ISSN:0038-075X    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

The characteristics of radioactive wastes and soils vary over a wide range. Liquid radioactive waste entering the environment will eventually contact the soil or geological matrix; interactions will be determined by the chemical and physical nature of the liquid, as well as the soil matrix. We report here the results from an investigation of certain of those characteristics as they relate to retention of radionuclides by soils. Three fractions were demonstrated in the waste as filterable, soluble-sorbable, and soluble-nonsorbable; the physical nature of each fraction was demonstrated using autoradiographic techniques. Isotopes of plutonium and uranium and americium-241 in the soluble fraction of the waste were shown to have a negative charge as determined by ion exchange techniques. In the soil-waste systems, the net charge for those radionuclides was shown to change from predominantly negative to predominantly positive. Nevertheless, cesium-137 was shown to be predominantly positively charged. The change in charge and the redistribution of radionuclides among the various fractions is important in assessing the degree of mobility of radionuclides in soil.

ISSN:0038-075X    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

We reacted four soils of widely different characteristics with liquid radioactive wastes in an experiment designed to evaluate differences in the abilities of the soils to sorb or to enhance mobilization of the radionuclides.Cesium-137 was sorbed almost completely by all four soils, whereas we noted large differences in the degree of sorption among soils for plutonium, uranium, and americium-241. Fuquay soil caused significant solubilization of the plutonium and americium-241 originally contained in the insoluble fraction of the waste. Upon reacting the waste with the four soils, we noted a change in charged species. Net removal of plutonium by Fuquay did not occur, however, suggesting the presence of complexing (chelating) ligands.Changes in the degree of sorption due to changes in solubility or charge speciation affect the short- and long-term fate of waste radionuclides in soils. Understanding those changes is useful in predicting radionuclide migration as the result of waste-burial operations or accidental releases from processing facilities.

ISSN:0038-075X    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

We interacted a low-level radioactive waste with the respective horizons of two soils series, the Fuquay and the Fayette. The sorption of the soluble radionuclides was determined by batch reaction methods. Cesium-137 was sorbed to a very high degree, greater than 95 percent, and that degree of sorption was independent of both the soil horizon and the soil series. Uranium also was sorbed to a high degree by all horizons, with sorption by the Fuquay A2 and Fayette Ap soils at 60 to 70 percent and at 90 percent or more by the other horizons. The lower degrees of sorption were attributed to the presence of a negatively charged uranium species, probably a uranium carbonate complex. Soluble plutonium and americium were sorbed to a high degree, greater than 75 percent, by all horizons except for Fuquay AP and A2. Those two horizons solubilized, at least in part, the plutonium and americium associated with the insoluble fraction of the waste. The complexing of those radionuclides into a nonsorbable form was attributed to an organic complex.

ISSN:0038-075X    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

Using an equilibrium batch technique, we determined the extractability of237Np,239Pu,241Am, and244Cm from widely different kinds of soils as a function of pH. Hydrochloric acid or NaOH was used to adjust the pH. The sorption and extractability of the transuranics studied varied considerably with pH and the kind of soil. A general pattern of extractability, common to all the transuranics studied, was exhibited to a varying degree by each mineral soil, except the calcareous soil. Typically, the extractability was relatively high under strongly acidic conditions, particularly below pH 2. Then, as the pH increased, there was a zone of rapid decrease, which was followed by a zone of relatively low extractability. Above the latter zone, there was an increase to a peak with increasing pH and then a decline. The organic soil used differed from this general pattern in that it showed a progressive increase of extractability in the alkaline pH range instead of peaking and declining. Among the mineral soils, the extractability of237Np was markedly greater than those of239Pu,241Am, or244Cm in the pH range below pH 6. Above this pH, the relative extractability of the radionuclides depended on the soil. The extractability of244Cm was practically the same as that of241Am over the entire pH range. The relative magnitudes of the distribution coefficient,Kd, values around the pH levels of the soils were237Np <239Pu <241Am,244Cm. Soil organic matter and hydrous oxides of Al, Fe, and Mn appeared to influence the sorption and extractability of the transuranics studied.

