Neutron capture cross section measurements and ...

Radiochim. Acta 2017; 105(5): 347–357

Mogahed Al-abyad* and Gehan Y. Mohamed

Neutron capture cross section measurements and theoretical calculation for the 186W(n,γ)187W reaction DOI 10.1515/ract-2016-2635 Received June 4, 2016; accepted October 4, 2016; published online November 9, 2016

Abstract: Neutron capture cross section (σ0) and resonance integral (I0) of the reaction 186W(n,γ)187W were measured experimentally using the research reactor (ETRR-2) and an Am–Be neutron source, also calculated using TALYS-1.6 code. The present results of σ0 are (39.08 ± 2.6, 38.75 ± 0.98 and 38.33 barn) and I0 are (418.5 ± 74, 439.3 ± 36 and 445.5 barn) by using the reactor, neutron source and TALYS-1.6, respectively. The present results are in acceptable agreement with most of the previous experimental and evaluated data as well as the theoretical calculations. Keywords: Neutron capture cross section, resonance integral, neutron source, research reactor, TALYS-1.6.

1 Introduction Tungsten (W) is one of the most important structural materials in consideration for fusion reactor because it can endure high temperatures. It is also often used as the target material in electron accelerators for producing photons. Knowledge of thermal neutron cross section and resonance integral for 186W(n,γ)187W reaction has become important in the calculation of decay heat and evaluating the radiation damage of the material [1–4]. A number of experimental and evaluated data on the thermal neutron capture cross section and the resonance integral for the 186W(n,γ)187W reaction have been reported in the literature but a large discrepancy is present among them. Most of the reported experimental data have been measured for this reaction during the time period 1940 to 2014, at 0.0253 eV and at 0.0536 eV neutron energy. The measured neutron capture cross section varied from 26.6 barn to 42.8 barn [5–7]. *Corresponding author: Mogahed Al-abyad, Experimental Nuclear Physics Department, Cyclotron Facility, Nuclear Research Centre, Atomic Energy Authority, Cairo 13759, Egypt, E-mail: [email protected] Gehan Y. Mohamed: Experimental Nuclear Physics Department, Cyclotron Facility, Nuclear Research Centre, Atomic Energy Authority, Cairo 13759, Egypt

The measured resonance integral also varied from 290 barn [8] to 534 barn [9], and there are still large discrepancies among the experimental data for the 186W(n,γ)187W reaction. Therefore, it is necessary to remeasure more data of this reaction for better comparison. Usually, the thermal neutron capture cross section and the resonance integral for the 186W(n,γ)187W reaction were measured by the well known activation method using the monitor reaction 197Au(n,γ)198Au, in which most of the resonance capture occurs at low energy. Therefore, the comparison with Au is correct only if the epithermal neutron spectrum has an ideal (1/E) dependence on energy [10]. However, the real epithermal neutron spectra in actual irradiation sites may deviate more or less from the ideal (1/E) distribution shape. It was shown that these deviating spectra approximately follow (1/E1+α) fluence distribution [11]. The term, α is an energy independent parameter representing the extent of non-ideality of epithermal fluence shape. It can be positive or negative, depending on the irradiation system configurations (moderator material, geometry of irradiation site, configuration of neutron source, etc.). The results were determined relative to the reference values of σ0,Au = 98.65 ± 0.09 barn and I0,Au = 1550 ± 28 barn for the 197Au(n,γ)198Au monitor reaction as a single comparator. The resonance energy of 197Au monitor is 4.9 eV and that for 186W 18.8 eV, both being far from 0.55 eV cadmium cut-off energy. The aim of the present work is to measure the neutron capture cross section and resonance integral for the 186W(n,γ)187W reaction by activation method, using cadmium ratios, relative to a single monitor, 197Au as a standard. The W samples and Au monitors were irradiated with and without cadmium covers at the irradiation sites of the second ETRR-2 and the Am–Be isotopic neutron source irradiation facility.

2 Nuclear model calculations 2.1 TALYS-1.6 TALYS [12] is a computer code system for the analysis and prediction of nuclear reactions. The basic objective Authenticated | [email protected] author's copy Download Date | 5/1/17 3:15 PM

348 M. Al-abyad and G. Y. Mohamed, Neutron capture cross section measurements and theoretical calculation behind its construction is the simulation of nuclear reactions that involve neutrons, photons, protons, deuterons, tritons, 3He- and a-particles, in the 1 keV–200 MeV energy range and for target nuclides of mass 12 and heavier. To achieve this, a suite of nuclear reaction models have been implemented into a single code system. This enables us to evaluate nuclear reactions from the unresolved resonance range up to intermediate energies.

2.1.1 Thermal reactions TALYS is meant for the analysis of data in the 1 keV–200 MeV energy range as mentioned above. But in the present work the neutron capture cross section for the 186W(n,γ)187W reaction was measured at the thermal energy Eth = 0.0253 eV and the resonance integral at 0.55 eV, the lower energy of 1 keV should not be taken too literally. More accurate is: above the resolved resonance range. The start of the unresolved resonance range differs from nucleus to nucleus and is related to the average resonance spacing D0 or, equivalently, the level density at the binding energy. Generally, the starting energy region is higher for light nuclides than for heavy nuclides. Only beyond this energy, the optical and statistical models rare expected to yield reasonable results, at least for the non fluctuating cross sections. The lower energies are the domain of R-matrix theory, which describes the resonances. Nevertheless, it would be useful to have a first-order estimate of the non-threshold reactions, not only for the obvious neutron capture channel, but also for the exothermal (n,p), (n,α) and fission channels. One could get at least an estimate of the 1/v-like behavior of the excitation function down to 10−5 eV.

2.1.2 Capture channel First, on the lower energy of validity of a TALYS nuclear model calculation EL. Somewhat arbitrarily, set as default EL = D0 when we wish to construct evaluated data libraries, where D0 is taken from the nuclear model database or,

if not present, derived from the level density. EL can also be entered as an input keyword (Elow). Next, the neutron capture cross section at the thermal energy Eth = 0.0253 eV, either determined from the experimental database, or, if not present, from the systematical relation (1) [13].

