Comparative ultrafast spectroscopy and structural analysis of OCP1 and OCP2 from Tolypothrix
Not Available
59 BASIC BIOLOGICAL SCIENCES↗
Engineering topics
Bao, Han
Publications and source records attributed to Bao, Han.
Demonstration of Integrated Hazard Analysis for Digital Reactor Trip Systems
Digital instrumentation and control (I&C) upgrades are a vital research area for nuclear industry. Despite their performance benefits, deployment of digital I&C in nuclear power plants (NPPs) has been limited. Digital I&C systems exhibit complex failure modes including common cause failures (CCFs) which can be difficult to identify. This paper describes the development of a redundancy-guided application of the Systems-Theoretic Process Analysis (STPA) and Fault Tree Analysis (FTA) for the hazard analysis of digital I&C in advanced NPPs. The resulting Redundancy-guided System-theoretic Hazard Analysis (RESHA) is applied for the case study of a representative state-of-the-art digital reactor trip system. The analysis qualitatively and systematically identifies the most critical CCFs and other hazards of digital I&C systems. Ultimately, RESHA can help researchers make informed decisions for how, and to what degree, defensive measures such as redundancy, diversity, and defense-in-depth can be used to mitigate or eliminate the potential hazards of digital I&C systems.
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
An Integrated Risk Assessment Process for Digital Instrumentation and Control Upgrades of Nuclear Power Plants
Most of the existing nuclear power plants (NPPs) in the world rely on traditional analog instrumentation and control (I&C) systems for monitoring, control, and protection functions. With the industrial base largely moving to digital systems, the operation and maintenance of plants involves managing issues including lack of needed analog spare parts, increasing maintenance costs, and the loss of vendor support. Compared with existing analog I&C systems, digital I&C systems have significant functional advantages, such as reliable system performance in terms of accuracy and computational capability, high data handling and storage capabilities to fully measure and display operating conditions, and improved capabilities (e.g., fault tolerance, self-testing, signal validation, process system diagnostics). Therefore, the U.S. nuclear power industry has initiated the replacement of existing, aging analog systems with digital I&C technology, and is developing new designs for advanced plants using digital systems in integrated control rooms to provide modern control and protection systems. However, the qualification of digital I&C systems remains a challenge, especially the issue of software common cause failure (CCF), which has been difficult to address. A CCF is the malfunction of two or more plant components or functions due to a single failure source. CCFs have the potential to generate unanalyzed events or sequences that may not be bounded by previous plant accident analyses, therefore, to challenge the plant safety. Existing analyses on CCF in I&C systems are mainly focusing on hardware failures. With the application and upgrades of new digital I&C systems, software CCFs due to design flaws have become a potential threat to plant safety considering most redundancy designs are using the similar digital platforms or software in the operating and application systems. With complex multi-layer redundancy designs to meet the single failure criterion, these I&C safety systems are of a particular concern in the U.S. Nuclear Regulatory Commission (NRC) licensing procedures. Therefore, there is a need to develop an integrated risk assessment strategy with digital CCF and plant transient responses considered to assure the long-term safety and reliability of vital digital systems and reduce uncertainties in costs, time, and support integration of digital systems in the plant. The overall goal of this project is to deliver a strong technical basis to support effective, licensable, and secure digital I&C technologies for the digital upgrades to existing NPPs. To deal with the expensive licensing justifications from regulatory insights, this technical basis is instructive for nuclear vendors and utilities to effectively lower the costs associated with digital compliance and speed-up industry advances by: (1) defining an integrated risk-informed analysis process for digital I&C upgrades including hazard analysis, reliability analysis, and consequence analysis; (2) applying systematic and risk-informed tools to address CCFs and quantify responding failure probabilities for digital I&C technologies; (3) evaluating the impact of digital failures at the individual level, system level, and plant level; and (4) providing insights and suggestions on designs to manage the risks, thus to support the development, licensing, and deployment of advanced digital I&C technologies on NPPs. Upgrading digital I&C (safety and non-safety related) systems in existing NPPs within a cost-effective and regulatory acceptable way offers the foremost means of performance improvements and cost-reductions for existing NPPs. One key outcome of this project is to perform plant-specific risk assessment to provide a sustainable scientific support for enabling industry to balance the digital-related risks, costs, reliability, and safety.
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
X-ray radiolytic labeling reveals the molecular basis of orange carotenoid protein photoprotection and its interactions with fluorescence recovery protein
Not Available
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
A data-driven framework for error estimation and mesh-model optimization in system-level thermal-hydraulic simulation
We report over the past decades, several computer codes have been developed for simulation and analysis of thermal-hydraulics and system response in nuclear reactors under operating, abnormal transient, and accident conditions. However, simulation errors and uncertainties still inevitably exist even while these codes have been extensively assessed and used. In this work, a data-driven framework (Optimal Mesh/Model Information System, OMIS) is formulated and demonstrated to estimate simulation error and suggest optimal selection of computational mesh size (i.e., nodalization) and constitutive correlations (e.g., wall functions and turbulence models) for low-fidelity, coarse-mesh thermal-hydraulic simulation, in order to achieve accuracy comparable to that of high-fidelity simulation. Using results from high-fidelity simulations and experimental data with many fast-running low-fidelity simulations, an error database is built and used to train a machine learning model that can determine the relationship between local simulation error and local physical features. This machine learning model is then used to generate insight and help correct low-fidelity simulations for similar physical conditions. The OMIS framework is designed as a modularized six-step procedure and accomplished with state-of-the-art methods and algorithms. A mixed-convection case study was performed to illustrate the entire framework.
