Low Flux Reactor Research Articles

Isotope selective three-step photoionization of 174Yb

A three-step photoionization scheme has been theoretically studied for the laser isotope separation of 174 Y b from natural Yb using density matrix formalism. The effects of bandwidth and peak power density of lasers, Doppler broadening, and the number density of atoms on the degree of enrichment and production rate have been studied, and the optimum conditions for the efficient separation of 174 Y b have been derived. It has been shown that it is possible to enrich the 174 Y b isotope up to ∼ 90 % using lasers with a bandwidth of 500 MHz with a production rate up to 48 mg/h. On the whole, the system required for the laser isotope separation of 174 Y b is much simpler than that required for the separation of any of the 176 L u , 177 L u , and 176 Y b isotopes. 1 g of the enriched isotope mixture upon irradiation for 21 days in widely available low flux reactors produces 759 doses (7.4 GBq each) of 175 Y b radionuclide for peptide receptor radionuclide therapy (PRRT) with 98.6% radionuclidic purity. It is envisaged that the production of the 175 Y b isotope through this route will be economical and widely available to the public at large as a PRRT drug for cancer therapy.

Isotope selective three-step photoionization of 177Lu

A 540-535-618 three-step photoionization scheme has been theoretically investigated for the laser isotope separation of 177 L u through density matrix formalism. Equations of motion for the three-step photoionization of odd isotopes have been derived. The effects of Doppler broadening, bandwidth and peak power density of excitation lasers, number density of atoms on the degree of enrichment of 177 L u and production rate have been studied. Optimum conditions for the laser isotope separation of 177 L u for the cases of initial abundances corresponding to the irradiation of natural Lu in low, medium, and high flux reactors have been derived. Under optimum conditions, the production rates of 177 L u in ranges of 0.87, 14.5, and 92.5 mg/h can be achieved with degrees of enrichment of 66%, 97%, and 100%, respectively, for the cases of initial abundances corresponding to the irradiation of natural Lu in low, medium, and high flux reactors. It has also been shown that the content of 177 m L u in the enriched isotope mixture will be in the range of 10 − 2 % to 10 − 4 % . This provides a comprehensive solution to the application of 177 L u for cancer therapy.

Development of a CCD based thermal neutron imaging detector for the Israeli Research Reactor IRR-1 at Soreq NRC

Among the imaging systems used for thermal neutron imaging worldwide, the most prevalent configuration is CCD camera based. At facilities with sufficiently high neutron flux (>1 × 106 n/cm2/sec), the basic design does not necessitate amplification of scintillation photons prior to their registration by the CCD camera. However, for high resolution imaging at low flux reactors, insufficient amount of scintillation photons may reach each CCD pixel, thus, photon statistics becomes the limiting factor over neutron statistics.As described in this work, introduction of an image-intensifier into the system’s optical chain removed photon statistics limitation, allowed fine focus adjustments and improved image quality. This led to the possibility of performing good quality tomographic scans.

Correlating Irradiation-Induced Solute Clustering with Changes of Hardness in Low and High Flux Reactor Pressure Vessel Steels

Correlating Irradiation-Induced Solute Clustering with Changes of Hardness in Low and High Flux Reactor Pressure Vessel Steels

Neutron flux and annealing effects on irradiation hardening of RPV materials

This paper aims to examine an eventual effect of neutron flux, sometimes referred to as dose rate effect, on irradiation hardening of a typical A533B reactor pressure vessel steel. Tensile tests on both low flux (reactor surveillance data) and high flux (BR2 reactor) were performed in a large fluence range. The obtained results indicate two features. First, the surveillance data exhibit a constant (∼90 MPa) higher yield strength than the high flux data. However, this difference cannot be explained from a flux effect but most probably from differences in the initial tensile properties. The hardening kinetic of both low and high flux is the same. Annealing at low temperature, 345 °C/40 h, to eventually reveal unstable matrix damage did not affect both BR2 and surveillance specimens. This is confirmed by other annealing experimental data including both tensile and hardness measurements and tensile data on A508 forging and weld. It is suggested that the absence of flux effect on the tensile properties while different radiation-induced microstructures can be attributed to thermal ageing effects.