σ n ,γ ( Eth ) = 1.5 × 10 −3 α( Sn − ∆)3.5 mb (1)

with α the level density parameter at the separation energy Sn and Δ the pairing energy. We assign a 1/v, i. e. 1/√E, dependence to the cross section from 10−5 eV to an upper limit E1/v which we set, again arbitrarily, at E1/v = 0.2 EL.

3 Experimental technique 3.1 S ample irradiation and γ-ray measurements Natural W consists of several stable isotopes as 180W (0.12%), 182W (26.49%), 183W (14.31%), 184W (30.64%) and 186 W (28.42%). Natural tungsten metallic foils (W), 10 mm2 in area by 0.2 mm in thickness, were used as the activation samples and the gold (Au) metallic foils with the same dimensions as of W foils were used as the single comparator monitor foils. The samples and monitors were irradiated with and without cadmium covers by using the second ETRR-2 and an (Am–Be) isotopic neutron source irradiation facility for suitable irradiation times. The activated bare and cadmium covered foils were counted with a γ ray spectrometer after a suitable cooling time according to the isotope half-life, it is recognized that there is no interference in the γ activity measurements for the 186W(n,γ)187W reaction. The nuclear decay data for the used isotopes are given in Table 1 [14, 15, 18, 19]. 3.1.1 (Am–Be) isotopic neutron irradiation facility In the present work, we used an Am–Be isotopic neutron irradiation facility [15, 20, 21]. The neutron source has 22 cm length and 4.4 cm diameter, with activity of about

Table 1: Nuclear decay data used for the cross-section measurements. Target

W(186W) 197 Au nat

Isotopic Nuclear abundance (%) reaction 28.6 (0.19) 100

Q0a

W(n,γ)187W 13.7 (1.85) 197 Au(n,γ)198Au 15.7 186

Er, (eV) Half-life

Detected γ-ray

k0;Au

Energy (keV) Intensity (%)

20.5 23.72 (0.06) h 479.5 (0.02) 685.8 (0.04) 5.65 2.69 (2.1 × 10−4) d 411.8 (1.7 × 10−4)

21.8 (0.7) 2.97 × 10−2 (1.0) 27.3 (0.9) 3.71 × 10−2 (0.5) 95.58 1

Qo = I0/σ0 (resonance integral to 2200 ms−1 cross-section ratio) [14–17].

a

Authenticated | [email protected] author's copy Download Date | 5/1/17 3:15 PM

M. Al-abyad and G. Y. Mohamed, Neutron capture cross section measurements and theoretical calculation 349

5 Ci of 241Am, surrounded by a cylinder of paraffin wax of 2.5 cm thickness, 30 cm length and 7 cm diameter in order to moderate the emitted fast neutrons. Targets were irradiated horizontally on a circle around the paraffin cylinder approximately at the neutron source hot area, as shown in Figure 1. The neutron source kept in a shielding house consists of an iron box with 3 mm wall thickness and has the dimensions 67 cm × 60 cm × 60 cm. The tank contains in its center a vertical cylindrical tube made of iron with 3 mm thickness and 6 cm in diameter, to facilitate the moving of the source. All of the inner tank surfaces are coated by a 5 cm layer of paraffin mixed with 5% boric acid for moderating and absorbing the neutrons. The upper surface of the tank is covered by a wood sheet of 3.5 cm thickness. The tank is filled with distilled water which provides neutron moderation and shielding. It is externally surrounded by normal paraffin blocks of 10 cm thickness to moderate neutrons that are not absorbed and get escaped from the tank. The facility is shielded against γ-rays by lead blocks of 5 cm thickness surrounding the outer two sides of the tank. The other two sides are facing thick concrete walls of about 2 m [22]. After an irradiation and an appropriate cooling time, the induced γ activities of the radioisotopes produced in the target and the monitor foils of 187W and 198Au, respectively, formed via the 186W(n,γ)187W and 197Au(n,γ)198Au reactions were measured nondestructively by using highpurity germanium (HPGe) γ-ray spectroscopy (Canberra, 70% relative efficiency, 2.3 keV resolution at 1332.5 keV of 60Co) coupled with a computer-based multichannel

(Am–Be) neutron source

analyzer (MCA) card system, which could determine the photopeak-area in γ-ray spectra by using the GENIE-2000 (Canberra) computer program. A γ ray spectrum of the tungsten sample irradiated with Am–Be isotopic neutron irradiation facility is shown in Figure 2. The detection efficiency versus energy curve of the HPGe γ-ray detector for counting distance was determined using a set of standard point sources such as 22Na, 60Co, 133 Ba, 137Cs and 241Am. The cooling and the measuring times were chosen based on the activity and the half-life of each radioactive isotope. 3.1.2 S econd Egyptian research reactor (ETRR-2) irradiation The samples and monitors were irradiated with and without Cd covers in one of the inner irradiation sites of the second ETRR-2. All samples and standards were placed in polyethylene vials and were irradiated in the thermal irradiation site for 1 h. After proper cooling time, the activities of the radioisotopes produced in the target and the monitor foils were measured nondestructively using HPGe γ-ray spectroscopy. The data acquisition was done by a MCA using Gamma Vision (Version 5.1, EG&G ORTEC) software program. The HPGe detector model Canberra GC-6020 of efficiency 60% and energy resolution of 2.9 keV full width at half maximum (FWHM) for the 1332.5 keV γ ray line of 60Co was used for activity measurements. The standard point γ ray sources 152,154,155Eu, 137 Cs and 60Co which have known γ ray energy lines were used for energy and efficiency calibration for the used γ ray spectrometer. A selected γ ray spectrum of tungsten sample which was irradiated using the second ETRR-2 neutrons is shown in Figure 3.

Source moving wire

67 cm

Counts

200

Shielding house

479.5 keV

134.2 keV

250

Sample holder

685.8 keV

Paraffin wax

150 100 50 0

50

150

250

350

450

550

650

750

Energy (keV) 60 cm

Figure 1: The layout of Am–Be neutron irradiation facility.

Figure 2: The γ-ray energy spectrum for the tungsten sample irradiated by the (Am–Be) isotopic neutron source. The three major peaks at 134.2, 479.5, and 685.7 keV are assigned to 187W.


