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At least 1,495 records · Page 83

Verification of AZTRAN v1.2 code with a PWR-MOX benchmark problem

The AZTLAN platform project is an effort focused on developing a modeling Mexican platform to design and analyze nuclear reactors. It is a national initiative lead by the National Institute of Nuclear Research (ININ), in collaboration with the main Mexico's public universities: the National Polytechnic Institute (IPN), the National Autonomous University of Mexico (UNAM) and the Autonomous Metropolitan University (UAM). The AZTRAN code is a module of AZTLAN that solves the 3D neutron transport equation using the discrete ordinates (SN) method and the nodal scheme RTN-0 on steady state and Cartesian geometry. AZTRAN works with cross sections generated externally by other code. It provides a solution to the eigenvalue problem and determine the neutron distribution for a specific medium at desired conditions. On the other hand, it is important to mention that the Working Group 4 (users group) of AZTLAN platform is responsible of verify and validate the codes development, in order to give feedback to the group of developers: neutronics and thermal-hydraulics. In this work, the AZTRAN v1.2 performance was studied for a PWR-MOX lattice, using as example the Yamamoto's benchmark for LWR fuels, comparing AZTRAN v1.2 results again those obtained with the well-known neutronic code SERPENT-2 (v1.27), and some results from an article presented at PHYSOR-2002. Results from AZTRAN for a BWR fuel lattice is presented in a companion paper in this meeting.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗

Testing of ENDF/B-VIII.0 in the GNDS format with LLNL transport codes - 25606

ENDF/B-VIII.0 was released in the Evaluated Nuclear Data Format and the Generalized Nuclear Data Structure format (GNDS), a new international standard for storing nuclear data developed under the auspices of the Nuclear Energy Agency Working Party on Evaluation Cooperation Subgroup 38. GNDS relies on modern coding practices, and offers a structured, flexible and physics-based standard for storing and exchanging nuclear data to address limitations in legacy nuclear data formats such as ENDF-6. GNDS supports the storage of evaluated nuclear data as well as processed data suitable for both deterministic (i.e., multi-group) and Monte Carlo transport codes. Lawrence Livermore National Laboratory has implemented a complete suite of codes to test GNDS data. Simulations for the ENDF/B-VIII.0 cross-section library in GNDS format are presented. Deterministic and Monte Carlo radiation transport simulations with the Ardra and Mercury codes respectively, are validated against reactivities in fast criticality safety benchmark assemblies. Finally, Mercury simulations of {sup 238}U(n,f), {sup 237}Np(n,f) and {sup 239}Pu(n,f) reaction rates in Godiva, Jezebel and Flattop are compared to MCNP results and measured data. (authors)

61 RADIATION PROTECTION AND DOSIMETRY↗

ITS version 6.4: The Integrated TIGER Series of Monte Carlo Electron/Photon Radiation Transport Codes - Paper 40

ITS (Integrated TIGER Series) is a suite of fully coupled electron/photon Monte Carlo radiation transport codes. The package contains programs to perform 1D, 2D and 3D simulations. The 3D geometry representations include the traditional combinatorial geometry (CG), facet-based models, CAD models for those users who have a license for the ACIS{sup R} CAD libraries, and hybrid models of any combination. There is a multigroup version which permits adjoint analysis. The availability of source code permits the more sophisticated user to tailor the code to specific applications and to extend the capabilities of the codes to more complex applications. ITS is presently available only through a U.S.-government-use license. It is available once again through the Radiation Safety Information Computational Center (RSICC). (authors)

61 RADIATION PROTECTION AND DOSIMETRY↗

Recent Advances in the Use of TRIPOLI-4 Monte Carlo Code for Radiation Protection and Shielding Calculations - Paper 47

TRIPOLI-4 is a general purpose radiation transport code. It uses the continuous-energy Monte Carlo method to simulate neutron, photon, electron and positron transport in three-dimensional geometries. The main application areas of TRIPOLI-4 code include radiation protection and shielding, fission reactor physics, nuclear criticality safety, fusion reactor design, and nuclear instrumentation. For the radiation protection and shielding calculations with TRIPOLI-4 code, miscellaneous radiation sources options, various variance reduction options, and many useful tally options are available. Perturbation calculations on material densities and nuclide concentrations are routinely used in radiation protection applications. Parallel calculations with TRIPOLI-4 are also easy to perform with a PC under the linux/unix OS. To help the users to get the feedback from their test runs during the input data preparation and adjustment and to analyze the intermediate and final results from their production runs, several user-interface tools have been introduced. By using some application cases in the fields of radiation shielding, radiation dosimetry, and gamma spectrometry, this paper summarizes and demonstrates some essential improvements and possibilities in the use of TRIPOLI-4 code on fixed source calculations. (authors)

