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Neutron activation cross-sections at (14.6 ± 0.3) MeV
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NUCLEAR ENERGY Annals of Nuclear Energy 35 (2008) 1713–1719 www.elsevier.com/locate/anucene
Neutron activation cross-sections at (14.6 ± 0.3) MeV H.M. Agrawal a,*,1, Kailash Pandey a, K. Surendra Babu b, Ashok Kumar c, R. Pepelnik d,2 a
Physics Department, G.B. Pant University, Pantnagar 263 145, India b Nuclear Data Evaluation Lab KAERI, Pohang, South Korea c Reactor Physics Design Division, BARC, Trombay, Mumbai, India d Institute of Physics, GKSS Research Centre, Geesthacht, Germany
Received 25 October 2007; received in revised form 25 January 2008; accepted 2 February 2008 Available online 24 March 2008
Abstract The activation method has been used to measure 14.6 MeV cross-sections for the following nine reactions which are important for nuclear energy programmes: 89Y(n, a)86mRb, 89Y(n, n0 )89mY, 89Y(n, 2n)88Y, 107Ag(n, n0 )107mAg, 107Ag(n, p)107mPd, 109Ag(n, n0 )109mAg, 109 Ag(n, p)109mPd, 139La(n, p)139Ba, 139La(n, a)136Cs. Special features included a high-intensity neutron generator ‘KORONA’ with a useable fast neutron flux of 3 1014 n/m2 s, a fast rabbit system suitable for cyclic irradiations and measurements for short-lived activities, and a c-ray spectroscopy system with real time correction of counting losses. The results of this investigation are compared with existing experimental cross-section values. The cross-sections have also been calculated using the EMPIRE code Version 2.19 involving Hauser Feshbach statistical theory with pre-compound emission. Default inputs have been used for nuclear model parameters taken from the RIPL-2 data base. The agreement with the experimental data is generally acceptable within the given experimental uncertainty. Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction Accurate measurement of neutron-induced cross-section data at 14 MeV are required for several physical applications, especially in designing future fusion reactors, advanced fission reactors, in neutron dosimetry and for developing refined nuclear theory. An enormous amount of neutron cross-section data in this energy range is found in the literature due to wide spread availability of 14 MeV neutron generator. However, knowledge of the pertinent cross-sections is often confounded by the presence of wide discrepancies between the various reported values. Most of the earlier measurements were done with GM counters and NaI (Tl) scintillation detectors for the detection of b and c activities, respectively. In complex cases, the problem of resolving the continuous b-spectrum into its different *
Corresponding author. E-mail address: hma001@rediffmail.com (H.M. Agrawal). 1 Guest Scientist at Institute of Physik, GKSS Research Centre, Geesthacht, Germany. 2 KOC/GKSS Research Centre Geesthacht Germany. 0306-4549/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.anucene.2008.02.004
half-life components results high cross-section values because of interfering activities. The NaI (Tl) systems, in spite of their superiority over GM counters for gamma counting, have low peak to Compton ratio, with the result that the weak activities are likely to be masked in the presence of strong activities. Later, the availability of high resolution c-ray detection techniques has made an impact on the precision of neutron cross-section data base. However, neutron energies has not been determined in most of the earlier works, which is essential because the excitation functions for many reactions vary significantly around 14 MeV. Since deuterons slow down in passing through the thick tritium targets in most of the 14 MeV neutron generators, it is therefore not possible to determine hEdi without an accurate knowledge of the tritium distribution in the target, which can vary from one target to another or change during deuteron bombardment, Consequently, it is not appropriate to employ the kinematical equation directly. A program to improve the overall data base is necessary for several reasons. There is presently diversity of candidate materials and design concepts of future fusion
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reactors. The probability of selecting a number of materials has changed and will continue to change over the years. Moreover, some reaction cross-sections (e.g. 89Y(n, 2n) and 139La(n, a) of present work) are relevant in studying the nuclear heating of high Tc superconductors (Markovskij et al., 1989; Csikai et al., 1991). The present work is motivated to refine the knowledge of cross-section for nine reactions where the existing data base is inadequate for a consistent and meaningful evaluation. 2. Experimental procedure 2.1. Apparatus For irradiation of samples an intense neutron generator KORONA was used. KORONA (Kombinierte RohrpostNeutroengenerator anlage) consisted a high intensity concentric, sealed neutron tube with a compact arrangement of an annular ion source, a cylindrical target and the irradiation terminal of a fast sample transport device. The ions of a mixed D–T gas are accelerated towards an inner target cylinder (80 mm 42 mm) and react with the hydrogen isotopes of the self-regenerating ScTD. A quite homogenous 14 MeV neutron flux is produced. Powdered as well as liquid samples are irradiated on the axis of thin cylindrical target in polyethylene containers (7 mm 10 mm). Usually an accelerator voltage of 180 kV and a total current of 340 mA are applied. Under these conditions neutron source strength of 3 1012 n/s and a neutron flux of 3 1010 n/cm2 s within the sample are produced with the maximum deviation of ±5% from the mean neutron flux value. The activated samples carried by a rugged polyamide rabbit are pneumatically transferred to a 16 m distant detector station in a separate building where, in a final phase of flight before stopping, rabbit and sample container are separated by means of centrifugal force in a curved branch of the guiding tube. Details have been already described elsewhere (Fanger et al., 1981; Pepelnik et al., 1982). Cyclic activation and measurement are possible with a minimum cycle period of 5 s. For the c-ray spectroscopy of activated samples, a Ge(Li) detector with a relative efficiency of 17% is used at a distance of 56.5 mm. During the first few seconds of short lived nuclide analysis, the counting rate can easily exceed 2 105 cps. Therefore, a special electronic unit determines the pile up and dead time losses and corrects the registered pulses in the memory of the multichannel analyzer by incrementing not one but a variable, loss dependent weighting factor (Pepelnik et al., 1984). The modified multichannel analyzer (Nuclear Data 66) is connected to a data processing system (ND 6620) for peak analysis and nuclide identification. For low activity measurements longer than about an hour, the background contribution of natural activities is reduced by a 5 cm thick lead shielding in almost 4p geometry around the detector. The fluorescence X-rays of lead are attenuated by 0.5 mm thick sheets of Cd and Cu, wrapped around the detector.