350 M. Al-abyad and G. Y. Mohamed, Neutron capture cross section measurements and theoretical calculation correcting the decay during the counting period and is 685.8 keV

given by

− λt

(1 − e m ) where tm is the measuring time. λtm

60,000

4.2 Resonance integral determination 772.8 keV

40,000

618.3 keV

551.5 keV

Counts

80,000

479.5 keV

134.2 keV

100,000

20,000

0

0

200

400

600

800

The resonance integral for the (n,γ) reaction in an ideal 1/E epithermal neutron spectrum is defined by the following relation: 1000

Io =

Energy (keV)

Figure 3: The γ-ray energy spectrum of the tungsten sample irradiated by the reactor (ETRR-2) neutrons. Due to the much higher neutron flux, besides the three major peaks of 187W thee weaker peaks at 551.5, 618.3 and 772.8 keV were also observed.

4 Data analysis 4.1 T hermal neutron capture cross section The thermal neutron capture cross section, σ0,W for the 186 W(n,γ)187W reaction, is calculated from equation (2) as follows [23]:

σ o,W = σ o,Au

RW − FW,Cd RW,Cd Gth,Au g Au RAu − FAu,Cd RAu,Cd Gth,W g W

(2)

where σ0,Au is the thermal neutron capture cross section of the197Au(n,γ)198Au reaction, RW(Au) and RW(Au),Cd are reaction rates per atom for bare and Cd-covered 186W isotope irradiation, respectively. The FW(Au),Cd is the cadmium correction factor and Gth,W(Au) is the thermal neutron selfshielding factor for the W (or Au) samples. The gW(Au), Westcott correction factor, i. e. correction for departure from 1/v cross section behavior, for the 186W(n,γ)187W reaction is 1.002 [24] and that for the 197Au(n,γ)198Au reaction is 1.006 [25, 26]. After a bare and Cd-covered sample irradiation, the reaction rates RW(Au) and RW(Au),Cd for W and Au samples were determined from equation (3) Do et al. [23].

RW(Au) or RW(Au),Cd =

λN P no εI γSDC

(3)

where Np is the net peak area under the γ-ray peak of interest, ε is the detector efficiency, Iγ is the intensity of the − λt γ-ray, S is the saturation factor (1 − e irr ), λ is the decay constant, tirr is the irradiation time, D is the decay factor − λt (e d ) where td is the decay time, C is a term used for

∞

∫

ECd

σ( E ) dE E

(4)

where σ(E) is the cross section as a function of neutron energy E and ECd is the effective cadmium cut-off energy, which is usually defined as 0.55 eV. The (1 eV)α term (numerically unity) originates from the definition of the 1 epithermal neutron flux in a 1± α . distribution, where α E is an epithermal neutron spectrum shaping factor. However, the resonance integral defined in this equation is not valid in a non-ideal, real epithermal neutron spectrum. The experimental values of resonance integral I0(α)x for a reaction of interest can be determined relative to that of 197Au(n,γ)198Au as a standard reaction by the following given equation (5) [27, 28]. I o ( α)x = I o ( α)Au

( g σ o )x ( RCd − FCd )Au Ge,Au Gth,x (5) ( g σ o )Au ( RCd − FCd )x Ge,x Gth,Au

where FCd is the cadmium transmission factor for e pithermal neutrons (usually FCd = 1 but FCd.Au = 0.991) and Er is the effective resonance energy.

5 Results and discussions The samples and monitors were activated with mixed neutrons of thermal and epithermal energies and the contribution of the epithermal neutron subtracted by the Cd cut-off technique. To measure the activities of 186W(n,γ)187W and 197 Au(n,γ)198Au reactions, the γ-ray peaks have been chosen with high intensities, well separated, and relatively low background. The activities of 187W and 198Au foils with and without Cd cover were determined by using 479.55 keV (21.8%) and 411.80 keV (95.58%) γ ray peaks, respectively. The total uncertainty for the thermal neutron capture cross section was estimated by taking the square root of Authenticated | [email protected] author's copy Download Date | 5/1/17 3:15 PM


the sum of all individual contributions in quadrature: absolute abundance of the used γ-lines (1–3%), determination of the peak areas including statistical errors (1–4%), sample mass (2%), detector efficiency (1–3%) and cross section of the monitor reaction (1%). The total uncertainty of the cross section value was evaluated to be approximately 2.5–6.5% for both the isotopic neutron source facility and the (ETRR-2) reactor.

measured by [3, 5, 14, 16, 23, 30, 38, 42–49, 52, 54, 55] and within 7.1–18.4% higher than the values reported by [9, 17, 29, 31, 33, 51, 53, 56, 57] but 8.7% lower than the value reported by [7].

5.1 T hermal neutron capture cross section of the 186W(n,γ)187W reaction

The weighted average of the available experimental values of the thermal neutron capture cross section, including the present result, is 37.4 barn for both the Am–Be isotopic neutron source irradiation facility and the research reactor. It is compared with the experimental data as well as the present results and the evaluated values as illustrated in Figure 4 and Table 3. The weighted average is in good agreement with the evaluated values of [32] and it is lower than [34] by 5.6%. Also it is lower than the present results by 3.5% and 4.3% of neutron source and research reactor, respectively.

The present results are compared with the literature data as well as the theoretical calculations as given in Table 2 and Figure 4. The experimental and the calculated values varied from 33 barn [53] to 42.8 barn [7]. The theoretical calculations of the nuclear model code TALYS-1.6 is 38.33 barn, which is in good agreement with the present experimental results (38.75 ± 1 and 39.1 ± 2.6 barn) for the isotopic neutron source facility and the (ETRR-2) reactor, respectively.

5.1.1 T hermal neutron cross section using the Am–Be isotopic neutron source The present result for thermal neutron capture cross section of the 186W(n,γ)187W reaction is σ0 = 38.75 ± 1 barn and is compared with the literature data in Table 2 which illustrates that the present result is in good agreement within 0.13–2.5% with the values measured by [3, 5, 16, 30, 38, 43, 44, 49, 54] but within 4.1–4.7% with those reported by [23, 42, 45, 46, 48]. The present values are higher by 5.9–17.4% than the values reported by [9, 17, 29, 31, 33, 47, 51, 53, 56, 57] and lower by 3.1–9.5% than the values given by [7, 14, 52, 55]. The evaluated thermal neutron capture cross section values for the 186W(n,γ)187W reaction [32, 34–37, 39–41, 50] are in good agreement with the present result.

