Mixed Fission Products Research Articles

ENVIRONMENTAL MONITORING ASSOCIATED WITH THE DISCHARGE OF LOW ACTIVITY RADIOACTIVE WASTE FROM WINDSCALE WORKS TO THE IRISH SEA.

Since 1952, low activity radioactive waste has been discharged by pipeline from Windscale Works to the Irish Sea off Sellafield. Environmental monitoring studies have been carried out throughout this period in order to assess the resultant radiation dose to man, and hence to estimate the discharge rate which would correspond to the maximum permissible radiation doses recommended by the International Commission on Radiological Protection. These studies have been concerned principally with those materials most likely to contribute substantially to the dose to man, and they have been supplemented by more widespread marine surveys and by laboratory studies aimed at gaining information about the movement and behaviour of radioactive nuclides in the marine environment. It has been concluded from these studies that the rate of discharge from Windscale Works to the Irish Sea cannot be permitted to exceed about 100,000 c/month of mixed fission products, and that specific restrictions are needed on a number of individual nuclides, namely, strontium-90 (about 2000 c/month), ruthenium-106 (about 5000 c/month) and cerium-144 (about 20,000 c/month). The present discharge rates are about 4000 c/month of mixed fission products, of which about half is ruthenium-106 and about 2 per cent strontium-90.

Reliability of Measurements of Gross Beta Radioactivity in Water

This article discusses the Analytical Reference Service Test for evaluation of gross beta radiation analysis methods with a sample consisting of cesium‐137. The participating laboratories that used internal proportional counters obtained counting rates that, when converted to activity in picocuries per liter, usually were within 20 per cent of the best estimate. Even when self‐absorption factors for mixed fission products were used, the estimates averaged less than 15 per cent higher than the best estimate.

Separation of Technetium from Mixed Fission Products by Solvent Extraction with Tributyl Phosphate.

Separation of Technetium from Mixed Fission Products by Solvent Extraction with Tributyl Phosphate.

Detection of 146Pm among the products of uranium fission

Rare earths were separated from a sample of aged mixed fission products and the sample was then reactor irradiated. The activity at reactor discharge was 1.23 x 10/sup -6/ total gamma from Pm/sup 146/ per beta from Pm/sup 147/. Using a value of 1.30 gamma per Pm/sup 146/ decay, the ratio at reactor discharge of Pm/sup 146/ atoms to Pm/sup 147/ atoms was found to be 6.9 x 10/sup -7/. Reactor conditions for different Pm/sup 146/ yields are discussed. (P.C.H.)

INTERNAL DOSES FROM MIXED FISSION PRODUCTS.

Internal doses from ingestion of fission products with aa admixture of neptuaium-239 were calculated for different i-estion periods. t is found that thyroid is the organ eceiving the highest dose during the first 15 to 30 days. (auth)

Root Transfer of Fission Products from Contaminated Soil

Dry yield of wheat grown for 117-days was not affected by solutions of nuclear reactor-produced mixed fission products (MFP) applied to the soil surface or mixed with equal amounts of potted soil at contamination level ranging from 0.01 to 1.0 µc. beta activity per g. of soil. Concentrations of beta and gamma activity in the above-ground parts of plants were increased as the soil contamination levels increased. Wheat removed from 0.07 to 0.09% of the total beta activity that had been mixed with the soil and from 0.10 to 0.15% of that which had been applied on to the soil surface. Concentrations of radioactivity in above-ground plant parts were highest in leaves, intermediate in stems and lowest in fruiting heads. Radiostrontium accounted for 50 to 80% of the beta activity transferred to above-ground plant parts; < 10% was attributable to root transfer of Y91, Ru106, Cs137 and Ce144 from soil.

Rapid Radiochemical Procedure for Antimony and Arsenic.

A very rapid radiochemical procedure was developed for antimony and arsenic. A sample is added to a 30% solution of H/sub 2/SO/sub 4/ containing a carrier for antimony or arsenic (or both). This solution is dropped into a flask containing granular zinc at 100 deg C. The volatile stibine and/or arsine formed is passed through a hot quartz tube and decomposed to the metal, which collects as a metallic mirror on a cooler portion of the quartz tube. This metal is dissolved in H/sub 2/SO/sub 4/ and assayed. The chemical yield is consistently between 70 and 80%. The time required ior separation of the metal from the other elements of a fission product solutlon is about 10 seconds. The decontamination factors for the antimony procedure are: Mixed fission products (2 weeks old) = 10/ sup 5/, I = 3 x 10/sup 4/, Te = 4 x 10/sup 4/, Sn =>10/sup 5/, As = 20-50. The decontamination factors for the arsenic procedure are: Mixed fission products == 10/sup 7/, Sb = 2 x 10/sup 3/, Sn =>10/sup 6/. (auth)

