Behavior of Natural Radionuclides in Western Coal-Fired Power Plants David G. Coles, Richard C. Ragaini", and John M. Ondov Lawrence Livermore Laboratory, University of California, Livermore, Calif. 94550
The behavior of the naturally occurring radionuclides 40K, ZlOPb, *zGRa, 22sTh, ZZsRa, 235U, and 238U in coal-fired power plants is described. The enrichment factors [EF = ([XI ~ a m p l e / [ ~ sample)/([X] ~K] ~oal/[~~ coal)] K ] for these nuclides in the finer stack fly ash particles indicate significant to a t least slight enrichments for all the nuclides studied. These values range from 5.0 for 210Pbto 1.2 for 22sTh.Uranium-235 and 238U E F values are both 2.8. Radium-226 and zzsRa E F values are 1.9 and 1.6, respectively. Thorium nuclides and 40K show little fractionation in the electrostatic precipitator(ESP) collected fly ash and the bottom ash (slag or klinkers) when compared to the original coal. Lead-210 shows a definite depletion in the bottom ash and the ESP fly ash. Uranium also tends to be depleted in these samples. An explanation for the behavior of U and nuclides derived from the 23sU decay chain includes a bimodal residence for this element in the coal. The projected dependence of the nation on coal-produced electrical energy necessitates a thorough study of the associated environmental risks. Much effort has been expended in studying the amounts and effects of gases, aerosols, and trace elements released from coal-fired power plants. Some studies have even investigated the release of natural radionuclides upon the combustion of coal and have attempted to compare these radioactive effluents from fossil-fuel plants to those of nuclear power plants ( I , 2). However, oversimplifications and lack of good emission data for radionuclides from the fossilfuel plants have led to differing conclusions. Hull (3)has compared the inorganic effluent releases of the fossil-fuel plants to the radionuclide releases from nuclear plants in terms of accepted environmental standards for each type of effluent. Moore et al. ( 4 ) have calculated that anthropogenic sources contribute 6.5% of the total zlOPoatmospheric flux from the continental U.S. Fossil-fuel burning makes up 14%of these anthropogenic sources or 1%of the total 210Poinput. One can determine a maximum concentration of 210Poindirectly from the zloPb content in the coal, since 210Pb is the grandparent of 210Poin the 23sU-decayseries. However, none of these fossil-fuel plant studies has concentrated on radionuclide combustion chemistry, which is necessary to make valid comparisons between fossil-fuel and nuclear
Table 1. Natural Radionuclides Observed in Coal, Bottom Ash, and Fly Ash Natural decay chain orlgln
Source aiier fractionation
232Th 232Th 232Th 232Th
228Ra 228Ra 228Th 228Th
2381)
2381)
228A~ 228A~ 212Pb 208T1 234Th
238u
226Ra
226Ra
2381)
226Ra 226Ra 226Ra 226Ra 226Ra '"Pb
*14Pb *14Pb
2351)
2351)
2381) 2381) 2381) 2381)
2381) 2351)
442
Gamma-producing nuclide
214~j 214~1
214~j
210Pb
Environmental Science & Technology
Gamma energy (keW
338 91 1 238 583 63 185 295 352 609 1120 1764 46 185
plants. The purpose of this work is to study only the chemical fractionation of the natural radionuclides in coal during combustion and from this information infer the behavior of the natural radionuclides from deposition in the coal through combustion and emission at the power plant.
