MASS DISTRIBUTION IN THERMAL NEUTRON FISSION OF ²³⁹Pu

Abstract

Improved radiochernical techniques have been used to study the distribution in mass of the fission f,ragments resulting froin thermal neutron fission in 2 3 9 P~.Disintegration rates atid half-lives were determined by measurement with a 474 gas flow proportional counter. Further identification of the nuclides was obtained by gamma scintillation spectro~netry. The flux intensity during irradiation was monitored by the 6To(n,r)coCo reaction.The absolute fission yields of 89Sr, 90Sr, OIY, 05Zr, 9 9 M~, '03Ru, 1 0 c R~, lo5Rh, 109Pd, l12Pd,

Fission Yields in the Thermal Neutron Fission of Plutonium-239

“…These experiments gave a fission yield value of (6.02 ± 0.16)% for 99 Mo in 23S U which was in reasonable agreement with the accepted value of (6.16±0.10)%. However, the values of "Mo fission yield in 239 Pu were (6.87 + 0.19)%, (6.82 ± 0.15)%, (6.66 ± 0.07)% obtained by using different methods and were higher than the earlier published values [2][3][4][5][6][7], The results of these investigations were reported [9][10][11], Fission yields for 19 mass numbers were also determined using radiochemical method and these included the fission yields in the symmetric region of the mass yield curve. All these investigations formed apart of Ph.…”

“…λ is the decay constant of "Mo or 131 1, Ν is the number of atoms of 239 Pu or 23S U, Of^ is the fission crosssection and Y is the fission yield of "Mo or 131 1 in the thermal neutron fission of 239 Pu or 235 U. Table 1 summarizes the different published fission yield values [2][3][4][5][6][7]9,11,[13][14][15][16][17][18][19][22][23][24][25][26][27][28] for "Mo in the thermal neutron fission of 239 Pu. It is seen that the latest three values [15][16][17] reported by different laboratories are in good agreement with one another and lead to an average value of 6.22% while a value of 6.80% was reported from this laboratory in 1970's [9,11 ].…”

“…The results obtained using gamma ray spectrometry were presented at the IAEA Symposium on Physics and Chemistry of Fission [1]. In these studies "Mo was used as an internal standard for which the reported fission yield values in 239 Pu determined experimentally varied over a wide range, the different values being 5.61% [2], 6.02% [3], 6.10% [4,5], 6.44% [6], 6.59% [7]. This large variation and the difficulty in selecting any particular value from them while determining the fission yields of other nuclides in the thermal neutron fission of 239 Pu using gamma ray spectrometry with Ge(Li) detector [1,8] prompted us to investigate this matter in detail.…”

Decay of 2.1-min and 4.1-min 132Sb Isomers and 2.3-min 133Sb

“…Several investigators have measured the fission" yield of 9 9 Mo in the thermal neutron fission of 239 Pu [1][2][3][4][5][6]. However, the values reported vary over a wide range, the different values being 5.61, 6.02,6.10, 6.17, 6.44 and 6.59%.…”

Absolute Yields of 99Mo in the Thermal Neutron-Induced Fission of 288U and 289Pu

“…Whereas general agreement has been reached for its yield in the thermal neutron fission of 23B U [1][2][3][4][5][6][7], there exist still large discrepancies between different measurements for 233 U and especially for 239 Pu [8][9][10][11][12][13][14][15]. The variations in the experimental values are of course reflected in the evaluations of fission yields which recommend different "best" values [1][2][3][4][5][6].…”