This paper presents the calibration of a neutron dose rate meter and the evaluation of its calibration factors(CFs)in several neutron standard fields(i.e.,two standard fields with bare sources of252Cf and241Am-Be,and ...This paper presents the calibration of a neutron dose rate meter and the evaluation of its calibration factors(CFs)in several neutron standard fields(i.e.,two standard fields with bare sources of252Cf and241Am-Be,and five simulated workplace fields with241Am-Be moderated sources).The calibration in standard fields with bare sources was conducted by following the recommendations of the ISO 8529 standard.The measured total neutron ambient dose equivalent rates,denoted as H*(10)tot,were analyzed to obtain direct components,denoted as H*(10)dir,using a reduced fitting method.The CF was then calculated as the ratio between the conventional true value of the neutron ambient dose equivalent rate in a free field,denoted as H*(10)FF,and the value of H*(10)dir.In contrast,in the simulated workplace neutron fields,the calibration of the neutron dose rate meter was conducted by following the ISO 12789 standard.The CF was calculated as the ratio between the values of H*(10)totmeasured by a standard instrument(i.e.,Bonner sphere spectrometer)and the neutron dose rate meter.The CF values were obtained in the range of 0.88–1.0.The standard uncertainties(k=1)of the CFs were determined to be in the range of approximately 6.6–13.1%.展开更多
For radiation protection purposes, the neutron dose in carbon ion radiation therapy at the HIRFL (Heavy Ion Research Facility in Lanzhou) was investigated. The neutron dose from primary ^12C ions with a specific ene...For radiation protection purposes, the neutron dose in carbon ion radiation therapy at the HIRFL (Heavy Ion Research Facility in Lanzhou) was investigated. The neutron dose from primary ^12C ions with a specific energy of 100 MeV/u delivered from SSC was roughly measured with a standard Anderson-Broun rem-meter using a polyethylene target at various distances. The result shows that a maximum neutron dose contribution of 19 mSv in a typically surface tumor treatment was obtained, which is less than 1% of the planed heavy ion dose and is in reasonable agreement with other reports. Also the T-ray dose was measured in this experiment using a thermo luminescent detector.展开更多
The secondary neutron fields at the deep tumor therapy terminal at HIRFL(Heavy Ion Research Facility in Lanzhou) were investigated. The distributions of neutron ambient dose equivalent were measured with a FHT762Wen...The secondary neutron fields at the deep tumor therapy terminal at HIRFL(Heavy Ion Research Facility in Lanzhou) were investigated. The distributions of neutron ambient dose equivalent were measured with a FHT762Wendi-II neutron ambient dose equivalent meter as ^(12)C ions with energies of 165, 207, 270, and 350 Me V/u were bombarded on thick tissue-like targets. The thickness of targets used in the experiments was larger than the range of the carbon ions. The neutron spectra and dose equivalent were simulated by using FLUKA code, and the results agree well with the experimental data. The experiment results showed that the neutron dose produced by fragmentation reactions in tissue can be neglected in carbon-ion therapy, even considering their enhanced biological effectiveness.These results are also valuable for radiation protection, especially in the shielding design of high energy heavy ion medical machines.展开更多
In this paper,fast neutron inactivation effects of Bacillus subtilis were investigated with fission fast neutrons from CFBR-Ⅱreactor of INPC(Institute of Nuclear Physics and Chemistry)and mono-energetic neutrons from...In this paper,fast neutron inactivation effects of Bacillus subtilis were investigated with fission fast neutrons from CFBR-Ⅱreactor of INPC(Institute of Nuclear Physics and Chemistry)and mono-energetic neutrons from the Van de Graaff accelerator at Peking University.The method for determining the absorbed dose in the Bacillus subtilis suspension contained in test tubes is introduced.The absorbed dose,on account of its dependence on the volume and the form of confined state,was determined by combined experiments and Monte Carlo method.Using the calculation results of absorbed dose,the fast neutron inactivation effects on Bacillus subtilis were studied.The survival rates and absorbed dose curve was constructed.展开更多