5.1.2 T hermal neutron capture cross section using the research reactor The present result on thermal neutron capture cross section for the 186W(n,γ)187W reaction is compared with the literature data in Table 2. The present result of 39.10 ± 2.6 barn is in agreement within 0.98–6.78% with the values

5.1.3 Weighted average of the thermal neutron capture cross section

5.2 Resonance integral cross section of the 186W(n,γ)187W reaction The epithermal neutron spectrum shaping factor α was determined in case of (Am–Be) neutron source irradiation facility by using the cadmium-ratio multi-monitor method [21] and found the value of the neutron flux shape α = 0.06. But in case of the second ETRR-2, the neutron flux shape α was found as α = − 0.05. The total uncertainty for the resonance integral cross section was estimated by taking the square root of the sum of all individual contributions in quadrature: absolute abundance of the used γ-lines (1–3%), determination of the peak areas including statistical errors (5–14%), sample mass (2%), detector efficiency (1–3%), α shape parameter (4.5%), cadmium correction factor (2.3–3.5%) and cadmium ratio (1.5–2.5%). The total uncertainty of the resonance integral value was evaluated to be approximately 7.5–17% for both the isotopic neutron source facility and the (ETRR-2) reactor. The theoretical calculation using the nuclear model code TALYS-1.6 gave a value of 445.5 barn, which is in good agreement with the present experimental results of the resonance integral I0 as (439.3 ± 36 and 418.5 ± 74 barn, respectively) for the isotopic neutron source facility and the (ETRR-2) reactor, respectively.


352 M. Al-abyad and G. Y. Mohamed, Neutron capture cross section measurements and theoretical calculation Table 2: Thermal neutron capture cross section for the 186W(n,γ)187W reaction. References

Neutron energy (eV)

Neutron capture cross section (barn)

Hurst et al. [29] Farina et al. [17] El Abd [30] Do et al. [23] Bondarenko et al. [31] Chadwick et al. [32] Mughabghab [5] Karadag and Yücel [3] Garland et al. [33] De Corte and Simonits [14] JENDL-3.3. [34] ENDF/B-VI [35] RNAL [36] Holden [37] Kopecky et al. [38] Kafala et al. [7] JENDL-3.2 [39] NuDat [40] JFF Report 14 [41] De Corte and Simonits [16] Gryntakis et al. [42] Knopf and Waschkowski [43] Mughabghab [44] Simonits et al. [45] Anufriev et al. [46] Heft [47] Gleason [48] Erdtmann [49] BNL [50] De Soete et al. [51] Hogg and Wilson [52] Damle et al. [9] Gillette [53] Friesenhahn et al. [54] Lyon [55] Pomerance [56] Seren et al. [57]

0.0253 0.0253 0.0253 0.0253 0.0253 0.0253 0.0253 0.0253 0.0253 0.0253 0.0253 0.0253 0.0253 0.0253 0.0253 0.0253 0.0253 0.0253 0.0253 0.0253 0.0253 0.0253 0.0253 0.0253

39.1 ± 2.6 38.75 ± 1.0 38.33 33.33 ± 0.62 34.9 ± 0.2 38.43 ± 4 37.2 ± 2.1 35.9 ± 1.1 37.5 38.1 ± 70.5 39.5 ± 2.3 36.5 ± 4.2 41.8 ± 2.9 39.6 38 ± 2 37.9 37 ± 2 37.90 42.8 ± 0.8 37.89 37.9 ± 0.6 38.27 38.7 ± 1.9 37 ± 15 38.5 ± 0.8 37.9 ± 0.6 37 ± 1.8 37 ± 3 36.6 ± 0.8 37 ± 1.5 37.8 ± 1.5 37.8 ± 1.5 36 40 ± 1.5 35.4 ± 0.8 33 37.8 ± 1.2 41.3 34.1 ± 2.7 34.2 ± 6.8

This work

5.2.1 R esonance integral cross section using the Am–Be isotopic neutron source The present result of the resonance integral I0 = 439.3 ± 36 barn and is compared with the literature data in Table 4, this value was obtained relative to the reference value of I0,Au = 1550 ± 28 barns for the 197Au(n,γ)198Au reaction with a cadmium cut-off energy of 0.55 eV. The present result is in agreement (0.07–2.4%) with the values measured by [60,

Facility

Monitor

Am–Be Reactor Reactor Reactor Reactor Reactor 252 Cf Reactor Reactor Reactor Linac Reactor Pile oscillator Reactor

Au-197 Au-197 –

Reactor Am–Be TALYS-1.6 Reactor Reactor Reactor Linac Reactor

Au-197 Au-197 Au-197 Mn-55 Co-59 – Au-197 Absolute measurement Sc-45 Au-197 Co-59 Au-197 – Au-197 Co-59 Au-197 Ta-182

Difference between present and literature value (%) Reactor − 17.25 − 11.97 − 1.69 − 5.05 − 8.85 − 4.21 − 2.57 1.06 − 7.06 6.50 1.31 − 2.84 − 3.11 − 5.62 − 3.11 8.69 − 3.14 − 3.11 − 2.11 − 0.98 − 5.62 − 1.50 − 3.11 − 5.62 − 5.62 − 6.77 − 5.62 − 3.38 − 3.38 − 8.55 2.30 − 10.39 − 18.42 − 3.38 5.37 − 14.60 − 14.26

Am–Be neutron source − 16.26 − 11.03 − 0.83 − 4.17 − 7.94 − 3.33 − 1.71 1.89 − 6.16 7.29 2.15 − 1.97 − 2.24 − 4.72 − 2.24 9.46 − 2.27 − 2.24 − 1.25 − 0.129 − 4.73 − 0.64 − 2.24 − 4.73 − 4.73 − 5.87 − 4.73 − 2.51 − 2.51 − 7.64 3.13 − 9.46 − 17.42 − 2.51 6.17 − 13.64 − 13.30

61, 64] and agrees within (3.1–4.7%) with the values measured by [16, 17, 23–31, 33, 38, 42–49, 53, 54]. It is (6.6–51.5%) higher than that of [8, 33, 49, 53, 58, 59, 62, 63, 66–68], while it is (7.7–17.7%) lower than the measurements of [3, 7, 9, 16, 30, 42, 44, 45, 48, 51, 65]. The evaluated resonance integral values of [39] are lower by 26.7% than the present measurement but our value is 9.4–16.9% higher than the values obtained by [32, 34, 35, 37, 40, 41, 50], as shown in Table 4.