Development of a neutron tomography system using a low flux reactor

Abstract A neutron tomography instrument was designed and developed at the Royal Military College (RMC) of Canada with Queen's University to enhance these institutions' non-destructive evaluation capabilities. The neutron imaging system was built around a Safe Low-Power C(K)ritical Experiment (SLOWPOKE-2) nuclear research reactor. The low power and physical geometry of the reactor required that a novel design be developed to facilitate tomography. A unique rotisserie style rotary stage and clamping apparatus was developed. Furthermore, the low flux at the image plane (3×104 n cm−2 s−1), necessitated that the image acquisition and reconstruction processes be optimized. Tomographs of numerous samples were obtained using the new tomography instrument at RMC.

Fibrin glue system for adjuvant brachytherapy of brain tumors with 188Re and 186Re-labeled microspheres

Brain tumors such as glioblastoma reappear in their original location in almost 50% of cases. To prevent this recurrence, we developed a radiopharmaceutical system that consists of a gel applied immediately after surgical resection of a brain tumor to deliver local radiation booster doses. The gel, which strongly adheres to tissue in the treatment area, consists of fibrin glue containing the β-emitters rhenium-188 and rhenium-186 in microsphere-bound form. Such microspheres can be prepared by short (2 h or less) neutron activation even in low neutron flux reactors, yielding a mixture of the two β-emitters rhenium-188 ( E max = 2.1 MeV, half life = 17 h) and rhenium-186 ( E max = 1.1 MeV, half life = 90.6 h). The dosimetry of this rhenium-188/rhenium-186 fibrin glue system was determined using gafchromic film measurements. The treatment efficacy of the radioactive fibrin glue was measured in a 9L-glioblastoma rat model. All animals receiving the non-radioactive fibrin glue died within 17 ± 3 days, whereas 60% of the treated animals survived 36 days, the final length of the experiment. Control animals that were treated with the same amount of radioactive fibrin glue, but had not received a previous tumor cell injection, showed no toxic effects over one year. The β-radiation emitting rhenium-188/rhenium-186-based gel thus provides an effective method of delivering high doses of local radiation to tumor tissue, particularly to wet areas where high adhesive strength and long-term radiation (with or without drug) delivery are needed.

The high resolution Powder Neutron Diffractometer PUS at the JEEP II reactor at Kjeller in Norway

Abstract The performance of the new Powder Neutron Diffractometer PUS at the 2 MW JEEP II reactor shows the large potential for high resolution powder neutron diffraction even at a low flux reactor. The different components of the instrument are optimised with respect to flexibility and relationship between intensity and resolution. Wavelengths in the range 0.7–2.6 A are available from a focussing composite Ge monochromator. The detector system consists of position sensitive proportional counters. The temperatures available for experiments range from 7 to about 1600K. Nearly no malfunctions during the first 2½ years of operation proves the robustness of the complete system. Several experiments show the potential for studies of rather complex crystallographic problems, even with small sample quantities (<200mg), and time-resolved in-situ type experiments.

Practical reactor production of [formula omitted] from argon clathrate

The radionuclide 41 Ar has many ideal properties as a gas flow tracer. However, the modest cross-section of 40 Ar for thermal neutron activation makes preparation of suitable activities of 41 Ar technically difficult particularly for low flux reactors. Argon can however be trapped in a molecular complex called a clathrate that can then be irradiated. We prepared argon clathrate and explored its irradiation and stability characteristics. Argon clathrate can be used to provide gigabecquerel quantities of 41 Ar even with low power reactors.