Experimental Twelve coal samples, seven bottom ash (slag or klinkers) samples, and nine electrostatic precipitator (ESP) fly ash samples were obtained from a western coal-fired power plant (Plant A) burning low-sulfur (0.52%), low-ash (9.2%) coal. Plant A is equipped with tangentially fired burners and a cold-side ESP. Three coal samples, 10 bottom ash samples, six ESP fly ash samples, and seven scrubber ash samples were obtained from a larger western coal-fired power plant (Plant B) burning low-sulfur (0.46%),high-ash (23.3%) coal. Plant B has three units equipped with variable-throat Venturi scrubbers and two units equipped with cold-side ESP emission-control systems. We also obtained from Plant B kilogram quantities of particle-sized stack fly ash. This stack fly ash was collected by a large cyclone separator mounted at the outlet of one of the ESP units ( 5 ) .Two separate sets of the four sized fractions were obtained. For each fraction as determined by centrifugal sedimentation ( 6 ) , the mass median diameters (mmd) were 18.5, 6.0, 3.7, and 2.4 pm. Geometric standard deviations of the fractions were approximately 2.3,2.0,1.7, and 1.8pm, respectively. All samples were ground to 200 mesh when necessary, homogenized, packaged to preclude radon emanation, and then counted for natural gamma radiation on an ultralow background Compton suppression Ge(Li) gamma-ray spectrometer (7). The computer code used for the gamma-ray spectral analysis (GAMANAL) is described by Gunnink and Niday (8).Table I lists the radioactive species observed. The specific techniques necessary for interpreting the counting data for these species along the natural decay chains (232Th,23sU,and 235U)are described by Coles et al. (9, I O ) . The 23sU natural radioactive-decay-chain series was found to be in secular equilibrium (considering the quoted analytical errors) in the coal samples but not in the ash samples. This was expected because during the combustion process a potential exists for decay chain disequilibrium, since many of the daughter radionuclides have quite different chemical and physical characteristics. The daughter radionuclides that emit gamma rays can be observed simultaneously, and the degree of disequilibrium can be determined. Table I lists all gamma rays that were used in the gammaray spectral analyses, along with the decay-chain origin, the secondary postfractionation source, and the daughter radionuclide that actually produces each gamma ray. Figures la-c illustrate the three naturally occurring radioactive decay chains. The secondary postfractionation sources are shown in boxes. These secondary radionuclides are those whose half-lives are long enough to produce gamma rays or gamma-ray emitting daughters after secular equilibrium has been disrupted by the combustion process. The actual measured gamma ray may originate from a daughter further along the decay chain but prior to the next long-lived species. The half-lives of these intermediary radionuclides are short enough so that secular equilibration can be assumed to have been reestablished for that section of the decay chain. The packaged samples were allowed to sit for 6 months. This provided
0013-936X/78/0912-0442$01 .OO/O
0 1978 American Chemical Society
‘i;
F)
Th 2 4 . 1 d
6.7 y
88
63-keY
185 keV z ,
*
. 4 7 x 105 y
-228
338-kev i 993 113 118-- kkkeeeV Vv YYi
f
‘ff Rr
89 Ac
6.13 h
-a --y-j 1 1.910 y 1.910 y
/
3.823 d
238-keV 1 2 Po 138.4! d !
/ : :2
Pb
STGBLE
Figure la. 238Udecay chain of naturally occurring radionuclides Half-lives and most prominent decay y-rays shown
/
‘3;
Th 25.5 h
7-
/
etc.
Figure IC. 235Udecay chain of naturally occurring radionuclides Half-lives and most prominent decay y-rays shown. 185-keV gamma is only intense transition in this decay chain
the longest-lived intermediary radionuclide, 234Th (24.1 days), the opportunity to come to within 1%of secular equilibration with its parent 23sU.
Results Table I1 presents the concentrations in ppm of uranium, thorium, and potassium observed in the various samples. The content in pCi/g of each postfractionation radionuclide is shown in Table 11. Table I11 presents a comparison between data for U, T h , and K obtained by gamma-counting (this work) and by Instrumental Neutron Activation Analysis (INAA). Many of the values agree within the 1u error quoted. Uranium results for the 18.5-pm-sized stack fly ash obtained by natural gamma-ray counting do not agree with the data obtained by INAA. This discrepancy may be due to sample inhomogeneities incurred by the use of small aliquots (100 mg) for INAA. Except for the 18.5-pm-sized fraction, T h values are all less for the INAA-derived data than for the gamma counting data. Potassium data are also lower, but the large
583-keV
Figure lb. 232Thdecay chain of naturally occurring radionuclides Half-lives and most prominent decay y-rays shown
INAA errors preclude making any conclusion concerning the accuracy of these analyses. It can be concluded that the uranium data, except for the 18.5-pm fraction, agree within the 1u errors and the T h data agree within the 2 u errors. Also, the overall INAA data are generally less than the gamma counting data, but both techniques indicate that the same trends exist for each element as a function of particle size. Enrichment factors relative to the input coal were calculated for the radionuclide contents observed. The enrichment factor (EF) is defined as the ratio of the concentration of a radionuclide (X) and 40K in the sample divided by the corresponding ratio in the input coal.
