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Absolute yields of some fission products in the fast neutron induced fission of 238U
Nuclear Instruments and Methods North-Holland, Amsterdam
ABSOLUTE YIELDS FISSION OF mu
in Physics
Research
B24/25
501
(1987) 501-502
OF SOME FISSION PRODUCTS
IN THE FAST NEUTRON
INDUCED
S. RAM, N.L. SINGH, S.K. BOSE and J. RAMA RAO Nuclear
Research Lrrboratoty,
Ph.vsics Depurtment,
Banarus
Hindu
University,
Vamnusi
??I
005. Indiu
Fission-track registration characteristics of Lexan plastic track detector immersed in aqueous solution of uranyl nitrate have been studied. An attempt has been made to measure absolute fission yields of some fission products in the 14 MeV induced fission of 23RU ’ using track etch-cum-gamma ray spectrometry. Yields of 10 fission-products with half life ranging up to several hours and mass numbers in the region 99-157 are reported.
1. Introduction
2.2. Measurement
Fission product nuclear data such as yields, half-life etc. are very useful for the development of fast reactor technology. These are necessary for the calculation of fission product inventories, shielding requirements, decay heat etc. Absolute yields of fission products have been determined using track etch-cum-gamma ray spectromettic technique. The fission events have been measured by the already calibrated Lexan plastic detector and fission fragments identified by the gamma activity measurements of the irradiated uranium sample in a HPGe detector having 2 keV resolution at 1.33 MeV gamma-ray energy.
The detector sample contained in uranyl nitrate solution was irradiated with fast neutrons along with a solid sample of uranyl nitrate of known amount (- 1 g) as shown in fig. 2. The fast neutrons of energy 14 MeV and flux 2.26 x lo9 n/(h cm’) were produced in a Van de Graaff accelerator using a T(d, n) reaction. The average neutron flux at the site of sample was measured by placing aluminium monitors on both sides of the sample. After irradiation the Lexan strips were etched in 6.25N NaOH solution for one hour at 60°C. The fission tracks were counted under an optical microscope. The gamma counting of the solid uranium sample was done on a precalibrated HPGe detector coupled to a multichannel analyzer.
offission yield
2. Experimental methods 2.1. Measurement
of
detector
3. Calculation
efficiency (K,,,)
An aqueous solution (25 mg/cm3) of uranyl nitrate was taken in a thin glass tube containing the Lexan plastic track detector and irradiated with fast neutrons along with another Lexan detector on which a known amount of uranyl nitrate was deposited by an evaporation method, as shown in fig. 1.
3.1. Detector efficiency (K,,,) The track registration efficiency of Lexan in an aqueous solution of uranyl nitrate is given by the expression [l]
(1)
K wet = T,K,,W/CT
e
I4MaN neutron
I4MeV neutron
ABC Fig. 1. Typical
geometry
of irradiation
A for determination
of
Kw,,.
0168-583X/87/$03.50 0 Elsevier Science Publishers B.V. (North-Holland Physics Publishing Division)
Fig. 2. Typical
irradiation
geometry
to measure
III, NUCLEAR
yields. PHYSICS
502
S. Ram et al. / Absolute~vields
Table 1 Yield of the fission products Nuclide
from 14 MeV neutron
99Mo “‘Cd tt,lmCd
5.84 & 0.29 0.57 Ir 0.02 0.15 f 0.01 0.25 f 0.01 0.21 rt 0.01 4.10+-0.20 4.34kO.17 4.46kO.17 0.89 i 0.04 0.11 i 0.01
“%b t2s@)Sb 131rnTe
lWBa 14’Ce t”Prn “‘Eu
fission of 23RU and the revelant
y-energy
Abundance
Ref. [3]
(keV)
(%)
5.60+0.50
739.4 527.7 564.4 666.3 314.1 113.7 537.2 145.0 167.7 410.6
12.6 33.9 15.2 99.7 61.0 38.0 23.6 48.4 7.7 19.0
Yield Present
induced
0.87 + 0.15 0.80+0.16 _ 3.83+0X 4.54+0.40 4.58 f 0.31 0.64 * 0.10 0.08 i 0.02
where T, = track density of the fission tracks in Lexan kept in the thin glass (see fig. 1) containing the uranyl nitrate solution, W= amount of the fissile substance deposited on the Lexan detector (labelled B in fig. 1); C = concentration of fissile solution, T = total number of fission tracks in Lexan tabelled B in fig. 1 and K = fission track registration efficiency in L.exan laglled B in fig. 1. 3.2. Fission yield The fission yields (Y) of fission products are obtained using the following relation Y=
na+(l
AX _ e@,)e-h(,
- e-h3)
’
(2)
where X is the decay constant and AX is the activity (disintegration rate) of any fission fragment formed in the target. t, and t, and A are the irradiation time, waiting time and data accumulation time, respectively. n, u and # are the total number of 238U atoms in the fissile target, fission cross section of 2’aU for 14 MeV neutrons and average neutron flux at the site of the target sample (solid uranyl nitrate labelled C in fig. 2), respectively. The quantitiy A is calculated by the equation A = A ,,‘p,@, t
(3)
where A.,, 0, and P, are the photopeak area, HPGe detector efficiency and abundance for the given gamma ray, respectively. no+ is determined by the relation [l]: no+ = T;S/K,,C’ti,
offissionproducts
(4)
where S is the amount of the target sample (solid uranyl nitrate) labelled C in fig. 2, Td is the track
data used for calculation HPGe detector efficiency (x10-J)
Half-life
8.282 11.828 11.017 9.245 20.465 7.894 11.607 46.318 39.720 15.420
66.02 h 53.38 h 3.31 h 12.4 d 9.1 h 30.0 h 12.789 d 32.55 d 28.4 h 15.15 h
density measured in the Lexan plastic track detector and C’ is the concentration of aqueous uranyl nitrate solution labelled in fig. 2.