With the complete shielding arrangement described, a reduction by a factor of 30 in the general background level for X-ray of energies greater than 300 keV has been observed in several measurements. 2.2. Efficiency and flux calibration The absolute efficiency calibration of the Ge(Li) detector for specific source-detector geometries was performed using a homogeneously mixed solution of radioactive sources. The commercially available solution contains 54Mn, 57Co, 88Y, 133 Ba, 137Cs isotopes, emitting c-rays of 80.9, 122.1, 136.5, 276.4, 302.9, 356.0, 383.8, 661.6, 634.8, 898.0, 1836.0 keV, respectively. At a confidence level of 99% a maximum error of 2% in the activity of the mixture of isotopes is guaranteed by the manufacturer. The standard solution of known mass is filled into an empty PE capsules; capsules of the same type are used in actual irradiation. All the measurements were made at a detector to source distance of 56.5 mm. For each nuclide having two or more coincident c-rays, the correction for coincidence summing, both losses for cascade c-rays and gains for cross over, was computed. These calculations were done with a computer program of (Debertin and Schotzig, 1979). For efficiency calibration in the low energy region, a 109 Cd source emitting 88 keV c-rays and 241Am source emitting 59.54 keV c-rays with an accuracy of 3% in the activity has been used. The uncertainties in the c-emission probabilities for 152Eu isotopes are now small enough that efficiency calibration uncertainties of <1% can be obtained and therefore we also used 152Eu liquid source for efficiency calibration over 121.78–1408.0 keV energy range. The reaction 27Al (n, a)24Na was used to obtain a calibration point at 2754 keV. The isotope 24Na emits lines at energies of 1368.6 and 2754 keV, respectively. Since the detector efficiency may change with time in an energy dependent manner (Helmer, 1983), c-ray efficiency calibration curve for the Ge(Li) detector is obtained every 3–4 months. The long counter which is used for the neutron flux monitoring has been calibrated by the well known crosssections of the 27Al (n, a) reaction (Winkler and Ryves, 1983). An aluminum oxide powder of 99% purity is filled and sealed in a PE capsule for this purpose. The time dependent fluctuations of flux were corrected for the simple case of single irradiation and measurement with the code FLUKOR and for cyclic activation and measurement with the code ZYKLA (Anders, 1983). 2.3. Neutron energy determination In the present work, both methods {(Zr, Nb) pair and Ni foil activation} have been used to determine the average neutron energy of the KORONA neutrons (Agrawal and Pepelnik, 1995).The average neutron energy was found to be 14.6 ± 0.3 MeV in agreement with the theoretical
H.M. Agrawal et al. / Annals of Nuclear Energy 35 (2008) 1713–1719
calculations of the neutron spectra of KORONA (Bahal and Fanger, 1983). The neutron energy spectrum within the cylindrical target of KORONA also contains contributions from elastically and inelastically scattered neutrons. These contributions were calculated to be 26% and 9% of the total flux, respectively. 2.4. Formulae and error analysis The following expression was used for computing the cross-section. ¼ r
P c ef N /I
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For the error calculations it has been assumed that the Þ, flux calibration relative errors in peak area analysis ðDP P DI ðD/ Þ, c-intensity ratio ð Þ, summing correction factor ðDSc Þ / I Sc and mass, half life and abundance determination ðDM Þ can M be treated independently. The error due to the efficiency calibration is considered to be included in the error of flux calibration. Thus, the error in the cross-section determination is given by Dr ¼ r
" 2 2 2 2 #1=2 2 DP D/ DI DM DSc þ þ þ þ P / I M Sc
3. Experimental results
is the average reaction cross-section over the where r energy of the neutron spectrum, P is the c-ray peak area, is the N is the number of nuclei of the chosen isotope, / average neutron flux, Ic is the c-ray intensity, e is the photopeak efficiency, and f is the time factor. If only one half life is important in the decay scheme the time factor is given by f ¼ g 1 ekti 1 ektm ektd k1 where g = 1 for a single activation and measurement and 1 2 g ¼ n 1 ekp ekp 1 enkp f1 ekp g for n cycles of activation and measurement (cyclic activation). One cycle period ‘p’ is defined as p ¼ ti þ td þ tm þ tr where ti is the irradiation time, td is the decay time, tm is the measurement time, and tr is the time between measurement and next irradiation. By means of the computer controlled sample transfer system, values of ti, td, tm, tr and p can be achieved which are constant within less than 1%.
The nuclear data, which are necessary for the analysis of reaction cross sections, are given in Table 1. The cross-section measurements in the present work are given in Table 2 together with the irradiation time, number of measurements used for evaluation and the literature cross section values for comparison (last three columns). For reactions leading to short-lived isotopes, a cyclic and for long lived isotopes, a single irradiation and measurement procedure was performed. The indicated errors are composed of: (a) The error of the peak area estimated by the peak analysis program, ranging from 0.1% to 3%. (b) The error in flux and c-ray efficiency calibration, estimated ±3%. (c) Summing correction errors, ranging from 1% to 2%. (d) c-ray intensity errors (taken into account individually). Errors due to half-lives (61%), mass determination (61%) and isotopic abundance (60.5%) can be neglected, compared to other errors.
Table 1 Nuclear data used for the determination of cross-sections Reaction
Target material purity (%) and procurement
Isotopic abundance (%)
89