In this work, natural neutron spectra at nine sites in Tibet region were measured using a multi-sphere neutron spectrometer. The altitude-dependence of the spectra total fluence rate and ambient dose equivalent rate w...In this work, natural neutron spectra at nine sites in Tibet region were measured using a multi-sphere neutron spectrometer. The altitude-dependence of the spectra total fluence rate and ambient dose equivalent rate were analyzed. From the normalized natural neutron spectra at different altitudes, the spectrum fractions for neutrons of greater than 0.1 MeV do not differ obviously, while those of the thermal neutrons differ greatly from each other. The total fluence rate, effective dose rate and the ambient dose equivalent rate varied with the altitude according to an exponential law.展开更多
The objective of this work was to use the Geant4 toolkit to perform simulation studies on the personal dose response of fluorescent nuclear track detectors(FNTDs).The entire structure of the FNTD response can be desig...The objective of this work was to use the Geant4 toolkit to perform simulation studies on the personal dose response of fluorescent nuclear track detectors(FNTDs).The entire structure of the FNTD response can be designed,and the detector's energy and dose responses can be optimized in a broad energy range(0.01 eV-20 MeV). In general, the detectors used ~6LiF and CH_2 converters that have high energy and high dose response at neutron energies lower than 10 eV and greater than 1 MeV, respectively. The method of least squares was used to optimize the dose response of H*(10) and the energy response corresponding to Rtotal. The values of the optimized response of H*(10) lie between 0.8 and 1.4, corresponding to the energy ranges 0.01 eV-70 keV and 4-14 MeV, respectively. This occupies nearly eight out of the nine orders of the total energy range. Even though the optimized response of Rtotal is constrained between 0.89 and 1.1 in the energy range of 0.01 eV-20 MeV, it is suitable for obtaining the broad neutron spectrum of fluence with good accuracy.展开更多
An analysis of the neutron activation and shutdown dose rates was performed for the EAST high-power deuterium neutral beam injector test facility(EAST NBITF) by using the multiparticle transport code FLUKA2011.2. Also...An analysis of the neutron activation and shutdown dose rates was performed for the EAST high-power deuterium neutral beam injector test facility(EAST NBITF) by using the multiparticle transport code FLUKA2011.2. Also, the neutron and neutron-induced gamma spectra of the facility's vacuum vessel were evaluated. The results identified the major radionuclides^(99) Mo,^(65)Ni,^(58) Co,^(56)Mn, and^(51) Cr for the vacuum vessel and the primary nuclide^(64) Cu for both the ion dump and the calorimeter.The simulated results indicated that, when the EAST NBITF operates within the design parameters of deuterium energy 80 ke V, current 50 A, and pulse 100 s, the neutron intensity will achieve 10^(11)n/s with no radiation safety problems after the EAST NBITF shuts down.展开更多
The Chinese Academy of Science has launched a thorium-based molten-salt reactor(TMSR)research project with a mission to research and develop a fission energy system of the fourth generation.The TMSR project intends to...The Chinese Academy of Science has launched a thorium-based molten-salt reactor(TMSR)research project with a mission to research and develop a fission energy system of the fourth generation.The TMSR project intends to construct a liquid fuel molten-salt reactor(TMSR-LF),which uses fluoride salt as both the fuel and coolant,and a solid fuel molten-salt reactor(TMSR-SF),which uses fluoride salt as coolant and TRISO fuel.An optimized 2 MWth TMSR-LF has been designed to solve major technological challenges in the Th-U fuel cycle.Preliminary conceptual shielding design has also been performed to develop bulk shielding.In this study,the radiation dose and temperature distribution of the shielding bulk due to the core were simulated and analyzed by performing Monte Carlo simulations and computational fluid dynamics(CFD)analysis.The MCNP calculated dose rate and neutron and gamma spectra indicate that the total dose rate due to the core at the external surface of the concrete wall was 1.91μSv/h in the radial direction,1.16μSv/h above and 1.33μSv/h below the bulk shielding.All the radiation dose rates due to the core were below the design criteria.Thermal analysis results show that the temperature at the outermost surface of the bulk shielding was 333.86 K,which was below the required limit value.The results indicate that the designed bulk shielding satisfies the radiation shielding requirements for the 2 MWth TMSR-LF.展开更多
