The Pilot Plant Denitration of Purex Wastes with Formaldehyde PDF Download
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Author: T. F. Evans
Publisher:
ISBN:
Category : Formaldehyde
Languages : en
Pages : 70
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Book Description
Author: T. F. Evans
Publisher:
ISBN:
Category : Formaldehyde
Languages : en
Pages : 70
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Book Description
Author:
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ISBN:
Category :
Languages : en
Pages :
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Book Description
The reaction between formaldehyde and nitric acid, in which the acid is destroyed with the production of predominantly gaseous products, has been recognized as of great potential value in the processing of radioactive fuels, particularly during waste treatment. Laboratory studies of the reaction at Harwell and at Hanford have shown that a major fraction of the nitric acid can be readily removed from an acidic solution containing nitrates by the addition of formaldehyde. The process possesses the advantages of low chemical cost; recoverability of nitric acid; and, in the case of waste treatment, the production of a solution relatively low in inert salt concentration suitable for fission product recovery or ultimate disposal. The primary purpose of the study was to confirm and extend existing information on the formaldehyde reaction to the destruction of nitric acid in Purex type waste (1WW) through operation of pilot plant scale apparatus. Operational behavior, formaldehyde utilization efficiency, and safety considerations were particular subjects of study. In addition, destruction of nitric acid in a Darex-type dissolver solution was investigated.
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Category :
Languages : en
Pages :
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Continuous denitration of Purex acid waste (PAW) with formaldehyde was successfully demonstrated in a fullscale plant prototype unit in the Hanford Purex plant. The reaction is smooth and is easily and safely controlled. Because severe foaming can occur in the reaction vessel, the use of an antifoam agent is required to attain acceptable plant processing rates. Extensive laboratory and pilot plant work, proper equipment design, and satisfactory oper ating procedures were the bases for developing adequate safeguards that assure complete control of the reaction at all times. During operation, the formaldehyde and the preheated PAW stream (with 50 to 100 parts antifoam per million parts PAW) are added continuously to the reactor which is maintained at 95 deg C. From an initial feed concentration of approximately 6.1M, the free acid is reduced to 0.5 to 1.0M in the treated waste. About 2.5 moles of free acid are destroyed per mole of formaldehyde added to the unit for a 60% reaction efficiency. A decontamination factor of 10/sup 4/ from feed to recovered acid is typical, which means that the ratio of radioactivity to HNO/sub 3/ in the recovered acid is reduced by a factor of 10,000 when compared to the same ratio in the high activity waste (PAW). Formaldehyde denitration of the Purex acid wastes reduces the chemical costs of waste treatment and storage. In addition, the process increases the storage capacity of underground tanks because of less salts in the waste, increases the flexibility of waste treatment equipment, and improves the quality of feed for fission product recovery. (auth).
Author: R. C. Forsman
Publisher:
ISBN:
Category :
Languages : en
Pages : 76
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Author: L. A. Bray
Publisher:
ISBN:
Category : Nitration
Languages : en
Pages : 54
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Author: L. Cécille
Publisher: Springer Science & Business Media
ISBN: 9401197571
Category : Technology & Engineering
Languages : en
Pages : 189
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Book Description
The purpose of the Seminar was to provide an international interdisciplinary forum for in-depth discussions on the pros and cons of a denitration step by chemical means in the course of solidification of MAW (medium active waste) and HAW (highly active waste), prior to feeding the calciner or melter. In particular, differences In the volatility of some components and aerosol formation during the vitrification step are of interest. Chemical rather than thermal denitration may have particular merits which could simplify off-gas purification. A reduction in the salt burden of waste solutions, leading to a reduction In the volume of solid waste, may also be achieved. The scientific programme of the Seminar consisted of invited lectures only, given by experts actively engaged in this field of research. The emphasis was on extensive discussions among the partiCipants, with the aim of leading to an objective understanding of the state-of-the-art. The meeting also indentified issues and options for future research.
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Category :
Languages : en
Pages :
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Batch denitration of synthetic Purex waste was investigated in 12 batch runs in the pilot plant denitration unit. Sugar was continuously added to 25 liters of hot waste. After sugar addition was complete, the hot solution was digested for several hours. The reaction proceeded smoothly and was easily controlled. About 19 to 22 moles of nitric acid were destroyed per mole of sugar with a reaction pot temperature of 100 deg C and a digestion period of 12 hours. About 17 moles of nitric acid were destroyed per mole of sugar when the reaction pot temperature was reduced to 95 deg C.A possible plant flowsheet for batch denitration with sugar was developed. This ilowsheet presumes batch denitration of large 2,500-gallon batches of waste in a standard 5,000-gallon Purex Plant tank and incorporates 12 hours of sugar addition and 12 hours of digestion. The flowsheet was successfully demonstrated in the pilot plant equipment. A 1.4M sugar solution was added to 25 liters of hot (100 deg C) waste for 12 hours and the mixture was digested for 18 hours. The initial nitric acid concentration was 6.14M. The residual nitric acid concentration was 0.94 and 0.90M after 12 and 18 hours of digestion, respectively. A residual carbon content equivalent to 1.9 and 0.4% of the total carbon fed as sugar was present after 12 and 18 hours of digestion, respectively. About 19 moles of nitric acid were destroyed per mole of sugar fed. Foaming was produced during batch denitration with sugar by addition of 0.4 gram of dibutyl phosphate per liter of synthetic waste. The addition of 0.2 gram of Dow-Corning Antifoam B per liter of waste reduced foam levels by about a factor of two. An induction period of about six to nine minutes was observed before the reaction started. The length of the induction period increased as initial sugar addition rates were reduced. Gentle air sparging reduced the induction period by about a factor of two. Attempts to use sodium nitrite as a means of decreasing the induction period were not successful. Sugar solution was added to cold waste, and the mixture was heated to determine the pot pressures and tower pressure drops that could be developed under abnormal conditions. A decrease in pot vacuum of 30 in. of water and a tower pressure drop of 8 in. of water were observed when 20 liters of waste and 2.7 liters of 2.5M sugar solution were mixed together and rapidly heated to 100 deg C. (auth).
Author: Stephen Cseplo
Publisher:
ISBN:
Category : Hydrometallurgy
Languages : en
Pages : 42
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Author:
Publisher:
ISBN:
Category : Nuclear energy
Languages : en
Pages : 1276
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Author: Hong Jiang
Publisher: Springer
ISBN: 9811023115
Category : Technology & Engineering
Languages : en
Pages : 951
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Book Description
This is the first in a series of three proceedings of the 20th Pacific Basin Nuclear Conference (PBNC). This volume covers the topics of Safety and Security, Public Acceptance and Nuclear Education, as well as Economics and Reducing Cost. As one in the most important and influential conference series of nuclear science and technology, the 20th PBNC was held in Beijing and the theme of this meeting was “Nuclear: Powering the Development of the Pacific Basin and the World”. It brought together outstanding nuclear scientist and technical experts, senior industry executives, senior government officials and international energy organization leaders from all across the world. The book is not only a good summary of the new developments in the field, but also a useful guideline for the researchers, engineers and graduate students.
