Short-lived Fission Products Research Articles

Gamma-ray spectrum of short lived fission products

The fission products from uranium-235 irradiated by slow neutrons have been analysed using a gamma-ray scintillation spectrometer. The spectra between 40 minutes and 40 hours after irradiation for 30 seconds have been recorded and twelve major activities identified.

Fission-Product Capture Cross Sections

Experimental measurements of fission product capture cross sections and statistical estimates of capture cross sections for energies at which no measurements have been made yielded a set of group cross sections for primary and secondary fission products covering the complete range of energies of interest for reactor calculations. Capture cross sections and fission product yield measurements were obtained from a comprehensive search covering published and some unpublished measurements available prior to May 196l. Unmeasured capture cross sections in the resonance region were statistically estimated using average neutron strcngth functions, level spacings, and radiation widths. The general techniques of obtaining reliable nuclear parameters and estimates of cross sections are discussed in detail. The importance of capture in shortlived fission products is considered. The group cross sections obtained in this work were combined and presented in a form useful for calculating fission product poisoning in reactors containing U/sup 233/, U/sup 235/, and/or Pu/sup 239/. Results are analyzed and compared with previously published fission product studies. (auth)

Natural and fallout gamma-activity in foodstuffs.

A study was undertaken to estimate the actual concentration of gamma-active isotopes in vegetables, tea. tobacco, powdered milk, wheat, rice, fish, etc., which are available in Bombay, India. A large-size NaI(Tl) crystal scintillator and a thirty-channel pulse-height analyser were used to identify and to estimate the concentration of the radioisotopes. The studies were carried out over a period of about 15 months which is broadly divided as (1) the year following the stoppage of nuclear weapon tests (in October 1958), (2) the month before the French atomic weapon test in Sahara desert on February 13, 1960, and (3) the month after this test. In addition to the presence of natural radioactivity of K40, fission product activities such as Zr95-Nb95, Ru103 I131, Cs137, Ba140-La140 Ce141 and Ce144 were noticed, but in varying amounts in different materials. The very high activities of Zr95-Nb95 and Ce144 in tea were found to be chemically bound in its leaves preventing this uptake by human beings. The presence of Zr95-Nb95 in carrots suggests its preferential pick up through the roots. The radioisotope Zn65 was detected in fish and prawns. The analysis of certain vegetables during the month following the French test clearly indicated the presence of short-lived fission products which should have originated in the test. The degree of contamination is found to depend upon the total surface offered to the fallout and its roughness to hold the activity.

Fallout from 1957 and 1958 nuclear test series.

The causes and effects of high concentrations of shorterlived fission products in fall-out in New York City during 1958 and 1959 are discussed. Data previously reported are supplemented with data on concentrations of Sr/sup 90/, Cs/sup 137/, Ru/sup 106/, Ce/sup 144/, Sr/sup 89/, Zr/sup 95/, and W/sup 18/ s/ sup 5/ measured in monthly fallout collections during 1959. Examination shows that the shorter-lived fission products predominated over Sr/sup 90/ and Cs/sup 137/ from the beginning of 1958 through the middle of 1959. Through analysis of isotope ratios, W/sup 185/ concentrations, and monthly rainfall volumes, it was established that more fallout arrived in New York City from the Soviet series in October 1958 than from earlier series, and that the Soviet debris was richer in short-lived nuclides because it was deposited sooner after its production. Methods, age and origin of debris, air activity concentrations, and gamma dose are all discussed. The calculated contributions of the fall-out that accumulated on the ground in New York City during 1958 and 1959 to external gamma radiation dose rates and to long term doses are both illustrated and tabulated. (P.C.H.)

The separation of In, Sn, and Sb by liquid-liquid extraction

The extraction behaviour of In, Sn and Sb in HI and HCl media has been investigated and several separation procedures have been developed. Removal of Sb(V) from Sn(IV) is accomplished by extraction of Sb(V) from 7M HCl solution with isoamylacetate. Selective removal of Sn(IV) or In(III), or both, from Sb(V) is effected by extraction with benzene or isopropylether from HI solutions. The extractions are quite simple, rapid and efficient and therefore useful in the study of short-lived fission products.