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

Adopting occupancy-based HVAC controls in commercial building energy codes: Analysis of cost-effectiveness and decarbonization potential

Recent research has shown the energy-saving potential of occupancy-based HVAC controls (OBCs) in commercial buildings. However, building energy codes have not fully adopted this technology. This study aims to evaluate the cost-effectiveness and decarbonization benefits of OBCs and provide guidance for integrating occupancy sensors into building energy code development. To this end, a parametric simulation using EnergyPlus and a nationwide cost-effectiveness analysis are carried out considering three building types and 40 representative cities in the U.S. Here, the findings reveal that the current cost-effectiveness performance of OBCs is limited due to the high cost of occupancy sensors. However, incorporating the societal cost of carbon factor in future energy and environmental policy could greatly enhance the actual cost-effectiveness performance. Besides, a reduction in the cost of occupancy sensors to approximately 60% of the current price level could also greatly shorten the discounted payback period of OBCs. Additionally, OBCs demonstrate significant potential in building decarbonization, with potential CO 2 emissions savings of more than 5.56 million metric tons across the three building types and 40 selected cities. Finally, policy implications are provided to guide the incorporation of occupancy-based HVAC controls in future energy codes.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗

CAFE: A NEW RELATIVISTIC MHD CODE

We introduce CAFE, a new independent code designed to solve the equations of relativistic ideal magnetohydrodynamics (RMHD) in three dimensions. We present the standard tests for an RMHD code and for the relativistic hydrodynamics regime because we have not reported them before. The tests include the one-dimensional Riemann problems related to blast waves, head-on collisions of streams, and states with transverse velocities, with and without magnetic field, which is aligned or transverse, constant or discontinuous across the initial discontinuity. Among the two-dimensional (2D) and 3D tests without magnetic field, we include the 2D Riemann problem, a one-dimensional shock tube along a diagonal, the high-speed Emery wind tunnel, the Kelvin–Helmholtz (KH) instability, a set of jets, and a 3D spherical blast wave, whereas in the presence of a magnetic field we show the magnetic rotor, the cylindrical explosion, a case of Kelvin–Helmholtz instability, and a 3D magnetic field advection loop. The code uses high-resolution shock-capturing methods, and we present the error analysis for a combination that uses the Harten, Lax, van Leer, and Einfeldt (HLLE) flux formula combined with a linear, piecewise parabolic method and fifth-order weighted essentially nonoscillatory reconstructors. We use the flux-constrained transport and the divergence cleaning methods to control the divergence-free magnetic field constraint.

79 ASTRONOMY AND ASTROPHYSICS↗

Verification of the CENTRM Module for Adaptation of the SCALE Code to NGNP Prismatic and PBR Core Designs

The generation of multigroup cross sections lies at the heart of the very high temperature reactor (VHTR) core design, whether the prismatic (block) or pebble-bed type. The design process, generally performed in three steps, is quite involved and its execution is crucial to proper reactor physics analyses. The primary purpose of this project is to develop the CENTRM cross-section processing module of the SCALE code package for application to prismatic or pebble-bed core designs. The team will include a detailed outline of the entire processing procedure for application of CENTRM in a final report complete with demonstration. In addition, they will conduct a thorough verification of the CENTRM code, which has yet to be performed. The tasks for this project are to: Thoroughly test the panel algorithm for neutron slowing down; Develop the panel algorithm for multi-materials; Establish a multigroup convergence 1D transport acceleration algorithm in the panel formalism; Verify CENTRM in 1D plane geometry; Create and test the corresponding transport/panel algorithm in spherical and cylindrical geometries; and, Apply the verified CENTRM code to current VHTR core design configurations for an infinite lattice, including assessing effectiveness of Dancoff corrections to simulate TRISO particle heterogeneity.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗

