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Title: Proposed Strategies for DWPF Melter Off-Gas Surge Control

Abstract

Off-gas surging is inherent to the operation of slurry-fed melters. Although the melter design and the feed chemistry are both known to significantly affect off-gas surging, the frequency and intensity of surges are in essence unpredictable. In typical off-gas surges, both condensable and non condensable flows spike simultaneously. Condensable or steam surges have been observed to occur as the boiling water layer occasionally falls into the crevices of the cold cap or flows over the edges of the cold cap, thereby coming in contact with the melt surface. The resulting steam surges can pressurize the melter considerably and, therefore, are responsible for the bulk of pressure transients that propagate throughout the off-gas system. The non condensable surges occur as the calcine gases that have been accumulating within the cold cap finally build up enough pressure to be released through the temporary openings of the cold cap. The analysis of off-gas data has shown that over 90 of the gas released during a surge is due to steam.1 Therefore, it is essential to have a large inventory of water in the cold cap for any significant pressure spikes to occur. With the Melter 2 vapor space temperature typically running at 720C,more » the water layer in the cold cap will quickly evaporate once the feeding stops, and the potential for any large pressure spikes should practically cease to exist. The analysis also showed that large pressure spikes well above 2 inches H2O cannot occur under the steam surge scenarios described above. More severe conditions should prevail and one such condition would be that the feed materials form a mound with a growing lake on top, while the melt below remains very fluidic due to its low viscosity, thus resulting in greater movements both in the lateral as well as vertical directions. Once the mound begins to grow, its rate should accelerate, since the heat transfer rate to the upper regions of the cold cap is inversely proportional to the cold cap thickness. Then, when the mound reaches some critical mass, it may begin sink into the bulk melt or tip over, thereby creating a condition almost like a steam explosion.« less

Authors:
Publication Date:
Research Org.:
Savannah River Site (US)
Sponsoring Org.:
US Department of Energy (US)
OSTI Identifier:
833397
Report Number(s):
WSRC-TR-2004-00156
TRN: US0406678
DOE Contract Number:  
AC09-96SR18500
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: 1 Jun 2004
Country of Publication:
United States
Language:
English
Subject:
12 MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; BOILING; CHEMISTRY; CRITICAL MASS; DESIGN; FEEDING; GASES; HEAT TRANSFER; OFF-GAS SYSTEMS; OPENINGS; STEAM; SURGES; THICKNESS; TRANSIENTS; VISCOSITY; WATER; DWPF; OFF-GAS; SURGE,CONTROLLER TUNING

Citation Formats

CHOI, ALEXANDERS. Proposed Strategies for DWPF Melter Off-Gas Surge Control. United States: N. p., 2004. Web. doi:10.2172/833397.
CHOI, ALEXANDERS. Proposed Strategies for DWPF Melter Off-Gas Surge Control. United States. doi:10.2172/833397.
CHOI, ALEXANDERS. Tue . "Proposed Strategies for DWPF Melter Off-Gas Surge Control". United States. doi:10.2172/833397. https://www.osti.gov/servlets/purl/833397.
@article{osti_833397,
title = {Proposed Strategies for DWPF Melter Off-Gas Surge Control},
author = {CHOI, ALEXANDERS},
abstractNote = {Off-gas surging is inherent to the operation of slurry-fed melters. Although the melter design and the feed chemistry are both known to significantly affect off-gas surging, the frequency and intensity of surges are in essence unpredictable. In typical off-gas surges, both condensable and non condensable flows spike simultaneously. Condensable or steam surges have been observed to occur as the boiling water layer occasionally falls into the crevices of the cold cap or flows over the edges of the cold cap, thereby coming in contact with the melt surface. The resulting steam surges can pressurize the melter considerably and, therefore, are responsible for the bulk of pressure transients that propagate throughout the off-gas system. The non condensable surges occur as the calcine gases that have been accumulating within the cold cap finally build up enough pressure to be released through the temporary openings of the cold cap. The analysis of off-gas data has shown that over 90 of the gas released during a surge is due to steam.1 Therefore, it is essential to have a large inventory of water in the cold cap for any significant pressure spikes to occur. With the Melter 2 vapor space temperature typically running at 720C, the water layer in the cold cap will quickly evaporate once the feeding stops, and the potential for any large pressure spikes should practically cease to exist. The analysis also showed that large pressure spikes well above 2 inches H2O cannot occur under the steam surge scenarios described above. More severe conditions should prevail and one such condition would be that the feed materials form a mound with a growing lake on top, while the melt below remains very fluidic due to its low viscosity, thus resulting in greater movements both in the lateral as well as vertical directions. Once the mound begins to grow, its rate should accelerate, since the heat transfer rate to the upper regions of the cold cap is inversely proportional to the cold cap thickness. Then, when the mound reaches some critical mass, it may begin sink into the bulk melt or tip over, thereby creating a condition almost like a steam explosion.},
doi = {10.2172/833397},
journal = {},
number = ,
volume = ,
place = {United States},
year = {2004},
month = {6}
}

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