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IRRADIATION EFFECTS ON UC$sub 2$ DISPERSED IN GRAPHITE. Final Report

Description: Postirradiation examinations were performed on four fuel cylinders containing UC/sub 2/ dispersed in graphite and sealed in low permeability graphite cans irradiated in the MTR. In all but one experiment, a flowing stream of He passed over the outside of the graphite cans. The estimated fuel cylinder central temperatures ranged from 2500 to 3500 deg F, and the maximum U/sup 235/ burnup was 21%. The most important radiation effects were fuel dimensional change, fission product and U migration, and microscopic structural changes. The fuel cylinders, in general, decreased in diameter and increased in lergth. The decrease in diameter was a function of fuel burnup. A 4.5% decrease in diameter was observed at a burnup of 6 x 10/sup 19/ of the fuel cylinders into the graphite cans. Fission products likewise were found throughout the walls of the graphite can, with steep concentration gradients near the inside surface of the can wall. The istopes Zr/sup 95/ and Ce/sup 144/ were more abundant near the outside wall surface than at midwall. There was no corresponding rise in the concentrations of Sr/sup 90/ and Cs/sup 137/ near the outside surface. Microstructural changes were observed in the UC/sub 2/ particles which were a function of burnup. At around 4 at.% U burnup the particles became porous and began to lose their angular shape. At 21 at.% U burnup, the particles had spheroidized and had begun to diffuse into the surrounding graphite matrix. (auth)
Date: January 1, 1963
Creator: Morgan, J.G. & Osborne, M.F.
Partner: UNT Libraries Government Documents Department

Iodine adsorption on steel in helium

Description: The equilibrium loading of iodine on low chromium alloy steel as functions of iodine partial pressure, temperature, and metal surface conditions were measured. Desorption rates as functions of temperature and He purity were found and the hazards of iodine release as related to licensing and operation were studied. (FS)
Date: January 1, 1979
Creator: Osborne, M.F. & Briggs, R.B.
Partner: UNT Libraries Government Documents Department

Fission product release and fuel cladding interaction in severe-accident tests of LWR fuel

Description: The examination of these samples indicated a correlation between the posttest fuel microstructure and the fission product release during the test. As expected, structural changes in the fuel and fission product release increased with test temperature. The effect of steam flow rate, which controls the extent of cladding oxidation, however, was less clear. The amount of fuel-cladding reaction and liquefaction was greatest in the test with a low steam flow rate, which was also the highest temperature test. Other data indicate, however, that extensive fuel-cladding reaction and liquefaction would be expected at approx. 1700/sup 0/C with reduced steam flow rate (i.e., with reduced oxidation). The similar gas release values and fuel microstructures for the 1700 and 2000/sup 0/C test are somewhat surprising, but may indicate the influence of the steam conditions on gas release as well as on fuel-cladding reaction. The extent of fuel-cladding interaction in these tests, and the resulting intermediate phases, appear to be consistent with the observations of Hofmann and Kerwin-Peck.
Date: November 1, 1983
Creator: Strain, R.V. & Osborne, M.F.
Partner: UNT Libraries Government Documents Department

VOLATILITY STUDIES OF SOME FISSION PRODUCT FLUORIDES

Description: A preliminary study of the volatility behavior of molybdenum indicated that MoF/sub 5/ was converted to MoF/sub 6/ by F/sub 2/; MoF/sub 6/ and Tc fluoride are absorbed on NaF at 100; technetium fluoride is more strongly held than molybdenum fluoride on NaF; MoF/sub 6/ may not be completely trapped by a dry ice trap. The behavior of volatile fission product fluorides was such that (a) Ru and Nb fluorides were volatile from fused salts during fluorination, (b) Mo and technetium were not volatile during hydrofluorination but were in excess F/ sub 2/> 100 deg C(auth).
Date: June 25, 1958
Creator: Brooksbank, W.A. Jr.; Carter, R.J. & Osborne, M.F.
Partner: UNT Libraries Government Documents Department

Sorption of iodine on low-chromium-alloy steel. [HTGR]

Description: The sorption behavior of iodine on the surfaces of 2 1/4% Cr-1% Mo steel was investigated as a part of the High Tmeperature Gas-Cooled Reactor (HTGR) Chemistry Program at Oak Ridge National Laboratory (ORNL). The primary objective of these tests was to determine the equilibrium sorptive capacity of this alloy, which comprises most of the cooler regions of HTGR coolant circuit, under representative conditions. The data will be used to improve the capability for predicting, with computer programs, iodine deposition as functions of temperature and location in the primary circuit.
Date: January 1, 1981
Creator: Osborne, M.F.; Briggs, R.B. & Wichner, R.P.
Partner: UNT Libraries Government Documents Department