Yttrium powder 99% Dr. Theodor Schuchardt GmbH & Co. Munchen Y2O2 99.9% Schuchardt Munchen Yttrium powder 99% Dr. Theodor Schuchardt Y2O2 99.9% Schuchardt Munchen Yttrium powder 99%
100
88.9059
61.02 s
100
88.9059
15.28 s
100
88.9059
106.65 days
Y(n, a)86mRb
89
Y(n, n0 )89mY
89
Y(n, 2n)88Y
107
Ag(n, n0 )107mAg Ag(n, p)107mPd 109 Ag(n, n0 )109mAg 107
109
Ag(n, p)109mPd La(n, p)139Ba 139 La(n, a)136Cs 139
4 Ag foils 99% Koch Chemicals Ltd. England Ag2O powder 99. 99% Koch Chemicals Ltd. England Ag2O powder 99.99% Koch Chemicals Ltd. England 4 Ag foils 99% Koch Chemicals Ltd. England 4 Ag foils 99% Lanthanium oxide 99% E. Merck Darmstadt Lanthanium oxide 99% E. Merck Darmstadt
Atomic weight
Half life
51.84 51.84 48.16
107.868 107.868 107.868
44.3 s 21.3 s 39.6 s
48.16 99.91 99.91
107.868 138.9055 138.9055
4.69 min 83.04 min 13.13 days
c-Ray intensity (%)
Summing correction factor at 56.5 mm
556
98.2
Not required
909
99.1
Not required
898 1836 93.1 214.9 88.04
94 99.4 4.67 68.7 3.6
1.0195 1.0205 1.0 1.0 1.0
188.9 165.84 1048.1 340.57
55.7 23.8 79.7 48.5
1.0 Not required 1.047 1.0397
c-Ray energy (keV)
1716
H.M. Agrawal et al. / Annals of Nuclear Energy 35 (2008) 1713–1719
Table 2 Neutron activation cross-sections at 14.6 ± 0.3 MeV along with the literature values Reaction
89
Y(n, a)86mRb
89
Y(n, n0 )89mY
89
Y(n, 2n)88Y
139
La(n, a)136Cs
Irradiation time
No. of measurements
5 cycles (90–60–120–10) s 5 cycles (120–50–120–10) s 6 cycles (90–50–120–10) s
3 3 4
5 cycles (90–60–120–10) s 5 cycles (120–50–120–10) s 6 cycles (90–50–120–10) s
3 3 4
1000 s 2000 s 2000 s
3 3 3
1980 s 1800 min
2 2
2000 s 1800 s
2 2
107
5 cycles (20–15–45–100) s 4 cycles (42–15–42–90) s
5 4
107
5 cycles (20–15–45–100) s 4 cycles (42–15–42–90) s 6 cycles (30–15–60–45) s
5 4 6
109
5 cycles (20–15–45–100) s 4 cycles (42–15–42–90) s
5 4
109
5 cycles (20–15–45–100) s 4 cycles (42–15–42–90) s 6 cycles (30–15–60–45) s
5 4 6
139
La(n, p)174Tm
Ag(n, n0 )107mAg Ag(n, p)107mPd
Ag(n, n0 )109mAg Ag(n, p)109mPd
Measured cross-section
1.78 ± 0.06
451 ± 22
950 ± 75
2.57 ± 0.12
4.43 ± 0.22
294 ± 12
7.5 ± 0.3 2 92 ± 12
4.6 ± 0.8
For some of reactions the volume of information is very large and it is considered that few values given in the last three columns of Table 2 do represent the existing knowledge of the cross-section. The present experimental values for all reactions are found to be close to the corresponding newer literature values. In view of short half lives of the
Literature values r (mb)
En (MeV)
References
1.84 ± 0.18 1.72 ± 0.03 2.02 ± 0.21 2.09 ± 0.17 0.91 ± 0.45 1.8 ± 0.39 1.8 ± 0.36
14.62 14.6 ± 0.2 14.55 ± 0.1 14.58 ± 0.09 14.7 ± 0.2 14.8 ± 0.2 14.8 ± 0.2
Filatenkov et al. (1999) Byegun et al. (2000) Doczi et al. (1998) Yamauchi et al. (1993) Bramlitt and Fink (1963) Kawade et al. (1990) Kasugai et al. (1997, 1998a,b)
404 ± 59 400 ± 47 524 ± 24 438 ± 44
14.7 ± 0.05 14.6 ± 0.3 14.7 ± 0.1 14.8
Doczi et al. (1998) Broadhead et al. (1965) Bornemisza-Pauspertl and Hille (1968) Rurarz et al. (1971)
948 ± 15 978 ± 30 966 ± 100 945 ± 40 1048 ± 52 907 ± 68 1011 ± 44 930 ± 84 929 ± 13 685 ± 137
14.6 ± 0.2 14.68 14.71 ± 0.12 14.67 ± 0.17 14.7 ± 0.23 14.7 ± 0.3 14.68 14.56 ± 0.2 14.5 ± 0.4 14.5 ± 0.2
Byegun et al. (2000) Filatenkov et al. (1999) Molla et al. (1998) Klopries et al. (1997) HuangJian-Zhou et al. (1989) Qaim and Stoecklin (1974) Konno et al. (1993) Bormann et al. (1976) Greenwood (1987) Tewes et al. (1960)
1.94 ± 0.07 2.37 ± 0.23 2.36 ± 0.13 1.6 ± 0.15 3.0 ± 0.8 1.8 ± .3 1.87 ± 0.18
14.6 14.38 ± 0.24 14.63 ± 0.08 14.5 ± 0.2 14.6 ± 0.1 14.7 ± 0.3 14.5
Maidanyuk et al. (1997) Woelfle et al. (1988) Achour et al. (1986) Zupranska et al. (1980) Kulisic et al. (1965) Qaim (1984) Coleman et al. (1959)
4.2 ± 0.3 4.79 ± 1 3.2 ± 0.6 5.7 ± 2.3 2.33 ± .34 3.8 ± 0.08 3.7 ± 0.5 4.5 ± 1.1 5.0 ± 1 6.0 ± 0.6 5.3 ± 1
14.66 14.6 14.63 ± 0.08 14.5 14.5 14.5 14.7 ± 0.15 14.7 14.8 ± 0.8 14.8 ± 0.2 14.8
Kasugai et al. (1997, 1998a,b) Maidanyuk et al. (1997) Achour et al. (1986) Paul and Clarke (1953) Coleman et al. (1959) Begun et al. (2002) Havlik (1971) Csikai et al. (1991) Wille and Fink (1960) Bari (1982) Levkovskiy et al. (1968)
312 ± 77 304 ± 37
14.48 ± 0.25 14.7 ± 0.5
Augustyniak et al. (1975) Wagner and Uhl (1971)
7.4 ± 0.81 10.8 ± 1
14.58 ± 0.05 14.7 ± 0.5
Kasugai et al. (1997, 1998a,b) Wagner and Uhl (1971)
419 ± 77 291 ± 34
14.48 ± 0.25 14.7 ± 0.5
Augustyniak et al. (1975) Wagner and Uhl (1971)
9.4 ± 1.3 5.8 ± 0.6
14.8 ± 0.12 14.7 ± .25
Augustyniak et al. (1975) Wagner and Uhl (1971)
activated products, 86mRb (61.02 s), 89mY (15.28 s), 107m Ag (44.3 s), 107mPd (21.3 s), 109mAg (39.6 s) fast transport system was employed in cyclic activation. In the case of the 109Ag(n, n0 )109mAg and 109Ag(n, p)109mPd reaction, our values do not agree with the values of (Augustyniak et al., 1975) but match with the measurement of (Wagner,
H.M. Agrawal et al. / Annals of Nuclear Energy 35 (2008) 1713–1719
4. Nuclear model calculations These experimental cross-sections (our value and others in MeV region) have been compared with the corresponding values obtained using EMPIRE-II code, (Herman et al., 2007) which is the most recent and versatile code. These theoretical calculations have been performed within the framework of Hauser Feshbach statistical model with pre-equilibrium contributions. The required inputs like nuclear masses, discrete energy levels and level densities
89
Filatenkov et al. Molla et al. Byegun et al. Klopries et al. Huang Jian-Zhou et al. Qaim and Stoecklin Konno et al. Bormann et al. Greenwood Tewes et al. Our expt. value EMPIRE-II
1400
1200
Cross section (mb)
1971). 139La(n, a)136Cs reaction is of particular importance to high temperature superconductors. Special attention was taken to dry the sample of La2O3 and the coincidence loss, which is significant in this case, was taken into account.
1717
1000
800
600
88
Y(n,2n) Y
14.6 MeV
400
200
0 8
10
12
14
16
18
20
Energy (MeV) Fig. 3. Excitation function of the 89
3
89
Y(n, 2n)88Y reaction.