45 186

W(n,γ)187W

Cross-section (Barn)

40

35

30

25

This work (Am-Be) Hurst et al. (2014) Do et al. (2008) Karadag and Yücel (2004) Kopecky et al. (1997) Gryntakis et al. (1987) Simonits et al. (1984) Gleason (1977) Hogg and Wilson (1970) Friesenhahn et al. (1966) Seren et al. (1947)

20 1940

1950

[29] [23] [3] [38] [42] [45] [48] [52] [54] [57]

1960

This work (TALYS-1.6) Farina et al. (2013) Bondarenko et al. (2008) Garland et al. (2003) Kafala et al. (1997) Knopf and Waschkowski (1987) Anufriev et al. (1981) Erdtmann (1976) Damle et al. (1967) Lyon (1960) The weighted average

1970

1980 Year

[17] [31] [33] [7] [43] [46] [49] [9] [55]

1990

This work (Reactor) El-Abd (2010) Mughabghab (2006) De Corte and Simonits (2003) De Corte and Simonits (1989) Mughabghab (1984) Heft (1978) De Soete et al. (1972) Gillette (1966) Pomerance (1952)

2000

2010

[30] [5] [14] [16] [44] [47] [51] [53] [56]

2020

Figure 4: Comparison of the evaluated and experimental values for the thermal neutron capture cross section of the 186W(n,γ)187W reaction. The solid line is the weighted average value of the experimental data, including the present result. Table 3: Comparison of the weighted average value of the experimental values including the present result with the evaluated values of the thermal neutron cross section of the 186W(n,γ)187W reaction. Evaluated values

Present work weighted average (barn) Reactor

Am–Be neutron irradiation facility

37.4

37.39

Difference between the weighted average value and the evaluated values (%) Chadwick et al. [32] JENDL-3.3. [34] ENDF/B-VI [35] RNAL [36] Holden [37] JENDL-3.2 [39] NuDat [40] JFF Report 14 [41] BNL [50] This work (reactor) This work (Am–Be neutron irradiation facility)

37.5 39.6 38 37.9 37 37.89 37.9 38.27 37.8 39.1 ± 2.6 38.75 ± 1.0

5.2.2 R esonance integral cross section using the research reactor The present result for the resonance integral I0 of the 186 W(n,γ)187W reaction is I0 = 418.5 ± 74 barn. Table 3 and Figure 5, show a comparison of the present work and the available literature data. The present result is in agreement within 1.6–2.1% with the values measured by [47, 49, 58, 66] while it agrees

0.26 5.55 1.57 1.32 − 1.08 1.29 1.32 2.27 1.05 4.29 –

0.29 5.58 1.60 1.34 − 1.05 1.31 1.35 2.29 1.08 – 3.51

within 4.7–9.2% with the values obtained by [23, 60, 61, 64]. The present result is 10.1–44.3% higher than the measurements of [8, 33, 53, 59, 62, 63, 67, 68] but it is 12.1–21.6% lower than the data of [3, 7, 9, 16, 30, 42, 44, 45, 48, 51, 65]. The present results are lower by 13.7–20.9% than the evaluated resonance integral values of [18, 32, 34, 35, 37, 41, 50] but 20.7% higher than the value obtained by [39].


354 M. Al-abyad and G. Y. Mohamed, Neutron capture cross section measurements and theoretical calculation Table 4: Resonance integrals for the 186W(n,γ)187W reaction. References

Resonance integrals (barn)

El Abd [30] Do et al. [23] Chadwick et al. [32] Karadag and Yücel [3] Garland et al. [33] JENDL-3.3 [34] ENDF/B-VI [35] Holden [37] JENDL-3.2 [39] Kafala et al. [7] NuDat [40] JFF Report 14 [41] De Corte and Simonits [16] Gryntakis et al. [42] Mughabghab [44] Simonits et al. [45] Heft [47] Gleason [48] Erdtmann [49] Van Der Linden et al. [58] BNL [50] De Soete et al. [51] De Corte et al. [8] Hayodom et al. [59] Pierce and Shook [60] Wall [61] Thai [62] Borchardt [63] Damle et al. [9] Beller et al. [64] Gillette [53] Baumann [65] Jacks [66] Macklin and Pomerance [67] Harris et al. [68]

418.5 ± 74 439.3 ± 36 445.5 502 ± 65 461 ± 39 522 493 ± 40 290.3 529 490 ± 50 510 ± 50 346.8 486 ± 5 485 ± 5 528.6 530 ± 28 490 ± 15 485 ± 15 507 ± 27 426 ± 32 490 ± 15 410 ± 47 410 ± 47 500 ± 35 476 290 345 ± 98 441 ± 22 439 ± 40 345 380 ± 84 534 ± 50 450 ± 36 318 476 ± 50 412 ± 59 355 320

This work

Facility

Monitor

Reactor Am–Be neutron source TALYS-1.6 Reactor Linac Am–Be neutron source Reactor Reactor Reactor 252 Cf Reactor Reactor Reactor

Au-197 Au-197 – Au-197 Au-197

5.2.3 W eighted average of the resonance integral cross section The weighted average of the experimental resonance integral values including the present results are 428.6 barn and 427.9 barn in case of the Am–Be isotopic neutron source irradiation facility and the research reactor, respectively. A comparison of the weighted average value of the experimental values including the present result with the evaluated values of the resonance integral of the 186W(n,γ)187W reaction is illustrated in Table 5 and Figure 5. The present results of the research reactor and the neutron source are in general good agreement.