EF
=
[XI~arnple/[4~K] sample [XI ~ o a l / [ ~ coal ~K]
This effectively normalizes the apparent enrichment resulting from loss of carbon during the combustion process. Potassium-40 is used in this normalization because its concentration remains more or less constant in all samples; hence, it was assumed to be a tracer for the alumino-silicate-dominated ash matrix. Table IV presents EF values for samples from both plants. The ESP fly ash and bottom ash from both plants show no enrichment of the 232Th-decay-chaindaughters although some slight depletion may be indicated. Such a depletion is uncertain due to the analytical errors quoted for these data. This lack of enrichment is expected since thorium and radium are essentially refractory elements and should remain with the 40K in the ash matrix. Thorium and R a do show a slight small particle preference in the size-classified fly ash. Uranium behaves in quite a different manner, Both 235Uand 238Ushow significant depletion in the fly ash from Plant A (low-ash coal) and the bottom ash from both plants. The fly ash is not nearly as depleted in these uranium isotopes from Plant B (high-ash coal). The EF values for *38Uand 235U are, within analytical error, identical. Since they are chemically the same and are Volume 12, Number 4, April 1978
443
Table II. Contents of Various Radionuclides in Coal, Bottom Ash, and Fly Asha ppm Th
u
(n)
K
40K
228~h
1.6 15 14
860 9440 7900
0.73 8.1 6.8
5.0 22 19 22
1660 7400 7200 7200
1.4 6.3 6.2 6.2
2 2 8 ~ ~
PCi4 210Pb
anaRa
0.17 1.7 1.5
0.26' 1.4" 0.58'
0.21 2.3 1.9
0.24' 1.9 1.5
0.012' 0.093 0.072
0.55 2.4 2.1 2.5
0.68' 2.2' 0.84' 2.8'
0.64 2.9 2.5 3.0
0.85' 3.5' 2.8' 3.6
0.037 0.14 0.11 0.14
2 3 8 ~
23SU
Plant A b Coal (72) ESP fly ash (9) Bottom ash (7)
0.71 5.6 4.6
0.17 1.7 1.5
Plant B c Coal (3) ESP fly ash (6) Bottom ash (IO) Scrubber ash (7)
2.6 11 8.4 11
0.56 2.4 2.2 2.5
Plant B C Post-ESP (stack) fly ash (mmd)d 18.5pm (2) 6.0pm (2) 3.7m (2) 2.4Fm (2)
25 31 36 38
16 20 30 36
7.0 7.3 7.4 7.0
8200 8600 8600 8100
2.8 3.3 3.3 3.3
2.7 3.5 4.0 4.2
4.3 10 14 17
3.3 4.6 5.3 5.9
5.4 6.8 10 12
0.17 0.28 0.39 0.50
a Errors 20% with", 10% without' (1 u error from the mean or counting statistics, whichever is larger). Samples from Plant A; input coal contains 11.3% H20, 9.2% ash, and 0.52% sulfur. Samples from Plant B: input coal contains 6.8% HZO,23.2% ash, and 0.46% sulfur. mmd = mass median diameter determined by centrifugal sedimentation.