Evaluation of Three Software Programs for Calculating True-Coincidence Summing Correction Factors

True-coincidence summing correction is an essential element in k0-based NAA1 and becomes important when samples are counted with a high efficiency detector. This may be the case where large detectors are used or where samples are counted in or in the vicinity of the detector in order to achieve low detection limits in conjunction with low-flux reactors. In some laboratories coincidence correction is accomplished by calculating the coincidence correction factors. Since experimental validation of the calculations will reveal only the most significant errors and is a laborious task due to the high number of radionuclides involved, three laboratories decided to compare their calculated coincidence factors. Each laboratory uses a different software package. A comparative performance analysis was made of COINCALC developed at the INW of the University of Gent (implemented in SOLCOI by DSM Research), the software of the IRI, University of Delft, the Netherlands, and the software of the Ecole Polytechnique, Montreal, Canada. The overall approach, data and algorithms were chosen independently by each institute as the software was being developed and, so, the comparison has yielded a number of interesting conclusions. A follow-up investigation of the discrepancies found will probably allow the performance of each program to be improved.

Transmutation Doping of III-Nitrides

ABSTRACTTransmutation doping of (In, Ga, Al)N compounds by neutron irradiation is a promising and totally unexplored field to date. It is much more effective than that of Si due to large neutron capture cross section and abundance of In, Al and Ga isotopes participating in reaction. This should make the irradiation possible in low-flux reactors and result in smaller radiation damage. Annealing of the radiation damage seems feasible.

A γ-ray telescope for on-line measurements of low boron concentrations in a head phantom for BNCT

In Boron Neutron Capture Therapy the 10B(n, α) 7 Li reaction is used to create a tumour-destructing field of high Linear Energy Transfer (LET) particles. The therapy requires a high boron concentration in the tumour and a low boron concentration in the healthy tissue. The boron neutron capture reaction is accompanied by the emission of a photon of energy 478 keV. It is investigated whether measuring of these photons can serve as a tool to determine the boron concentration during therapy in the tumour as well as in the healthy tissue. Such a measurement is complicated by the presence of a large background photon field. To study the feasibility, an experimental configuration has been designed at a test facility of the Low-Flux Reactor (LFR). The LFR provides an epithermal neutron beam for irradiation of a head phantom which simulates a human head with a tumour. This paper shows that the reconstruction of the position and the size of the tumour as well as the ratio of the boron concentrations appeared to be possible. In a second stage it is shown that these measurements can be expanded to experiments with the therapy neutron beam of the High-Flux Reactor (HFR).

Parameterization of detector efficiency for the standardization of NAa with stable low flux reactors

With SLOWPOKE and MNS reactors which have reproducible neutron fluxes, the standardization of multielement NAA can be reduced to measuring activation constants once for all elements and then determining relative detection efficiencies for new detectors and counting geometries. In this work, a method has been developed for the parameterization of the efficiency of gemanium detectors. The gamma-ray detection efficiency was measured as a function of energy and distance for three detectors. The variation with distance was found to follow a modified EID law, within 1%, for point sources 1 mm to 250 mm from the detector. A model, including coincidence summing corrections, was developed to calculate efficiency for NAA samples; it requires 16 measured parameters. Tests showed that the calculated relative detection efficiencies are accurate to better than 3% for close counting geometries and sample volumes up to a few millilitres. Areas of possible improvement to the accurarcy of the method are suggested.

A thermal neutron facility for radiobiological studies

Within the Petten BNCT project a thermal neutron facility for radiobiological studies is needed for further test and development of boron compounds. The Argonaut reactor of ECN, the Low Flux Reactor operating at a power of 30 kW, offers opportunities for the development of thermal neutron beams. Optimising calculations have been performed with the Monte Carlo code MCNP, resulting in a design of an extended graphite moderator followed by a lead shield with a bismuth window. This assembly has been built as a modular construction for easy positioning on and removal from an irradiation trolley of the reactor. The facility yields a thermal fluence rate of φ therm = 1.2 · 10 9 cm −2s −1, and a resulting dose rate from the unwanted beam components (γ-rays, fast and epithermal neutrons) lower than 1 Gy/h (physical dose). Experimental validation of the calculations has been performed by neutron activation detectors. Finally, the fluence rates in the vials used for the radiobiological experiments are determined with a set of neutron activation detectors.