Behavior of Cs, I, and Te in the fission product release program at ORNL

Description: Experiments have been conducted at ORNL with highly irradiated light-water reactor (PWR and BWR) fuel rod segments to investigate fission product release in steam in the temperature range 500 to 2000/sup 0/C. Objectives were to quantify and characterize the releases under conditions postulated for LOCA) and severe accident conditions. In all, 26 experiments have been conducted - 24 with high burnup and 2 with low burnup fuels. To aid in the interpretation of fission product release, 12 implant and 18 control experiments were also conducted; the behavior of HI, I/sub 2/, Cs/sub 2/O, CsOH, Te, and TeO/sub 2/ (individually and in different combinations) was studied. This paper discusses only the observed behavior of cesium, iodine, and tellurium. Cs and I were released primarily as CsOH and CsI, and Te release was controlled by steam oxidation of Zircaloy cladding.
Date: January 1, 1984
Creator: Collins, J.L.; Osborne, M.F. & Lorenz, R.A.
Partner: UNT Libraries Government Documents Department

Behavior of fission product tellurium under severe accident conditions

Description: Fission product release tests at Oak Ridge National Laboratory (ORNL) have provided new experimental data that help characterize the behavior of tellurium under severe light-water reactor (LWR) accident conditions. The release of tellurium from the fuel rods is dependent upon the rate and extent of cladding oxidation. Tellurium has been found to be considerably retained by metallic Zircaloy cladding at test temperatures up to 1975/sup 0/C. The results indicate that the tellurium is bound by the Zircaloy cladding as zirconium telluride, but once the available zirconium metal is oxidized by the steam, tellurium is released in favor of continued zirconium oxide formation. The collection behavior of the released tellurium indicates that it is probably released from the fuel rods as SnTe and CsTe, rather than as elemental tellurium.
Date: January 1, 1986
Creator: Collins, J.L.; Osborne, M.F. & Lorenz, R.A.
Partner: UNT Libraries Government Documents Department

Effects of time and other variables on fission product release rates

Description: The releases of krypton and cesium from highly irradiated LWR fuel have been examined in detail. The main interest has been the effect of time on the rate of release and the effects of heatup and cooldown cycles. The minute-by-minute release rates for fission product /sup 85/Kr from commercial fuel irradiated in the H.B. Robinson PWR are shown. The release rate, fraction per minute, is calculated in the same manner as release rates given in NUREG-0772; the fission gas, cesium, and iodine release rate curve from that report is also shown.
Date: January 1, 1986
Creator: Lorenz, R.A.; Osborne, M.F. & Collins, J.L.
Partner: UNT Libraries Government Documents Department

Fission product release from irradiated LWR fuel under accident conditions

Description: Fission product release from irradiated LWR fuel is being studied by heating fuel rod segments in flowing steam and an inert carrier gas to simulate accident conditions. Fuels with a range of irradiation histories are being subjected to several steam flow rates over a wide range of temperatures. Fission product release during each test is measured by gamma spectroscopy and by detailed examination of the collection apparatus after the test has been completed. These release results are complemented by a detailed posttest examination of samples of the fuel rod segment. Results of release measurements and fuel rod characterizations for tests at 1400 through 2000/sup 0/C are presented in this paper.
Date: January 1, 1984
Creator: Strain, R.V.; Sanecki, J.E. & Osborne, M.F.
Partner: UNT Libraries Government Documents Department

Fission-product release from irradiated LWR fuel

Description: An experimental investigation of fission product release from commercial LWR fuel under accident conditions is being conducted at Oak Ridge National Laboratory (ORNL). This work, which is sponsored by the US Nuclear Regulatory Commission (NRC), is an extension of earlier experiments up to 1600/sup 0/C and is designed to obtain the experimental data needed to reliably assess the consequences of accidents for fuel temperatures up to melting. The objectives of this program are (1) to determine fission product release rates from fully-irradiated commercial LWR fuel in high-temperature steam; (2) to collect and characterize the aerosol released; (3) to identify the chemical forms of the released material; (4) to correlate the results with related experimental data and develop a consistent source term model; and (5) to aid in the interpretation of tests using simulated LWR fuel.
Date: January 1, 1982
Creator: Osborne, M.F.; Lorenz, R.A. & Wichner, R.P.
Partner: UNT Libraries Government Documents Department