Mn-55 Co-59 Au-197 Sc-45 Au-197 Co-59, In-113, Au-197 Au-197

Difference between present and literature value (%) Reactor 16.63 9.22 19.83 15.11 − 44.16 20.89 14.59 17.94 − 20.67 13.89 13.71 20.83 21.04 14.59 13.71 17.46 1.76 14.59 − 2.07 − 2.07 16.30 12.08 − 44.31 − 21.30 5.10 4.67 − 21.30 − 10.13 21.63 7.00 − 31.60 12.08 − 1.58 − 17.89 − 30.78

Am–Be neutron source 12.49 4.71 15.84 10.89 − 51.33 16.96 10.35 13.86 − 26.67 9.61 9.42 16.89 17.11 10.35 9.42 13.35 − 3.12 10.35 − 7.15 − 7.15 12.14 7.71 − 51.48 − 27.33 0.39 − 0.07 − 27.33 − 15.61 17.73 2.38 − 38.14 7.71 − 6.63 − 23.75 − 37.28

The weighted average value is 11.5–19.0% lower than the evaluated values of [32, 34, 35, 37, 40, 41, 50] but it is 23% higher than [39].

6 Conclusion The thermal neutron capture cross section and the resonance integral of the 186W(n,γ)187W reaction have been measured experimentally relative to the reference reaction197Au(n,γ)198Au by the activation method at the Am–Be isotopic neutron source irradiation facility and Authenticated | [email protected] author's copy Download Date | 5/1/17 3:15 PM


600 186

W(n,γ)187W)

Cross-section (Barn)

500

400

300

200

100

2020

2010

2000

1990

1980

1970

1960

1950

1940

0

Year

Figure 5: The resonance integral of the 186W(n,γ)187W reaction compared with the literature data as well as the theoretical calculations. The solid line is the weighted average value of the reactor data, while the dashed line is for the Am–Be neutron source data including the present result. Table 5: Comparison of the weighted average value of the experimental values including the present result with the evaluated values of the resonance integral of the 186W(n,γ)187W reaction. Evaluated values

Present work weighted average (barn) Reactor

Am–Be neutron irradiation facility

427.85

428.59

Difference between the weighted average value and the evaluated values (%) Chadwick et al. [32] JENDL-3.3 [34] ENDF/B-VI [35] Holden [37] JENDL-3.2 [39] NuDat [40] JFF Report 14 [41] BNL [50] This work (reactor) This work (Am–Be neutron irradiation facility)

522 529 490 510 346.8 485 528.6 500 418.5 ± 74 439.3 ± 36

the second ETRR-2. The experimental results are compared with the theoretical calculations using the nuclear model code TALYS-1.6 The wide variation in previously reported data for the thermal neutron capture cross section and resonance integral for the 186W(n,γ)187W reaction indicate that there is still a consistency problem among those measured and evaluated data.

18.04 19.12 12.68 16.11 −23.37 11.78 19.05 14.43 −2.23 –

17.89 18.98 12.53 15.96 −23.6 11.63 18.92 14.28 – 2.44

Acknowledgments: The authors would like to express their sincere thanks to Prof. Dr. Mohamed Ahmed Ali, Nuclear Physics Department, NRC, AEA. The crew of the second Egyptian Research Reactor (ETRR-2) is greatly acknowledged. Gehan Y. Mohamed also acknowledges late Prof. Dr. Nabiha F. Soliman, Reactor Physics Department, NRC, AEA for her helpful advices, guidance and continuous encouragement. Authenticated | [email protected] author's copy Download Date | 5/1/17 3:15 PM

356 M. Al-abyad and G. Y. Mohamed, Neutron capture cross section measurements and theoretical calculation

References 1. Barabash, V., Federici, G., Rodig, M., Snead, L. L., Wu, C. H.: Neutron irradiation effects on plasma facing materials. J. Nucl. Mater. 283–287, 138 (2000). 2. Barabash, V., Federici, G., Linke, J., Wu, C. H.: Material/plasma surface interaction issues following neutron damage. J. Nucl. Mater. 313–316, 42 (2003). 3. Karadag, M., Yücel, H.: Measurement of thermal neutron cross section and resonance integral for the 186W(n,γ)187W reaction by the activation method using a single monitor. Ann. Nucl. Energy 31, 1285 (2004). 4. Maekawa, F., Wada, M., Konno, C., Kasugai, Y., Ikeda, Y.: Decay heat experiment featuring low-energy neutron induced tungsten-187 production in ITER baffle plates and its analysis. Fusion Eng. Des. 51–52, 809 (2000). 5. Mughabghab, S. F.: Resonance Parameters and Thermal Cross Sections, Z=1–100, Atlas of Neutron Resonances. Elsevier, Amsterdam (2006). 6. Uddin, M. S., Chowdhury, M. H., Hossain, S. M., Latif, Sk. A., Hafiz, M. A., Islam, M. A., Zakaria, A. K. M., Azharul Islam, S. M.: Neutron capture cross section measurement for the 186W(n,γ)187W reaction at 0.0536 eV energy. Appl. Radiat. Isot. 66, 1235 (2008). 7. Kafala, S. I., MacMahon, T. D., Borzakov, S. B.: Neutron activation for precise nuclear data. J. Radioanal. Nucl. Chem. 215, 193 (1997). 8. De Corte, F., Speecke, A., Hoste, J.: Activation analysis of highpurity silicon. III. Multi-element activation analysis: application of the triple comparator method. J. Radioanal. Nucl. Chem. 9, 9 (1971). 9. Damle, P. P., Fabry, A., Jacquemin, R.: Study of the reaction 186 W(n,γ)187W, Report from Euratom to EANDC-76, 107 (1967). 10. Orvini, E., Gaggero, G., Lesca, L., Bresesti, A. M., Bresesti, M.: Determination of the neutron capture resonance integrals of 55 Mn, 115In, 121Sb, 123Sb and139La. J. Inorg. Nucl. Chem. 30, 1353 (1968). 11. Ryves, T. B.: A new thermal neutron flux convention. Metrologia 5, 119 (1969). 12. Koning, A. J., Hilaire, S., Duijvestijn, M. C.: “TALYS-1.0”, Proceedings of the International Conference on Nuclear Data for Science and Technology, April 22-27, 2007, Nice, France, editors O. Bersillon, F. Gunsing, E. Bauge, R. Jacqmin, S. Leray, EDP Sciences, 211 (2008). 13. Kopecky, J., Delfini, M. G., van der Kamp, H. A., Nierop, J. D.: Revisions and extensions of neutron capture cross sections in the European Activation File EAF-3, ECN-C–92-051 (1992). 14. De Corte, F., Simonits, A.: Recommended nuclear data for use in the k0 standardization of neutron activation analysis. At. Data Nucl. Data Tables 85, 47 (2003). 15. Soliman, N. F., Mohamed, G. Y., Fayez-Hassan, M., Ali, M. A.: The k0-NAA standardization method using an am-be neutron source. Third International Conference on Radiation Sciences and Applications. 12–16 November 2012/Hurghada, Egypt. J. Rad. Res. Appl. Sci. 5, 613 (2012). 16. De Corte, F., Simonits, A.: k0-Measurements and related nuclear data compilation for (n,γ) reactor neutron activation analysis: IIIb: tabulation. J. Radioanal. Nucl. Chem. 133, 43 (1989).

