BF3 Counter Research Articles

Neutron Leakage From Polyethylene Slit

A measurement of neutron dose rate on iron-polyethylene shielding structure was carried out by 252Cf source. Simulated geometry was slit-like opening of polyethylene in iron slab and polyethylene slab shielding.These experiment was done at research facility of Hazama Co,. Iron slab and polyethylene slab thickness were 10 cm each. A gap of the polyethylene was simulated. Neutron REM-counter, polyethylene covered BF3 counter (STUDSVIK 2202-D), was used for measurement of streaming neutron dose equivalent. The solid state track detector (SSTD), allyl-diglycol-carbonate, were used for measurement of fast neutron dose equivalent in the range of 170Kev to 15Mev.The experimental data was obtained against gap width, source location and detector location.Obtained data shows strong correlation between dose rate and above parameters.These data was investigated in the view of to make use of actual facility design and compared with calculation such as MCNP4B.From the result of gap streaming experiment and calculation, we obtained allowable gap width as 6mm for this case (10cm polyethylene thickness).

Measurements of Neutron-induced Fission Cross Section of Americium-243 from Thermal Neutron Energy to 15 keV Using Lead Slowing-down Spectrometer and Thermal Neutron Facility

The neutron-induced fission cross section of 243Am was measured relative to that of 235U from thermal neutron energy to 15 keV making use of a double fission chamber with 243Am and 235U electrodeposited layers.The data above 0.05 eV were measured using a lead slowing-down spectrometer coupled to an electron linear accelerator. A relative measurement to the 10B(n, α) reaction was also made using a BF3 counter at energies below 1 keV, and normalized to the absolute value obtained by using the cross section of the 235U(n,/) reaction between 200eV and IkeV. The existing experimental data by Wisshak and Käppeler, and by Knitter and Budtz-Jørgensen are in general agreement with the current measurement in the relevant energy region. However, the data by Seeger are considerably higher. The evaluated nuclear data in JENDL-3.2, ENDF/B-VI and JEF-2.2, whose data were broadened by the energy resolution function of the spectrometer, have been compared with the measured result.The fission cross section for thermal neutrons was measured in a neutron field with a pure Maxwellian spectrum. The derived result at 0.0253 eV is 81.3±2.5 mb. The data by Wagemans et al. and in ENDF/B-VI are close to the current measurement. However, the values by Asghar et al., Gavrilov et al. and Mughabghab, and the evaluated data in JENDL-3.2 and JEF-2.2 are discrepant from the current result by a factor of 1.4 to 2.4.

Measurements of Neutron-induced Fission Cross Section of Americium-243 from Thermal Neutron Energy to 15 keV Using Lead Slowing-down Spectrometer and Thermal Neutron Facility.

The neutron-induced fission cross section of 243Am was measured relative to that of 235U from thermal neutron energy to 15 keV making use of a double fission chamber with 243Am and 235U electrodeposited layers. The data above 0.05 eV were measured using a lead slowing-down spectrometer coupled to an electron linear accelerator. A relative measurement to the 10B(n, α) reaction was also made using a BF3 counter at energies below 1 keV, and normalized to the absolute value obtained by using the cross section of the 235U(n,/) reaction between 200eV and IkeV. The existing experimental data by Wisshak and Käppeler, and by Knitter and Budtz-Jørgensen are in general agreement with the current measurement in the relevant energy region. However, the data by Seeger are considerably higher. The evaluated nuclear data in JENDL-3.2, ENDF/B-VI and JEF-2.2, whose data were broadened by the energy resolution function of the spectrometer, have been compared with the measured result. The fission cross section for thermal neutrons was measured in a neutron field with a pure Maxwellian spectrum. The derived result at 0.0253 eV is 81.3±2.5 mb. The data by Wagemans et al. and in ENDF/B-VI are close to the current measurement. However, the values by Asghar et al., Gavrilov et al. and Mughabghab, and the evaluated data in JENDL-3.2 and JEF-2.2 are discrepant from the current result by a factor of 1.4 to 2.4.

Measurements and simulations of the neutron production at W7-AS

The 2.5 MeV neutron diagnostic system on the W7-AS stellarator comprises a set of BF3 and He3 neutron counters, a NE-213 scintillator and activation foils. The neutron counter set provides a dynamic range of several orders of magnitude while the scintillator provides fast resolution needed for studying transient events. The counters are calibrated in situ using a Pu/B238 neutron source placed at discrete points inside the vacuum vessel. The activation samples have been used to determine the total neutron yields as well as to measure the fluence of fast and thermal neutrons at various positions in the diagnostic hall of W7-AS. Neutron transport calculations have been performed using the Monte Carlo neutron photon transport code in order to determine the neutron fluence and energy distribution at the irradiation positions and to simulate the measured counter signals for the in situ calibration. The accuracy of the neutronics simulations depends on the quality of the geometric model and the material composition of major structural components.