FISSION-GAS-RELEASE FROM UO$sub 2$, INTERIM REPORT NO. 1

Description: The evolution of fission products from UO/sub 2/ during irradiation at high temperatures is of primary interest to the Gas-cooled Reactor Project. Fuel tests consisting of UO/sub 2/ pellets encapsulated in Inconel or stainless steel were irradiated in the LITR, ORR, and ETR. The capsules were pierced in hot cells, and the gases collected in evacuated systems. Fractions of this gas, of suitable activity for counting, were taken and then analyzed by gamma spectrometry. Larger fractions of gas were analyzed by mass spectrometry. Percentage of gas release varied widely, increasing with temperature, impurity content, oxygen-to-uranium ratio of the UO/sub 2/, and decreasing with bulk density. For high density, stoichiometric UO/sub 2/, the gas release was generally less than 3% up to a temperature of about 2800 deg F, about which it was greatly accelerated. Fuel burn-ups of up to 22,000 Mwd/MT were obtained. Maximum measured central fuel temperatures of 3150 deg F were reached. The lower- density nonstoichiometric UO/sub 2/ released greater amounts of fission gas, particularly Kr/sup 85/. (auth)
Date: August 16, 1960
Creator: Morgan, J. G.; Morgan, M. T. & Osborne, M. F.
Partner: UNT Libraries Government Documents Department

Fission product release from fuel under LWR accident conditions

Description: Three tests have provided additional data on fission product release under LWR accident conditions in a temperature range (1400 to 2000/sup 0/C). In the release rate data are compared with curves from a recent NRC-sponsored review of available fission product release data. Although the iodine release in test HI-3 was inexplicably low, the other data points for Kr, I, and Cs fall reasonably close to the corresponding curve, thereby tending to verify the NRC review. The limited data for antimony and silver release fall below the curves. Results of spark source mass spectrometric analyses were in agreement with the gamma spectrometric results. Nonradioactive fission products such as Rb and Br appeared to behave like their chemical analogs Cs and I. Results suggest that Te, Ag, Sn, and Sb are released from the fuel in elemental form. Analysis of the cesium and iodine profiles in the thermal gradient tube indicates that iodine was deposited as CsT along with some other less volatile cesium compound. The cesium profiles and chemical reactivity indicate the presence of more than one cesium species.
Date: January 1, 1983
Creator: Osborne, M.F.; Lorenz, R.A.; Norwood, K.S.; Collins, J.L. & Wichner, R.P.
Partner: UNT Libraries Government Documents Department

Characterization and chemistry of fission products released from LWR fuel under accident conditions

Description: Segments from commercial LWR fuel rods have been tested at temperatures between 1400 and 2000/sup 0/C in a flowing steam-helium atmosphere to simulate severe accident conditions. The primary goals of the tests were to determine the rate of fission product release and to characterize the chemical behavior. This paper is concerned primarily with the identification and chemical behavior of the released fission products with emphasis on antimony, cesium, iodine, and silver. The iodine appeared to behave primarily as cesium iodide and the antimony and silver as elements, while cesium behavior was much more complex. 17 refs., 7 figs., 1 tab.
Date: January 1, 1984
Creator: Norwood, K.S.; Collins, J.L.; Osborne, M.F.; Lorenz, R.A. & Wichner, R.P.
Partner: UNT Libraries Government Documents Department

Fission product release from high gap-inventory LWR fuel under LOCA conditions

Description: Fission product release tests were performed with light water reactor (LWR) fuel rod segments containing large amounts of cesium and iodine in the pellet-to-cladding gap space in order to check the validity of the previously published Source Term Model for this type of fuel. The model describes the release of fission product cesium and iodine from LWR fuel rods for controlled loss-of-coolant accident (LOCA) transients in the temperature range 500 to 1200/sup 0/C. The basis for the model was test data obtained with simulated fuel rods and commercial fuel irradiated to high burnup but containing relatively small amounts of cesium and iodine in the pellet-to-cladding gap space.
Date: January 1, 1980
Creator: Lorenz, R.A.; Collins, J.L.; Osborne, M.F. & Malinauskas, A.P.
Partner: UNT Libraries Government Documents Department

Fission product release from LWR fuel defected in steam in the temperature range 500 to 1600/sup 0/C

Description: For practical purposes the release of cesium and iodine from LWR fuel rods in the temperature range 500 to 1600/sup 0/C can be considered to originate from three sources: (1) the gap inventory with release by both burst (vented gas) and diffusion; (2) grain boundary with release by tunnel formation; and (3) UO/sub 2/ matrix with release by solid state diffusion. The chemical behavior of released iodine and cesium (at least after contact with steam) is predominantly that of CsI and CsOH. Fission gas release is the sum of the plenum inventory, gas embedded in the fuel and cladding surface layers and that released by tunnel formation, and solid state diffusion from the UO/sub 2/ matrix. A small amount of large particle-sized fuel dust is ejected at time of rupture.
Date: January 1, 1979
Creator: Lorenz, R.A.; Collins, J.L.; Osborne, M.F. & Malinauskas, A.P.
Partner: UNT Libraries Government Documents Department