The possibility of using 209Bi as a new threshold detector to measurc high-energy neutrons was investigated for the first time. At the same time the experiment measured successfully the emitted neutron fiuence rate, e...The possibility of using 209Bi as a new threshold detector to measurc high-energy neutrons was investigated for the first time. At the same time the experiment measured successfully the emitted neutron fiuence rate, energy spectrum and dose equivalent rate distributions in the heavy ion target area using a detector complex including 209Bi, 115In, 27A1, 19F and 12C samples.展开更多
This paper presents the experimental results of a combined irradiation environment of neutron and gamma rays on 80C196KC20, which is a 16-bit high performance member of the MCS96 microcontroller family. The electrical...This paper presents the experimental results of a combined irradiation environment of neutron and gamma rays on 80C196KC20, which is a 16-bit high performance member of the MCS96 microcontroller family. The electrical and functional tests were made in three irradiation environments: neutron, gamma rays, combined irradiation of neutron and gamma rays. The experimental results show that the neutron irradiation can affect the total ionizing dose behaviour. Compared with the single radiation environment, the microcontroller exhibits considerably more severe degradation in neutron and gamma ray synergistic irradiation. This phenomenon may cause a significant hardness assurance problem.展开更多
Neutron energy, fluence rate, angular distributions and dose equivalent rate distributions around the thick Be, Cu, An targets bombarded by 50 MeV/u 18O-ion were measured using a threshold detector activation method. ...Neutron energy, fluence rate, angular distributions and dose equivalent rate distributions around the thick Be, Cu, An targets bombarded by 50 MeV/u 18O-ion were measured using a threshold detector activation method. At the same time,the neutron yields of 18O-ion and the neutron emission rates in the forward direction were obtained approximately.展开更多
INTRODUCTIONTo date ,the major therapy for rectal carcinoma is extensive abdomino-perineal resection[1]. Unfortunately ,after resection of rectal carcinoma ,many patients still die of blood-borne metastases ,usually i...INTRODUCTIONTo date ,the major therapy for rectal carcinoma is extensive abdomino-perineal resection[1]. Unfortunately ,after resection of rectal carcinoma ,many patients still die of blood-borne metastases ,usually in the liver or lungs ,or local prlvic recurrence[2,3],which is the major cause of morbidity and mortality in patients with rectal carcinoma .Pre-or postoperative radiotherapy can reduce the incidence of local rdcurrence[4-7].展开更多
Correction factors of both Rem-meters, the 10 inch diameter single-sphere Remmeter and the standard A-B Rem-meter, were estimated for measuring high energy neutron dose equivalent outside a concrete shielding wall and...Correction factors of both Rem-meters, the 10 inch diameter single-sphere Remmeter and the standard A-B Rem-meter, were estimated for measuring high energy neutron dose equivalent outside a concrete shielding wall and the effects that the emitted neutron spectra become remarkably "harder" penetrated through a concrete shielding wall, and the energy response of the Rem-meter were taken in account. The estimated results could be applied in the measurement of neutron dose equivalent for the intermediate energy heavy ion reactions to avoid the difficulty induced by the energy response of the Rem-meters.展开更多
Fluence rates and angular distributions of the neutron emitted by75 MeV/u 12C-ion bombardment on thick Be and An targets have been measured bymeans of the threshold detector activation method. Based on that, the neutr...Fluence rates and angular distributions of the neutron emitted by75 MeV/u 12C-ion bombardment on thick Be and An targets have been measured bymeans of the threshold detector activation method. Based on that, the neutron yields,emission rates in the forward direction and neutron dose equivalent rate distributionswere deduced.展开更多