Review of diagnostic methods for TFTR D–T radiation shielding and neutronics studies

The methods and instrument systems used for TFTR D–T radiation shielding and neutronics studies involving signal strengths ranging over 10 orders of magnitude are reviewed. Neutron and gamma dose-equivalent, fluence, spectral, and materials activation measurements have been performed at various locations from the TFTR vessel to the nearest property lines. The detection systems include 3He, BF3, and 235U proportional counters in moderated spheres, Bonner sphere arrays, advanced thermoluminescent detectors, argon ionization chambers, intrinsic Ge gamma detectors, and activation foil spectrometry methods.

Absolute calibration of neutron counters on the Compact Helical System

A calibration experiment of the neutron counters of the Compact Helical System (CHS) has been carried out in order to determine the calibration factor which relates the neutron-counter output to the extended neutron source of a torus plasma. The instruments employed in the present experiment include a BF3 proportional counter, a 3He proportional counter, an NE213 organic liquid scintillator. The BF3 counter was installed at the center of the CHS torus and the other two detectors were installed outside the torus. A total of 64 toroidal angles along the magnetic axis of plasma were surveyed by the movement of a 252Cf neutron source. The poloidal cross section of the CHS plasma is elliptical in shape and rotates toroidally with the same period as that of the helical coil. The spatial distribution of 25 local point efficiencies in three poloidal cross sections with elongated orientations of 0°, 45°, and 90° were investigated in order to determine the influence of the plasma profile on the calibration factor. The shadow and scattering effects were clearly observed by the center counter when the source was located behind the helical coil. The calibration factor for the BF3 counter, obtained by averaging the point efficiencies over all the toroidal angles, was 3.6×10−4 counts per neutron, about several ten times greater than those of the counters located outside the torus. Details of the calibration setup and the analysis of experimental results are presented.

Treatment Planning of Boron Neutron Capture Therapy: Measurements and Calculations

A clinical boron neutron capture therapy (BNCT) facility, employing a high intensity epithermal neutron beam, has recently become available at the High Flux Reactor (HFR) in Petten. Another epithermal beam has been constructed at the Low Flux Reactor (LFR) to test the behaviour of a mixed epithermal neutron and photon field in water phantoms. The neutron and photon fluence distributions have been measured with a BF3 counter and a 235U fission counter and with a GM counter and a Mg(Ar) ionisation chamber, respectively. Absolute determination of the neutron fluence has been performed with foil stacks and of the gamma ray dose with TLD chips. For the design of a treatment planning system for BNCT, the use of a Monte Carlo technique has been investigated. The outcome of these calculations fits the measurements within 1%.

Treatment Planning of Boron Neutron Capture Therapy: Measurements and Calculations

A clinical boron neutron capture therapy (BNCT) facility, employing a high intensity epithermal neutron beam, has recently become available at the High Flux Reactor (HFR) in Petten. Another epithermal beam has been constructed at the Low Flux Reactor (LFR) to test the behaviour of a mixed epithermal neutron and photon field in water phantoms. The neutron and photon fluence distributions have been measured with a BF3 counter and a 235U fission counter and with a GM counter and a Mg(Ar) ionisation chamber, respectively. Absolute determination of the neutron fluence has been performed with foil stacks and of the gamma ray dose with TLD chips. For the design of a treatment planning system for BNCT, the use of a Monte Carlo technique has been investigated. The outcome of these calculations fits the measurements within 1%.

Determination of water in zeolites by a neutron reflection method

Water content in zeolites has been determined by an improved neutron reflection method using a Pu-Be neutron source of 106 n·s−1 intensity and a BF3 counter. It was found that the water content of different types of zeolites collected in Hungary varies between 9 and 12 wt.%. The standard deviation of the determination does not exceed 0.5 wt.%. The matrix effect on the sensitivity and accuracy was also studied. An approximate relation is given between the count rate and the neutron physical parameters of the samples.

