Nuclear Science and Technology

ANN-based model integrated in thermal-hydraulics codes: A case study of two-phase wall friction model

Nguyen Van Thai, Nguyen Ngoc Dat — Thu, 25 Apr 2024 00:00:00 +0700

Accurate prediction of two-phase parameters is essential for the development, operation and safety of nuclear power plants. In this paper, the ANN-based model has been developed, implemented with PDE (Partial Differential Equation) solver in case study of two-phase frictional pressure drop prediction.

Preliminary MELCOR Input Deck for Steady State and Turbine Trip Analysis of the NuScale US600 SMR

Thu, 25 Apr 2024 00:00:00 +0700

This paper models NuScale’s SMR using MELCOR by relying on specifications in the latest Final Safety Assessment Report (FSAR) submitted to the U.S. Nuclear Regulatory Commission (USNRC). The input deck was crafted from scratch using only publicly available data and reasonable assumptions. Benchmark results for steady state and a turbine trip transient are presented, with the former showing excellent agreement with the reference values, while the latter produces shows slight deviations in the mass flow rates. As a preliminary study, the results are within acceptable limits and encourage further refinement to the model for use in other accident progression cases.

Thermal and Fast Neutron Measurement in the STU Mini Labyrinth Experiment

Štefan Čerba, Branislav Vrban, Jakub Luley, Vendula Filova, Vladimír Nečas — Thu, 25 Apr 2024 00:00:00 +0700

The Mini Labyrinth experiment is a neutron and gamma shielding experiment constructed at the Slovak University of Technology in Bratislava (STU). The STU Mini Labyrinth consists of NEUTRONSTOP shielding, blocks of moderators, various neutron sources, a graphite prism, and the detector handling robot. It was designed for research and education purposes, while several experiments are also available online or a hybrid form. There have been several versions of the Mini Labyrinth developed, while currently the V3 version is available. This paper presents the methodology to effectively perform thermal and fast neutron measurements using a PuBe neutron source. In the experiment presented in this paper also active and passive detectors were used, and moderator materials were investigated to slightly shift the neutron spectrum. As for active detectors, the SNM-11 boron coated corona detector was used. Among passive detectors the CR-39 track detectors were investigated. The measurements were carried out in two configurations and the results were evaluated by simulations using the SCALE6 system

Application of β-NMR to spectroscopy and imaging

Thu, 25 Apr 2024 00:00:00 +0700

Nuclear magnetic resonance (NMR) using β-decay radioisotopes, known as “β-NMR,” is used for research in nuclear physics. Recently, nuclear magnetic moments of β-decay radioisotopes have been precisely measured by β-NMR. Therefore, β-decay radioisotopes can be used for NMR spectroscopy in material sciences. Nuclei, whose spin is zero, such as ¹²C and ¹⁶O, cannot be used in conventional NMR. However, nonzero-spin radioactive isotopes of carbon and oxygen can be used in β-NMR. This advantage is powerful for investigating organic materials that cannot be investigated using conventional NMR. A technique is being developed to extend β-NMR for imaging use in magnetic resonance imaging (MRI). In this study, the imaging function was realized by installing β-ray tracking detectors in a β-NMR device. Nuclear-spin-polarized radioisotopes were injected into a sample, and β-rays were emitted from their positions. Consequently, one could track back β-ray source positions on the sample. These detectors were installed into a dipole magnet to observe the magnetic resonances. A radio frequency coil was installed surrounding the sample. By combining information about the β-ray tracks and magnetic resonances, it was possible to obtain NMR spectra and images. This method is called “β-MRI.” The system was evaluated, and its performances were estimated.

Developing methodology to evaluate eye lens dose for medical staff

Tran Yen Nhi, Nhu Tuyen Pham, Thanh Luong Dang — Thu, 25 Apr 2024 00:00:00 +0700

Due to epidemiological evidence on the increasing incidence of cataracts in interventional doctors, The International Commission on Radiological Protection (ICRP) recommended decreasing the eye lens dose limit from 150 mSv/year to 20 mSv/year. Thus, The current status of dose assessment for healthcare workers shows that it requires more precise measurements of eye lens dose. we have researched Investigating dosimetric characteristics of OSLD nanoDot and Inlight type, using a multi–filter technique to determine the average air kerma of the incident beam and other essential dosimetric factors such as the relative energy responses and conversion coefficients from the air kerma to personal dose equivalent operational quantities Hp(d). Based on it developed the methodologies to evaluate eye lens dose for medical staff, especially high-risk subjects such as interventional doctors. Results show that 3 methods to evaluate eye lens dose have been deployed in the cardiovascular intervention department: directly by nanoDot dosimeter, indirectly by personal dosimeter (Inlight), and quick method based on the relationship with exposure duration. In one case, the doctor exceeded the threshold dose of 20 mSv/year without protective measures. Besides that, the risk of cataracts is possible when considering the cumulative dose for 30 years of work.

Wide-Aperture Backscattering Detector (BSD-A) for The High-Resolution Fourier Diffractometer

Thu, 25 Apr 2024 00:00:00 +0700

The high-resolution Fourier diffractometer (HRFD) has been in routine operation since 1994 at the long-pulse neutron source, the IBR-2 reactor, in Dubna. Its fast Fourier chopper provides probably the best compromise between very high resolution in reciprocal space (Δd/d ≈ 0.001) and the intensity. For further improving intensity of TOF-diffraction pattern, a wide-aperture ring backscattering detector (BSD) has been developed on the basis of ZnS(Ag)/⁶LiF scintillator. BSD is designed in the form of 6 concentric rings, each of which is subdivided into 12 identical parts. The main parameters of the detector are the following: range of scattering angles is 2θ = (133 - 175) degrees, covered solid angle is Ω_d ≈ 2.0 sr, average percentage absorption efficiency gets closer to 85%, geometrical contribution to resolution function does not exceed Δd/d = 0.0005. In the report the concept of the detector is described and its data acquisition system is presented. The start of operation of the detector at the HRFD is scheduled for 2024.