ISSN:0038-075X    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

Using an equilibrium batch technique, we determined the effect of clay minerals on the extractability of239Pu(IV). The <2 μm size fractions of three American Petroleum Institute reference clay minerals (montmorillonite No. 26, Kaolinite No. 3, and illite No. 35) were used. The extractability of Pu from clay suspensions prepared on an equal weight basis differed to some extent from those prepared on an equal equivalency basis. The Pu extractability also depended on clay-solution ratio, clay mineral type, clay particle size distribution, NO3−concentration, and pH.

ISSN:0038-075X    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

Crops of peas, soybeans, tomatoes, and wheat were grown in seven different soils uniformly contaminated with mixtures of237Np,239,240Pu,241Am, and244Cm. The soils were representative of major food production areas of the United States. The plant uptake experiments were performed in 200-liter containers, to simulate field conditions. Crop yields varied with the fertility conditions of the soils. Differences in soil properties were a major cause of variability in the concentration ratios (CR) that measure the transuranic element uptake by food crop plants through root systems. Root uptake of239,240Pu was lowest, with CR values for vegetative parts of plants ranging from 10−6to 10−4. The CR values for241Am and244Cm were essentially the same, ranging from 10−5to 10−2. The CR values for237Np in vegetative parts ranged from 10−4to 10−1. The CR values for seed, grain, and fruit parts of plants generally were a factor of 10 lower than values for foliage (10−7to 10−5for239,240Pu, 10−6to 10−4for241Am and244Cm, and 10−5to 10−3for237Np). From 60 to 90 percent of the variation for a given crop and radionuclide was attributable to soil difference; from 10 to 40 percent was attributable to differences between soil replicates and between samples from the same container. Plant uptake of237Np through roots was about 1000 times greater than plant uptake of239,240Pu; the uptakes of241Am and244Cm were essentially equal. Root uptake of237Np was 60 to 70 times that of241Am, and244Cm, and both241Am and244Cm were taken up about 20 times more than239,240Pu under the same cropping conditions.

ISSN:0038-075X    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

We studied the relationship between chemical extractability and wheat plant uptake of237Np,239,240Pu,241Am, and244Cm from seven widely different kinds of soils. The chemical extractants used were distilled H2O, 0.05MCaCl2, and 1MNH4OAc. The relative order of magnitude of237Np extractability by the extractants was H2O < CaCl2< NH4OAc. The relative order of magnitude of239,240Pu,241Am, and244Cm extractabilities were generally H2O, CaCl2< NH4OAc. The amount of the extractable fraction of each tracer nuclide was conditioned by soil type. The241Am and244Cm uptake by wheat plants correlated with the extractability of these nuclides by H2O, CaCl2, and NH4OAc at the 5 percent level of significance or better. The237Np uptake by the plants correlated with its extractability by CaCl2and NH4OAc, but not by using H2O. With239,240Pu, poor correlation was obtained with all of the extractants used when no soil was excluded from statistical analyses. When one (Lyman silt loam) of the seven soils was excluded, the correlation was significant at the 5 percent level for NH4OAc. The most suitable extractant for237Np,241Am, and244Cm was CaCl2.

ISSN:0038-075X    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

This paper reports experiments conducted to determine the relative amount of adsorption and plant uptake of Plutonium-238 and Plutonium-239 from soils contaminated by these isotopes in the soluble nitrate form. Wheat plants were used for uptake studies. The results showed no appreciable difference of plant uptake between238Pu and239Pu. As determined by ammonium acetate extraction, there was no difference in the amount of adsorption between238Pu and239Pu.

ISSN:0038-075X    

出版商:OVID    

年代:1981

数据来源: OVID

摘要:

We describe a procedure for the sequential determination of237Np,238Pu,239,240Pu,241Am, and244Cm in plant material. The plant sample is decomposed completely by a combination of dry ashing and wet digestion; the radionuclides are then coprecipitated with ferric hydroxide. Americium-curium, plutonium, and neptunium fractions are sequentially extracted with tri-isooctylamine (TIOA). Excess salts are then removed from the americium-curium fraction by ferric hydroxide precipitations in a two-step procedure, first using ammonium hydroxide and then sodium hydroxide, followed by iron removal by cation exchange. Trace amounts of iron are removed from the plutonium and neptunium fractions by ion exchange. Each fraction is electrodeposited and analyzed by alpha spectrometry. Recovery for the neptunium fraction is about 80 percent, and for plutonium, americium, and curium, better than 90 percent. Yields are corrected by recovery of added tracers.

ISSN:0038-075X    

出版商:OVID    

年代:1981

数据来源: OVID