Table 111. Comparison of Natural Gamma-Ray Countlng Data with INAA for U, Th, and K ppm
Post-ESP stack fly ash, pm
18.5 6.0 3.7 2.4
U
y-Counting Th
+ 1 u error
lNAAa
K
1 6 f 3 2 5 f 2 8200f 900 2 0 f 2 31 f 1 8600f 700 30 f 4 36 f 1 8600 f 800 3 6 f 5 3 8 f 2 8100f 800
9.f 2. 26. f 1. 7400 f 2000 1 6 f 3 28. f 1. 7700f 2300 2 2 f 4 2 9 f 1 7800% 2900 2 9 f 4 3 0 f 2 7200f 1500
Instrumental neutron activation analysis from Ondov et al. (6').
Table IV. Enrichment Factor Relative to Input Coal and Normalized to 40Ka 238~ Decay-chain orlgin 232Th Source after fractionation 228Th 2 2 8 ~21opb ~ 22aRa
235,, 23EU
23su
Plant A b ESP fly ash Bottom ash
0.89 0.90 0.48' 1.0 0.71" 0.70" 0.96 0.97 0.24" 0.99 0.70 0.64'
Plant 0 ESP fly ash Bottom ash Scrubber ash
0.96 0.98 0.74" 1.0 0.94' 0.85' 0.91 0.89 0.29" 0.90 0.76 0.73' 0.97 0.88' 1.0 0.95' 1.1 1.0
Plant B C Post-ESP fly ash (mmd)d 18.5pm 6.0p m 3.7pm 2.4p m
1.0 1.1 1.1 1.2
1.0 1.2 1.4 1.6
1.3 3.0 4.1 5.0
1.1 1.4 1.6 1.9
1.3 1.6 2.3 2.8
0.94 1.4 2.0 2.8
Errors 20% with'. 10% without' (1 u error from the mean or counting statistics, whichever is larger). Samples from Plant A; input coal contains 11.3% H20, 9.2% ash, and 0.52% sulfur. Samples from Plant B; input coal contains 6.8% H20, 23.2% ash, and 0.46% sulfur. dmmd = mass median diameter determined by centrifugal sedimentation.
*
444
Environmental Science & Technology
both origin nuclides for their respective decay chains, they should behave identically. Although the Ra nuclides are chemically identical, they originate from very different sources, and as a consequence they may not behave similarly. Their E F data for the size-classified post-ESP fly ash shows that z2sRatends to be more associated with the smaller fly ash particles than 228Ra.An explanation for this observation is presented later. Lead-210 appears to be the most volatile radionuclide measured. It is quite depleted in the bottom ash from both plants and is less depleted in the fly ash from Plant B (highash coal). Lead-210 also shows the greatest small particle preference in the size-classified fly ash than any of the other nuclides measured. All EF values for radionuclides in the scrubber ash are close to unity. The wet scrubber is more efficient than the ESP for fly ash removal (99.2%vs. 97%) and therefore retains more ash by weight than the ESP unit although it releases higher numbers of submicron particles to the atmosphere (11).Since the wet scrubber is more efficient, the EF value of the scrubber ash might be expected to be near unity; consequently, any chemical enrichment in the submicron particles would be obscured.
Discussion The Z10Pb depletion in the ESP bottom ash probably occurs as volatilization and later condensation onto the fly ash matrix. Since heterogeneous condensation is a surface-area phenomenon, the lead should be enriched on the finer fly ash particles. In Figure 2 the stack- (post-ESP) sized fly ash shows a very strong increase in E F with decreasing particle size. This effect is consistent with the depletion of lead on the largersized ESP fly ash. Davison et al. (12) discuss this condensation mechanism more fully. Assuming that secular equilibration exists between zloPb and ZlOPo in the coal samples, the specific activity for both nuclides will be identical; therefore, the total inventory of 2lOPo for the coal combustion system can be estimated. Its postcombustion behavior was not studied in this work; but since polonium is more volatile than lead, it will probably condense onto the extremely small fly ash particles after
,
I
I
5.
4.
*0
10
c
y-COUNTING DATA:
: .oi
3.
o "OPb
Y r
A 238U V
226Ra
0 228Ra
0
228Th
INAA data: 2.