86m
Y(n,α)
Filatenkov et al. Doczi et al. Yamauchi et al. Byegun et al. Bramlitt and Fink Kawade et al. Kasugai et al. Our expt. value EMPIRE-II
Rb
Cross section (mb)
Cross section (mb)
4
14.6 MeV
2
1
Achour et al. Woelfle et al. Zupranska et al. Kulisic et al. Havlik Qaim Coleman et al. Maidanyuk et al. Our expt. value EMPIRE-II
6
4
139
136
La(n,α) Cs
14.6 MeV
2
0 9
10
11
12
13
14
15
16
0
Energy (MeV) Fig. 1. Excitation function of the
89
9
10
11
12
13
14
15
16
17
18
19
20
21
Energy (MeV)
Y(n, a)86mRb reaction.
Fig. 4. Excitation function of the
139
La(n, a)136Cs reaction.
Doczi et al. Broadhead et al. Bornemisza-Paus Rurarz et al. Peto et al. Hudson and Alford Our expt. value EMPIRE-II
89m
Y(n,n')
Y
Cross section (mb)
1600
1200
800
400
Cross section (mb)
10 89
8
6
4
139
Kasugai et al. Achour et al. Maidanyuk et al. Cuzzocrea et al. Paul and Clarke Coleman et al. Begun et al. Havlik Csikai and Nagy Wille and Fink Bari Levkovskiy et al. Our expt. value EMPIRE-II
139
La(n,p) Ba
14.6 MeV
2
14.6 MeV
0
0 4
6
8
10
12
14
16
18
20
22
Energy (MeV) Fig. 2. Excitation function of the 89Y(n, n0 )89mY reaction. See abovementioned reference for further information.
10
12
14
16
18
20
Energy (MeV) Fig. 5. Excitation function of the 139La(n, p)174Tm reaction. See above mentioned reference for further information.
H.M. Agrawal et al. / Annals of Nuclear Energy 35 (2008) 1713–1719
of the nuclides involved in the calculations have been taken from latest RIPL-2 (Belgya et al., 2006). The recent and well tested global optical model potentials for neutrons and protons (Koning and Dclaroche, 2003) and for alphas (Avrigeanu et al., 1994) have been employed in the present calculations. The EMPIRE specific level densities (BCS + Fermi gas with deformation dependent collective effects) adjusted to experimental ‘a’ values and to discrete levels have been used. Preequilibrium contributions have been computed by the exciton model code using PCROSS for (n, a) reactions (Capote et al., 1991) and DEGAS (Betak and Oblozinsky, 1993) for others.
109
109m
Ag(n,n')
1200
Cross section (mb)
1718
Augustyniak et al. Wagner and Uhl Our expt. value EMPIRE-II
Ag
1000
800
600
14.6 Mev
400
200
5. Discussion
0 8
10
12
14
16
18
20
22
Energy (MeV)
The results of this work are shown in Figs. 1–9 together with the previous experimental data in MeV region and cal-
Fig. 8. Excitation function of the
109
Ag(n, n0 )109mAg reaction.
700 107
107m
Ag(n,n')
Ag
Augustyniak et al. Wagner and Uhl Our expt. value EMPIRE-II
14
12
500
Cross-section (mb)
Cross section (mb)
600
14.6 MeV
400
300
200
109m
Ag(n,p)
Pd
10
8
6
4
100
14.6 MeV
2
0 10
12
14
16
18
20
Energy (MeV)
0 10
Fig. 6. Excitation function of the
107
Ag(n, n0 )107mAg reaction.
12
14
107
Kasugai et al. Wagner and Uhl Prasad and Sarkar Our expt. value EMPIRE-II
107m
Ag(n,p)
Pd
16 14 12 10 8 6 14.6 MeV
4 2 0 10
12
14
16
18
20
Energy (MeV) 107
107m
Fig. 7. Excitation function of the Ag(n, p) mentioned reference for further information.
Pd reaction. See above
16
18
20
Energy (MeV) Fig. 9. Excitation function of the
18
Cross section (mb)
109
Augustyniak et al. Wagner and Uhl Our Expt.Value EMPIRE-II
109
Ag(n, p)109mPd reaction.
culated values based on EMPIRE code. As can be seen from the figures, the calculated values of cross-sections for all reactions are in reasonable agreement with the recent available experimental data. Thus, it can be concluded that the present results contribute substantially to improving the knowledge of the crosssections and optimizing the input parameters required in model based evaluations of cross-section at high energies which are essential to support new nuclear energy systems. An updated evaluation for these reactions would now be possible with this additional information in hand. Acknowledgement One of the authors (H.M.A.) would like to thank G.B. Pant University, India for granting leave of absence; GKSS research centre, Geesthacht, for the financial support; and
H.M. Agrawal et al. / Annals of Nuclear Energy 35 (2008) 1713–1719
Prof. Dr. W. Michaelels for the possibility to work at his institute. H.M.A. and K.P. acknowledge the financial support of BRNS Govt. of INDIA (Project No. 2005/36/19). References Achour, M. et al., 1986. In: Int. Nucl. Phys. Conf., vol. 1. Harrogate, UK, p. 130 (25–30 Aug). Agrawal, H.M., Pepelnik, R., 1995. Nucl. Instrum. Meth. A 366, 349–353. Anders, B., 1983. Report GKSS E/25, GKSS Forschungscentrwn, Geesthacht, FRG. Augustyniak, W. et al., 1975. Nucl. Phys. A 247, 231–237. Avrigeanu, V. et al., 1994. Phys. Rev. C 49, 2136–2141. Bahal, B.M., Fanger, H.U., 1983. Nucl. Instrum. Methods 211, 469. Bari, A., 1982. J. Radioanal. Chem. 75, 189. Begun, S.V. et al., 2002. J. Nucl. Sci. Technol. Tokyo (Suppl. 2, Issue 1), 425. Belgya, T., Bersillon, O., Capote, R., Fukahori, T. Zhigang, G., Goreily, S., Herman, M., Ignatyuk, A.V., Kailas, S., Koning, A., Oblozinsky, P., Pluzko, V., Young, P., 2006. Handbook for Calculations of Nuclear Reaction Data, RIPL-2. IAEA-TECDOC-1506 IAEA, Vienna. Available online at
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Greenwood, L.R., 1987. American Society of Testing and Materials Reports No. 956, p. 743. Havlik, E., 1971. Acta Phys. Austriaca 34, 209. Helmer, R.G., 1983. Report EGC-PHYS-5735 (Idaho National Engineering Laboratory, Idaho, USA). Herman, M., Capote, R., Carlson, B., Oblozinsky, P., Sin, M., Trkov, A., Wienke, H., Zerkin, V., 2007. Nucl. Data Sheets 108 2007 2655-2715. Available online at
NUCLEAR ENERGY Annals of Nuclear Energy 35 (2008) 1713–1719 www.elsevier.com/locate/anucene
Neutron activation cross-sections at (14.6 ± 0.3) MeV H.M. Agrawal a,*,1, Kailash Pandey a, K. Surendra Babu b, Ashok Kumar c, R. Pepelnik d,2 a
Physics Department, G.B. Pant University, Pantnagar 263 145, India b Nuclear Data Evaluation Lab KAERI, Pohang, South Korea c Reactor Physics Design Division, BARC, Trombay, Mumbai, India d Institute of Physics, GKSS Research Centre, Geesthacht, Germany
Received 25 October 2007; received in revised form 25 January 2008; accepted 2 February 2008 Available online 24 March 2008
Abstract The activation method has been used to measure 14.6 MeV cross-sections for the following nine reactions which are important for nuclear energy programmes: 89Y(n, a)86mRb, 89Y(n, n0 )89mY, 89Y(n, 2n)88Y, 107Ag(n, n0 )107mAg, 107Ag(n, p)107mPd, 109Ag(n, n0 )109mAg, 109 Ag(n, p)109mPd, 139La(n, p)139Ba, 139La(n, a)136Cs. Special features included a high-intensity neutron generator ‘KORONA’ with a useable fast neutron flux of 3 1014 n/m2 s, a fast rabbit system suitable for cyclic irradiations and measurements for short-lived activities, and a c-ray spectroscopy system with real time correction of counting losses. The results of this investigation are compared with existing experimental cross-section values. The cross-sections have also been calculated using the EMPIRE code Version 2.19 involving Hauser Feshbach statistical theory with pre-compound emission. Default inputs have been used for nuclear model parameters taken from the RIPL-2 data base. The agreement with the experimental data is generally acceptable within the given experimental uncertainty. Ó 2008 Elsevier Ltd. All rights reserved.
