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Journal Articles

Shielding performance of newly developed boron-loaded concrete for DT neutrons

Sato, Satoshi*; Konno, Chikara; Nakashima, Hiroshi; Shionaga, Ryosuke*; Nose, Hiroyuki*; Ito, Yuji*; Hashimoto, Hirohide*

Journal of Nuclear Science and Technology, 55(4), p.410 - 417, 2018/04

 Times Cited Count:1 Percentile:11.6(Nuclear Science & Technology)

In order to enhance the neutron shielding performance, we developed concrete with boron of more than 10 wt%. We performed a neutron shielding experiment using the mockup of the newly developed boron-loaded concrete and DT neutrons at FNS in JAEA, and measured the reaction rates of the $$^{93}$$Nb(n,2n)$$^{92m}$$Nb and $$^{197}$$Au(n,$$gamma$$)$$^{198}$$Au reactions in the mockup. The calculations were conducted by using MCNP-5.14 and FENDL-2.1. The calculation results agreed well with the measured ones, and we confirmed that the accuracy was very good on the atomic composition data of the boron-loaded concrete and their nuclear data. In addition, we calculated effective dose rates and reaction rates of the $$^{59}$$Co(n,$$gamma$$)$$^{60}$$Co and $$^{151}$$Eu(n,$$gamma$$)$$^{152}$$Eu reactions in the boron-loaded concrete and other concretes. It is concluded that the boron-loaded concrete has much better shielding performance for DT neutrons than other concretes.

Journal Articles

Selective detection using pulse time interval analysis for correlated events in Rn-progeny with a microsecond lifetime

Sanada, Yukihisa; Kobayashi, Hirohide; Furuta, Sadaaki; Nemoto, Kazuhiko*; Kawai, Keiichi*; Hashimoto, Tetsuo*

Radioisotopes, 55(12), p.727 - 734, 2006/12

The purpose of this study is to develop new measurement methods of radon progenies that discharged alpha-ray focused on pulse time interval. It is calculated that a delayed coincidence method, time-interval-analysis (TIA), has been applied to decay events on the microsecond time-scale (164microsecond). The measurement system with silicon detectors was produced and examined a basic performance of the system by using $$^{230}$$Th electrodeposited sources. This system was designed that it have shorter dead times. The results were as follows. (1) The theory of measurement $$^{214}$$Po using TIA methods was established. (2) Development of the system that measured $$^{214}$$Po. (3) Suggested that methods to examine a basic performance by using $$^{230}$$Th electrodeposited sources. It is scheduled to examine the method of subtracting the progenies of the thorium series, and to reflect this system in an actual work of radiation control in the future.

Journal Articles

Development of dust monitor for rapid detection of plutonium with background compensation system

Sanada, Yukihisa; Kobayashi, Hirohide; Hashimoto, Tetsuo*

Proceedings of 2nd Asian and Oceanic Congress Radiological Protection (AOCRP-2) (CD-ROM), p.313 - 317, 2006/10

The dust monitor for rapid detection of artificial nuclides such as Plutonium with Rn-progeny background compensation system was developed to apply a time interval analysis (TIA). The TIA method was applied to beta and $$alpha$$ decay events with microsecond scale (half-life of $$^{214}$$Po: 164 microsecond). In actual experiments, dust sample on the filter (HE-40T pore size: 8micrometer) was collected in a workspace at the JAEA reprocessing facility to compensate $$^{214}$$Bi-$$^{214}$$Po correlated events. As a result, total alpha-ray counting rate except for $$^{214}$$Po was 0 $$pm$$ 0.05 cps. The small $$^{241}$$Am source with dust sampling was measured for simulation of unexpected additional $$alpha$$-ray emitted radionuclides. The increment for $$alpha$$-ray counting rate due to the $$^{241}$$Am source could be clearly detected. The present method will apply for on-line monitoring of $$alpha$$-ray measurement, because the method is able to detect artificial nuclides by compensating any changes of background due to Rn-progeny.

JAEA Reports

Development of new $$alpha$$-ray measurement methods with radon suppression focused on pulse time interval

Sanada, Yukihisa; Nohara, Naofumi*; Adachi, Yasuyuki*; Nemoto, Kazuhiko*; Kawai, Keiichi*; Kobayashi, Hirohide; Hashimoto, Tetsuo*

JAEA-Technology 2005-009, 33 Pages, 2006/01

JAEA-Technology-2005-009.pdf:1.42MB

An $$alpha$$-ray measurement methods based on analyzing the time interval of pulses was newly developed. This method was developed aiming to suppress the background counts originated in progeny of uranium series. A delayed coincidence and time interval analysis (TIA) methods have been applied to measure a-b decay successive events (correlated events) on microsecond time-scale (164$$mu$$s). The measurement system have such functions with silicon detectors was developed intending to shorten the dead time. The basic performance of the system was examined by using $$^{230}$$Th electrodeposited sources. Follows were obtained in this work : The theory of measurement $$^{214}$$Po using TIA methods was established. Measurement system of $$^{214}$$Po was developed. Conformation methods of correlated events by using $$^{230}$$Th electrodeposited sources was suggested. The efficiency of correlated events in aerosol samples was estimated. The methods to measure correlated events was indicated by addition of $$^{230}$$Th. The method of subtracting the progenies of the thorium series are to examine.

Oral presentation

Rapid evaluation method of concentrations of radioactive material in air using background-compensated dust monitor

Sanada, Yukihisa; Kobayashi, Hirohide; Nemoto, Kazuhiko*; Kawai, Keiichi*; Hashimoto, Tetsuo*

no journal, , 

no abstracts in English

Oral presentation

Development of dust monitor for rapid detection of plutonium with background compensation system

Sanada, Yukihisa; Kobayashi, Hirohide; Hashimoto, Tetsuo*

no journal, , 

A dust monitor for rapid detection of artificial nuclides with Rn-progeny background compensation system was developed by applying a time interval analysis (TIA). A dust monitor with silicon semiconductor detector was constructed in combination with a special time recording device and a personal computer. Data of time intervals of neighboring pulses was analyzed by single time interval analysis (STA), which is one kind of the TIA method. Aerosol sample of natural nuclides was measured by this system. As a result, the counts derived from $$^{214}$$Bi-$$^{214}$$Po correlated events were certainly observed from 0 to 1ms of time interval region. This result suggested that selective detection of $$^{214}$$Bi-$$^{214}$$Po correlated events could be measured with this system. The present method will be applied for on-line monitoring of alpha-ray measurement, because the method is able to detect any additional artificial nuclides by compensating any changes of background due to Rn-progeny.

Oral presentation

Shielding experiment for new concrete with high concentration of boron by using DT neutrons, 1; Development of new concrete with high concentration of boron

Shionaga, Ryosuke*; Nose, Hiroyuki*; Ito, Yuji*; Kato, Hiroaki*; Hashimoto, Hirohide*; Sato, Satoshi

no journal, , 

In order to enhance the neutron shielding performance in nuclear power facilities, medical facilities and research facilities with large-scale accelerators, we have developed a new concrete with high concentration of boron of 10 weight %. Natural Colemanite minerals with a mass of boron were applied to the aggregates for the concrete. In addition, modification of the cement type and application of the special mixture material were performed to eliminate bad effects of the insufficient hardening and the strength degradation of the cement, and we successfully increased the boron concentration in the concrete up to 10 weight %. The flow rate in JIS flow test was about 150 mm before hardening of the material, which showed good flow property. We also confirmed that the compressive strength was about 40 N/mm$$^{2}$$ at the material age of 7 days. Based on the results, the block specimens were fabricated for the shielding experiment using DT neutrons.

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