Critical Boron Concentrations Research Articles

Validation of DDC-3D code system for neutronics and thermal-hydraulics coupling analysis using BEAVRS benchmark

The direct whole-core calculations can provide accurate results and insights to the physics phenomena of the reactor. It can also capture the local effects of temperature and density fields on fuel depletion. However, the computational cost of the direct whole-core calculations is expensive. To compromise between computational cost and accuracy, the DDC-3D code system has been developed to perform neutronics and thermal-hydraulics coupling analysis. The DDC-3D code system couples the open-source codes DRAGON & DONJON based on two-step method and subchannel code COBRA-EN. The Picard iteration method is applied to ensure the stability of numerical calculation. Then the BEAVRS benchmark is used to validate the computational capabilities of DDC-3D code system. The critical boron concentrations, control rod worths and fission rate distributions are calculated in HZP condition. The results show a good agreement with measured data. The results demonstrate that the two-step method is applicable and valid for multiphysics simulations. For the result of HFP condition for cycle 1, the results also agree well with measured data, including the trend of the critical boron concentrations and power distributions throughout the cycle 1. Although the detailed thermal–hydraulic experimental values are not available, the thermal-hydraulics analysis of the hot fuel assemblies indicates that the calculation results are reasonable. In general, the results demonstrate the feasibility and accuracy of DDC-3D code system for neutronics and thermal-hydraulics coupling calculations and life cycle simulation of PWRs.

Validation of the SCALE/Polaris−PARCS Code Procedure with the ENDF/B-VII.1 AMPX 56-Group Library: Pressurized Water Reactor

This study was conducted to validate the SCALE/Polaris v6.3.0–PARCS v3.4.2 code procedure with the Evaluated Nuclear Data File (ENDF)/B-VII.1 AMPX 56-group library for pressurized water reactor (PWR) analysis, by comparing simulated results with measured data for critical experiments and operating PWRs. Uncertainties of the SCALE/Polaris–PARCS code procedure for PWR analysis were evaluated in the validation for the PWR key nuclear parameters such as critical boron concentrations, reactivity, control bank work, temperature coefficients, and pin and assembly power peaking factors.

Validation of the CORD-2 System for the NPP Krško Nuclear Core Design Calculations

The CORD-2 package intended for core design calculations of PWRs has been recently updated with some improved models. Since the modifications could substantially influence the obtained results, a technical validation process is required. This paper presents comparison of some calculated and measured parameters of the NPP Krško core needed to qualify the package. Critical boron concentrations at hot full power for selected cycle burnup points and several parameters obtained during the start-up testing at the beginning of each cycle (hot zero power critical concentration, isothermal temperature coefficient and rods worth) for all 27 finished cycles of operation are considered. In addition, assembly-wise power distribution for some selected cycles is checked. Comparison has shown very good agreement of the CORD-2 calculated values with the selected measured parameter of the NPP Krško core.

Validating the serpent-ants Calculation Chain Using BEAVRS Fresh Core Hot Zero Power Data

Abstract The serpent Monte Carlo code and the serpent-ants two-step calculation chain are used to model the hot zero power physics tests described in the BEAVRS benchmark. The predicted critical boron concentrations, control rod group worths, and isothermal temperature coefficients are compared between serpent and serpent-ants as well as against the experimental measurements. Furthermore, radial power distributions in the unrodded and rodded core configurations are compared between serpent and serpent-ants. In addition to providing results using a best practices calculation chain, the effects of several simplifications or omissions in the group constant generation process on the results are estimated. Both the direct and two-step neutronics solutions provide results close to the measured values. Comparison between the measured data and the direct serpent Monte Carlo solution yields root-mean-square (RMS) differences of 12.1 mg/kg, 25.1×10−5 and 0.67×10−5 K−1 for boron, control rod worths and temperature coefficients, respectively. The two-step serpent-ants solution reaches a similar level of accuracy with RMS differences of 17.4 mg/kg, 23.6×10−5 and 0.29×10−5 K−1. The match in the radial power distribution between serpent and serpent-ants was very good with the RMS and MAXimum (MAX) for pin power errors being 1.31% and 4.99%, respectively, in the unrodded core and 1.67% (RMS) and 8.39% (MAX) in the rodded core.

Method research and engineering application of the B10-abundance correction for PWR

In this paper, the method research and engineering application of the B10-abundance correction for PWR have been implemented. The boric acid is one of the main neutron-absorber materials, within which the B10 is the most significant isotope for absorbing the thermal neutron. Due to the depletion effect and boronation effect, the B10 abundance would variate with the time. These effects would result in the phenomenon that the calculation values of the critical boron concentrations (CBC) provided by nuclear-design code would be smaller than corresponding measurement values. Therefore, for reducing the calculation errors of CBC, the B10-abundance correction method has been proposed based on the Bamboo-C code. Applying the B10-abundance correction method, the engineering validation has been implemented, comparing the calculation values of CBC and B10 abundances with corresponding measurement values. The numerical results indicated that the proposed correction method for B10 abundance can notably improve the calculation accuracy.