1. Introduction Accurate measurement of neutron-induced cross-section data at 14 MeV are required for several physical applications, especially in designing future fusion reactors, advanced fission reactors, in neutron dosimetry and for developing refined nuclear theory. An enormous amount of neutron cross-section data in this energy range is found in the literature due to wide spread availability of 14 MeV neutron generator. However, knowledge of the pertinent cross-sections is often confounded by the presence of wide discrepancies between the various reported values. Most of the earlier measurements were done with GM counters and NaI (Tl) scintillation detectors for the detection of b and c activities, respectively. In complex cases, the problem of resolving the continuous b-spectrum into its different *
Corresponding author. E-mail address: hma001@rediffmail.com (H.M. Agrawal). 1 Guest Scientist at Institute of Physik, GKSS Research Centre, Geesthacht, Germany. 2 KOC/GKSS Research Centre Geesthacht Germany. 0306-4549/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.anucene.2008.02.004
half-life components results high cross-section values because of interfering activities. The NaI (Tl) systems, in spite of their superiority over GM counters for gamma counting, have low peak to Compton ratio, with the result that the weak activities are likely to be masked in the presence of strong activities. Later, the availability of high resolution c-ray detection techniques has made an impact on the precision of neutron cross-section data base. However, neutron energies has not been determined in most of the earlier works, which is essential because the excitation functions for many reactions vary significantly around 14 MeV. Since deuterons slow down in passing through the thick tritium targets in most of the 14 MeV neutron generators, it is therefore not possible to determine hEdi without an accurate knowledge of the tritium distribution in the target, which can vary from one target to another or change during deuteron bombardment, Consequently, it is not appropriate to employ the kinematical equation directly. A program to improve the overall data base is necessary for several reasons. There is presently diversity of candidate materials and design concepts of future fusion
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reactors. The probability of selecting a number of materials has changed and will continue to change over the years. Moreover, some reaction cross-sections (e.g. 89Y(n, 2n) and 139La(n, a) of present work) are relevant in studying the nuclear heating of high Tc superconductors (Markovskij et al., 1989; Csikai et al., 1991). The present work is motivated to refine the knowledge of cross-section for nine reactions where the existing data base is inadequate for a consistent and meaningful evaluation. 2. Experimental procedure 2.1. Apparatus For irradiation of samples an intense neutron generator KORONA was used. KORONA (Kombinierte RohrpostNeutroengenerator anlage) consisted a high intensity concentric, sealed neutron tube with a compact arrangement of an annular ion source, a cylindrical target and the irradiation terminal of a fast sample transport device. The ions of a mixed D–T gas are accelerated towards an inner target cylinder (80 mm 42 mm) and react with the hydrogen isotopes of the self-regenerating ScTD. A quite homogenous 14 MeV neutron flux is produced. Powdered as well as liquid samples are irradiated on the axis of thin cylindrical target in polyethylene containers (7 mm 10 mm). Usually an accelerator voltage of 180 kV and a total current of 340 mA are applied. Under these conditions neutron source strength of 3 1012 n/s and a neutron flux of 3 1010 n/cm2 s within the sample are produced with the maximum deviation of ±5% from the mean neutron flux value. The activated samples carried by a rugged polyamide rabbit are pneumatically transferred to a 16 m distant detector station in a separate building where, in a final phase of flight before stopping, rabbit and sample container are separated by means of centrifugal force in a curved branch of the guiding tube. Details have been already described elsewhere (Fanger et al., 1981; Pepelnik et al., 1982). Cyclic activation and measurement are possible with a minimum cycle period of 5 s. For the c-ray spectroscopy of activated samples, a Ge(Li) detector with a relative efficiency of 17% is used at a distance of 56.5 mm. During the first few seconds of short lived nuclide analysis, the counting rate can easily exceed 2 105 cps. Therefore, a special electronic unit determines the pile up and dead time losses and corrects the registered pulses in the memory of the multichannel analyzer by incrementing not one but a variable, loss dependent weighting factor (Pepelnik et al., 1984). The modified multichannel analyzer (Nuclear Data 66) is connected to a data processing system (ND 6620) for peak analysis and nuclide identification. For low activity measurements longer than about an hour, the background contribution of natural activities is reduced by a 5 cm thick lead shielding in almost 4p geometry around the detector. The fluorescence X-rays of lead are attenuated by 0.5 mm thick sheets of Cd and Cu, wrapped around the detector.
