The 232Th(n, f) cross-section for thermal and 2.44 MeV neutrons

The thermal neutron induced fission cross-section of ²³²Th was measured at an intense and very pure thermal neutron beam of the Grenoble High Flux Reactor, yielding a value of (3 ± 1) μbarn. For control purposes, the same targets were used at the VandeGraaff accelerator of the CBNM (Geel), where a ²³²Th (n, f) cross-section value of (0.12 ± 0.02) barn was obtained with 2.44 MeV neutrons, in agreement with other published data.     

Cross section measurements of the 23Na(n, 2n)22Na, 58Ni(n, 2n)57Ni and 115In(n,n′)115mIn reactions

Cross sections for two high energy threshold reactions ²³Na(n, 2n)²²Na and ⁵⁸Ni(n, 2n)⁵⁷Ni were measured by the activation method in the neutron energy range from 14 to 18 MeV. Inelastic scattering cross section for ¹¹⁵In was measured in the threshold region, i.e. from 0.5 to 1.3 MeV. The results of measurements are compared with scarce and divergent earlier data.     

29—1100keV能区75As中子俘获截面测量

用活化法相对于Au的中子俘获截面，测量了29－1100keV能区^75As(n, γ）^76As的反应截面，测量精度为6．7－7．8％，并将测量结果与现有的实验数据作了比较。     

Total cross sections for the 40Ca(n,p) and (n, α) reactions between 2.7 and 5.5 MeV

Measurements have been made of the ⁴⁰Ca(n,p), ⁴⁰Ca(n,α), ⁴⁰Ca(n,n′) ⁴⁰Ca(3.35) cross sections in the energy range 2.7–5.5 MeV. Neutron flux measurements are made using the associated particle technique. The data are compared to previous data and the recent Hauser-Feshbach calculations made by Fu (1979).     

山西、河南三地土壤样品中239+240Pu、137Cs分析

采用电感耦合等离子体质谱(ICP-MS)分析了中国中部地区三地(山西长治、河南濮阳和商丘)钻芯(0～30 cm)土壤样品中的239 240 Pu活度浓度和240Pu/239pu同位素比值,并对239 240 Pu和137Cs在土壤中的深度分布进行了研究.结果表明,三地表层土壤(0～2 cm)中239+ 240pu活度浓度为0.078 ～0.122mBq/g,137Cs为1.56 ～2.91 mBq/g,且浓度整体随深度增加而降低;240Pu/239 Pu原子比的平均值为0.188±0.016(全球沉降平均值为0.180±0.014),137Cs/239240Pu活度比值为34.61 ±5.91(1998年7月,全球沉降平均值为34±4).三地土壤中放射性核素137 Cs、239+240Pu浓度及钚同位素比值均与全球沉降值相当,说明其来源可能属于全球沉降.     

Fission spectrum averaged cross-section of 94Zr(n, α)91Sr

The fission spectrum averaged cross-section of ⁹⁴Zr(n, α)⁹¹Sr reaction was obtained by comparing that of ²⁷Al(n, α)²⁴Na reaction as reference. Highly enriched ⁹⁴ZrO₂ and ²⁷Al samples were irradiated with fast neutrons having a fission-like spectrum above about 5.6 MeV. After the neutron irradiation, the produced ⁹¹Sr was chemically separated from the irradiated sample. Gamma-rays from ⁹¹Sr and ²⁴Na were measured with a Ge(Li) detector. The obtained value is 5.37 ± 0.43 μb assuming the averaged cross-section of the reference reaction to be 0.61 mb.     

Measurement of neutron capture cross-section of indium in the energy region from 0.003 eV to 30 keV

The neutron capture cross-section of indium (In) has been measured in the energy region from 0.003 eV to 30 keV by the neutron time-of-flight (TOF) method with a 46-MeV electron linear accelerator (linac) of the Research Reactor Institute, Kyoto University. An assembly of Bi₄Ge₃O₁₂ (BGO) scintillators, which was composed of 12 pieces of BGO and placed at a distance of 12.7±0.02 m from the neutron source, was employed as a total energy absorption detector for the prompt capture γ-ray measurement from the sample. In order to determine the neutron flux impinging on the capture sample, a plug of ¹⁰B powder sample and the ¹⁰B(n,α) standard cross-section were used. The data measured by Haddad et al. (Haddad, E., Friesenhahn, S., Lopez, W.M., 1963. Report of Gulf Energy and Environmental Systems, p. 3874) seem to be in good agreement with the present measurement. Popov et al. obtained the poor energy resolution data in the resonance region with a lead slowing-down spectrometer and the consistent data with the present above about 300 eV. The experimental data measured by Kononov et al. (Kononov, U.N., Jurlov, B.D., Poletaev, E.D., Timokhov, V.M., Manturov, G.N., 1977. Report of Obninsk, pp. 22–29) and Gibbons et al. (Gibbons, J.H., Macklin, R.L., Miller, P.D., Neiler, J.H., 1961. Phys. Rev. 122, 182) showed good agreement with the present values in the higher energy region. However, the data measured by Block et al. (Block R.C., Kaushal, N.N., Hockenbury, R.W., 1972. Conference on New Developments in Reactor Physics and Shielding at Kiamesha Lake, Vol. 2, p. 1107) seem to be a little higher than the present measurement above 800 eV. The evaluated data in ENDF/B-VI, JENDL-3.2, and JEF-2.2 have been in general agreement with the present result in the relevant energy region, although the JENDL-3.2 are higher than the measurement, the ENDF/B-VI and the JEF-2.2 from 2 to about 10 keV. Most of the previous experimental and the evaluated thermal neutron cross-sections are generally close to the present value of 199.6±5.6 b at 0.0253 eV.     