The problems of formation of neutron fields are using the radionuclide neutron sources. Theoretical estimates of the contribution to the values of the neutron flux density, kerma and ambient dose equivalent scattered ...The problems of formation of neutron fields are using the radionuclide neutron sources. Theoretical estimates of the contribution to the values of the neutron flux density, kerma and ambient dose equivalent scattered neutron radiation under various conditions of use of neutron sources. The coefficients for calculating the values of different variables at different distances from the source are using the measured values at certain distances from the source. The values of the average energies for neutron spectra are obtained using the radionuclide neutron sources.展开更多
The 252Cf neutron brachytherapy devices were designed and manufactured after solving those problems:the shield difficulties for 252Cf neutron;the method and facilities for 252Cf neutron source deliver;the dose calcula...The 252Cf neutron brachytherapy devices were designed and manufactured after solving those problems:the shield difficulties for 252Cf neutron;the method and facilities for 252Cf neutron source deliver;the dose calculation and measurement for 252Cf neutron.From 1999 to 2009,more than twenty 252Cf neutron brachytherapy devices had been installed in China.The Chinese radiation oncologists implemented the 252Cf neutron brachytherapy on more than 5 000 different kinds of cancer patients,including cervix cancer;endometrium cancer and achieved ideal results.For special presentation,they had breakthrough on radical treatment for low lying rectal adenocarcinoma with sphincter preservation and melanoma patients after the modification of 252Cf neutron intracavitary applicator and dose calibration.展开更多
基金by the National Foundation for Science and Technology Development of Vietnam(No.103.04-2017.37)。
文摘This paper presents the calibration of a neutron dose rate meter and the evaluation of its calibration factors(CFs)in several neutron standard fields(i.e.,two standard fields with bare sources of252Cf and241Am-Be,and five simulated workplace fields with241Am-Be moderated sources).The calibration in standard fields with bare sources was conducted by following the recommendations of the ISO 8529 standard.The measured total neutron ambient dose equivalent rates,denoted as H*(10)tot,were analyzed to obtain direct components,denoted as H*(10)dir,using a reduced fitting method.The CF was then calculated as the ratio between the conventional true value of the neutron ambient dose equivalent rate in a free field,denoted as H*(10)FF,and the value of H*(10)dir.In contrast,in the simulated workplace neutron fields,the calibration of the neutron dose rate meter was conducted by following the ISO 12789 standard.The CF was calculated as the ratio between the values of H*(10)totmeasured by a standard instrument(i.e.,Bonner sphere spectrometer)and the neutron dose rate meter.The CF values were obtained in the range of 0.88–1.0.The standard uncertainties(k=1)of the CFs were determined to be in the range of approximately 6.6–13.1%.
基金Supported by Foundation of Director of the Institute of Moderm Physics,Chinese Academy of Sciences,China
文摘For radiation protection purposes, the neutron dose in carbon ion radiation therapy at the HIRFL (Heavy Ion Research Facility in Lanzhou) was investigated. The neutron dose from primary ^12C ions with a specific energy of 100 MeV/u delivered from SSC was roughly measured with a standard Anderson-Broun rem-meter using a polyethylene target at various distances. The result shows that a maximum neutron dose contribution of 19 mSv in a typically surface tumor treatment was obtained, which is less than 1% of the planed heavy ion dose and is in reasonable agreement with other reports. Also the T-ray dose was measured in this experiment using a thermo luminescent detector.
文摘The secondary neutron fields at the deep tumor therapy terminal at HIRFL(Heavy Ion Research Facility in Lanzhou) were investigated. The distributions of neutron ambient dose equivalent were measured with a FHT762Wendi-II neutron ambient dose equivalent meter as ^(12)C ions with energies of 165, 207, 270, and 350 Me V/u were bombarded on thick tissue-like targets. The thickness of targets used in the experiments was larger than the range of the carbon ions. The neutron spectra and dose equivalent were simulated by using FLUKA code, and the results agree well with the experimental data. The experiment results showed that the neutron dose produced by fragmentation reactions in tissue can be neglected in carbon-ion therapy, even considering their enhanced biological effectiveness.These results are also valuable for radiation protection, especially in the shielding design of high energy heavy ion medical machines.