0
Ce
1.
5
10 Particle s i z e , u
15
Figure 2. Enrichment factors of nroPb,238U, n2eRa,228Ra,and 228Th vs. size in stack fly ash collected downstream from electrostatic precipitator (ESP) For comparison enrichment factors for cerium are plotted. Cerium concentrations taken from INAA analysis of same samples (6)
combustion. A study of the combustion chemistry and deposition properties of this important radionuclide is in progress. Uranium's definite association with small particles has been previously observed (13, 14). I t is slightly depleted in the bottom ash from both plants. Plant B (high-ash coal) has a fly ash EF near unity. However, this plant's sized stack fly ash shows a very definite increase in EF with decreasing particle size (see Figure 2). We propose a bimodal mechanism to explain this behavior. The coal contains uranium in two different phases, which affects its volatility upon combustion. Klein et al. (14) observed that uranium behaves in a manner intermediate between those elements remaining with the slag and those elements concentrating on the fly ash. Breger (15)suggests that uranium enters the coal bed from ground water as the soluble sodium uranyl decarbonate (Naz or the sodium uranyl tricarbonate (Na4 [UOZ(CO~)Z]) [UO2(CO3)3])complex. Breger also suggests that this slightly acidic environment of the coal decomposes these complexes, and the uranium quickly becomes absorbed by the coal with subsequent reduction to uraninite (U02). If sufficient silica is present in solution, the mineral coffinite (U(Si04)1-x(OH)4x)can form instead of uraninite. Since the uranium is quite highly dispersed in the coal, it must have migrated from cracks and joints for some distance into the coal matrix. Uranium can therefore be expected to reside in the coal in a very highly dispersed state, and be mineralized as both
uraninite and coffinite, depending on the composition of the original mineralizing fluid. Uranium is enriched over thorium in these samples (Th/U = 2.0) compared to the average crustal ratio (Th/U = 4.0) (16),thus indicating the high mobility of uranium compared to thorium during ground and surface water transport. The characteristics of uranium during the combustion process are determined by the conditions of the furnace as well as its chemical and physical form in the input coal. Coal-fired power plants operate their burners with about a 10% stoichiometric excess of oxygen (17).This should result in an oxidizing combustion environment with a temperature range of 1500-1600 OC. Under these conditions the volatile species UO3 should be formed (18, 19). Uranium might be incorporated into a silica melt during combustion if it is originally associated with a silicate (i.e., coffinite). A bimodal existence of uranium in the coal can therefore give rise simultaneously to both a volatile and nonvolatile species, since both uraninite and coffinite can coexist in the pulverized and semihomogenized coal. The data in Table IV tend to support this relationship although the analytical errors do not merit a definitive conclusion. The Plant B (high-ash coal) fly ash shows less uranium depletion than the Plant A (low-ash coal) fly ash. A higher percentage of the uranium is probably associated with the alumino-silica matrix of the fly ash. Thorium-228 could be slightly enriched in the stack fly ash when compared to INAA data for cerium, a nonenriched element (see Figure 2). Thorium (and to some extent uranium) is normally associated with the very chemically resistant mineral zircon (ZrSi04) (20), which is a ubiquitous accessory mineral in many common rocks. Zircon does not weather easily and is commonly found in sedimentary environments. It is conceivable that the thorium observed in the coal system was deposited as zircon contemporaneously with the coal along with the other silicate-based minerals. These minerals make up the ash after the coal is burned. The small resistant mineral grains could be carried with the gases after combustion and follow the course of the fly ash. The thorium behavior in the sized fly ash could be explained if thorium existed in the coal as submicron particles. The enrichment of zzsRaand 226Ra(see Figure 2 and Table IV) is difficult to explain. Klein et al. (13)observed that barium (and hence probably radium) and