Whole-core analyses on recriticality of conventional high power pressurized water reactor in Korea during early phase of severe accidents

In this paper, first, MELCOR calculations for a conventional high power pressurized water reactor are performed to obtain the geometrical configurations and remaining fraction of the fission products in the degraded reactor core during the early phase of a severe accident. Then, based on the coupling between MELCOR and Serpent 2 code, sensitivity analyses on the criticality are performed for various water levels, burnup, and release of fission products with whole-core modelling on the degraded reactor. Sub-critical boron concentrations are obtained on the configuration of the degraded reactor core showing the largest criticality. The sub-critical boron concentrations are compared to critical boron concentrations of the intact reactor core to quantify additional boron concentrations required to make the reactor sub-critical during the early phase of the severe accident. Effects of control rod degradation and fission product release are also presented in terms of boron concentrations from the results of sensitivity analyses.

RMC/CTF multiphysics solutions to VERA core physics benchmark problem 9

High-fidelity life-cycle coupling simulations are attractive for increasing reactor power, increasing the fuel burnup and prolonging the reactor lifetime, which makes reactors much more economical. In this work, the continuous energy Reactor Monte Carlo code RMC was coupled to the subchannel code CTF. With the great support of the high-performance computing techniques, the coupled codes were then used to analyze VERA benchmark Problem 9 for the depletion of the fuel and burnable absorbers in a typical 18-month fuel cycle. Existing Monte Carlo burnup codes suffer from instabilities caused by spatial xenon oscillations. Therefore, a xenon equilibrium correction based on a simplified xenon-iodine burnup chain was used to restrain the spatial xenon oscillations and to improve simulation stability. The neutronics and thermal-hydraulics coupling convergence were investigated in terms of power distribution and Keff. The power distribution and Keff variations show that the neutronics/thermal-hydraulics coupling converges in the third iteration. To verify the neutronics/thermal-hydraulics coupling, the critical boron search algorithm and equilibrium xenon correction method, RMC/CTF solutions to a nominal flow and power critical calculation, VERA Benchmark Problem 7, were compared with the VERA reference solutions (MPACT/CTF) and MC21/CTF. The maximum relative difference of radial assembly power between this work and reference solutions was 2.8%. For the VERA Benchmark Problem 9, the measured critical boron concentrations were provided to validate coupling codes. The critical boron concentration prediction by RMC/CTF is consistent with the measured boron concentrations with absolute errors within 20 ppm, which is about 200 pcm in reactivity. The RMC/CTF solution for VERA Core Physics Benchmark Problem 9 is the first published coupled Monte Carlo neutronics/subchannel thermal-hydraulics solution for this problem.

Analysis of the BEAVRS PWR benchmark using SCALE and PARCS

Abstract This paper presents an analysis of the Benchmark for Evaluation And Validation of Reactor Simulations (BEAVRS) performed using SCALE 6.1.2 and PARCS 3.2 computer codes. The benchmark specification contains a detailed design, operational data and measurements for a real 4-loop Westinghouse pressurized water reactor (PWR). The lattice physics simulations were prepared using TRITON depletion sequence and NEWT neutron transport solver (SCALE package). The 238-neutron group library based on evaluated nuclear data file – ENDF/B-VII nuclear data libraries was applied. A set of branch and burnup calculations was prepared, and group constants in the form of PMAXS files were generated with GenPMAXS. The full-core models were prepared using the PARCS nodal-diffusion core simulator. The PMAXS libraries were used with PARCS to investigate the core operation. The hot zero power measurement data, including control rod worths and critical boron concentrations, were compared using simulations, and satisfactory results were achieved. The first fuel cycle was simulated, and acceptable agreement with boron letdown curve and measurements were obtained. Finally, conclusions and recommendations for future research were presented.

Uncertainty quantification for the first-cycle modeling and simulations of the BEAVRS benchmark problem

In this paper, the uncertainty quantification has been implemented to the first-cycle modeling and simulations for the BEAVRS benchmark problem, propagating the nuclear-data uncertainties to the key core parameters. NJOY has been applied to generate the nuclear-data covariance library based on ENDF/B-VII.1 in the research. The statistical sampling method has been utilized for the uncertainty quantification, based on the conventional “two-step” scheme. First, the nuclear-data uncertainties are propagated to the few-group constants through the lattice modeling and simulations; and then the uncertainties of the key core parameters are quantified through the reactor modeling and simulations. As interests, the uncertainties have been quantified to the critical boron concentrations, axial-power offset and radial assembly-power distributions through the whole life of first cycle. From the numerical results, it can be observed that for the critical boron concentration, the nuclear-data introduced uncertainties can up to be 51 ppm as maximum; for the axial-power offset, the relative uncertainties vary within 1.3% and for the radial assembly-power distributions, the maximum relative uncertainties is about 3.8% at BOL and 0.8% at EOL.