Radioactive Fall-Out in Israel Resulting from the Nuclear Tests in the Sahara Desert

On February 13 and April 1, 1960, nuclear test devices, reportedly in the kiloton range, were exploded in southern Algeria. These tests followed a prolonged period during which no nuclear tests were conducted, with the result that fall-out of short-lived fission products had decreased to a very low level. The tests offered an opportunity of observing fall-out from isolated and well- defined sources of activity in this area. Radioactive materials resulting from those tests were first picked up by the Israel Fall-out Moritoring Network on February 17, and were repeatedly observed again during the following months. The irterpretation of the resulting fall-out deposition pattern in the light of the meteorolcgical data gives some insight into the movement of radioactive clouds and their mode of deposition of activity. Data are presented graphically. (auth)

THE IDENTIFICATION AND HALF LIVES OF FISSION-PRODUCT Rb92 AND Rb93

The existence of two new rubidium isotopes, Rb92 and Rb93, has been established and their half lives measured. The half lives of these short-lived fission products were determined using a technique of timed precipitations. The values obtained for Rb92 and Rb93 were 5.3 ± 0.5 sec and 5.6 ± 0.5 sec respectively. The half lives of the strontium and yttrium daughters were also determined. The strontium isotopes were studied by observing the decay rate of a characteristic γ-ray peak. For Sr92, the decay of the 1.37-Mev line gave a value of 2.71 ± 0.02 hr. A γ-ray peak at 590 kev, which was found to be associated with Sr93, decayed with a half life of 7.54 ± 0.06 min. The half lives of the yttrium daughters were determined by β counting. The values found for Y92 and Y93 were 3.53 ± 0.02 hr and 10.1 ± 0.1 hr respectively.

Meteorological Fractionation of Nuclear Bomb Debris

Radioactive particles are produced by nuclear bomb explosions which are widely different in size and nature. Systematic differences in properties are expected for particles formed under different conditions. Differences in particle properties may cause sorting during deposition because of systematic differences in weather trends at different geographical locations and thus bring to light information about the particles. Deposits at a mountain station in Norway appear to have contained more short-lived fission products than those at lowland stations, especially during periods when considerable fresh fission products have been present in the atmosphere. This could be due to a substantial chemical fractionation on particle sizes taking place during formation, or to the general formation of particles somewhat larger than 0.5 micron diameter during high-yield explosions. DOI: 10.1111/j.2153-3490.1960.tb01313.x

Fallout in New York City during 1958.

Data are presented on the levels of strontium-90, strontium-89, cesium- 137, zirconium-95, cerium-144, yttrium-91, and tungsten-185 in samples of air and rain water and air collected in New York City during 1968. The data indicate that short-lived fission products make a major contribution to fall-out radiation dose rates. (C.H.)

Radioactive fallout during 1959.

ABS>The concentration of strontium-90 In rain falling over Great Britain rose sharply during the first half of 1959 despite the suspension of nuclear weapons testing from November 1955 until February 1960 Results are presented from measurements of the radiostrontium content of rain water sampled through 1959. and the concentration of various short-lived fission products present In surface air durIng the same period The results are dlscussed in relation to current theories on the transport of fission products In the atmosphere. (C H)

Shorter-lived fission products in fallout.

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Meteorological Fractionation of Nuclear Bomb Debris

Radioactive particles are produced by nuclear bomb explosions which are widely different in size and nature. Systematic differences in properties are expected for particles formed under different conditions. Differences in particle properties may cause sorting during deposition because of systematic differences in weather trends at different geographical locations and thus bring to light information about the particles.
 Deposits at a mountain station in Norway appear to have contained more short-lived fission products than those at lowland stations, especially during periods when considerable fresh fission products have been present in the atmosphere. This could be due to a substantial chemical fractionation on particle sizes taking place during formation, or to the general formation of particles somewhat larger than 0.5 micron diameter during high-yield explosions.

THE METABOLISM OF RADIONUCLIDES BY MARINE ORGANISMS. II. THE UPTAKE, ACCUMULATION, AND LOSS OF YTTRIUM91BY MARINE FISH, AND THE IMPORTANCE OF SHORT-LIVED RADIONUCLIDES IN THE SEA ,

Only about 2 per cent of an ingested dose of yttrium91 was left in Tilapia mossambica after two days. This is much less than the amount of strontium retained by Tilapia in similar experiments. About 40 per cent of the radioisotope remaining is found in the visceral organs, but the muscles retain about 30 per cent after 14 days. The skeleton retained less than 20 per cent, the integument about 10 per cent, and the gills 5 per cent. These findings are in marked contrast with those obtained with strontium89 in similar experiments. Attention is focused on the fact that yttrium91 may have little direct effect on man compared with the possible effects of Sr90, but the retention of this and other short-lived fission products in marine organisms having a brief life span may possibly affect the biota, and thus affect man indirectly.

Short-Lived Fission Products. II. Cs139 and Cs140

Half-life values have been obtained for Cs139 and Cs140 by extraction of the Ba descendent activities from cesium silicotungstate precipitates. The half-life of Cs139 was found to be 9.5±0.2 min. by this technique and that of Cs140, 66±2 sec. The value for the Cs139 half-life was confirmed by observation of a Cs sample isolated directly from irradiated uranyl nitrate.