With the complete shielding arrangement described, a reduction by a factor of 30 in the general background level for X-ray of energies greater than 300 keV has been observed in several measurements. 2.2. Efficiency and flux calibration The absolute efficiency calibration of the Ge(Li) detector for specific source-detector geometries was performed using a homogeneously mixed solution of radioactive sources. The commercially available solution contains 54Mn, 57Co, 88Y, 133 Ba, 137Cs isotopes, emitting c-rays of 80.9, 122.1, 136.5, 276.4, 302.9, 356.0, 383.8, 661.6, 634.8, 898.0, 1836.0 keV, respectively. At a confidence level of 99% a maximum error of 2% in the activity of the mixture of isotopes is guaranteed by the manufacturer. The standard solution of known mass is filled into an empty PE capsules; capsules of the same type are used in actual irradiation. All the measurements were made at a detector to source distance of 56.5 mm. For each nuclide having two or more coincident c-rays, the correction for coincidence summing, both losses for cascade c-rays and gains for cross over, was computed. These calculations were done with a computer program of (Debertin and Schotzig, 1979). For efficiency calibration in the low energy region, a 109 Cd source emitting 88 keV c-rays and 241Am source emitting 59.54 keV c-rays with an accuracy of 3% in the activity has been used. The uncertainties in the c-emission probabilities for 152Eu isotopes are now small enough that efficiency calibration uncertainties of <1% can be obtained and therefore we also used 152Eu liquid source for efficiency calibration over 121.78–1408.0 keV energy range. The reaction 27Al (n, a)24Na was used to obtain a calibration point at 2754 keV. The isotope 24Na emits lines at energies of 1368.6 and 2754 keV, respectively. Since the detector efficiency may change with time in an energy dependent manner (Helmer, 1983), c-ray efficiency calibration curve for the Ge(Li) detector is obtained every 3–4 months. The long counter which is used for the neutron flux monitoring has been calibrated by the well known crosssections of the 27Al (n, a) reaction (Winkler and Ryves, 1983). An aluminum oxide powder of 99% purity is filled and sealed in a PE capsule for this purpose. The time dependent fluctuations of flux were corrected for the simple case of single irradiation and measurement with the code FLUKOR and for cyclic activation and measurement with the code ZYKLA (Anders, 1983). 2.3. Neutron energy determination In the present work, both methods {(Zr, Nb) pair and Ni foil activation} have been used to determine the average neutron energy of the KORONA neutrons (Agrawal and Pepelnik, 1995).The average neutron energy was found to be 14.6 ± 0.3 MeV in agreement with the theoretical
H.M. Agrawal et al. / Annals of Nuclear Energy 35 (2008) 1713–1719
calculations of the neutron spectra of KORONA (Bahal and Fanger, 1983). The neutron energy spectrum within the cylindrical target of KORONA also contains contributions from elastically and inelastically scattered neutrons. These contributions were calculated to be 26% and 9% of the total flux, respectively. 2.4. Formulae and error analysis The following expression was used for computing the cross-section. ¼ r
P c ef N /I
1715
For the error calculations it has been assumed that the Þ, flux calibration relative errors in peak area analysis ðDP P DI ðD/ Þ, c-intensity ratio ð Þ, summing correction factor ðDSc Þ / I Sc and mass, half life and abundance determination ðDM Þ can M be treated independently. The error due to the efficiency calibration is considered to be included in the error of flux calibration. Thus, the error in the cross-section determination is given by Dr ¼ r
" 2 2 2 2 #1=2 2 DP D/ DI DM DSc þ þ þ þ P / I M Sc
3. Experimental results
is the average reaction cross-section over the where r energy of the neutron spectrum, P is the c-ray peak area, is the N is the number of nuclei of the chosen isotope, / average neutron flux, Ic is the c-ray intensity, e is the photopeak efficiency, and f is the time factor. If only one half life is important in the decay scheme the time factor is given by f ¼ g 1 ekti 1 ektm ektd k1 where g = 1 for a single activation and measurement and 1 2 g ¼ n 1 ekp ekp 1 enkp f1 ekp g for n cycles of activation and measurement (cyclic activation). One cycle period ‘p’ is defined as p ¼ ti þ td þ tm þ tr where ti is the irradiation time, td is the decay time, tm is the measurement time, and tr is the time between measurement and next irradiation. By means of the computer controlled sample transfer system, values of ti, td, tm, tr and p can be achieved which are constant within less than 1%.
The nuclear data, which are necessary for the analysis of reaction cross sections, are given in Table 1. The cross-section measurements in the present work are given in Table 2 together with the irradiation time, number of measurements used for evaluation and the literature cross section values for comparison (last three columns). For reactions leading to short-lived isotopes, a cyclic and for long lived isotopes, a single irradiation and measurement procedure was performed. The indicated errors are composed of: (a) The error of the peak area estimated by the peak analysis program, ranging from 0.1% to 3%. (b) The error in flux and c-ray efficiency calibration, estimated ±3%. (c) Summing correction errors, ranging from 1% to 2%. (d) c-ray intensity errors (taken into account individually). Errors due to half-lives (61%), mass determination (61%) and isotopic abundance (60.5%) can be neglected, compared to other errors.
Table 1 Nuclear data used for the determination of cross-sections Reaction
Target material purity (%) and procurement
Isotopic abundance (%)
89
Yttrium powder 99% Dr. Theodor Schuchardt GmbH & Co. Munchen Y2O2 99.9% Schuchardt Munchen Yttrium powder 99% Dr. Theodor Schuchardt Y2O2 99.9% Schuchardt Munchen Yttrium powder 99%