4. Results and discussion Table 1 gives the detection efficiency of the HPGe detector, the fission yield values and other necessary data, collected from the Table of Isotopes 121, that are used to calculated the fission yield. The yield values from a recent calculation [3] are also included for comparison It can be seen that the agreement between the two sets of yield values is reasonably good. This proves the soundness of the track etch-cum-gamma ray spectroscopy method. Similar work is in progress for 232Th and will be reported elsewhere. One of the authors (S.R.) is grateful to the Department of Atomic Energy, Government of India for providing a research fellowship during the course of this work.
References [I] A. Ramaswami. V. Natarajan, B.K. Srivastava. K. Kumar Sampath, N.K. Chaudhuri and R.H. Iyer, J. Inorg. Nucl. Chem. 41 (1979) 1532. [2] CM. Lederer and V.S. Shirley, Table of Isotopes, 7th ed. (Wiley. New York, 1978). [3] B.E. Adams, W.D. James, J.N. Beck and P.K. Kurode, J. Inorg. Nucl. Chem. 37 (1975) 419.
ABSOLUTE YIELDS FISSION OF mu
in Physics
Research
B24/25
501
(1987) 501-502
OF SOME FISSION PRODUCTS
IN THE FAST NEUTRON
INDUCED
S. RAM, N.L. SINGH, S.K. BOSE and J. RAMA RAO Nuclear
Research Lrrboratoty,
Ph.vsics Depurtment,
Banarus
Hindu
University,
Vamnusi
??I
005. Indiu
Fission-track registration characteristics of Lexan plastic track detector immersed in aqueous solution of uranyl nitrate have been studied. An attempt has been made to measure absolute fission yields of some fission products in the 14 MeV induced fission of 23RU ’ using track etch-cum-gamma ray spectrometry. Yields of 10 fission-products with half life ranging up to several hours and mass numbers in the region 99-157 are reported.
1. Introduction
2.2. Measurement
Fission product nuclear data such as yields, half-life etc. are very useful for the development of fast reactor technology. These are necessary for the calculation of fission product inventories, shielding requirements, decay heat etc. Absolute yields of fission products have been determined using track etch-cum-gamma ray spectromettic technique. The fission events have been measured by the already calibrated Lexan plastic detector and fission fragments identified by the gamma activity measurements of the irradiated uranium sample in a HPGe detector having 2 keV resolution at 1.33 MeV gamma-ray energy.
The detector sample contained in uranyl nitrate solution was irradiated with fast neutrons along with a solid sample of uranyl nitrate of known amount (- 1 g) as shown in fig. 2. The fast neutrons of energy 14 MeV and flux 2.26 x lo9 n/(h cm’) were produced in a Van de Graaff accelerator using a T(d, n) reaction. The average neutron flux at the site of sample was measured by placing aluminium monitors on both sides of the sample. After irradiation the Lexan strips were etched in 6.25N NaOH solution for one hour at 60°C. The fission tracks were counted under an optical microscope. The gamma counting of the solid uranium sample was done on a precalibrated HPGe detector coupled to a multichannel analyzer.
offission yield
2. Experimental methods 2.1. Measurement
of
detector
3. Calculation
efficiency (K,,,)
An aqueous solution (25 mg/cm3) of uranyl nitrate was taken in a thin glass tube containing the Lexan plastic track detector and irradiated with fast neutrons along with another Lexan detector on which a known amount of uranyl nitrate was deposited by an evaporation method, as shown in fig. 1.
