An intense 14 MeV neutron source facility named OKTAVIAN was installed in the A15 building,Osaka University in 1981.Along the operation period,new radioisotopes with various half-life have been produced as neutron act...An intense 14 MeV neutron source facility named OKTAVIAN was installed in the A15 building,Osaka University in 1981.Along the operation period,new radioisotopes with various half-life have been produced as neutron activation products in its concrete wall shield.In this work,we investigated the concrete wall in the heavy irradiation room of OKTAVIAN using gamma spectrometry method to discover the presence of radioisotope having large half-life value(long-lived radioisotope)as neutron activation products.Computational simulations were performed prior to measurement to predict the presence of long-lived radioisotopes by employing MCNP5 and FISPACT codes.A pre-calibrated Germanium detector with high energy resolution was employed to measure the concrete.Several long-lived activation products have been observed such as 152 Eu,54 Mn,65 Zn,22 Na and 60 Co.The activity of each radioisotope was derived after estimating the detector efficiency using MCNP5.As a result of the measurement and analysis,the followings are concluded:(1)Though presence of activation products represents radiological risk to everyone who performs an experimental activity in the irradiation room of the OKTAVIAN facility,the present result shows that past experiments were carried out safely without any significant additional exposure dose coming from the wall for the last 38 years.(2)The approximated total fluence of D-T neutrons to the wall was successfully estimated from the produced radioisotope,152 Eu,because it has the longest half-life of 13.5 years among the observed radioisotopes.(3)From the results of(1)and(2),it could be possible to estimate the total activity of the concrete wall in the OKTAVIAN facility,which is very essential and important information,because this would be very valuable for decommissioning or disposal of the facility in the future.展开更多
A new nuclide (238)Th has been produced via multinucleon transferreaction by 60 MeV/u 18O ion irradiation of the natural uranium. The thorium wasradiochemically separated from the fixture of uranium and reaction produ...A new nuclide (238)Th has been produced via multinucleon transferreaction by 60 MeV/u 18O ion irradiation of the natural uranium. The thorium wasradiochemically separated from the fixture of uranium and reaction products. Theactivity of thorium was measured by using an HPGe detector and a planar HPGedetector. The 238Th has been identified for the first time by measuring the growthand decay of the 7-rays from its daughter 238Pa. The half-life of 238Th was determinedto be 9.4f2.0 min. In addition, a new 7-ray of 89.010.3 keV with TI/2=8.911.5minwas found in the 7 spectrum gated with X-rays of Pa and assigned to 238Th P-- decaybased on measurements of transition energy and half life.展开更多
文摘An intense 14 MeV neutron source facility named OKTAVIAN was installed in the A15 building,Osaka University in 1981.Along the operation period,new radioisotopes with various half-life have been produced as neutron activation products in its concrete wall shield.In this work,we investigated the concrete wall in the heavy irradiation room of OKTAVIAN using gamma spectrometry method to discover the presence of radioisotope having large half-life value(long-lived radioisotope)as neutron activation products.Computational simulations were performed prior to measurement to predict the presence of long-lived radioisotopes by employing MCNP5 and FISPACT codes.A pre-calibrated Germanium detector with high energy resolution was employed to measure the concrete.Several long-lived activation products have been observed such as 152 Eu,54 Mn,65 Zn,22 Na and 60 Co.The activity of each radioisotope was derived after estimating the detector efficiency using MCNP5.As a result of the measurement and analysis,the followings are concluded:(1)Though presence of activation products represents radiological risk to everyone who performs an experimental activity in the irradiation room of the OKTAVIAN facility,the present result shows that past experiments were carried out safely without any significant additional exposure dose coming from the wall for the last 38 years.(2)The approximated total fluence of D-T neutrons to the wall was successfully estimated from the produced radioisotope,152 Eu,because it has the longest half-life of 13.5 years among the observed radioisotopes.(3)From the results of(1)and(2),it could be possible to estimate the total activity of the concrete wall in the OKTAVIAN facility,which is very essential and important information,because this would be very valuable for decommissioning or disposal of the facility in the future.
文摘A new nuclide (238)Th has been produced via multinucleon transferreaction by 60 MeV/u 18O ion irradiation of the natural uranium. The thorium wasradiochemically separated from the fixture of uranium and reaction products. Theactivity of thorium was measured by using an HPGe detector and a planar HPGedetector. The 238Th has been identified for the first time by measuring the growthand decay of the 7-rays from its daughter 238Pa. The half-life of 238Th was determinedto be 9.4f2.0 min. In addition, a new 7-ray of 89.010.3 keV with TI/2=8.911.5minwas found in the 7 spectrum gated with X-rays of Pa and assigned to 238Th P-- decaybased on measurements of transition energy and half life.
