen generation rates can be calculated for a given tank waste composition and its physical condition (e.g., waste density, waste volume, temperature, etc.) using the empirical rate equation model provided in Empirical Rate Equation Model and Rate Calculations of Hydrogen Generation for Hanford Tank Waste, HNF-3851. The release rate of other insoluble gases and the mass transport properties of the soluble gas can be derived from the observed steady-state gas concentration under normal ventilation conditions. The off-normal ventilation rate is assumed to be natural barometric breathing only. A large body of data is required to do both the hydrogen generation rate calculation and the flammability level evaluation. For tank waste that does not have sample-based data, a statistical-based value from probability distribution regression was used based on data from tanks belonging to a similar waste group. This report (Revision 3) updates the input data of hydrogen generation rates calculation for 177 tanks using the waste composition information in the Best-Basis Inventory Detail Report in the Tank Waste Information Network System, and the waste temperature data in the Surveillance Analysis Computer System (SACS) (dated July 2003). However, the release rate of methane, ammonia, and nitrous oxide is based on the input data (dated October 1999) as stated in Revision 0 of this report. Scenarios for adding waste to existing waste levels (dated July 2003) have been studied to determine the gas generation rates and the effect of smaller dome space on the flammability limits to address the issues of routine water additions and other possible waste transfer operations. In the flammability evaluation with zero ventilation, the sensitivity to waste temperature and to water addition was calculated for double-shell tanks 241-AY-102, 241-AN-102,241-AZ-101,241-AN-107,241-AY-101 and 241-AZ-101. These six have the least margin to flammable conditions among 28 double-shell tanks.
- Research Organization:
- CH2M Hill Hanford Group, Inc., Richland, WA (United States); Hanford Site (HNF), Richland, WA (United States)
- Sponsoring Organization:
- USDOE Office of Environmental Management (EM) (US)
- DOE Contract Number:
- AC27-99RL14047
- OSTI ID:
- 820638
- Report Number(s):
- RPP-5926, Rev.3; TRN: US200405%%51
- Resource Relation:
- Other Information: PBD: 30 Sep 2003
- Country of Publication:
- United States
- Language:
- English
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