| 1. |
- Alhassan, E., et al.
(författare)
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TENDL-based evaluation and adjustment of p+111Cd between 1 and 100 MeV
- 2023
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Ingår i: Applied Radiation and Isotopes. - : Elsevier. - 0969-8043 .- 1872-9800. ; 198
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Tidskriftsartikel (refereegranskat)abstract
- Proton induced reaction data are needed in the optimization of various radioisotope production routes, among others. In this work, the evaluation of proton-induced reactions on 111Cd between 1 and 100 MeV using the TALYS code system within an iterative Bayesian Monte Carlo (iBMC) framework, is presented. The method involves the simultaneous variation of a large number of nuclear reaction models included in the TALYS code system as well as their parameters. Each random TALYS calculation yields a vector of calculated values of cross section observables as well as the angular distributions, among others, which were compared with corresponding vectors of carefully selected differential experimental data for reaction channels where data were available. The random nuclear data file with the maximum likelihood function value obtained from combining the individual chi 2s computed for the considered reaction channels was chosen as the parent vector and the starting point for the generation of a further set of random TALYS calculations. This was repeated multiple times until a targeted convergence of 5% was reached. The final evaluated file was compared with available experimental data from the EXFOR database as well as with the evaluations from the TENDL-2021 and JENDL5.0 libraries, and found to compare favorably.
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| 2. |
- dos Santos Matias, Lucilio, et al.
(författare)
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Characterization of the radiation field surrounding the Leksell Gamma Knife® and shielding applications
- 2023
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Ingår i: Applied Radiation and Isotopes. - 0969-8043 .- 1872-9800. ; 198
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study is to improve the characterization and modeling of the radiation field surrounding the Leksell Gamma Knife®-PerfexionTM. The improved characterization of the radiation field enables more accurate shielding calculations to be performed for the areas adjacent to the treatment room. With the aid of a high-purity germanium detector and a satellite dose rate meter, ?-ray spectra and ambient dose equivalent H*(10) data were acquired at various locations in the field of a Leksell Gamma Knife unit in a treatment room at Karolinska University Hospital, Sweden. These measurements were used to validate the results of the PEGASOS Monte Carlo simulation system with a PENELOPE kernel. The levels of the radiation that passes through the shielding of the machine (leakage radiation) are shown to be much lower than what is suggested by various bodies, e.g. the National Council on Radiation Protection and Measurements, to be used when calculating radiation shielding barriers. The results clearly indicate that Monte Carlo simulations may be used in structural shielding design calculations for γ? rays from the Leksell Gamma Knife.
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| 3. |
- Kossert, Karsten, et al.
(författare)
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Activity standardization of two enriched 40K solutions for the determination of decay scheme parameters and the half-life
- 2022
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Ingår i: Applied Radiation and Isotopes. - : Elsevier. - 0969-8043 .- 1872-9800. ; 188
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we describe experiments on two enriched K-40 solutions to accurately determine decay data. The first solution was measured in 2004/2005 by means of a gamma-ray spectrometer with low background and a liquid scintillation (LS) counter to apply the CIEMAT/NIST efficiency tracing method. A combination of results yields an emission probability of the 1461 keV gamma-rays of P-gamma = 0.1030(11) which is lower than current results of data evaluations. The activity concentration of the second solution was also determined by means of LS counting, but here, the CIEMAT/NIST efficiency tracing method as well as the TDCR method were applied. Again, the result was combined with that of independent gamma-ray spectrometry and the gamma-ray emission probability was found to be P-gamma = 0.1029(9) in good agreement with the result obtained from the first solution. A combination of both experiments yields P-gamma = 0.1029(9). The spectra of a TriCarb LS counter were carefully analyzed and a beta minus emission probability P beta- = 0.8954(14) was determined. The new results for P-gamma and P-beta-indicate that the overall probability of the decay via EC in recent data evaluations is overestimated. The LS counting efficiencies were computed with a stochastic model and up-to-date calculations of the beta spectrum and fractional EC probabilities were used. The final activity result of the second solution is combined with the outcome of a comprehensive isotopic analysis to determine the half-life of K-40 which is found to be 1.2536(27) .10(9) years. All above-stated uncertainties are standard uncertainties (k = 1).
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| 4. |
- Lindahl, Patric, et al.
(författare)
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Total dissolution of environmental samples for the determination of uranium and thorium by ICP-MS and alpha-particle spectrometry
- 2022
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Ingår i: Applied Radiation and Isotopes. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0969-8043 .- 1872-9800. ; 181
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Tidskriftsartikel (refereegranskat)abstract
- A low-cost total dissolution method for accurate determination of uranium and thorium isotopes in environmental samples (soil and sediment) was introduced, optimised and validated. The method included alkaline fusion based on sodium hydroxide (NaOH) and sodium peroxide (Na2O2), followed by sequential extraction chromatography separation and measurements with ICP-MS or alpha-particle spectrometry. The overall chemical recoveries for U and Th for the entire procedure were about 80% and 90%, respectively. The U-238 contribution from partial dissolution of the nickel crucibles accounted for about 80% of the total background activity.
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| 5. |
- Ramebäck, Henrik, 1967, et al.