基金Supported by Science and Technology Foundation of China Academy of Engineering Physics(No.2008A0103002)
文摘In this paper,fast neutron inactivation effects of Bacillus subtilis were investigated with fission fast neutrons from CFBR-Ⅱreactor of INPC(Institute of Nuclear Physics and Chemistry)and mono-energetic neutrons from the Van de Graaff accelerator at Peking University.The method for determining the absorbed dose in the Bacillus subtilis suspension contained in test tubes is introduced.The absorbed dose,on account of its dependence on the volume and the form of confined state,was determined by combined experiments and Monte Carlo method.Using the calculation results of absorbed dose,the fast neutron inactivation effects on Bacillus subtilis were studied.The survival rates and absorbed dose curve was constructed.
基金Supported by the National Natural Science Foundation of China(No.11575294)
文摘In this work, natural neutron spectra at nine sites in Tibet region were measured using a multi-sphere neutron spectrometer. The altitude-dependence of the spectra total fluence rate and ambient dose equivalent rate were analyzed. From the normalized natural neutron spectra at different altitudes, the spectrum fractions for neutrons of greater than 0.1 MeV do not differ obviously, while those of the thermal neutrons differ greatly from each other. The total fluence rate, effective dose rate and the ambient dose equivalent rate varied with the altitude according to an exponential law.
基金funded by the International Fusion Reactor Experiment Program(No.2014GB112004)
文摘The objective of this work was to use the Geant4 toolkit to perform simulation studies on the personal dose response of fluorescent nuclear track detectors(FNTDs).The entire structure of the FNTD response can be designed,and the detector's energy and dose responses can be optimized in a broad energy range(0.01 eV-20 MeV). In general, the detectors used ~6LiF and CH_2 converters that have high energy and high dose response at neutron energies lower than 10 eV and greater than 1 MeV, respectively. The method of least squares was used to optimize the dose response of H*(10) and the energy response corresponding to Rtotal. The values of the optimized response of H*(10) lie between 0.8 and 1.4, corresponding to the energy ranges 0.01 eV-70 keV and 4-14 MeV, respectively. This occupies nearly eight out of the nine orders of the total energy range. Even though the optimized response of Rtotal is constrained between 0.89 and 1.1 in the energy range of 0.01 eV-20 MeV, it is suitable for obtaining the broad neutron spectrum of fluence with good accuracy.
基金supported by the International S&T Cooperation Program of China(No.2014DFG61950)National Magnetic Confinement Fusion Science Program(No.2013GB101001)the National Natural Science Foundation of China(No.11405207)
文摘An analysis of the neutron activation and shutdown dose rates was performed for the EAST high-power deuterium neutral beam injector test facility(EAST NBITF) by using the multiparticle transport code FLUKA2011.2. Also, the neutron and neutron-induced gamma spectra of the facility's vacuum vessel were evaluated. The results identified the major radionuclides^(99) Mo,^(65)Ni,^(58) Co,^(56)Mn, and^(51) Cr for the vacuum vessel and the primary nuclide^(64) Cu for both the ion dump and the calorimeter.The simulated results indicated that, when the EAST NBITF operates within the design parameters of deuterium energy 80 ke V, current 50 A, and pulse 100 s, the neutron intensity will achieve 10^(11)n/s with no radiation safety problems after the EAST NBITF shuts down.
基金Supported by the"Strategic Priority Research Program"of the Chinese Academy of Sciences(No.XD02005002)
文摘The Chinese Academy of Science has launched a thorium-based molten-salt reactor(TMSR)research project with a mission to research and develop a fission energy system of the fourth generation.The TMSR project intends to construct a liquid fuel molten-salt reactor(TMSR-LF),which uses fluoride salt as both the fuel and coolant,and a solid fuel molten-salt reactor(TMSR-SF),which uses fluoride salt as coolant and TRISO fuel.An optimized 2 MWth TMSR-LF has been designed to solve major technological challenges in the Th-U fuel cycle.Preliminary conceptual shielding design has also been performed to develop bulk shielding.In this study,the radiation dose and temperature distribution of the shielding bulk due to the core were simulated and analyzed by performing Monte Carlo simulations and computational fluid dynamics(CFD)analysis.The MCNP calculated dose rate and neutron and gamma spectra indicate that the total dose rate due to the core at the external surface of the concrete wall was 1.91μSv/h in the radial direction,1.16μSv/h above and 1.33μSv/h below the bulk shielding.All the radiation dose rates due to the core were below the design criteria.Thermal analysis results show that the temperature at the outermost surface of the bulk shielding was 333.86 K,which was below the required limit value.The results indicate that the designed bulk shielding satisfies the radiation shielding requirements for the 2 MWth TMSR-LF.