17. Farina, F. A., Vermaercke, P., Smits, K., Sneyers, L., Strijckmans, K.: Experimental determination of k0, Q0, factors and neutron cross sections for 41 isotopes of interest in neutron activation analysis. Radioanal. Nucl. Chem. 296, 931 (2013). 18. NuDat. The NuDat Program for Nuclear Data on the Web, National Nuclear Data Center, Brookhaven National Laboratory, Version 2.6, http://www.nndc.bnl.gov/nudat2/ (2016). 19. Firestone, R. B., Ekström, L. P.: Table of Radioactive Isotopes, Data base version 2.1. http://ie.lbl.gov/toi/ (2004). 20. Gehan, Y. M.: “Transmission and Reflection of Neutrons Using Foil Activation Technique”. Ph.D.Thesis, Ain Shams University (2012). 21. Uddin, M. S., Zaman, M. R., Hossain, S. M., Spahn, I., Sudar, S., Qaim, S. M.: An Am/Be neutron source and its use in integral tests of differential neutron reaction cross section data. Appl. Radiat. Isot. 68, 1656 (2010). 22. Mohamed, G. Y., Hassan, M. F., El-Wahab, M. A., Ali, M. A., Aziz, M.: Characteristics of a new neutron irradiation facility proceedings 8th Conference on Nuclear and Particle Physics 20-24 Nov., Hurghada, Egypt NUPPAC’ 11, 173 (2011). 23. Do, N. V., Khue, P. D., Thanh, K. T., Son, L. T., Kim, G., Lee, Y. S., Oh, Y., Lee, H.-S., Cho, M.-H., Ko, I. S., Namkung, W.: Thermal neutron cross section and resonance integral of the 186W(n,γ)187W reaction. Nucl. Instr. Meth. B 266, 863 (2008). 24. Garrison, J. D., Roos, B. W.: Fission-product capture cross sections. Nucl. Sci. Eng. 12, 115 (1962). 25. Goldman, D. T., Aline, P., Sher, R., Stehn, J. R.: 2200 m/s Neutron Absorption Cross sections, Internal Report FFX-105. AB Atom energi, Studsvik, Sweden (1968). 26. Ge, Z. G., Zhuang, Y. X., Liu, T. J., Zhang, J. S., Wu, H. C., Zhao, Z. X., Xia, H. H.: The updated version of Chinese evaluated nuclear data library (CENDL-3.1). J. Korean Phys. Soc. 59, 1052 (2011). 27. Goldstein, H., Harvey, J. A., Story, J. S., Westcott, C. H.: Recommended definitions for resonance integral cross section. EANDC Report. 12 (1961). 28. Kim, G. N., Kovalchuk, V., Lee, Y. S., Skoy, V., Cho, M. H., Ko, I. S., Namkung, W., Lee, D. W., Kim, H. D., Ko, S. K., Park, S. H., Kim, D. S., Ro, T. I., Min, Y. G.: Measurement of photoneutron spectrum at Pohang Neutron Facility. Nucl. Instr. and Meth. A 485, 458 (2002). 29. Hurst, A. M., Firestone, R. B., Sleaford, B. W., Summers, N. C., Revay, Zs., Szentmiklosi, L., Basunia, M. S., Belgya, T., Escher, J. E., Krticka, M.: Investigation of the tungsten isotopes via thermal neutron capture. Phys. Rev. C 89, 014606 (2014). 30. El Abd, A.: Measurements of the thermal neutron cross sections and resonance integrals for 186W(n,γ)187W and 98Mo(n,γ)99Mo reactions. Radioanal. Nucl. Chem. 284, 321 (2010). 31. Bondarenko, V., Tomandl, I., Wirth, H.-F., Honzatko, J., Sukhovoj, A. M., Malov, L. A., Simonova, L. I., Hertenberger, R., von, T., Egidy, J.: Berzins, nuclear structure of 187W studied with (n,γ) and (d,p) reactions. Nucl. Phys. A 811, 28 (2008). 32. Chadwick, M. B., Obložinský, P., Herman, M., Greene, N. M., McKnight, R. D., Smith, D. L., Young, P. G., MacFarlane, R. E., Hale, G. M., Frankle, S. C., Kahler, A. C., Kawano, T., Little, R. C., Madland, D. G., Moller, P., Mosteller, R. D., Page, P. R., Talou, P., Trellue, H., White, M. C., Wilson, W. B., Arcilla, R., Dunford, C. L., Mughabghab, S. F., Pritychenko, B., Rochman, D., Sonzogni, A. A., Lubitz, C. R., Trumbull, T. H., Weinma, J. P., Brown, D. A., Cullen, D. E., Heinrichs, D. P., McNabb, D. P., Derrien, H., Dunn, M. E., Larson, N. M., Leal, L. C., Carlson, A. D., Block, R. C.,