100
88.9059
61.02 s
100
88.9059
15.28 s
100
88.9059
106.65 days
Y(n, a)86mRb
89
Y(n, n0 )89mY
89
Y(n, 2n)88Y
107
Ag(n, n0 )107mAg Ag(n, p)107mPd 109 Ag(n, n0 )109mAg 107
109
Ag(n, p)109mPd La(n, p)139Ba 139 La(n, a)136Cs 139
4 Ag foils 99% Koch Chemicals Ltd. England Ag2O powder 99. 99% Koch Chemicals Ltd. England Ag2O powder 99.99% Koch Chemicals Ltd. England 4 Ag foils 99% Koch Chemicals Ltd. England 4 Ag foils 99% Lanthanium oxide 99% E. Merck Darmstadt Lanthanium oxide 99% E. Merck Darmstadt
Atomic weight
Half life
51.84 51.84 48.16
107.868 107.868 107.868
44.3 s 21.3 s 39.6 s
48.16 99.91 99.91
107.868 138.9055 138.9055
4.69 min 83.04 min 13.13 days
c-Ray intensity (%)
Summing correction factor at 56.5 mm
556
98.2
Not required
909
99.1
Not required
898 1836 93.1 214.9 88.04
94 99.4 4.67 68.7 3.6
1.0195 1.0205 1.0 1.0 1.0
188.9 165.84 1048.1 340.57
55.7 23.8 79.7 48.5
1.0 Not required 1.047 1.0397
c-Ray energy (keV)
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H.M. Agrawal et al. / Annals of Nuclear Energy 35 (2008) 1713–1719
Table 2 Neutron activation cross-sections at 14.6 ± 0.3 MeV along with the literature values Reaction
89
Y(n, a)86mRb
89
Y(n, n0 )89mY
89
Y(n, 2n)88Y
139
La(n, a)136Cs
Irradiation time
No. of measurements
5 cycles (90–60–120–10) s 5 cycles (120–50–120–10) s 6 cycles (90–50–120–10) s
3 3 4
5 cycles (90–60–120–10) s 5 cycles (120–50–120–10) s 6 cycles (90–50–120–10) s
3 3 4
1000 s 2000 s 2000 s
3 3 3
1980 s 1800 min
2 2
2000 s 1800 s
2 2
107
5 cycles (20–15–45–100) s 4 cycles (42–15–42–90) s
5 4
107
5 cycles (20–15–45–100) s 4 cycles (42–15–42–90) s 6 cycles (30–15–60–45) s
5 4 6
109
5 cycles (20–15–45–100) s 4 cycles (42–15–42–90) s
5 4
109
5 cycles (20–15–45–100) s 4 cycles (42–15–42–90) s 6 cycles (30–15–60–45) s
5 4 6
139
La(n, p)174Tm
Ag(n, n0 )107mAg Ag(n, p)107mPd
Ag(n, n0 )109mAg Ag(n, p)109mPd
Measured cross-section
1.78 ± 0.06
451 ± 22
950 ± 75
2.57 ± 0.12
4.43 ± 0.22
294 ± 12
7.5 ± 0.3 2 92 ± 12
4.6 ± 0.8
For some of reactions the volume of information is very large and it is considered that few values given in the last three columns of Table 2 do represent the existing knowledge of the cross-section. The present experimental values for all reactions are found to be close to the corresponding newer literature values. In view of short half lives of the
Literature values r (mb)
En (MeV)
References
1.84 ± 0.18 1.72 ± 0.03 2.02 ± 0.21 2.09 ± 0.17 0.91 ± 0.45 1.8 ± 0.39 1.8 ± 0.36
14.62 14.6 ± 0.2 14.55 ± 0.1 14.58 ± 0.09 14.7 ± 0.2 14.8 ± 0.2 14.8 ± 0.2
Filatenkov et al. (1999) Byegun et al. (2000) Doczi et al. (1998) Yamauchi et al. (1993) Bramlitt and Fink (1963) Kawade et al. (1990) Kasugai et al. (1997, 1998a,b)
404 ± 59 400 ± 47 524 ± 24 438 ± 44
14.7 ± 0.05 14.6 ± 0.3 14.7 ± 0.1 14.8
Doczi et al. (1998) Broadhead et al. (1965) Bornemisza-Pauspertl and Hille (1968) Rurarz et al. (1971)
948 ± 15 978 ± 30 966 ± 100 945 ± 40 1048 ± 52 907 ± 68 1011 ± 44 930 ± 84 929 ± 13 685 ± 137
14.6 ± 0.2 14.68 14.71 ± 0.12 14.67 ± 0.17 14.7 ± 0.23 14.7 ± 0.3 14.68 14.56 ± 0.2 14.5 ± 0.4 14.5 ± 0.2
Byegun et al. (2000) Filatenkov et al. (1999) Molla et al. (1998) Klopries et al. (1997) HuangJian-Zhou et al. (1989) Qaim and Stoecklin (1974) Konno et al. (1993) Bormann et al. (1976) Greenwood (1987) Tewes et al. (1960)
1.94 ± 0.07 2.37 ± 0.23 2.36 ± 0.13 1.6 ± 0.15 3.0 ± 0.8 1.8 ± .3 1.87 ± 0.18
14.6 14.38 ± 0.24 14.63 ± 0.08 14.5 ± 0.2 14.6 ± 0.1 14.7 ± 0.3 14.5
Maidanyuk et al. (1997) Woelfle et al. (1988) Achour et al. (1986) Zupranska et al. (1980) Kulisic et al. (1965) Qaim (1984) Coleman et al. (1959)
4.2 ± 0.3 4.79 ± 1 3.2 ± 0.6 5.7 ± 2.3 2.33 ± .34 3.8 ± 0.08 3.7 ± 0.5 4.5 ± 1.1 5.0 ± 1 6.0 ± 0.6 5.3 ± 1
14.66 14.6 14.63 ± 0.08 14.5 14.5 14.5 14.7 ± 0.15 14.7 14.8 ± 0.8 14.8 ± 0.2 14.8
Kasugai et al. (1997, 1998a,b) Maidanyuk et al. (1997) Achour et al. (1986) Paul and Clarke (1953) Coleman et al. (1959) Begun et al. (2002) Havlik (1971) Csikai et al. (1991) Wille and Fink (1960) Bari (1982) Levkovskiy et al. (1968)
312 ± 77 304 ± 37
14.48 ± 0.25 14.7 ± 0.5
Augustyniak et al. (1975) Wagner and Uhl (1971)
7.4 ± 0.81 10.8 ± 1
14.58 ± 0.05 14.7 ± 0.5
Kasugai et al. (1997, 1998a,b) Wagner and Uhl (1971)
419 ± 77 291 ± 34
14.48 ± 0.25 14.7 ± 0.5
Augustyniak et al. (1975) Wagner and Uhl (1971)
9.4 ± 1.3 5.8 ± 0.6
14.8 ± 0.12 14.7 ± .25
Augustyniak et al. (1975) Wagner and Uhl (1971)
activated products, 86mRb (61.02 s), 89mY (15.28 s), 107m Ag (44.3 s), 107mPd (21.3 s), 109mAg (39.6 s) fast transport system was employed in cyclic activation. In the case of the 109Ag(n, n0 )109mAg and 109Ag(n, p)109mPd reaction, our values do not agree with the values of (Augustyniak et al., 1975) but match with the measurement of (Wagner,
H.M. Agrawal et al. / Annals of Nuclear Energy 35 (2008) 1713–1719
4. Nuclear model calculations These experimental cross-sections (our value and others in MeV region) have been compared with the corresponding values obtained using EMPIRE-II code, (Herman et al., 2007) which is the most recent and versatile code. These theoretical calculations have been performed within the framework of Hauser Feshbach statistical model with pre-equilibrium contributions. The required inputs like nuclear masses, discrete energy levels and level densities
89
Filatenkov et al. Molla et al. Byegun et al. Klopries et al. Huang Jian-Zhou et al. Qaim and Stoecklin Konno et al. Bormann et al. Greenwood Tewes et al. Our expt. value EMPIRE-II
1400
1200
Cross section (mb)
1971). 139La(n, a)136Cs reaction is of particular importance to high temperature superconductors. Special attention was taken to dry the sample of La2O3 and the coincidence loss, which is significant in this case, was taken into account.
1717
1000
800
600
88
Y(n,2n) Y
14.6 MeV
400
200
0 8
10
12
14
16
18
20
Energy (MeV) Fig. 3. Excitation function of the 89
3
89
Y(n, 2n)88Y reaction.
