JAEA-Conf 2011-002 - 日本原子力研究開発機構

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3.1 Experimental Set up JAEA-Conf 2011-002 A target in a 244Cm sample was 0.6-mg curium oxide, its activity was 1.8GBq and isotopic abundance was 89.6%. That in 246Cm sample was 2.1-mg curium oxide with a 27.5% contamination of 244Cm and its activity was 12.1 MBq from 246Cm and 1.7 GBq from 244Cm. [14] The samples were sealed in aluminum capsules 9 mm in diameter and 0.5 mm thick walls. Using the “4π Ge spectrometer” with a neutron time-of-flight method, both energy of neutrons and prompt-γ rays from the samples were measured at the same time. The measurement time for the 244Cm sample was about 80 hours and that for the 246Cm sample was about 100 hours. For the background estimation, a measurement with a dummy sample of the aluminum case without curium oxide powder was done for 40 hours and a measurement with neither of a sample material nor the sample case (only with a sample holder) was done for 32 hours. In the measurements, MLF was operated at an average beam power of 120 kW, and a repetition rate of 25 Hz. For dead-time correction, pulses from a random-pulse generator (Berkeley Nucleonics : DB-2) were input through the “test input” of the pre-amplifier of every Ge crystal. 3.2 Data Processing and Analysis Fig. 4 shows neutron-capture -ray yields of the 244Cm, the 246Cm sample, and the dummy case. In these experiments, neutron energies were calibrated with resonances in 197Au(n,) reaction. Resonance peaks of 244Cm, 246Cm, and 248Cm are clearly observed. In the experiments, pulses from the random-pulse generator were input and measured with the DAQ. The stored counts were used for the dead time correction by comparing the counts of input pulses with actually stored pulses. Time dependent dead time was obtained from this method. [15] Neutron-energy dependent backgrounds were mainly caused by prompt γ rays from the Al case and scattered neutrons by the Al case and the helium in the beam duct. The backgrounds were derived from the neutron-capture γ-ray yields of the Al case and the blank measurement using the full-energy peaks of 7724-keV prompt γ rays from 27Al(n, γ) reactions. The effect from the decay γ rays from 244Cm, 28Al, and the other activated nuclides was also deduced from the counts in the TOF time range after 30 ms by extrapolation with exponential and constant function. Self-shielding and multi-scattering factors of the Cm samples and the Al case were calculated with the MCNP code. The incident neutron flux shape was deduced from neutron-capture γ-ray yields of the 478-keV γ ray from 10B(n,αγ) reactions. [16] Fig. 4. Neutron-capture γ-ray yields of the 244Cm sample (dashed line), the 246Cm sample (solid line), and the dummy Al case (dashed-dotted line).
3.3 Preliminary Results Relative cross sections were deduced with these corrections and the incident neutron flux. Absolute values were normalized to the values of those in JENDL 4.0 at the 1st resonances. Fig. 5 (a) shows a comparison of our preliminary neutron-capture cross section of 244Cm with the one given by Moore [13], and the evaluated value of JENDL 4.0 [17]; and Fig. 5 (b) shows a comparison for 246Cm. The results of the 7.67-eV and 16.77-eV resonance peaks of 244Cm and the 4.32-eV and 15.30-eV resonance peaks of 246Cm are the first experimental results in the world. The results show that neutron-capture cross section can be obtained using a small amount (less than 1 mg) of a high radioactive sample in ANNRI. 4. Summary Neutron-capture cross section measurements of MAs and LLFPs using a new experimental apparatus, ANNRI, have been started. Results of these measurements show that neutron-capture cross sections can be obtained using a small amount (less than 1 mg) of a high radioactive sample in ANNRI. In near future, ANNRI will be used not only for nuclear data but also nuclear astrophysics and quantitative analysis. Acknowledgments Present study includes the result of "Study on nuclear data by using a high intensity pulsed neutron source for advanced nuclear system" entrusted to Hokkaido University by the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT). This work is supported by JSPS KAKENHI (22226016 and 22760675). JAEA-Conf 2011-002 (a) Preliminary results of 244 Cm. (b) Preliminary results of 246Cm. Fig.5 Preliminary results of neutron capture cross-sections of 244 Cm and 246 Cm (circles with error bars) and comparison to the one measured by Moore [13](triangles with error bars) and JENDL 4.0 [17](solid line). The experimental values were normalized at 1st resonances with the data in JENDL 4.0.
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The Institute's staff of about 280
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3. Nuclear Theory Laboratory JAEA-C
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JAEA-Conf 2011-002 References [1] P
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JAEA-Conf 2011-002 reaction 6 Li +
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Using the approximated distribution
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momentum of the constituents of P.
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dσ/dΩ (mb/sr) c.m. scattering ang
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JAEA-Conf 2011-002 [2] N. Austern,
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moderating fast neutrons emitted fr
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JAEA-Conf 2011-002 3. Results and d
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JAEA-Conf 2011-002 the detection de
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Fig.1. Experimental arrangement for
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in this work was confirmed. (2) 153
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Neutron Capture Cross Section of 15
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ENDF resonance parameters are based
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sample changer. The measured flux s
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REFERENCES JAEA-Conf 2011-002 [1] W
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JAEA-Conf 2011-002 Fig. 4: The rela
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Fig. 10: The PHITS2 calculation geo
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for such a low energy region should
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MCNPX calculation was performed bas
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JAEA-Conf 2011-002 We measured dou
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1mm-thick carbon target 22mm in dia
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JAEA-Conf 2011-002 Figure 2 shows e
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The double-differential (n,xp) and
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JAEA-Conf 2011-002 forward angles.
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Fig.3. Two-dimensional plot of PI v
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JAEA-Conf 2011-002 Fig. 7. Deuteron
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JAEA-Conf 2011-002 The new detector
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4. Off line data analysis Double di
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eports of data of carbon-ion incide
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Count [-] 4 10 3 10 2 10 10 1 Charg
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Acknowledgement We are grateful to
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Beam Line BM1 Copper Target BM2 5×
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φ = φbm · ρtof · ρmulti (2) E
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References [1] K. Ishibashi, H. Tak
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JAEA-Conf 2011-002 hint at the orig
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Neutron Dose Rate [Sv/hr/src neutro
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JAEA-Conf 2011-002 radiation protec
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Ztarget, Atarget are the numbers fo
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We described our formalism for calc
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2. Model
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JAEA-Conf 2011-002 reactions. Figur
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analysis of integral experiments [6
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A modified SRAC library was prepare
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JAEA-Conf 2011-002 approximately 0.
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JAEA-Conf 2011-002 constructing the
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Fig.9 Spectrum of gamma-ray followi
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JAEA-Conf 2011-002 in the same way
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JAEA-Conf 2011-002 [7]. For example
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JAEA-Conf 2011-002 (5.0-9.0MeV), a
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components, the 0.56Wt% for hydroge
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Sensitivities of curium isotope con
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decreases of (n,g) reaction rates,
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5. Conclusion JAEA-Conf 2011-002 Wi
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2. Foundation of sensitivity analys
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JAEA-Conf 2011-002 where f g and f
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Fig.1 Sensitivity coefficient of th
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An outline of core configurations o
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0.010% 0.000% -0.010% -0.020% -0.03
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To clarify what nuclides and reacti
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Calculation was performed by the MV
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among these libraries, and the diff
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JAEA-Conf 2011-002 - 日本原子力研究開発機構

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