Photofission and photoneutron cross sections for

A specific objective of the recent IAEA Coordinated Research Project on Photonuclear Data and Photon Strength Functions (Code F41032; Duration 2016-2019) has been to measure photonuclear cross-section data where needed, for unexplored nuclei and cases of discrepant existing data. A dedicated experimental campaign has been conducted at the laser Compton-scattering γ-ray source of the NewSUBARU synchrotron radiation facility of SPring8, Japan, where photoneutron reactions for 11 nuclei from 9Be to 209Bi have been investigated in the Giant Dipole Resonance energy region. The measurements followed the development of a flat-effi ciency moderated neutron detection array and the associated neutron-multiplicity sorting techniques. The IAEA CRP campaign has been followed at NewSUBARU by new measurements of photofission and photoneutron reactions on 238U and 232Th in the energy range of 5.87 MeV – 20.14 MeV. The neutron-multiplicity sorting of high-multiplicity fission neutron coincidence events has been performed using a dedicated energy dependent, multiple firing statistical treatment. The photoneutron (γ, xn) and photofission (γ, fxn) reactions have been discriminated by considering a Gaussian distribution of prompt-fission-neutrons (PFN) multiplicities predicted by the evaporation theory. We here provide preliminary experimental (γ, n), (γ, 2n) and (γ, F) cross sections, average energies of PFN and of photoneutrons emitted in (γ, n) and (γ, 2n) reactions, as well as the mean number of PFN per fission act. The new 238U cross sections are compared with recent statistical-model calculations performed with the EMPIRE code on existing data

Simultaneous 3D-PTV and UVP measurements of unsteady three-dimensional flow in a suction sump

本研究では，三次元粒子追跡流速測定法(3D-PTV)を用いて，vertical-wet-pit-pump形状のポンプ吸込水槽内に生じる複雑な流れの三次元非定常速度分布計測を試みる．3D-PTVの低い信頼性と計測精度を克服する為，3D-PTVと共通のトレーサー粒子を用いた超音波ドップラ速度分布計(UVP)との同時計測を実施する．その結果，高精度計測に適した条件を見出すことに成功している．さらに見出された条件下で，吸込水槽内の時間平均流れ場および瞬間流れ場を定量的に明らかにしている．The authors attempt to understand the complicated flow inside a suction sump in the vertical-wet-pit-pump configuration. A three-dimensional particle tracking velocimetry (3D-PTV) technique is appropriate for this kind of flow. However, this technique includes more unknown factors in reliability and accuracy than other well-established measuring techniques. So, the authors examine the simultaneous measurement using both of the 3D-PTV and an ultrasonic velocity profiler with common tracer particles. As a result, the authors have successfully found out the suitable condition for the simultaneous measurement with high accuracy. Then, under this condition, the authors have revealed the time-mean and instantaneous velocity vectors of the flow inside the suction sump