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Title: Improved drying rate diagnostics for saturated fuel debris at the INEEL

Abstract

A fuel canning station (FCS) has been operated for {approximately}2 yr to prepare for the dry storage of a variety of spent reactor fuels stored in pools at the Idaho National Engineering and Environmental Laboratory (INEEL). The FCS dewaters the fuel and then passivates possibly pyrophoric components in the fuel. Fuel-loaded canisters are placed into a heated insert, the canister is connected to a vacuum system, and the fuel is heated under a vacuum to remove the water. The dewatering system must also verify that the water was removed. The dryness criteria state that the canister pressure shall not exceed a defined pressure for a specified isolation time. Dewatering did not work well for defected TRIGA elements that had corroded in pool storage, leaving the intact fuel meat mixed with a bed of fines from metal oxides and from sludge that continuously accumulated within the pool. Dewatering these cans proved to be very time consuming. Fueled canisters were heated to 60 C and evacuated between 5 and 10 torr. At these conditions, intact fuels were rapidly dried (<10 h). TRIGA drying periods extended to 9 days. Dryness was qualitatively monitored using the canister pressure-control valve position. The valve closes asmore » the gas flow rate declines, providing an indication that drying is complete. However, the valve remained open when drying TRIGA fuel, leaving no indication of dryness. In addition, dryness could not be verified because the canister pressure exceeded the defined pressure during isolation. Air leakage into the evacuated canister prevented the dryness from being verified. Air in-leakage and water vapor cannot easily be discriminated by the aforementioned procedures. Because the canister design does not seal above atmospheric pressure, a drying temperature that yielded a vapor pressure less than atmospheric pressure was chosen. A sufficiently long isolation test could then determine if air was accumulating in the canister; however, the low temperature reduced the drying rate unacceptably. Herein the authors answer two questions. First, at a higher drying temperature, can fuel be verified dry in the presence of air leaks? Second, can an indicator of drying progress be developed?« less

Authors:
;  [1]
  1. Idaho National Engineering and Environmental Laboratory, Idaho Falls, ID (United States)
Publication Date:
OSTI Identifier:
678103
Report Number(s):
CONF-990605-
Journal ID: TANSAO; ISSN 0003-018X; TRN: 99:009088
Resource Type:
Journal Article
Journal Name:
Transactions of the American Nuclear Society
Additional Journal Information:
Journal Volume: 80; Conference: 1999 annual meeting of the American Nuclear Society (ANS), Boston, MA (United States), 6-10 Jun 1999; Other Information: PBD: 1999
Country of Publication:
United States
Language:
English
Subject:
05 NUCLEAR FUELS; DRY STORAGE; SPENT FUEL STORAGE; FUEL STORAGE POOLS; WATER REMOVAL; DEWATERING EQUIPMENT; IDAHO NATIONAL ENGINEERING LABORATORY; SPENT FUEL CASKS; DRYING; DIAGNOSTIC TECHNIQUES

Citation Formats

Childs, K., and Christensen, A. Improved drying rate diagnostics for saturated fuel debris at the INEEL. United States: N. p., 1999. Web.
Childs, K., & Christensen, A. Improved drying rate diagnostics for saturated fuel debris at the INEEL. United States.
Childs, K., and Christensen, A. Wed . "Improved drying rate diagnostics for saturated fuel debris at the INEEL". United States.
@article{osti_678103,
title = {Improved drying rate diagnostics for saturated fuel debris at the INEEL},
author = {Childs, K. and Christensen, A.},
abstractNote = {A fuel canning station (FCS) has been operated for {approximately}2 yr to prepare for the dry storage of a variety of spent reactor fuels stored in pools at the Idaho National Engineering and Environmental Laboratory (INEEL). The FCS dewaters the fuel and then passivates possibly pyrophoric components in the fuel. Fuel-loaded canisters are placed into a heated insert, the canister is connected to a vacuum system, and the fuel is heated under a vacuum to remove the water. The dewatering system must also verify that the water was removed. The dryness criteria state that the canister pressure shall not exceed a defined pressure for a specified isolation time. Dewatering did not work well for defected TRIGA elements that had corroded in pool storage, leaving the intact fuel meat mixed with a bed of fines from metal oxides and from sludge that continuously accumulated within the pool. Dewatering these cans proved to be very time consuming. Fueled canisters were heated to 60 C and evacuated between 5 and 10 torr. At these conditions, intact fuels were rapidly dried (<10 h). TRIGA drying periods extended to 9 days. Dryness was qualitatively monitored using the canister pressure-control valve position. The valve closes as the gas flow rate declines, providing an indication that drying is complete. However, the valve remained open when drying TRIGA fuel, leaving no indication of dryness. In addition, dryness could not be verified because the canister pressure exceeded the defined pressure during isolation. Air leakage into the evacuated canister prevented the dryness from being verified. Air in-leakage and water vapor cannot easily be discriminated by the aforementioned procedures. Because the canister design does not seal above atmospheric pressure, a drying temperature that yielded a vapor pressure less than atmospheric pressure was chosen. A sufficiently long isolation test could then determine if air was accumulating in the canister; however, the low temperature reduced the drying rate unacceptably. Herein the authors answer two questions. First, at a higher drying temperature, can fuel be verified dry in the presence of air leaks? Second, can an indicator of drying progress be developed?},
doi = {},
journal = {Transactions of the American Nuclear Society},
number = ,
volume = 80,
place = {United States},
year = {1999},
month = {9}
}