(författare)
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A Monte Carlo method for calculation of the characteristic limits decision threshold and detection limit in low-level radioactivity measurements
- 2021
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Ingår i: Applied Radiation and Isotopes. - : Elsevier BV. - 0969-8043 .- 1872-9800. ; 178
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Tidskriftsartikel (refereegranskat)abstract
- In this study, calculation of decision threshold and detection limit expressed in counts for low-level radioactivity measurements were evaluated and compared to a Monte Carlo method for the case of paired Poisson-distributed observations, i.e. for discrete variables. The calculated characteristic limits obtained from Monte Carlo calculations were compared with analytical expressions given in literature. The results in this study show that the equations given by Currie are in good agreement with the results from the Monte Carlo calculations simulating nuclear counting applications with a low number of observed counts. An exception is observed for a background corresponding to zero counts. This study also shows that at a low number of counts, the specific boundary conditions of the interval that represents counts corresponding to the presence of the analyte (>or ≥), have an impact on the false positives and negatives rates as defined by the parameters α and β.
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| 6. |
- Ramebäck, Henrik, 1967, et al.
(författare)
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Calculation of decision threshold and detection limit in radiometric measurements using a Monte Carlo Method
- 2020
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Ingår i: Applied Radiation and Isotopes. - : Elsevier BV. - 0969-8043 .- 1872-9800. ; 156
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Tidskriftsartikel (refereegranskat)abstract
- Calculation of the decision threshold and detection limit of a measurement, or measurement method, are crucial in order to decide if an analyte is present or not and with what confidence it can be quantified. That decision is important in view of possible actions if something would be detected. In this work, a method for calculating these limits using a Monte Carlo method is presented. In the Monte Carlo method any a priori distribution (e.g. normal distribution, rectangular distribution, triangular distribution) of an input quantity can be selected. Differences between the Monte Carlo calculated characteristic limits and the ones calculated according to ISO 11929:2010 is presented. Moreover, suggestions how to calculate the detection limit when it can not be calculated according to the ISO 11929:2010 are given.
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| 7. |
- Ramebäck, Henrik, 1967, et al.
(författare)
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Gamma spectrometric measurement of uranium isotopic composition and mass in sintered UO 2 pellets using the efficiency transfer method
- 2023
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Ingår i: Applied radiation and isotopes : including data, instrumentation and methods for use in agriculture, industry and medicine. - : Elsevier BV. - 0969-8043 .- 1872-9800. ; 192, s. 110607-
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Tidskriftsartikel (refereegranskat)abstract
- Gamma spectrometric measurements to determine the isotopic composition and total uranium mass in UO2 pellets (D = 7.5 mm; H = 3.5 mm, ρ = 10 g/cm3) were carried out. The required efficiency curve was obtained by applying the efficiency transfer method from a calibration standard (D = 65 mm; H = 20 mm) of a slightly acidified water solution. The average isotopic composition of ten UO2 pellets was consistent with values of natural uranium given by IUPAC. The average relative bias for the 235U/238U amount ratio was -0.73% using the 1001 keV gamma line for 238U and 0.50% using the 63 keV gamma line (186 keV was always used for 235U). For the total uranium mass, the mean deviation as compared to mass determinations using a balance was 5.5% using the 1001 keV gamma line for 238U and 4.3% using the 63 keV gamma line.
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| 8. |
- Siikanen, J, et al.
(författare)
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Cyclotron-produced 68Ga from enriched 68Zn foils
- 2021
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Ingår i: Applied radiation and isotopes : including data, instrumentation and methods for use in agriculture, industry and medicine. - : Elsevier BV. - 1872-9800. ; 176, s. 109825-
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Tidskriftsartikel (refereegranskat)
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| 9. |
- Finck, Robert, et al.
(författare)
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Maximum detection distances for gamma emitting point sources in mobile gamma spectrometry
- 2022
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Ingår i: Applied Radiation and Isotopes. - : Elsevier BV. - 0969-8043. ; 184
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Tidskriftsartikel (refereegranskat)abstract
- In this study an algorithm was developed for calculating maximum detectable distance (MDD) for mobile gamma-ray detection of lost sources in-situ for some common mobile spectrometer systems and gamma sources (137Cs and 60Co). The MDD is a function of detector efficiency, vehicle speed, acquisition time interval, radiation background level and accepted frequency of false alarms. To test its accuracy in predicting the MDD experiments were conducted in-situ. Results indicate agreement with experimental mobile detection distance measurements for 60Co and 137Cs point sources. Both the algorithm and the field test show that at a vehicle speed of 50 km/h, the optimal acquisition time intervals range between 3 and 10 s when searching for unshielded sources with activities of 137Cs and 60Co in the order of 100 MBq. Longer acquisition time intervals (20–30 s) are better to detect higher activity sources at the same speed. However, at higher speeds, shorter time intervals should be selected to increase the MDD. The developed algorithm can help select the optimal combination of detectors, vehicle speed, and instrument settings when using mobile searching in the event of loss of gamma-ray sources.
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| 10. |
- Herrnsdorf, L., et al.
(författare)
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Optimization of energy and directional response of a small 4π silicon dosemeter for quality control of CT/CBCT-units – A 3D CAD, Monte-Carlo, AM approach
- 2020
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Ingår i: Applied Radiation and Isotopes. - : Elsevier BV. - 0969-8043. ; 158
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Tidskriftsartikel (refereegranskat)abstract
- A 4π radiation dosemeter for use in medical radiology was designed. It is based on a solid state silicon detector, a sensor wafer, a flex card, a 3D plastic holder and a spherical stainless steel filter with a distribution of holes around the detector. The detector is attached to the wafer using only low Z material. To achieve an energy and directional response which is as uniform as possible for various radiation qualities and beam directions, the filter was designed using a series of Monte Carlo calculations. The energy filter and its hole pattern were created using Additive Manufacturing (AM) in the form of metal 3D printing. The functionality of the dosemeter was designed to fulfill the quality criteria of a combined energy and angular dependence of less than 5% for the IEC beam qualities RQR and RQT in the range of 65–145 kV. This is a major improvement to the existing solutions that may need software corrections to be used for the same beam quality range.
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