3.1. Detector efficiency (K,,,) The track registration efficiency of Lexan in an aqueous solution of uranyl nitrate is given by the expression [l]
(1)
K wet = T,K,,W/CT
e
I4MaN neutron
I4MeV neutron
ABC Fig. 1. Typical
geometry
of irradiation
A for determination
of
Kw,,.
0168-583X/87/$03.50 0 Elsevier Science Publishers B.V. (North-Holland Physics Publishing Division)
Fig. 2. Typical
irradiation
geometry
to measure
III, NUCLEAR
yields. PHYSICS
502
S. Ram et al. / Absolute~vields
Table 1 Yield of the fission products Nuclide
from 14 MeV neutron
99Mo “‘Cd tt,lmCd
5.84 & 0.29 0.57 Ir 0.02 0.15 f 0.01 0.25 f 0.01 0.21 rt 0.01 4.10+-0.20 4.34kO.17 4.46kO.17 0.89 i 0.04 0.11 i 0.01
“%b t2s@)Sb 131rnTe
lWBa 14’Ce t”Prn “‘Eu
fission of 23RU and the revelant
y-energy
Abundance
Ref. [3]
(keV)
(%)
5.60+0.50
739.4 527.7 564.4 666.3 314.1 113.7 537.2 145.0 167.7 410.6
12.6 33.9 15.2 99.7 61.0 38.0 23.6 48.4 7.7 19.0
Yield Present
induced
0.87 + 0.15 0.80+0.16 _ 3.83+0X 4.54+0.40 4.58 f 0.31 0.64 * 0.10 0.08 i 0.02
where T, = track density of the fission tracks in Lexan kept in the thin glass (see fig. 1) containing the uranyl nitrate solution, W= amount of the fissile substance deposited on the Lexan detector (labelled B in fig. 1); C = concentration of fissile solution, T = total number of fission tracks in Lexan tabelled B in fig. 1 and K = fission track registration efficiency in L.exan laglled B in fig. 1. 3.2. Fission yield The fission yields (Y) of fission products are obtained using the following relation Y=
na+(l
AX _ e@,)e-h(,
- e-h3)
’
(2)
where X is the decay constant and AX is the activity (disintegration rate) of any fission fragment formed in the target. t, and t, and A are the irradiation time, waiting time and data accumulation time, respectively. n, u and # are the total number of 238U atoms in the fissile target, fission cross section of 2’aU for 14 MeV neutrons and average neutron flux at the site of the target sample (solid uranyl nitrate labelled C in fig. 2), respectively. The quantitiy A is calculated by the equation A = A ,,‘p,@, t
(3)
where A.,, 0, and P, are the photopeak area, HPGe detector efficiency and abundance for the given gamma ray, respectively. no+ is determined by the relation [l]: no+ = T;S/K,,C’ti,
offissionproducts
(4)
where S is the amount of the target sample (solid uranyl nitrate) labelled C in fig. 2, Td is the track
data used for calculation HPGe detector efficiency (x10-J)
Half-life
8.282 11.828 11.017 9.245 20.465 7.894 11.607 46.318 39.720 15.420
66.02 h 53.38 h 3.31 h 12.4 d 9.1 h 30.0 h 12.789 d 32.55 d 28.4 h 15.15 h
density measured in the Lexan plastic track detector and C’ is the concentration of aqueous uranyl nitrate solution labelled in fig. 2.
4. Results and discussion Table 1 gives the detection efficiency of the HPGe detector, the fission yield values and other necessary data, collected from the Table of Isotopes 121, that are used to calculated the fission yield. The yield values from a recent calculation [3] are also included for comparison It can be seen that the agreement between the two sets of yield values is reasonably good. This proves the soundness of the track etch-cum-gamma ray spectroscopy method. Similar work is in progress for 232Th and will be reported elsewhere. One of the authors (S.R.) is grateful to the Department of Atomic Energy, Government of India for providing a research fellowship during the course of this work.
References [I] A. Ramaswami. V. Natarajan, B.K. Srivastava. K. Kumar Sampath, N.K. Chaudhuri and R.H. Iyer, J. Inorg. Nucl. Chem. 41 (1979) 1532. [2] CM. Lederer and V.S. Shirley, Table of Isotopes, 7th ed. (Wiley. New York, 1978). [3] B.E. Adams, W.D. James, J.N. Beck and P.K. Kurode, J. Inorg. Nucl. Chem. 37 (1975) 419.