Alabama Residential Energy Code Field Study: Baseline Report

A research project in the state of Alabama identified opportunities to reduce homeowner utility bills in residential single-family new construction by increasing compliance with the state energy code. The study was initiated in March 2014 and continued through May 2014. During this period, research teams visited 134 homes during various stages of construction, resulting in a substantial data set based on observations made directly in the field. Analysis of the data has led to a better understanding of the energy features present in homes, and indicates nearly $1.3 million in potential savings to Alabama homeowners that could result from increased code compliance. Public and private entities within the state can use this information to justify and catalyze future investments in energy code training and related energy-efficiency programs.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗

Data Driven Commercial Building Energy Code Compliance and Technology Inventory for New York City

Building Performance Standards (BPS) are gaining national traction. A BPS will require new processes in the design, construction, and operation of buildings that take the occupants into account and enable predictive analysis to ensure compliance with current and future GHG emissions caps. In New York City, most buildings over 25,000 square feet will be regulated by a BPS starting in 2024, regardless of whether it is new construction permitted under current energy codes or an existing building. This research is one of the first to begin the evaluation of a long-term series of building policies in the context of an open data ecosystem, in cooperation with city agencies. Existing building policies enacted in NYC have ranged from building energy benchmarking and labeling to energy audits to the regulation of GHG emission in buildings. Through the development of a dataset related to building technologies and energy consumption, this project can help to evaluate if meaningful conclusions can be drawn for the data that has been largely self-reported in compliance with city regulations. This project will also provide lessons learned from a deep dive into these types of datasets to provide best practices for municipalities or states seeking to embark on policies like those enacted in NYC. In addition, a Building Automation System (BAS) Stretch Standard of Care (SSOC) for owners, designers, and building operators will enable the measurement and predictive analysis of energy consumption and GHG emissions at the plant, system, or component level, in anticipation of regulated GHG limits on buildings based on energy use. The SSOC is expected to be suitable for use on a national level. The primary feature of an SSOC is a standardized format for a set of BAS points that can be used to control and to gather data from individual plants, systems, or components that are related to building energy consumption. This project examined how measurements compare to prescriptive or simulation-based energy code targets, finding little correlation between predictive 8760-hour energy modeling and actual energy consumption for a small sample (n=27) of buildings constructed after 2015. Other analysis found that, while large multifamily housing (MFH) buildings showed a general trend similar to predicted reductions in energy use from the implementation of model commercial energy codes, this trend was not evident in the office, K-12 school, and hotel use groups in NYC. No upward or downward trends in energy consumption were found when buildings were grouped by size. Energy audit data were analyzed and it appears that there is bias by audit company on measures recommended to clients. Further research should be performed to cross-analyze this with other attributes, such as building size, vintage, and number of stories. Analysis found that for 281 buildings that were permitted and completed after 2015 and had submitted benchmarking data in 2022, between 81% and 96% (by use group) were found to be in compliance with the 2024 to 2029 NYC BPS emission caps, and between 55% and 89% were in compliance with the 2030-2034 caps. This work is beneficial to the public in helping policymakers and building stakeholders better understand the wide-ranging implications of a BPS.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗

Electric Readiness in Residential Energy Code: Technical Brief

This technical brief provides requirements for electric readiness that could be incorporated into model residential energy codes. It provides background on the basis and benefits of the provisions, and model code language that can be plugged into the IECC or adapted into other energy codes. This brief has been updated to reflect changes in the 2024 IECC.

2021 IECC↗

Maximum likelihood decoding analysis of accumulate-repeat-accumulate codes

In this paper, the performance of the repeat-accumulate codes with (ML) decoding are analyzed and compared to random codes by very tight bounds. Some simple codes are shown that perform very close to Shannon limit with maximum likelihood decoding.