基金Supported by the National Natural Science Foundation of China(19875070)
文摘The possibility of using 209Bi as a new threshold detector to measurc high-energy neutrons was investigated for the first time. At the same time the experiment measured successfully the emitted neutron fiuence rate, energy spectrum and dose equivalent rate distributions in the heavy ion target area using a detector complex including 209Bi, 115In, 27A1, 19F and 12C samples.
文摘This paper presents the experimental results of a combined irradiation environment of neutron and gamma rays on 80C196KC20, which is a 16-bit high performance member of the MCS96 microcontroller family. The electrical and functional tests were made in three irradiation environments: neutron, gamma rays, combined irradiation of neutron and gamma rays. The experimental results show that the neutron irradiation can affect the total ionizing dose behaviour. Compared with the single radiation environment, the microcontroller exhibits considerably more severe degradation in neutron and gamma ray synergistic irradiation. This phenomenon may cause a significant hardness assurance problem.
文摘Neutron energy, fluence rate, angular distributions and dose equivalent rate distributions around the thick Be, Cu, An targets bombarded by 50 MeV/u 18O-ion were measured using a threshold detector activation method. At the same time,the neutron yields of 18O-ion and the neutron emission rates in the forward direction were obtained approximately.
基金Supported by the National Natural-Scientific Foundation,No.39500043
文摘INTRODUCTIONTo date ,the major therapy for rectal carcinoma is extensive abdomino-perineal resection[1]. Unfortunately ,after resection of rectal carcinoma ,many patients still die of blood-borne metastases ,usually in the liver or lungs ,or local prlvic recurrence[2,3],which is the major cause of morbidity and mortality in patients with rectal carcinoma .Pre-or postoperative radiotherapy can reduce the incidence of local rdcurrence[4-7].
文摘Correction factors of both Rem-meters, the 10 inch diameter single-sphere Remmeter and the standard A-B Rem-meter, were estimated for measuring high energy neutron dose equivalent outside a concrete shielding wall and the effects that the emitted neutron spectra become remarkably "harder" penetrated through a concrete shielding wall, and the energy response of the Rem-meter were taken in account. The estimated results could be applied in the measurement of neutron dose equivalent for the intermediate energy heavy ion reactions to avoid the difficulty induced by the energy response of the Rem-meters.
文摘Fluence rates and angular distributions of the neutron emitted by75 MeV/u 12C-ion bombardment on thick Be and An targets have been measured bymeans of the threshold detector activation method. Based on that, the neutron yields,emission rates in the forward direction and neutron dose equivalent rate distributionswere deduced.
文摘The problems of formation of neutron fields are using the radionuclide neutron sources. Theoretical estimates of the contribution to the values of the neutron flux density, kerma and ambient dose equivalent scattered neutron radiation under various conditions of use of neutron sources. The coefficients for calculating the values of different variables at different distances from the source are using the measured values at certain distances from the source. The values of the average energies for neutron spectra are obtained using the radionuclide neutron sources.
文摘The 252Cf neutron brachytherapy devices were designed and manufactured after solving those problems:the shield difficulties for 252Cf neutron;the method and facilities for 252Cf neutron source deliver;the dose calculation and measurement for 252Cf neutron.From 1999 to 2009,more than twenty 252Cf neutron brachytherapy devices had been installed in China.The Chinese radiation oncologists implemented the 252Cf neutron brachytherapy on more than 5 000 different kinds of cancer patients,including cervix cancer;endometrium cancer and achieved ideal results.For special presentation,they had breakthrough on radical treatment for low lying rectal adenocarcinoma with sphincter preservation and melanoma patients after the modification of 252Cf neutron intracavitary applicator and dose calibration.