In the framework of the ASTRID project, a new 23Na evaluation, containing re-evaluated nuclear data and associated covariances, has been prepared to be submitted for the future JEFF-3.2 library. This ...work has been motivated mainly because the current JEFF-3.1.1 sodium evaluation showed large differences with microscopic measurements and does not have covariances data. Recent experimental data from IRMM and high resolution measurements from Larson have been simultaneously analyzed with the data assimilation code CONRAD and a good agreement with the evaluated cross-sections has been achieved. Experimental systematic uncertainties have been propagated to the nuclear reaction model parameters in order to produce a coherent set of covariance data. Several figures are provided in this paper to illustrate the new features of this evaluation.
Non-destructive analysis of materials by neutron resonance transmission Noguere, G.; Cserpak, F.; Ingelbrecht, C. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
06/2007, Letnik:
575, Številka:
3
Journal Article
Recenzirano
In this paper a non-destructive technique Neutron Resonance Transmission Analysis (NRTA) is presented and demonstrated. The technique has been applied at the Time-Of-Flight facility GELINA of the ...Institute for Reference Materials and Measurements at Geel in Belgium to characterize a radioactive PbI
2 sample, which was used to study the transmutation capabilities of
129I. A transmission experiment divided into three measuring sequences allowed the identification and quantification of light (
16O,
23Na and
32S) and heavy nuclei (
127I,
206Pb,
207Pb and
208Pb) with an accuracy better than 7%. In addition, an upper limit of the hydrogen content was deduced from the attenuation of the neutron beam by the non-resonant scattering contribution.
The Gamma Array for Neutron Inelastic Scattering (GAINS) is currently operating at the GELINA (Geel Linear Accelerator) neutron source producing highly precise neutron inelastic scattering data. A ...series of recent investigations explored the limits of the experimental setup and technique. Measurements on 12C and 57Fe attempted the determination of very high and very low energy gamma production cross sections, respectively. An extended analysis was directed towards the generation of covariance matrices specifically for this experimental approach.
Improvements have been made to the nuclear data standards largely as a result of an IAEA Data Development Project. The work includes the traditional activities related to standards, extending the ...energy ranges of some standards, and reference data that are not as well known as the standards but can be very useful in the measurements of certain types of cross sections. Also included is an effort to improve evaluations of 235U thermal and 252Cf spontaneous fission neutron spectra.
A measurement campaign to determine neutron induced fission cross sections of
240
Pu and
242
Pu at 2.51 and 14.83 MeV has been carried out at the 3.7 MV Van De Graaff linear accelerator at ...Physikalisch-Technische Bundesanstalt (PTB) in Braunschweig. Two identical Frisch Grid fission chambers, housing back to back a
238
U and a
A
Pu fertile sample (A = 240 or A = 242), were employed to detect the total fission yield. The neutron fluence was measured with the recoil proton telescope (T1) (Dangendorf et al. Nucl Instrum Methods Phys Res A 469:205–215, 2001), which is the German primary standard for neutron fluence measurements. The two measurements were related using a de Pangher long counter (Nolte and Thomas Metrologia 48:274–291, 2011) and the integrated beam current as monitors. The experimental results have an average uncertainty of 3–4% both at 2.51 MeV and at 14.83 MeV and have been compared to the data available in literature. The employed set-up allowed measurements of
238
U
σ
(
n
,
f
)
in parallel. The results confirm the most recent standard libraries at 2.51 and 14.83 MeV.
Over the last decade, the EC–JRC–IRMM, in collaboration with other institutes such as INRNE Sofia (BG), INFN Bologna (IT), ORNL (USA), CEA Cadarache (FR) and CEA Saclay (FR), has made an intense ...effort to improve the quality of neutron-induced cross section data in the resonance region. These improvements relate to both the infrastructure of the facility and the measurement setup, and the data reduction and analysis procedures. As a result total and reaction cross section data in the resonance region with uncertainties better than 0.5 % and 2 %, respectively, can be produced together with evaluated data files for both the resolved and unresolved resonance region. The methodology to produce full ENDF compatible files, including covariances, is illustrated by the production of resolved resonance parameter files for 241Am, Cd and W and an evaluation for 197Au in the unresolved resonance region.