Luftkontamination durch Atombombentests

Fission products produced by atomic bomb explosions give rise to local and world-wide radioactive fallout. The local fallout consists of large particles, but from bombs of approximates 20-kt range the world-wide fallout consists of particles with diameters less than 0.01 mm which are distributed throughout the troposphere, at 10,000 to 20,000 m. Because of the prevailing westerly winds it is distributed over a relatively narrow band and is washed to earth by rains. With bombs in the Mt range the radioactive dust is found essentially in the stratosphere, from where a small portion continuously descends through the tropopause into the troposphere and to the earth. The fallout is readily incorporated into drinking water and foodstuffs, or may be inspired as an aerosol. In Switzerland air concentrations of fallout in 1956 were slightly increased above the normal radiation level, and increased to maxima at the beginning of 1959 and the end of 1961. These maxima were related to French and Russian bomb tests. Although a truly valid evaluation of the biological risk is difficult, a permissible level of 5 rem (gonads and whole body), 30 rem (bone, skin, and thyroid), and 15 rem (other organs) has been established in Switzerland formore » radiation workers. For the general population these values are less by a factor of 100 (gonads) and 30 (all other organs). The maximum permissible concentration (MPC) in air, water, and foods of any radionuclide depends on its metabolism. For Sr the MPC(air) is 3 pC/m/sup 3/, and for tritium the MPC(air) is 50,000 pC/mg. The MPC (air) for mixed uranium fission products at 10 days is 506 pC/m/sup 3/, and at 365 days it is 92 pC/m/sup 3/. For I/sup 131/ the MPC(air) is 100 pC/m/sup 3/, but because it is incorporated into milk the I/sup 131/ hazard to small children is about 1000 times greater from this source than from respiration. At an air contamination of 0.07 pC/m/sup 3/ of I/sup 131/ milk contains an MPC of 130 pC/l. The present value of approximates 3 pC/m/sup 3/ for mixed fission products is much less than the MPC(air) of 229 pC/m/sup 3/. This present value does not endanger the population, but steps must be taken to control bomb tests. (BBB)« less

The complexometric determination of plutonium in reactor fuel processing plant solutions—I: Nitric acid solutions of irradiated uranium

An accurate and precise method for the determination of plutonium in nitric acid solutions of irradiated uranium is described. Plutonium IV is extracted using the quaternary amine Hyamine 1622 dissolved in benzene; the benzene is removed by evaporation and, after dissolution of the residue in acetone, an excess of ethylenediaminetetra-acetic acid (EDTA) is added and the uncomplexed EDTA determined by photometric titration using standard zinc chloride solution and dithizone as indicator. The extraction is highly specific for plutonium and a two-stage cycle results in a decontamination factor of approximately 10 5 for mixed fission products and 10 2 for uranium. Under carefully controlled conditions the method yields a standard deviation of 0–4% for 10 2-μg amounts of plutonium.

The Radiochemical Determination of Promethium-147 in Fission Products

A solvent extraction method was developed for the determination of Pm/ sup 147/ in solutions of mixed fission products derived from irradiated natural uranium. Di(2-ethylhexyl)orthophosphoric acid diluted with an inent diluent (Ultrasene) was used as the extractant. After separation, the Pm/sup 147/ activity was determined by liquid scintillation counting. The precision of the method, based on six determinatione was 3.2% at the 95% confidence limit. (auth)

Maximum Permissible Activity (MPA) for Fission Products in Air and Water

When mixed fission products are present in air and water, the maximum permissible activity (MPA) is dependent on the relative activtty of the individual isotopes. This, in turn, is dependent on the age of the products. The MPA can be determined most accurately from measurements of the isotopic concentrations; however, the separation of mixed fission products into their constituent activities is extremely complicated and costly. In order to provide a simple method of evaluating the internal radiation hazard, MPA's for an ideal mixture of fission products vs. its age were calculated and plotted. The resulting curves show that the MPA's change appreciably with time. Between 1 day and 3 years for 40 hr per week occupational exposure, they decrease from 2.7 x 10/ sup -//sup 7/ to 1.2 x 10/sup -//sup 9/ mu c/cm/sup 3/ (microcuries per cubic centimeter) for air, and from 1.6 x 10/sup -//sup 3/ to 1.7 x 10/sup -//sup 5/ mu c/cm/sup 3/ for water. From the curves a first approximatton of the MPA-s and therefore the allowable fission product activity in air and water, can be obtained. In order to use the curves, one needs to know only the disintegration rate per unit volume andmore » the approximate age of the products. (auth)« less

