Nuclear-Charge Distribution of Fission-Product Chains of Mass Numbers 131-133

Abstract

New information on the nature of the nuclear charge distribution in thermal-neutron fission of 235 U has been obtained from measurements of fission yields of the principal constituents in each of three adjacent mass chains. A regular variation in the width of the charge-distribution curves with mass number has been shown, and values of the most probable nuclear charge (Z p ) have been determined. No effects attributable to the 50-proton or 82-neutron closed shells have been observed in the charge-distribution curves examined. Independent and cumulative fission yield values were determined for the principal constituents in each of the three mass chains 131, 132, and 133. Values measured are: 131 Sn, (1.28=1=0.21)% cumulative; 131 Sb, (1.66d=0.40)% independent; 132 Sn, (0.59=b0.17)% cumulative; 132 Sb, (2.76=1=0.35) % independent; 132 Te, (0.86=1=0.10)% independent; 133 Sn, <0.015% cumulative; 133 Sb, (3.05=1=0.39)% independent; 133w Te, (2.19d=0.33)% independent; 133 *Te, (2.07=1=0.31)% independent; and 133 I, (0.17=±=0.06)% independent. The charge distribution curve for each mass chain was established from the fission yield data. The data were fitted to the Gaussian relationship, P(Z) -A exp-(Z-Z p ) 2 /c. The widths of the curves as given by values of c for mass chains 131, 132, and 133 are, respectively: 1.10=1=0.05, 0.74=b0.08, and 0.57=1=0.05. The data show a monotonic decrease in the width of the charge distribution curves with increasing fission-product mass number. Implications of this observation are discussed in respect to previous assumptions of a single charge distribution curve for all fission-product masses in low-energy fission. Values of Z v as given by the Gaussian curves for mass chains 131, 132, and 133 are, respectively: 50.72=b0.07, 51.07=b0.06, and 51.59 d=0.04. These values are compared with published values derived from assumptions of a single charge distribution curve for all mass chains. Predicted effects of nuclear shells on charge distribution have been examined in the light of the present data. No effect was detected in mass chains 131, 132, and 133. New half-life values determined are: 131 Sn, 1.32=b0.23 min; 132 Sn, 1.00=1=0.17 min; 132 Sb, 3.13=1=0.33 min; and 133 Sb, 2.67=L0.33 min. The half-life of 133 Sn was estimated to be 55 sec.

Discovery of the calcium, indium, tin, and platinum isotopes

“…It has been possible by the above technique to determine independent fission yields of the tin fission products in thermal neutron fission of uranium-235, tin half-lives, generic relationships, and also prominent gamma photopeak energies from pulse-height distributions taken of the rapidly separated tin fractions''. The measured half-life of 65(10) s for 131 [116] could not be confirmed. 134 …”

“…115 In was detected using the accelerated anode ray method with a solution of hydrofluoric acid: ''This incorporated into the anode gave a mass spectrum showing one line only at 115''. 116 In…”

NRDS nuclear rocket effluent program, 1959--1970

“…For example, the I chain may be represented as: (20,21) Release of core material through corrosion and/or erosion is more difficult to describe and measure than the migration of fission products from the core. The hydrogen coolant reacts with graphite at operating temperatures to produce methane and other hydro-(22) carbons.…”

Rapid Chemical Separations

“…., 1000° C. The method was used for fission yield measurements of antimony isotopes via iodine descendants (169,170 (174)(175)(176) or have produced it by reduction with sodium borohydride (176).…”

“…Rapid volatilization of tin hydride was described by Greendale & Love (180) using sodium borohydridc as reducing agent and sodium hydroxide impregnated asbestos for removal of antimony hydride. The method was applied in fission-yield measurements (169). Some modifications were given by Treyti (181).…”