thorium become incorporated into the fly ash matrix. However, barium is known to form the volatile species Ba(0H)Z in the presence of steam (211, and radium may also form a corresponding species. Figure 2 shows zzsRawith a greater E F than 2z8Ra.A portion of the zz6Rawill reside with the uraninite fraction of its 238U parent as described earlier. This probably allows zzsRato form a more mobile species than the silicate associated zz8Ra (from the 232Thchain) in a manner similar to the bimodally bound uranium. The behavior of the natural radioactive-decay series throughout the coal deposition, combustion, and emission system can be described by the following scenario: Associated with the accumulation of organic matter is a significant fraction of clay minerals, silt, and other inorganic sedimentary material. These materials contain the aluminosilicate minerals that will later comprise the coal fly ash and bottom ash. Herein is found the source of the 232Th,40K,and a part of the silicate-associated uranium. The organic accumulation environment ceases, and a deposition environment prevails, which buries the organic matter. Coal metamorphism occurs. Ground and surface waters penetrate down through the overburden, invading the coal. These waters contain uranium as soluble uranyl carbonate salts and varying amounts of soluble silica. Volume 12, Number 4, April 1978
445
Uranium is absorbed by the coal and reduced to uraninite or coffinite, depending on the silica content of the water. Coal is mined, pulverized, and fed into the furnace for power production. Much of the alumino-silicate minerals (mostly clay) form a melt and drop out as slag. Most of the thorium and radium isotopes follow. Lead-210 remains volatile and continues along with the gases and fly ash t o the emission control system. Much of the uranium that is associated with the clays, or that which was mineralized as coffinite, also remains with the bottom ash. T h e uranium that is dispersed in the coal as uraninite becomes volatile as the UOs species and continues along with the gases, lead, and the fly ash. Somewhere down the flue line, first uranium and then lead preferentially condense out on the finer fly ash particles because they have a high surface to mass ratio. The ESP collects most of the particulate mass. Those finer particles that bypass the ESP continue up the stack with the gases. They are very enriched in 210Pb relative t o the coal and moderately enriched in 235Uand 238Urelative to coal. Some slight enrichment is observed for 226Ra(probably that associated with uraninite), 22sRa,and 228Th.The thorium is probably associated with fine zircon grains. The degree to which each of the many possible mechanisms affects the final radionuclide concentrations cannot be ascertained from these data. T h e actual situation may be one mechanism or, more probably, a combination of mechanisms. The mineralogical or chemical form in which the radionuclides or trace elements exist in the coal does have an important effect on their subsequent combustion chemistry and emission characteristics.
Acknowledgment We thank G. L. Fisher of the Radiobiology Laboratory at the University of California at Davis for his advice and cooperation during this experiment. H e provided the support for the construction of the cyclone separator and allowed our group to take samples with it. We also thank A. H. Biermann of Lawrence Livermore Laboratory for performing t h e particle-size analyses of the fly ash; 0. H. Krikorian of Lawrence Livermore Laboratory for his valuable suggestions concerning volatile radium and uranium species; and D. Garvis, R. Wikkerink, and J. Stevens for field and laboratory support. Literature Cited (1) Eisenbud, M., Petrow, H. G., Science, 144,228 (1964). (2) Martin, J. E., Harward, E. D., Oakley, D. T., Smith, J. M., Bedrosian, P. H., “Radioactivity from Fossil-Fuel and Nuclear Power Plants”, IAEA Symp. on Environmental Aspects of Nuclear Power Stations, New York, N.Y., IAEA Conf. 700810-24, paper IAEASm-146/19, pp 325-37,1969. (3) Hull, A. P., Nucl. News, pp 51-5 (Apr. 1974). (4) Moore, H. E., Martell, E. A., Poet, S. E., Environ. Sci. Technol., 10, 586 (1976). (5) McFarland, A. R., Fisher, G. L., Prentice, B. A., Bertch, R. W., ibid., submitted for publication (1976).