Solution of the BEAVRS benchmark using the nTRACER direct whole core calculation code

The BEAVRS (Benchmark for Evaluation and Validation of Reactor Simulation) benchmark is solved by the nTRACER direct whole core calculation code to assess its accuracy and to examine the solution dependence on modeling parameters. A sophisticated nTRACER core model representing the BEAVRS core is prepared after a series of sensitivity study to ensure solution accuracy. The resulting solutions for several hot-zero-power (HZP) states are compared first with the corresponding Monte Carlo solutions, which consist of the McCARD solutions for the assembly problems and the OpenMC solutions for the core problems, and then with the measured data which include the control rod worths (CRWs) and incore detector signals as well as the critical boron concentrations (CBC). The core depletion calculation is performed for the initial and second cycles with a set of approximated power histories and the calculated CBCs are compared with the measured data. The comparison results show that the criticality, control rod bank worths at HZP and the boron let-down curves of two cycles agree well with the measurements within 180 pcm and 25 ppm, respectively.

Impact of thicker cladding on the nuclear parameters of the NPP Krško fuel

To make fuel rods more resistant to grid-to-rod fretting or other cladding penetration failures, the cladding thickness could be increased or strengthened. Implementation of thicker fuel rod cladding was evaluated for the NPP Krško that uses 16 × 16 fuel design. Cladding thickness of the Westinghouse standard fuel design (STD) and optimized fuel design (OFA) is increased. The reactivity effect during the fuel burnup is determined. To obtain a complete realistic view of the fuel behaviour a typical, near equilibrium, 18-month fuel cycle is investigated. The most important nuclear core parameters such as critical boron concentrations, isothermal temperature coefficient and rod worth are determined and compared.

Critical concentrations of superconductor to insulator transition in (1 1 1) and (0 0 1) CVD boron-doped diamond

The superconducting transition temperatures (TC) of (111) and (001) boron-doped diamond films deposited by microwave plasma assisted chemical vapor deposition (MPCVD) are investigated in the wide boron concentration range of 1×1020−1×1022cm−3. The critical boron concentrations of superconductor to insulator transition in (111) and (001) films are 3×1020cm−3. TC in (111) films does not have the tendency to saturate up to 1×1022cm−3, while TC in (001) films saturates.

BN type inclusions formed in high Cr ferritic heat resistant steel

Scanning electron microscopy observations of fractured steel rod samples were made to clarify the formation and dissolution behaviour of boron nitrides in high Cr ferritic heat resistant steels during heat treatment at high temperature. A large number of coarse size BN type inclusions of 2 to 5 μm were distributed at the bottom of the dimples. They did not dissolve during annealing at 1150°C. However, they had a tendency to begin dissolving and reducing its particle size with time at 1200°C and dissolved completely in a short time at 1250°C. From the chemical analyses of boron and nitrogen in many high Cr heat resistant steels and SEM observations of their fractured samples, critical boron and nitrogen concentrations for the formation of coarse size BN type inclusions of 0·001%B and 0·015%N were found, and the solubility limit of BN was represented as log [%B]=−2·45log [%N]−6·81 at 1150°C.

Response of ‘Bluecrop’ Highbush Blueberry to Boron Fertilization

ABSTRACT The objective of this experiment was to examine the vegetative and generative responses of highbush blueberry to boron fertilization. The study was carried out in 2002–2003 in Central Poland on mature ‘Bluecrop’ blueberries (Vaccinium corymbosum L.) planted at a spacing of 3 × 1 m on a sandy loam soil with pH value of 3.9 and low hot water soluble boron status. Blueberries were soil- or foliar-supplied with boron. Foliar boron sprays were done four times per season: at the beginning of blooming, at petal fall, and three and six weeks after the ending of flowering. In each spray treatment, boron was applied at a rate of 0.2 kg ha−1. Soil boron was applied at the stage of bud break at a rate of 2 kg ha−1. Plants untreated with boron served as control. The results showed that boron fertilization increased boron levels in flower and leaf tissues. This treatment, regardless of boron application mode, did not affect plant vigor, the number of flowers per cane, fruit set, nor yield. Also mean fruit weight and berry firmness were not influenced by boron fertilization. Fruit of boron-supplied blueberries had higher soluble solids concentrations than those of the control plants. It is concluded that boron requirements of highbush blueberry are relatively low compared to most fruit crops and that critical leaf boron concentrations of ‘Bluecrop’ blueberry are below 15 mg kg−1 DW.