One-Dimensional Sans Employing Bent-Single Crystal Optics: Theory and Demonstration

ABSTRACTA recent small-angle neutron scattering (SANS) instrumentation development at the University of Missouri Research Reactor Center (MURR) using bent, double Si crystal diffraction is presented. Neutron rocking curves of flat single crystals are only a few seconds of arc with correspondingly low integrated intensities. The rocking curve can be significantly broadened if the crystals are bent. However, the phase-space acceptance and emergence windows of two bent crystals in parallel can be matched only if the reflecting planes have different d-spacing. We have used a combination of the Si (111) and (220) reflections in the work presented here. The peak intensity of the rocking curve with this configuration was approximately 2.5 x 105 neutrons per second over a 5 cm2 area of sample at 1.5 Å. The rocking curve wings fell sharply (approximately as Q"11), permitting accurate scattered intensity measurements down to a minimum Q value of 0.005 1/Å at a Q resolution of 0.003 1/Å. The technique also offers the possibility of variable resolution without too much difficulty; changes up to a factor of 2 can be made by adjusting the sample-to-analyzer crystal distance, while changes of a factor of 10 can be made by using different Si reflections. Since the incident neutron wavelength can be tuned to the peak of the leakage spectrum, this technique is ideal for low-flux reactors, which otherwise cannot be used for SANS research. The usefulness of one-dimensional SANS is demonstrated by measurements of Portland cement.

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%.

TRACE ELEMENT ANALYSIS OF TEN U.S. GEOLOGICAL SURVEY ROCK STANDARDS BY NEUTRON ACTIVATION USING A LOW FLUX REACTOR

Ten U.S. Geological Survey rock standards have been analyzed for trace elements by instrumental neutron activation using a low flux reactor and Ge detectors. Results compare favorably with the current working values for all elements except Mo. REE values that have been determined are generally slightly lower than accepted values. Data obtained for rocks that have very low trace element concentrations (e.g., BIR‐1) will aid in refining the working values for these standards.

Indigenous development of fatigue and creep resistant steels: Ramaswamy, V. and Mediratta, S.R. Trans. Indian Inst. Met. 1989 42, (Suppl.). S83–S92

This paper aims to examine an eventual effect of neutron flux, sometimes referred to as dose rate effect, on irradiation hardening of a typical A533B reactor pressure vessel steel.Tensile tests on both low flux (reactor surveillance data) and high flux (BR2 reactor) were performed in a large fluence range. The obtained results indicate two features. First, the surveillance data exhibit a constant (∼90 MPa) higher yield strength than the high flux data. However, this difference cannot be explained from a flux effect but most probably from differences in the initial tensile properties. The hardening kinetic of both low and high flux is the same. Annealing at low temperature, 345 °C/40 h, to eventually reveal unstable matrix damage did not affect both BR2 and surveillance specimens. This is confirmed by other annealing experimental data including both tensile and hardness measurements and tensile data on A508 forging and weld. It is suggested that the absence of flux effect on the tensile properties while different radiation-induced microstructures can be attributed to thermal ageing effects.

Intereferences from uranium fission in neutron-activation analysis in an Argonaut-type Low Flux Reactor

The interferences by uranium fission on the determination by neutron activation analysis of Zr, Mo, Ru, La, Ce, Nd and Sm are investigated for the Argonaut-type Low Flux Reactor at ECN, Petten, The Netherlands. In addition, the spectral interference of the determination of Sm by239Np is considered. The experimental values for fission yields are found to be in good agreement with calculated values based on recent cross-section compilations.