M. Al-abyad and G. Y. Mohamed, Neutron capture cross section measurements and theoretical calculation 357 Briggs, J. B., Cheng, E. T., Huria, H. C., Zerkle, M. L., Kozier, K. S., Courcelle, A., Pronyaev, V., van der Marck, S. C.: ENDF/B-VII.0: next generation evaluated nuclear data library for nuclear science and technology. Nucl. Data Sheets 107, 2931 (2006). 33. Garland, M. A., Mirzadeh, S., Alexander, C. W., Hirtz, G. J., Hobbs, R. W., Pertmer, G. A., Knapp, J. F. F.: Neutron flux characterization of a peripheral target position in the High Flux Isotope Reactor. Appl. Radiat. Isot. 59, 63 (2003). 34. JENDL-3.3. Japan Atomic Energy Research Institute. Nuclear Data Center. Copyright, JAERI (2002). 35. ENDF/B-VI (McLane, V., Ed.), ENDF-102 data formats and procedures for the evaluated nuclear data file. Report: BNL-NCS44945-01/04-Rev, BNL, Upton, New York (2001). 36. RNAL (Reference Neutron Activation Library), Nuclear Data Section IAEA-NDS-CD-08(Cd-Rom) Vienna (2000). 37. Holden, N. E.: Neutron scattering and absorption properties (Revised 1996). In: D. R. Lide (Ed.), CRC Handbook of Chemistry and Physics, 79th ed., CRC Press, New York, (1998). 38. Kopecky, J., Ch. Sublet, J., Simpson, J. A., Forrest, R. A., Nierop, D.: Atlas of neutron capture cross sections (NGATLAS-Cd Rom). Report: INDC (NDS)-362, IAEA, Vienna (1997). 39. JENDL-3.2, Fukahori, T., Iwamoto, O., Kakagawa, T., Shibata, S., Narita, T., Katakura, J., Hasegawa, A. (Eds.), JENDL-3.2 Cd Rom, JAERI-Data/Code 97-044 (1997). 40. NuDat (Kinsey, R.R., Ed.). The NuDat program for nuclear data on the web, version 2.5, NNDC, BNL, New York (1996). Available online from http://www.nndc.bnl.gov/nndc/nudat/. 41. JFF Report 14, Table of simple integral neutron cross section data from JEFF-2.2, ENDF/B-VI, JENDL-3.2, BROND-2 and CENDL-2, OECD (1994). 42. Gryntakis, E., Cullen, D. E., Mundy, G.: Handbook on Nuclear Activation Data, IAEA Technical Reports Series 273, Vienna (1987). 43. Knopf, K., Waschkowski, W.: Interaction of neutrons with tungsten and its isotopes (in German) Z. Naturforschung A 42, 909 (1987). 44. Mughabghab, S. F.: Neutron Cross Section, Vol. 1, Academic Press Inc., Santiago-New York-Boston-London-Sydney-TokyoToronto (1984). 45. Simonits, A., De Corte, F., Elnimr, T., Moens, L., Hoste, J.: Comparative study of measured and critically evaluated resonance integral to thermal cross section ratios. Part II. J. Radioanal. Nucl. Chem. 81, 379 (1984). 46. Anufriev, V. A., Babich, S. I., Kolesov, A. G., Nefjodov, V. N., Poruchikov, V. A.: Neutron resonances of W-186 in the energy range up to 300 eV. Atom. Energy 50, 67 (1981). 47. Heft, R. E.: A consistent set of nuclear parameter values for absolute INAA. International Conference on Computers in Activation Analysis and Gamma-ray Spectroscopy, vol. 495, Mayaguez, Puerto Rico., 30 April–4 May, 495 (1978).

48. Gleason, G.: Thermal Neutron (n,γ) Cross Sections and Resonance Integrals – Part 2. Private Communication to NEA-Data Bank, Paris, ORL, USA (1977). 49. Erdtmann, G.: Neutron Activation Tables. Verlag Chemie, Weinheim, (1976). 50. Mughabghab, S. F., Garber, D. I.: Neutron cross sections. Volume I. Resonance parameters (No. BNL-325 (3rded.)(Vol. 1); EANDC (US)-183 (L); INDC (USA)-58 (L)). Brookhaven National Lab., Upton, NY (USA) (1973). 51. De Soete, D., Gijbels, R., Hoste, J.: Neutron Activation Analysis, John Wiley & Sons Ltd., London (1972). 52. Hogg, C. H., Wilson, W. L.: Reactor thermal neutron cross section of 64Zn, 68Zn, 121Sb, 123Sb, 55Mn, and 186W. Idaho Nucl. Corp. Rep. 1317, 53 (1970). 53. Gillette, J. H.: Preprint: ORNL-4013, Vol. 5, Oak Ridge National Laboratory, Tennessee (1966). 54. Friesenhahn, S. J., Haddad, E., Froehner, F. H., Lopez, W. M.: The neutron capture cross section of the tungsten isotopes from 0.01 to 10 electron volts. Nucl. Sci. Eng. 26, 487 (1966). 55. Lyon, W. S.: Reactor neutron activation cross sections for a number of elements. Nucl. Sci. Eng. 8, 378 (1960). 56. Pomerance, H.: Thermal neutron capture cross sections. Phys. Rev. 88, 412 (1952). 57. Seren, L., Friedlander, H. N., Turkel, S. H.: Thermal neutron activation cross sections. Phys. Rev. 72, 888 (1947). 58. Van Der Linden, R., De Corte, F., Hoste, J.: A compilation of infinite dilution resonance integral. Radioanal. Chem. 20, 695 (1974). 59. Hayodom, V., Boonkong, W., Mahapanyawong, S., Chaimonkon, C.: Thai-AEC 23 Progress Report, Thailand (1969). 60. Pierce, C. R., Shook, D. F.: Determination of dilute 186W and 184W resonance integral by activation. Nucl. Sci. Eng. 31, 431 (1968). 61. Wall, T.: Australian AEC technical memo, AAEC/TM-466 (1968). 62. Thai -AEC-10, Certain accounts on the utilization of the Thai research reactor. Conf. Rep., Office of Atomic Energy of Peace, Bangkok (1967). 63. Borchardt, G.: Activation resonance integral and factor of the neutron self-shielding, report series: 503, Kernforschungsanlage, Juelich, Germany (1967). 64. Beller, L. S., Latham, D. W., Otter, J. M.: Measurements of the resonance integral and Doppler effect in 186W. North American Aviation Reports, NAA-SR-12500 (1967). 65. Baumann, N. P.: Resonance integral and self-shielding factors for detector foils. Savannah River Reports, Du Pont, 817 (1963). 66. Jacks, C. M.: Savannah River Reports, Du Pont, 608 (1961). 67. Macklin, R. L., Pomerance, H. S.: Proc. Conf. Peaceful Uses of Atomic Energy, Geneva, 5, 96 (1956). 68. Harris, S. P., Muehlhause, C. O., Thomas, G. E.: Low energy neutron resonance scattering and absorption. Phys. Rev. 79, 11 (1950).