Electrochemical cold fusion trials at IPP garching

Following the report of Fleischmann and Pons,(1) we (The Bavarian Bubble Bottle Team) have attempted to reproduce their claims of cold nuclear fusion, and failed. We note that our measurements would not be able to detect neutrons at the level of Joneset al.(2) Three electrolytic cell experiments were conducted using palladium cathodes and Platinum anodes, in a 0.1-Molar solution of LiD in heavy water, without any signs of neutrons, tritium, or gammas above backgrounds, and within ±0.3 watt accuracy calorimetry, no excess heating. Excess heating at the levels of F&P would have been easily detected, if present. Intrinsic tritium, differing from each D2O bottle tested, was however observed. The longest duration experiment ran for 21 days, and was an attempt to duplicate the large “melting incident” of F&P. This was terminated on April 28, 1989, by throwing the vacuum-cast 22 gram, deuterium-loaded palladium cathode directly into liquid nitrogen, immediately next to a bare BF3 counter (backed by 25 cm of moderator), in order to attempt one of the Italian ENEA neutron production variants. No neutrons above backgrounds were seen, while counting for 1 hour, and also none while the piece warmed to room temperature over the next hour. Post-mortem analysis of the darkened, hardened Pd piece showed large crystal grains (up to 2 mm × 2 mm), and continuing evolution of gas bubbles at the grain boundaries even days after the experiment was ended. eight weeks after loading, the catalytically-active palladium piece continued to create heavy water (with exposure to oxygen in the air).

Deep underground neutron flux measurement with large BF3 counters

In this paper, we present deep underground neutron flux measurements performed by large BF3 counters in the Gran Sasso underground laboratory. A neutron flux of (1.08±0.02)·10−6 cm−2 s−1 for the thermal component and (1.98±0.05)·10−6 cm−2 s−1 for the epithermal one [here (50·10−3÷1·103) eV] is found. The fast component with an energy over 2.5 MeV turns out to be equal to (0.23±0.07)·10−6 cm−2 s−1 and its energy distribution appears to be compatible with a fission spectrum.

The photoneutron cross section of 10B

The photoneutron cross section of 10B was measured from threshold to 24.5 MeV with bremsstrahlung from a 30 MeV electron synchrotron using yield scanning techniques. Neutrons were detected by a high efficiency BF 3-counter detection system. The cross section shows a split E1-giant resonance region with major maxima at 20.2 and 23.0 MeV and a very minor resonance at 17.0 MeV. Apart from these the cross section is void of structure.

球形減速材付ＢＦ３比例計数管のエネルギー応答特性の評価

Presented are experimental and theoretical determinations of multisphere moderated BF3 counter responses. Eight spheres are used with different thicknesses ranging from 1 to 14cm of polyethylene moderators, and the central thermal neutron detector is a 2 inch diameter BF3 counter. The counter responses were measured for thermal and monoenergetic neutrons of energies 0.051, 0.144, 0.350, 0.565, 1.20, 2.50, 5.0, 15.2MeV. Calculations of the counter responses were also carried out by using one-dimensional discrete ordinates transport code, ANISN-JR. The experimental and theoritical results were in a good agreement except in the case for 1cm thickness of moderator at neutron energies higher than 2.5MeV. Energy response functions were finally estimated by using the experimental and calculated results. The measured and calculated sensitivities of the counter for 252Cf neutrons also showed good agreements.

A feasibility study for the in vivo measurement of beryllium by photonuclear activation

Diagnosis of the beryllium-induced disease, berylliosis, is often difficult and always requires that the presence of the metal in tissue be demonstrated. The feasibility of developing an in vivo method of measurement, which exploits the uniquely low photonuclear reaction threshold of 1.67 MeV in beryllium, has been investigated. Suitable photon sources and detector systems were assessed, both experimentally by phantom studies and theoretically by use of a Monte-Carlo neutron transport code. It is concluded that by using a filtered source of 124Sb for bilateral irradiation of the chest, and an array of twenty BF3 counters, beryllium could be measured to an accuracy of 0.33 mg per lung, which corresponds to a 2 SD detection limit of 0.67 mg, for a skin dose of 50 mGy delivered within a period of 90 s. Such a facility would be capable of contributing to the aetiology of the disease in a large proportion of cases, but the wider use of the method for screening exposed workers would require further improvements in detection efficiency.

The preparation and characterization of transition metal nitride films: P T Dawson and S A J Stazky,J Vac Sci Technol, 20 (4), 1982, 966–967

This paper describes the measurement of D-D fusion neutrons in the toroidal stellarator plasmas on Heliotron E. We used three moderated 3He counters and a moderated BF3 counter. Calibration of neutron detectors was previously done with a 252Cf spontaneous fission neutron source. We describe the measured fusion neutron emissions with several discharge conditions with hydrogen neutral beam injection heating to the deuterium plasmas. The Heliotron E plasmas are usually initiated by electron cyclotron resonance heating at a magnetic field of 1.9 T without an ohmic heating plasma current. We have tried to deduce the central deuterium ion temperature from measured neutron flux and line-averaged electron density. We have compared the central ion temperatures by neutron flux, with the passive charge exchanged particle analyses and diamagnetic stored energy. We discuss the possible error sources for the central neutron deduced deuterium temperature.

Development of long-life BF3 counters.