The selective adsorption of hexavalent uranium by a non-ionic phosphorylated resin from solutions of di-n-butyl phosphoric acid in benzene

Uranium is quantitatively adsorbed by the non-ionic phosphorylated resin diethyl polystyrene-methylenephosphonate (EPMP) from 2 per cent solutions of dibutyl phosphoric acid (HDBP) in benzene. Iron (Fe 3+), lanthanum, zirconium, niobium, thorium and mixed fission products when present in the HDBP/benzene phase are not adsorbed. Adsorption of uranium from solutions containing the complex UO 2(DBP) 2·2HDBP results in the liberation of approximately two equivalents of HDBP and is considered to occur via the mechanism. 2EPMP + UO 2(DBP) 2·2HDBP ⇌ UO 2(DBP) 2·2EPMP + (HDBP) 2. The uranium is quantitatively eluted with a benzene solution of dimethyl formamide. Under low loading conditions HDBP is adsorbed in the absence of uranium as EPMP·HDBP. The selectivity for uranium is compared with the synergic enhancement of uranium extraction with combinations of non-ionic and acidic phosphorylated solvents.

The radiation hazard from contaminated aircraft.

A study of the relative importance of the external, inhalation, and ingestion hazards associated with surface contamination of aircraft that have penetrated atomic clouds or the stratosphere is described. Experiments were conducted at Operations Redwing and Plumbbob. They included - and helial phagocyt - -aircraft surveys, air sampling, swipe sampling, radiochemical and biological analyses, and personnel dosimetry. The latest maximum permissible total radiation dose limits and the NCRP total organ burdens are interpreted in terms of the aircraft maintenance problem. Curves are drawn to show the maximum permissible concentration of mixed fission products in air as a function of age of the debris assuming a 40-hr work week for both controlled and uncontrolled situations. Similar curves are given for the ingestion hazard. The radiological hazard from external radiation is compared with that presented by inhalation and ingestion. It is found for mixed fission debris on aircraft ranging in age from 1 hr to 1 year that the external radiation hazard is dominant by large factors under all normal working conditions. It is concluded that -surveying is generally adequate to define the radiation problem. Release to uncontrolled areas appears warranted if the average measured -field in potential working areas around themore » aircraft or its parts is less than 0.5 mr/hr regardless of age. Swipe sampling cannot be used to evaluate the local air concentration and thus the inhalation hazard. For mixed fission products on aircraft surfaces swipe sampling is no more reliable than the close helial phagocyt -survey of the surface for estimating the potential ingestion hazard. (auth)« less

A Rapid Method for Determining Fission Products Contained in Waters Using an Ion Exchanger

Abstract The essential point of this method is the use of the formate buffer solution. This method would be used for the analysis of fission products in natural waters and for the preparation of pure and carrier-free radioactive elements from mixed fission products.

Quantitative Gamma-Ray Spectrometric Analysis of Nuclide Mixtures Consecutive Standard Sources Nullification

Conventional methods for analysing fission product mixtures are lengthy and difficult. Gamma scintillation spectrometry shortens the analysis time and gives a visible picture of what is being counted. However, for complex spectra, the graphical representation and interpretation of data requires tedious plotting and data reduction time. In the proposed method a sample of mixed fission products is scanned by a 256 channel gamma-ray spectrometer. Instrumental analysis of this spectrum is made, using complement nuclide subtraction technique. Specific activities are determined for each nuclide using standard sources. The time required to make an analysis where four isotopes are present would be about 30 min. Statistical evaluation of the method has been made for Ce 144 , Ru 106 , Cs 137 and Nb 95 in the experimental work. Since standard sources are required for the analysis, this method is limited to reasonably long half-lived fission products. A similar method for other nuclides was published in Analytical Chemistry at the time this paper was being written.