86m
Y(n,α)
Filatenkov et al. Doczi et al. Yamauchi et al. Byegun et al. Bramlitt and Fink Kawade et al. Kasugai et al. Our expt. value EMPIRE-II
Rb
Cross section (mb)
Cross section (mb)
4
14.6 MeV
2
1
Achour et al. Woelfle et al. Zupranska et al. Kulisic et al. Havlik Qaim Coleman et al. Maidanyuk et al. Our expt. value EMPIRE-II
6
4
139
136
La(n,α) Cs
14.6 MeV
2
0 9
10
11
12
13
14
15
16
0
Energy (MeV) Fig. 1. Excitation function of the
89
9
10
11
12
13
14
15
16
17
18
19
20
21
Energy (MeV)
Y(n, a)86mRb reaction.
Fig. 4. Excitation function of the
139
La(n, a)136Cs reaction.
Doczi et al. Broadhead et al. Bornemisza-Paus Rurarz et al. Peto et al. Hudson and Alford Our expt. value EMPIRE-II
89m
Y(n,n')
Y
Cross section (mb)
1600
1200
800
400
Cross section (mb)
10 89
8
6
4
139
Kasugai et al. Achour et al. Maidanyuk et al. Cuzzocrea et al. Paul and Clarke Coleman et al. Begun et al. Havlik Csikai and Nagy Wille and Fink Bari Levkovskiy et al. Our expt. value EMPIRE-II
139
La(n,p) Ba
14.6 MeV
2
14.6 MeV
0
0 4
6
8
10
12
14
16
18
20
22
Energy (MeV) Fig. 2. Excitation function of the 89Y(n, n0 )89mY reaction. See abovementioned reference for further information.
10
12
14
16
18
20
Energy (MeV) Fig. 5. Excitation function of the 139La(n, p)174Tm reaction. See above mentioned reference for further information.
H.M. Agrawal et al. / Annals of Nuclear Energy 35 (2008) 1713–1719
of the nuclides involved in the calculations have been taken from latest RIPL-2 (Belgya et al., 2006). The recent and well tested global optical model potentials for neutrons and protons (Koning and Dclaroche, 2003) and for alphas (Avrigeanu et al., 1994) have been employed in the present calculations. The EMPIRE specific level densities (BCS + Fermi gas with deformation dependent collective effects) adjusted to experimental ‘a’ values and to discrete levels have been used. Preequilibrium contributions have been computed by the exciton model code using PCROSS for (n, a) reactions (Capote et al., 1991) and DEGAS (Betak and Oblozinsky, 1993) for others.
109
109m
Ag(n,n')
1200
Cross section (mb)
1718
Augustyniak et al. Wagner and Uhl Our expt. value EMPIRE-II
Ag
1000
800
600
14.6 Mev
400
200
5. Discussion
0 8
10
12
14
16
18
20
22
Energy (MeV)
The results of this work are shown in Figs. 1–9 together with the previous experimental data in MeV region and cal-
Fig. 8. Excitation function of the
109
Ag(n, n0 )109mAg reaction.
700 107
107m
Ag(n,n')
Ag
Augustyniak et al. Wagner and Uhl Our expt. value EMPIRE-II
14
12
500
Cross-section (mb)
Cross section (mb)
600
14.6 MeV
400
300
200
109m
Ag(n,p)
Pd
10
8
6
4
100
14.6 MeV
2
0 10
12
14
16
18
20
Energy (MeV)
0 10
Fig. 6. Excitation function of the
107
Ag(n, n0 )107mAg reaction.
12
14
107
Kasugai et al. Wagner and Uhl Prasad and Sarkar Our expt. value EMPIRE-II
107m
Ag(n,p)
Pd
16 14 12 10 8 6 14.6 MeV
4 2 0 10
12
14
16
18
20
Energy (MeV) 107
107m
Fig. 7. Excitation function of the Ag(n, p) mentioned reference for further information.
Pd reaction. See above
16
18
20
Energy (MeV) Fig. 9. Excitation function of the
18
Cross section (mb)
109
Augustyniak et al. Wagner and Uhl Our Expt.Value EMPIRE-II
109
Ag(n, p)109mPd reaction.
culated values based on EMPIRE code. As can be seen from the figures, the calculated values of cross-sections for all reactions are in reasonable agreement with the recent available experimental data. Thus, it can be concluded that the present results contribute substantially to improving the knowledge of the crosssections and optimizing the input parameters required in model based evaluations of cross-section at high energies which are essential to support new nuclear energy systems. An updated evaluation for these reactions would now be possible with this additional information in hand. Acknowledgement One of the authors (H.M.A.) would like to thank G.B. Pant University, India for granting leave of absence; GKSS research centre, Geesthacht, for the financial support; and
H.M. Agrawal et al. / Annals of Nuclear Energy 35 (2008) 1713–1719
Prof. Dr. W. Michaelels for the possibility to work at his institute. H.M.A. and K.P. acknowledge the financial support of BRNS Govt. of INDIA (Project No. 2005/36/19). References Achour, M. et al., 1986. In: Int. Nucl. Phys. Conf., vol. 1. Harrogate, UK, p. 130 (25–30 Aug). Agrawal, H.M., Pepelnik, R., 1995. Nucl. Instrum. Meth. A 366, 349–353. Anders, B., 1983. Report GKSS E/25, GKSS Forschungscentrwn, Geesthacht, FRG. Augustyniak, W. et al., 1975. Nucl. Phys. A 247, 231–237. Avrigeanu, V. et al., 1994. Phys. Rev. C 49, 2136–2141. Bahal, B.M., Fanger, H.U., 1983. Nucl. Instrum. Methods 211, 469. Bari, A., 1982. J. Radioanal. Chem. 75, 189. Begun, S.V. et al., 2002. J. Nucl. Sci. Technol. Tokyo (Suppl. 2, Issue 1), 425. Belgya, T., Bersillon, O., Capote, R., Fukahori, T. Zhigang, G., Goreily, S., Herman, M., Ignatyuk, A.V., Kailas, S., Koning, A., Oblozinsky, P., Pluzko, V., Young, P., 2006. Handbook for Calculations of Nuclear Reaction Data, RIPL-2. IAEA-TECDOC-1506 IAEA, Vienna. Available online at
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Greenwood, L.R., 1987. American Society of Testing and Materials Reports No. 956, p. 743. Havlik, E., 1971. Acta Phys. Austriaca 34, 209. Helmer, R.G., 1983. Report EGC-PHYS-5735 (Idaho National Engineering Laboratory, Idaho, USA). Herman, M., Capote, R., Carlson, B., Oblozinsky, P., Sin, M., Trkov, A., Wienke, H., Zerkin, V., 2007. Nucl. Data Sheets 108 2007 2655-2715. Available online at