In order to improve the well-known short operational life time of BF3 counters, three potential adsorbents for impurity gases (graphite, activated charcoal and a zirconium-aluminum mixture) were introduced into BF3 counters in the form of coating on the aluminum cathode surface. Tests in γ fields revealed that a partial coating of activated charcoal provides the best result. The improvement of their operational life in γ fields was about three orders of magnitude in terms of tolerable exposure. Many counters with a partial coating of activated charcoal were further tested from the following viewpoints: background noise, vibration and shock, γ pulse discrimination, operational life in a neutron field and non-operational in-reactor exposure life. The results were satisfactory for reactor control and protection usage.

Environmental neutron measurements around nuclear facilities with moderated-type neutron detector.

A cylindrical BF3 counter with cylindrical polyethylene moderators of 1-, 3-, 6- and 10-cm wall thickness were developed for neutron spectrometry, having response functions calculated by the time-dependent multi-group Monte Carlo code, TMMCR, and evaluated by a time-of-flight experiment in the energy region from epithermal to about 50 keV. This system of neutron detectors was used to measure the environmental neutron spectrum and dose equivalent around a 252Cf fission neutron source, a fast neutron source reactor, a cyclotron and an electron synchrotron. The neutron spectrum and dose obtained by this detector system showed very good agreement with those measured by a commercially available neutron rem counter and calculated by our MMCR Monte Carlo code. As a result of these comparisons, this detector system has been established as a standard spectrometer and dosimeter for environmental measurements around nuclear facilities.

A Non-Destructive Method for Determining the Distribution of Soil Water Content by Measuring Fast Neutron Transmission Using an NE-213 Organic Scintillator

A method of measuring the water content distribution in a soil layer packed in a column, using fast neutron transmission, has been developed. The calibration curve of the water content was obtained from the rate of decrease of fast neutrons per unit of water content. An NE-213 organic scintillator (2'' in diameter × 2'' in length) and Cf-252(273 µCi) were used as the fast neutron detector and neutron source respectively. The distribution curve of soil water content obtained by the present method was consistent with that obtained by the destructive drying method. The NE-213 scintillator was superior to other conventional detectors (3He, BF3 counter) in measurement accuracy, spatial resolution and measurement sensitivity. The relative error and sensitivity of the present method are discussed in detail in this report.

Measuring Snow Water Equivalent by Cosmic Radiation

We have reduced the time taken for measurement of snow water equivalent using cosmic radiation by two to four hours with an accuracy of 1 cm of water equivalent. When BF3 counters were used by Kodama in 1975, it took three days. For comparison we sometimes still have to make measurements manually or automatically in flat areas. These measurements can then be compared with measurements from avalanche starting zones where conditions can be quite different because of wind or ablation.For avalanche forecasting, or in similar situations, when an accuracy of 1 cm is needed within a few hours, we suggest the use of scintillation counters with a doped plastic material. The greatest accuracy is obtained by using a separate site where values are recorded without snow. In this case 200 000 pulses per hour are obtained (absorption length of 400 cm) which after measurements of 2 h duration gives the desired error of 1 cm of water. After 8 h the error is 0.5 cm of water, and after 24 h it is 0.3 cm of water. At an altitude of 2 000 m at which most avalanches are released, the count rate is doubled and the measuring error is 0.7 of that at sea-level. At an altitude of 3 000 m the count rate is four times that at sea-level. In other regions at other latitudes and elevations other values would be found.The necessary equipment can be built into the ground in autumn so that the surface is level with the ground. A slot antenna of frequency around 400 MHz is used for transmission of the data.

Measuring Snow Water Equivalent by Cosmic Radiation

We have reduced the time taken for measurement of snow water equivalent using cosmic radiation by two to four hours with an accuracy of 1 cm of water equivalent. When BF3 counters were used by Kodama in 1975, it took three days. For comparison we sometimes still have to make measurements manually or automatically in flat areas. These measurements can then be compared with measurements from avalanche starting zones where conditions can be quite different because of wind or ablation. For avalanche forecasting, or in similar situations, when an accuracy of 1 cm is needed within a few hours, we suggest the use of scintillation counters with a doped plastic material. The greatest accuracy is obtained by using a separate site where values are recorded without snow. In this case 200 000 pulses per hour are obtained (absorption length of 400 cm) which after measurements of 2 h duration gives the desired error of 1 cm of water. After 8 h the error is 0.5 cm of water, and after 24 h it is 0.3 cm of water. At an altitude of 2 000 m at which most avalanches are released, the count rate is doubled and the measuring error is 0.7 of that at sea-level. At an altitude of 3 000 m the count rate is four times that at sea-level. In other regions at other latitudes and elevations other values would be found. The necessary equipment can be built into the ground in autumn so that the surface is level with the ground. A slot antenna of frequency around 400 MHz is used for transmission of the data.