Correlation of recent fission product release data

Description: For the calculation of source terms associated with severe accidents, it is necessary to model the release of fission products from fuel as it heats and melts. Perhaps the most definitive model for fission product release is that of the FASTGRASS computer code developed at Argonne National Laboratory. There is persuasive evidence that these processes, as well as additional chemical and gas phase mass transport processes, are important in the release of fission products from fuel. Nevertheless, it has been found convenient to have simplified fission product release correlations that may not be as definitive as models like FASTGRASS but which attempt in some simple way to capture the essence of the mechanisms. One of the most widely used such correlation is called CORSOR-M which is the present fission product/aerosol release model used in the NRC Source Term Code Package. CORSOR has been criticized as having too much uncertainty in the calculated releases and as not accurately reproducing some experimental data. It is currently believed that these discrepancies between CORSOR and the more recent data have resulted because of the better time resolution of the more recent data compared to the data base that went into the CORSOR correlation. This document discusses a simple correlational model for use in connection with NUREG risk uncertainty exercises. 8 refs., 4 figs., 1 tab.
Date: January 1, 1989
Creator: Kress, T.S.; Lorenz, R.A.; Nakamura, T. & Osborne, M.F.
Partner: UNT Libraries Government Documents Department

Iodine sorption/desorption from low-alloy steel and graphite. Draft

Description: Tests have been performed at Oak Ridge National Laboratory on the sorptive behavior of iodine on two prominent HTGR primary circuit materials - type H-451 graphite, which is the selected core graphite, and a low-alloy steel (T-22), a type which is employed in the lower temperature regions of the primary system. The main emphasis of the work is the determination of equilibrium sorptive capacities for very low iodine partial pressures. Toward this goal, the test procedures allow on-line determination of sorptive capacity down to iodine partial pressures of approx. 10/sup -11/ bar in helium at a total pressure of 1 atm. The apparatus employed is of the helium flow-through type. Detectors monitor the degree of sorption on specimens and traps, which, together with the helium flowrate and source vapor pressure, yield a continuous determination of iodine mass transport.
Date: January 1, 1980
Creator: Wichner, R.P.; Osborne, M.F.; Lorenz, R.A. & Briggs, R.B.
Partner: UNT Libraries Government Documents Department

Measurement and characterization of fission products released from LWR fuel

Description: Samples of commercial LWR fuel have been heated under simulated accident conditions to determine the extent and the chemical forms of fission product release. This project was sponsored by the USNRC under a broad program of reactor safety studies. Of the five tests discussed, the fractional releases of Kr, I, and Cs varied from approx. 2% at 1400/sup 0/C to >50% at 2000/sup 0/C; much smaller fractions of Ru, Ag, Sb, and Te were measured in some tests. The major chemical forms in the effluent appeared to include CsI, CsOH, Sb, Te, and Ag.
Date: January 1, 1984
Creator: Osborne, M.F.; Collins, J.L.; Lorenz, R.A.; Norwood, K.S. & Strain, R.V.
Partner: UNT Libraries Government Documents Department

Fission product source terms for the LWR loss-of-coolant accident

Description: The principal objectives of the fission product release program currently in progress at Oak Ridge National Laboratory are to determine the quantity of radiologically significant fission products released from defected light water reactor (LWR) fuel rods under accident conditions, identify their chemical and physical forms, and interpret the results for use as input to computer models of postulated spent fuel transportation accidents (SFTAs) and loss-of-coolant accidents (LOCAs). The purpose of the paper is to summarize the source term models which have been developed for cesium and iodine by this program, and to demonstrate the application of the source term models to the analysis of cesium and iodine release during a Pressurized Water Reactor (PWR) LOCA.
Date: January 1, 1978
Creator: Malinauskas, A.P.; Lorenz, R.A.; Collins, J.L.; Osborne, M.F. & Towns, R.L.
Partner: UNT Libraries Government Documents Department

ORNL studies of fission product release under LWR accident conditions

Description: High burnup Zircaloy-clad UO{sub 2} fuel specimens have been heated to study the release of fission products in tests simulating LWR accident conditions. The dominant variable was found to be temperature, with atmosphere, time, and burnup also being significant variables. Comparison of data from tests in steam and hydrogen, at temperatures of 2000 to 2700 K, have shown that the releases of the most volatile species (Kr, Xe, I, and Cs) are relatively insensitive to atmosphere. The releases of the less-volatile species (Sr, Mo, Ru, Sb, Te, Ba, and Eu), however, may vary by orders of magnitude depending on atmosphere. In addition, the atmosphere may drastically affect the mode and extent of fuel destruction.
Date: January 1, 1991
Creator: Osborne, M.F.; Lorenz, R.A. & Collins, J.L.
Partner: UNT Libraries Government Documents Department