The 10B(n, αγ)7Li cross-section between 0.1 and 2.2 MeV

The shape of the excitation function for the standard neutron reaction ¹⁰B(n, αγ)⁷Li in the energy range from 0.1 to 2.2 MeV has been determined relative to the angular distribution of the neutron source reaction T(p, n)³He at 1.6, 2.3, and 3.0 MeV proton energy. The 478 keV γ's produced in a 3-mm thick boron carbide sample were observed in a Ge(Li)-detector. The time-of-flight method was used to discriminate against events from neutrons of degraded energy.     

Activation cross sections for Os(n,p)Re, Os(n,p)Re and Os(n,n′)Os reactions from 13.5 to 14.8 MeV

Cross sections for (n,p) and (n,n′) reactions have been measured on osmium isotopes at the neutron energies from 13.5 to 14.8 MeV using the activation technique in combination with high-resolution gamma-ray spectroscopy. Neutrons were produced via the ³H(d,n)⁴He reaction using solid TiT. The neutron fluences were determined using the monitor reaction ⁹³Nb(n,2n)^92mNb. Data are reported for the following reactions: ¹⁹⁰Os(n,p)^190mRe, ¹⁹⁰Os(n,p)^190gRe, ¹⁹⁰Os(n,p)¹⁹⁰Re, ¹⁸⁸Os(n,p)¹⁸⁸Re and ¹⁹⁰Os(n,n′)^190mOs. Nuclear model calculations using the code HFTT, which employs the Hauser-Feshbach (statistical model) and exciton model (precompound effects) formalisms, were undertaken to describe the formation of the products. The cross sections were discussed and compared with experimental data found in the literature, with values of model calculations including the pre-equilibrium contribution, and with evaluation data of JEFF-3.1/A.     

The (He, tf) as a surrogate reaction to determine (n, f) cross sections in the 10-20 MeV energy range

The surrogate reaction ²³⁸U(³He, tf) is used to determine the ²³⁷Np(n, f) cross section indirectly over an equivalent neutron energy range from 10 to 20 MeV. A self-supporting ∼761 μg/cm² metallic ²³⁸U foil was bombarded with a 42 MeV ³He²⁺ beam from the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory (LBNL). Outgoing charged particles and fission fragments were identified using the Silicon Telescope Array for Reaction Studies (STARS) consisted of two 140 μm and one 1000 μm Micron S2 type silicon detectors. The ²³⁷Np(n, f) cross sections, determined indirectly, were compared with the ²³⁷Np(n, f) cross section data from direct measurements, the Evaluated Nuclear Data File (ENDF/B-VII.0), and the Japanese Evaluated Nuclear Data Library (JENDL 3.3) and found to closely follow those datasets. Use of the (³He, tf) reaction as a surrogate to extract (n, f) cross sections in the 10-20 MeV equivalent neutron energy range is found to be suitable.     

Measurement of thermal neutron cross section and resonance integral for (n,γ) reaction in Sm

This study implies that ⁵⁵Mn(n,γ)⁵⁵Mn monitor reaction may be a convenient alternative comparator for the activation method and thus, it was used for the determination of thermal neutron cross section (TNX) and the resonance integral (RI) of the reaction ¹⁵²Sm(n,γ)¹⁵³Sm. The samples of MnO₂ and Sm₂O₃ diluted with Al₂O₃ powder were irradiated within and without a cylindrical 1 mm-Cd shield case in an isotropic neutron field obtained from the ²⁴¹Am–Be neutron sources. The γ-ray spectra from the irradiated samples were measured by high resolution γ-ray spectrometry with a calibrated n-type Ge detector. The correction factors for γ-ray attenuation, thermal neutron and resonance neutron self-shielding effects and epithermal neutron spectrum shape factor (α) were taken into account in the determinations. The thermal neutron cross section for ¹⁵²Sm(n,γ)¹⁵³Sm reaction has been determined to be 204.8 ± 7.9 b at 0.025 eV. This result has been obtained relative to the reference thermal neutron cross section value of 13.3 ± 0.1 b for the ⁵⁵Mn(n,γ)⁵⁶Mn reaction. For the TNX, most of the experimental data and evaluated one in JEFF-3.1, ENDF/B-VI, JENDL 3.3 and BROND 2.0, in general, agree well with the present result. The RI value for ¹⁵²Sm(n,γ)¹⁵³Sm reaction has also been determined to be 3038 ± 214 b, relative to the reference value of 14.0 ± 0.3 b for the ⁵⁵Mn(n,γ)⁵⁶Mn monitor reaction, using a 1/E^1+α epithermal neutron spectrum and assuming Cd cut-off energy of 0.55 eV. In surveying literature, the existing experimental and evaluated data for the RI values are distributed from 1715 to 3462 b. However, when the Cd cut-off energy is defined as 0.55 eV, the present RI value agrees with some previously reported RI values, 3020 ± 163 b by Simonits et al., 3141 ± 157 by Van Der Linden et al., and 2962 ± 54 b by Kafala et al., within the limits of error.