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Environmental Science & Technology
(6) Ondov,J. M., Ragaini, R. C., Heft, R. E., Fisher, G. L., Silberman, D., Prentice, B. A., “Interlaboratory Comparison of Neutron Activation and Atomic Absorption Analysis of Size-Classified Stack Fly Ash”, presented at 8th Materials Research Symp. on Methods and Standards for Environmental Measurement, Gaithersburg, Md., Sept. 1976;Lawrence Livermore Lab, Preprint UCRL-78194, 1976. (7) . . CamD. D. C.. Gatrousis., C.. .Mavnard. “ . L. A.. Nucl. Instrum. Methdds, 117,189 (1974). (8) Gunnink, R., Niday, J. B., “Computerized Quantitative Analysis by Gamma-Ray Spectrometry”, Lawrence Livermore Lab, Rep. UCRL-51061,1972. (9) . , Coles. D. G.. Meadows. J.W.T.. Lindeken. C. K.. Sci. Total Enuiron., 5, 171 (1976). ’ (10) Coles. D. G.. Meadows. J.W.T.. “Radionuclide Release from Non-Nuclear Energy Production: A Sensitive Technique for the Measurement of zloPb on Air Filters”, presented at Environmental Chemistry and Cycling Processes Symp., Augusta, Ga., 1976; Lawrence Livermore Lab, Preprint UCRL-77871,1976. (11) Ondov, J. M., Ragaini, R. C., Biermann, A. H., “Comparison of Particulate Emissions from Wet Scrubber and Electrostatic Precipitator at a Coal-Fired Power Plant”, presented at American Chemical Society Meeting, Div. of Environ. Chem., San Francisco, Calif., Aug. 1976;Lawrence Livermore Lab, Preprint UCRL-78050, 1976. (12) Davison, R. L., Natusch, D.F.S., Wallace, J. R., Environ. Sci. Technol., 8,1107 (1974). (13) Ragaini, R. C., Ondov, J. M., “Trace Element Emission from Western U S . Coal-Fuel Power Plants,” in Proc. Int. Conf. Modern Trends in Activation Analysis, Munich, Germany, 1976, I, p 654; Lawrence Livermore Lab, Preprint UCRL-77669,1976. (14) Klein, D. H. Andren, A. W., Carter, J. A., Emery, J. F., Feldman, C., Fulkerson, W., Lyon, W. S., Ogle, J. C., Talmi, Y., Van Hook, R. I., Bolton, N., Environ. Sci. Technol., 9,973 (1975). (15) Breger, I. A., “The Role of Organic Matter in the Accumulation of Uranium-The Organic Geochemistry of the Coal-Uranium Association”, in IAEA Symp. on the Formation of Uranium Ore Deposits, Athens, Ga., 1974,IAEA-SM-183/29,pp 99-124,1974. (16) Mason, B., “Principles of Geochemistry”, 3rd ed., Wiley, New York, N.Y., 1966. (17) Babcock and Wilcox, “Steam, Its Generation and Use”, 38th ed., Babcock and Wilcox, New York, N.Y., 1972. (18) Rand, M. H., Kubaschewshi, O., “The Thermochemical Properties of Uranium Compounds”, Interscience (Wiley), 1963. (19) Ackermann, R. J., Thorn, R. J., Alexander, C., Tetenbaum, M., J . Phys. Chem., 64,350 (1960). (20) Kirby, H. U., “Geochemistry of the Naturally Occurring Radioactive Series”, Mound Lab Rep. MLM-2111, 1974. (21) Newbury, R. S., “Vapor Species of the Barium-Oxygen-Hydrogen System”, Lawrence Livermore Lab Rep. UCRL-17725-T, 1964. ’
Received for review January 24, 1977. Accepted October 31, 1977. Work performed under the auspices of the U S . Energy Research and Development Administration under Contract No. W-7405-Eng-48. “This report was prepared as an account of work sponsored by the United States Government. Neither the United States nor the United States Energy Research & Development Administration, nor any of their employees, nor any of their contractors, subcontractors, or their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness of usefulness of any information, apparatus, product or process disclosed, or represents that its use would not infringe privately-owned rights.”