LDPC codes turbo-like codes maximum likelihood dec↗

An Efficient Variable Length Coding Scheme for an IID Source

A scheme is examined for using two alternating Huffman codes to encode a discrete independent and identically distributed source with a dominant symbol. This combined strategy, or alternating runlength Huffman (ARH) coding, was found to be more efficient than ordinary coding in certain circumstances.

data decompression Huffman code coding scheme↗

Turbo Codes for PCS Applications

A number of the claims for turbo codes as a great advance in coding theory are confirmed, and a complete description is presented of an encoder/decoder pair that could be suitable for PCS applications. A new simple method for trellis termination is described, the effect of interleaver choice on the weight distribution of the code is analyzed, and unequal rate components (which yield better performance) are introduced.

coding turbo codes personal communication systems ↗

Implementation of a Coded Modulation for Deep Space Optical Communications

We present an efficient implementation of a coded modulation for the deep space optical channel. NASA designed this so called serially concatenated pulse position modulation (SCPPM) code to provide an optical link that can operate within one dB signal energy of the Shannon capacity during a nominal mission condition from Mars. Here, we describe some of the challenges in realizing the SCPPM decoder on a field-programmable gate array (FPGA). Through various architectural optimizations, we achieve a 6 Mbps decoder on a single FPGA. Moreover, we demonstrate that it is possible to communicate reliably on an efficient bits-per-photon count in an end-to-end SCPPM coded system.

turbo codes↗

Convolutional Encoding of Self-Dual Codes

Self-dual block codes of rate 1/2 are constructed here, The codes are of length 8m with weights w, w = 0 mod 4. The codes have a convolutional portion of length 8m-2 and non-systematic information length 4m-1.

self↗

Energy Cost Impact of Non-Residential Energy Code Requirements

The 2012 International Energy Conservation Code contains 396 separate requirements applicable to non-residential buildings; however, there is no systematic analysis of the energy cost impact of each requirement. Consequently, limited code department budgets for plan review, inspection, and training cannot be focused on the most impactful items. An inventory and ranking of code requirements based on their potential energy cost impact is under development. The initial phase focuses on office buildings with simple HVAC systems in climate zone 4C. Prototype building simulations were used to estimate the energy cost impact of varying levels of non-compliance. A preliminary estimate of the probability of occurrence of each level of non-compliance was combined with the estimated lost savings for each level to rank the requirements according to expected savings impact. The methodology to develop and refine further energy cost impacts, specific to building type, system type, and climate location is demonstrated. As results are developed, an innovative alternative method for compliance verification can focus efforts so only the most impactful requirements from an energy cost perspective are verified for every building and a subset of the less impactful requirements are verified on a random basis across a building population. The results can be further applied in prioritizing training material development and specific areas of building official training.

code compliance↗

Energy Cost Impact of Non-Residential Energy Code Requirements

The 2012 International Energy Conservation Code contains 396 separate requirements applicable to non-residential buildings; however, there is no systematic analysis of the energy cost impact of each requirement. Consequently, limited code department budgets for plan review, inspection, and training cannot be focused on the most impactful items. An inventory and ranking of code requirements based on their potential energy cost impact is under development. The initial phase focuses on office buildings with simple HVAC systems in climate zone 4C. Prototype building simulations were used to estimate the energy cost impact of varying levels of non-compliance. A preliminary estimate of the probability of occurrence of each level of non-compliance was combined with the estimated lost savings for each level to rank the requirements according to expected savings impact. The methodology to develop and refine further energy cost impacts, specific to building type, system type, and climate location is demonstrated. As results are developed, an innovative alternative method for compliance verification can focus efforts so only the most impactful requirements from an energy cost perspective are verified for every building and a subset of the less impactful requirements are verified on a random basis across a building population. The results can be further applied in prioritizing training material development and specific areas of building official training.

Energy Codes, code compliance↗

Highly-detailed neutronic and thermal-hydraulic coupled calculations for OPAL reactor using diverse codes and approaches

The industry-standard approach for designing and operating research reactors cores relies on well-established methodologies that consider uncoupled neutronic calculations and a subchannel analysis of the Thermal-Hydraulic (TH) associated problem. Advancements in computing power and codes allow detailed Multiphysics approaches to be implemented, thereby reducing conservatism. In this study, a comparative analysis of results from diverse detailed neutronic-TH coupled core approaches is developed. To address a realistic application case, the comparison is made for a reported critical configuration from the Open Pool Australian Lightwater research reactor (OPAL) at Hot Full Power (HFP) and low burnup. Both cell-core and stochastic methodologies for neutronics are evaluated, whereas two different subchannel codes are considered for TH. In conclusion, the convergence of the coupled schemes, and the consistency of the main parameters are discussed, showing the compatibility of the alternative methods and their ability to offer critical insights not captured by standard practices.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