Safety in the operation of radiation sources and use of irradiated foods

The utilization of ionizing radiation for the preservation of foods represents an important advance in the field of food processing. Careful evaluation of the wholesomeness of irradiated foods has been made, and work is continuing; but, thus far, these foods have not been found io be toxic to experimental animals or man. In animal feeding experiments, with a broad spectrum of foods tested, longevity, reproduction, and lactation performance in general are the same as for animals maintained on diets of unirradiated food. Investigations conducted io the present time with mice and rats have not revealed any evidence as to radiation induced carcinogens. While some radiation damage to the macronutrients and micronutrients has been noted, the nutritive value for these foods is equivalent to, or in some cases better than, that for heat processed foods. Ionizing radiation has been shown to be quite effective in alteration of proteins, with the result that certain foods exhibit reduced allergenic properties. Of clinical significance, also, is the fact that low radiation doses of 14,000 rads effectively interrupt the reproductive cycle of the trichinae present in pork, and thereby eliminate the public health problem of trichinosis. Under present methods of processing, none of the irradiatedmore » foods has induced radioactivity. High energy radiation in the area of 24 Mev has been shown to produce transient and short lived radioactive isotopes. In the event that accelerated electrons with high energies are utilized in radiation treatment of food, the potential hazard of these radioactive isotopes, which are induced, will then be explored. An excellent safety program in the operation of radiation sources has been achieved. Radioactive contamination of food cans, by gamma - irradiation with mixed fission products in the canal water, has been eliminated. Health physics procedures guarantee the safety of the product as to both contamination and induced radioactivity. Careful monitoring of personnel and equipment at the radiation sourre has resulted in an excellent record for safety. (auth)« less

Decontaminating Radioactive Ocean Areas through Flocculation

The removal of radioactivity from natural sea water was studied in regard to the feasibility of decontaminating ocean areas. A quantitative study of selected decontaminants showed the over-all superiority of sodium silicate, 0.55 gram of which removed up to 35% of the radioactivity from a 4-foot-high sea water column. Multiple additions of the silicate showed that up to 80% of the mixed fission product may be removed in a static sea water system. A successful decontaminant for sea water could be used to reduce the radiological hazard from marine foods as well as to reduce greatly the radiation in a contaminated harbor. (auth)

Rapid Separation of Radioactive Strontium by Solvent Extraction with TTA-Hexone

Abstract Radioactive strontium in mixed fission products could be rapidly separated by the two-step extraction deviced by the authors. The solution of the material was first adjusted to pH 7 and extracted with 0.05 m TTA-benzene. By this treatment rare earths and yttrium were made to go into the organic phase out of the solution. The remaining aqueous phase was transferred into another separatory funnel, adjusted to pH 8, and extracted with 0.05 m TTA-hexone. In this case the radioactive strontium was completely extracted into the organic phase. Only less than 5% of ruthenium present in the solution was extracted at the same time. Detailed data of the experiments on the extraction involving the determination of distribution coefficient, and the equilibrium constant were tabullated.

Radiochemical procedure for beryllium

A radiochemical procedure is given for the determination of beryllium activity in the presence of mixed fission products and uranium. Decontamination is achieved by adsorption of contaminants on anion-exchange resin from HCl solution, by ferric hydroxide scavenging, and by extraction of beryllium acetylacetonate from a weakly acidic EDTA solution. Two cycles of the procedure have results in a decontamination factor of 3 × 10 8 and a chemical yield of 90 per cent.

A System of Obtaining and Reducing Neutron Flux Data from a Critical Assembly

Some new techniques have been applied in the determination of relative neutron fluxes in water moderated critical assemblies. Alloy wires of Mn-Fe, In-Al, Au-Al, and U-Zr have been prepared with a high degree of uniformity between individual samples of a given material. Beta activation of these wires is measured by thin scintillation crystals in conjunction with specially stabilized electronics. This procedure results in good “plateaus” of counting rate vs photomultiplier voltage, discriminator setting, and amplifier gain. The counting time of a wire is controlled by a decaying sample of the activated material. Thus, as the counting continues, the counting interval becomes progressively longer, providing automatic decay correction of the data. Several benefits obtain from this method. The statistics of counting for a wire of a given activation level are independent of the time of counting; nonuniform decay (e.g., mixed fission product decay) is handled with the same facility as simple exponential decay.Automatic sample changers are used which make possible the counting of larger numbers of samples (approximately 1500 per day) with a minimum of personnel. These changers have been so adjusted that good precision in positioning is maintained. The automatic features of the counting system permit a rapid qualitative evaluation of the data.An error analysis has been made which indicates an experimental counting error (exclusive of statistical error due to decay) of approximately 0.8%. This error, when combined with the appropriate statistical error, has been applied to improve the use of computer codes in obtaining accurate least square fits of theoretical curves to the experimental data.