高Crフェライト系耐熱鋼に生成するBN系介在物

AbstractScanning electron microscopy observations of fractured steel rod samples were made to clarify the formation and dissolution behaviour of boron nitrides in high Cr ferritic heat resistant steels during heat treatment at high temperature. A large number of coarse size BN type inclusions of 2 to 5 μm were distributed at the bottom of the dimples. They did not dissolve during annealing at 1150°C. However, they had a tendency to begin dissolving and reducing its particle size with time at 1200°C and dissolved completely in a short time at 1250°C. From the chemical analyses of boron and nitrogen in many high Cr heat resistant steels and SEM observations of their fractured samples, critical boron and nitrogen concentrations for the formation of coarse size BN type inclusions of 0·001%B and 0·015%N were found, and the solubility limit of BN was represented as log [%B]=−2·45log [%N]−6·81 at 1150°C.

Analysis of MISTRAL Experiments with JENDL-3.2

Nuclear Power Engineering Corporation has been analyzing measurement data of MISTRAL, a LWR MOX core physics experimental program, with a deterministic code system of the diffusion and the transport theories, SRAC, and a Monte Carlo transport code, MVP, based on JENDL-3.2. The program consists of one reference U02 core, two homogeneous full MOX cores and one full MOX PWR mock-up core that have higher moderation ratio than the conventional lattice. The measurement parameters cover critical masses, boron concentrations, radial and axial core power distribution, spectrum indexes, conversion factors, effective delayed neutron fractions, iso-thermal temperature coefficients, boron efficiency, single absorber worth, water hole worth, absorber cluster worth and void worth. Critical keff calculations show a slight overestimate for MOX cores and a small systematic trend with aging of MOX fuel. Power distribution calculations show good agreement with the measurements in both homogeneous and mock-up cores. Measured spectrum indexes of fissile isotopes are well reproduced by the calculation. For other measurements, calculated results well reproduce the measurements within one or two times of the experimental error. The analysis verifies the validity of JENDL-3.2 and the analysis methods for the high moderation LWR MOX cores.

Oxygen incorporation and precipitation behavior in heavily boron-doped Czochralski silicon crystals

To understand the effect of heavy boron-doping, p+-type (100) silicon crystals doped with boron in the order of 1 × 1019atoms cm−3 (0.006–0.01 Ω cm) and a p-type (100) silicon crystal doped with boron in the order of 1 × 1015atoms cm−3 (12–16 Ω cm) were grown in a Czochralski puller and studied. The oxygen contents in the p+-type crystals were determined by gas fusion analysis and shown to be on the average about 23% higher than those in a comparable p-type crystal. Etch pit features of oxide precipitates after a high-low-high annealing were generally different between the two types of silicon, and three distinct regimes of behavior about the critical boron and oxygen concentrations were identified. Those are: with resistivity ≳ 0.007 Ω cmor oxygen concentration ≲ 30 ppma (Old ASTM), the oxide precipitate density, in the order of 1010 cm−3, is basically unaffected by heavy boron-doping and dependent on oxygen concentration; with resistivity ≲ 0.007 Ω cmand oxygen concentration ≳ 37 ppma, however, large platelets, which are 10–15 μm in size and in the order of 107 cm−3 in density, are formed instead and completely gettered oxide precipitates. In a medium-oxygen range of about 28–30 ppma, both p- and p+-type (100) silicon wafers formed an ideal internal gettering structure, consisting of a well-defined precipitate-free zone (PFZ) to a depth of about 15 μm from the surface and dense bulk oxide precipitates in the order of 1010 cm−3 below the PFZ, after a high-low-high annealing.

Critical Boron Concentrations in Plant Tissues of Two Sunflower Cultivars1

AbstractMarked responses of sunflowers (Helianthus annuus L.) to boron fertilization have been recorded but little information exists on the B nutritional requirements of this crop. In order to study this aspect, field trials were conducted in which five rates of B fertilizer (0 to 4 kg B/ha) were applied to two cultivars, ‘Smena’ and ‘SO 320’, on two soil types. The cultivars differed in visual susceptibility to B deficiency in the vegetative stage but differed only slightly in B uptake. B fertilization increased seed yields by an average of 48% in both cultivars. To establish critical B concentrations in plant tissues, relationships were investigated between seed yield and the B concentrations in I‐mo‐old seedlings and in the topmost mature leaf at flowering. Seedlings proved unsatisfactory as index tissue, particularly with SO 320, but meaningful relationships were recorded between seed yield and B concentration in the topmost mature leaf at flowering in both cultivars. Critical concentrations in this tissue were determined as 32 and 35 ppm B for Smena and SO 320, respectively. No significant differences were recorded between the two cultivars in the relationship between seed yield and the B concentration in the leaf below the critical levels, and the data were combined. The critical concentration in the topmost mature leaf at flowering was determined as 34 ppm B for both cultivars, the confidence interval (95%) being from 31 to 38 ppm B.