Flammable gas generation, retention, and release in high-level waste tanks -- physical and chemical models

Conference · Tue Mar 01 04:00:00 EST 1994

OSTI ID:10144122

McDuffie, N G

The most evident dangers from flammable gas release in ventilated high-level waste tanks at Hanford are those caused by periodic release of gases generated and retained in depths of the tanks. In Hanford Tank 101-SY the flammable gases and hydrogen, ammonia and methane are accumulated along with oxidizer nitrous oxide in bubbles while the ammonia and nitrous oxide are also deposited in solution. Accumulation of both the free and dissolved gases is enhanced by hydrostatic pressure. The free gases are apparently held by several mechanisms -- viscous trapping of bubbles, stabilization in three-phase foams at hydrophobic surfaces, capillary channel gas accumulation, mechanical trapping in crystal clusters, and tight engulfment in armored bubbles. Episodic release is brought about by the ascension from the bottom of large conglomerates which release gases by bubble detachment and by slower diffusion-controlled mass-transfer processes. Density of the conglomerates increases in this process, whereupon they settle to repeat the cycle again. The flammable gases are produced by a combination of radiolytic and non-radiolytic chemical processes in breakdown of water and organic and inorganic constituents. Hydrogen production is enhanced by organic destruction while radiolytic hydrogen production is depressed by nitrite ion. Most of the nitrous oxide and ammonia appear to be derived from reduction of nitrite by organics, with smaller amounts coming from amine nitrogen in chelators. Methane is produced in only small amounts. Formate, oxalate, and carbonate are refractory end-products from degradation of organic constituents such as the chelators ethylenediaminetetraacetate (EDTA) and N-(2-hydroxyethyl)ethylenediaminetriacetate (HEDTA).

• Research Organization: Westinghouse Hanford Co., Richland, WA (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States); Los Alamos National Lab., NM (United States); Argonne National Lab., IL (United States); Georgia Inst. of Tech., Atlanta, GA (United States); Department of the Interior, Washington, DC (United States); Texas Univ., Austin, TX (United States)
• DOE Contract Number: AC06-87RL10930
• OSTI ID: 10144122
• Report Number(s): WHC-SA--2129; CONF-940225--100; ON: DE94010347; BR: 35AF11201/35AF11202
• Country of Publication: United States
• Language: English

Related Subjects

052002
12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
CHEMICAL COMPOSITION
DECOMPOSITION
ENTRAINMENT
FLAMMABILITY
GAS ANALYSIS
GASES
HANFORD RESERVATION
HIGH-LEVEL RADIOACTIVE WASTES
LIQUID WASTES
RADIOACTIVE WASTE STORAGE
RADIOLYSIS
SYNTHESIS
WASTE DISPOSAL AND STORAGE