The neutron flux of the n_TOF facility at CERN was measured, after installation of the new spallation target, with four different systems based on three neutron-converting reactions, which represent ...accepted cross sections standards in different energy regions. A careful comparison and combination of the different measurements allowed us to reach an unprecedented accuracy on the energy dependence of the neutron flux in the very wide range (thermal to 1 GeV) that characterizes the n_TOF neutron beam. This is a pre-requisite for the high accuracy of cross section measurements at n_TOF. An unexpected anomaly in the neutron-induced fission cross section of
235
U is observed in the energy region between 10 and 30keV, hinting at a possible overestimation of this important cross section, well above currently assigned uncertainties.
Cross sections have been measured with the activation technique at various neutron energies in the range of 16.0 to 20.5 MeV for the following 22 reactions:
19
F(n,p)
19
O,
23
Na(n,p)
23
Ne,
23
...Na(n,α)
20
F,
25
Mg(n,p)
25
Na,
27
Al(n,p)
27
Mg,
28
Si(n,p)
28
Al,
29
Si(n,p)
29
Al,
29
Si(n, np + pn + d)
28
Al,
31
P(n,α)
28
Al,
35
Cl(n,2n)
34m
Cl,
37
Cl(n,p)
37
S,
46
Ti(n,p)
46m
Sc,
50
Ti(n,p)
50g+m
Sc,
51
V(n,p)
51
Ti,
55
Mn(n,α)
52
V,
56
Fe(n,p)
56
Mn,
57
Fe(n, np + pn + d)
56
Mn,
57
Fe(n,p)
57
Mn,
93
Nb(n,α)
90m
Y,
93
Nb(n,2n)
92m
Nb,
119
Sn(n,p)
119g
In, and
138
Ba(n,2n)
137m
Ba. The half-lives for the reaction products range from 11 s to 10.15 days. Quasi-monoenergetic neutrons were produced via the
3
H(d, n)
4
He reaction. In some cases isotopically enriched materials were used to enhance the reaction yield or to facilitate correction for interfering reactions leading to the same product. The gamma rays emitted from the irradiated samples were measured with a high-purity germanium detector. A pneumatic sample transport system was used to limit the decay of the radioactive products between neutron irradiation and gamma-ray counting. All cross sections were obtained as ratios to the standard reaction
27
Al(n,α)
24
Na, using as secondary neutron fluence references the
27
Al(n,p)
27
Mg reaction as well as a calibrated Bonner sphere. Corrections have been applied for sample-irradiation and counting environment geometric effects, neutron absorption and multiple scattering, time variation of neutron-source strength, neutron-source angular distributions, secondary neutrons from the target, gamma-ray absorption, and gamma-ray sum coincidences. A detailed analysis of the uncertainty sources was performed. The present results are compared with other measurements and evaluated data. For seven reactions, measured cross sections have been obtained for the first time beyond 15 MeV. These new data help appreciably to resolve discrepancies in evaluated data files.
.
This paper presents
13
C(n,
)
10
Be cross section measurements performed at the Van de Graaff facility of the Joint Research Centre Geel. The
13
C(n,
)
10
Be cross section was measured relative to ...the
12
C(n,
)
9
Be cross section at 14.3 MeV and 17.0 MeV neutron energies. The measurements were performed with an sCVD (single-crystal chemical vapor deposition) diamond detector which acted as sample and as sensor simultaneously. A novel analysis technique was applied, which is based on the pulse-shape analysis of the detector’s ionization current. This technique resulted in an efficient separation of background events and consequently in a well-determined selection of the nuclear reaction channels
12
C(n,
)
9
Be and
13
C(n,
)
10
Be.
Resonance parameters for neutron-induced reactions on
241
Am below 110 eV have been determined. The parameters result from a resonance shape analysis of transmission and capture data measured at the ...time-of-flight facility GELINA, with the accelerator operating at a 50 Hz repetition rate. The transmission experiments were carried out at a 25 m station using a Li glass scintillator. The capture experiments were performed at a 12.5 m station by applying the total energy detection principle in combination with the pulse height weighting technique using a pair of C
6
D
6
detectors. The normalization of the capture data was determined by a combined least squares adjustment of the transmission and capture data. From the adjusted resonance parameters a capture cross section of 749 ± 35 b for a neutron energy of 0.0253 eV and an average radiation width of 〈
Γ
γ
〉 = 42.0 meV for
s
-wave resonances were obtained. A missing-level analysis for
s
-wave neutron resonances within the statistical model results in compatible values with previous estimates. The neutron widths obtained in this work are approximately 22% larger compared to other experimental data and evaluated data libraries. Also the thermal capture cross section is larger than most of the recommended values. However, the resonance parameter file presented in this work is consistent with results of both integral experiments and of the experimentally determined resonance integrals.