22 GENERAL STUDIES OF NUCLEAR REACTORS↗
Impact of D1-V185 on the Water Molecules That Facilitate O 2 Formation by the Catalytic Mn 4 CaO 5 Cluster in Photosystem II
The oxidations of the O 2 -evolving Mn 4 CaO 5 cluster in Photosystem II are coupled to the release of protons to the thylakoid lumen via one or more proton egress pathways. These pathways are comprised of extensive networks of hydrogen-bonded water molecules and amino acid side chains. The hydrophobic residue, D1-V185, is adjacent to numerous water molecules in one of these pathways. The D1-V185N mutation dramatically slows O–O bond formation. This impairment has been attributed to a disruption of the hydrogen-bonded water molecules that are crucial for proton egress or whose rearrangement is required for catalysis. In this study, Fourier transform infrared spectroscopy was employed to characterize the impact of the D1-V185N mutation on the carboxylate groups and water molecules that form a network of hydrogen bonds in this putative proton egress pathway. By analyzing carboxylate stretching modes, carbonyl stretching modes of hydrogen-bonded carboxylic acids, O–H stretching modes of hydrogen-bonded water molecules, and D–O–D bending modes, we obtain evidence that the D1-V185N mutation perturbs the extensive network of hydrogen bonds that extends from Y Z to D1-D61 to a greater extent than any mutation yet examined but does not alter the water molecules that interact directly with D1-D61. The mutation also alters the environments of the carboxylate groups whose pK a values change in response to the S 1 to S 2 and S 2 to S 3 transitions. Lastly, the mutation alters the environment of the water molecule whose bending mode vanishes during the S 2 to S 3 transition, consistent with assigning the Ca 2+ -bound W3 as the water molecule that deprotonates and joins oxo bridge O5 during the S 2 to S 3 transition, possibly as the second substrate water molecule for O 2 formation.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Study of Data-Driven Mesh-Model Optimization in System Thermal-Hydraulic Simulation
Quantification of nuclear power plant safety risk requires a systematic and yet practical approach to identification of accident scenarios, assessment of their likelihood and consequences. Instrumental to this goal is risk-informed safety margin characterization (RISMC) framework, whose realization requires computationally robust and affordable methods for sufficiently accurate simulation of complex multi-dimensional physical phenomena, such as turbulent and multi-phase flow. The CFD-like correlation-based codes with 3D simulation capability (e.g., GOTHIC) ensure computational efficiency using coarse mesh size and the sub-grid phenomena in the boundary layer that can be captured by adequate constitutive correlations. However, the error sources and user effects on the selection of mesh size and models lead to unpredictable simulation error, while rich High-Fidelity (HF) data from experiments and numerical simulation using validated code or DNS are not fully explored. It would be useful to have a “smart” data-driven multi-scale framework in which the low-resolution models can be “taught” to emulate high-resolution models. The objective of this work is to develop and evaluate a physical-based data-driven mesh-model optimization approach (Optimized Mesh/Model Information System, OMIS) to estimate the simulation error and give advice on the optimized selection of coarse mesh size and Low-Fidelity (LF) models for System Thermal Hydraulic (STH) simulation to achieve accuracy comparable to that of HF models. This approach takes advantages of computational efficiency of coarse-mesh simulation and application of Machine Learning (ML) algorithms.
97 MATHEMATICS AND COMPUTING↗
Synthetic OCP heterodimers are photoactive and recapitulate the fusion of two primitive carotenoproteins in the evolution of cyanobacterial photoprotection
The orange carotenoid protein (OCP) governs photoprotection in the majority of cyanobacteria. It is structurally and functionally modular, comprised of a C-terminal regulatory domain (CTD), an N-terminal effector domain (NTD) and a ketocarotenoid; the chromophore spans the two domains in the ground state and translocates fully into the NTD upon illumination. Using both the canonical OCP1 from Fremyella diplosiphon and the presumably more primitive OCP2 paralog from the same organism, we show that an NTD-CTD heterodimer forms when the domains are expressed as separate polypeptides. The carotenoid is required for the heterodimeric association, assembling an orange complex which is stable in the dark. Both OCP1 and OCP2 heterodimers are photoactive, undergoing light-driven heterodimer dissociation, but differ in their ability to reassociate in darkness, setting the stage for bioengineering photoprotection in cyanobacteria as well as for developing new photoswitches for biotechnology. Additionally, we reveal that homodimeric CTD can bind carotenoid in the absence of NTD, and name this truncated variant the C-terminal domain-like carotenoid protein (CCP). This finding supports the hypothesis that the OCP evolved from an ancient fusion event between genes for two different carotenoid-binding proteins ancestral to the NTD and CTD. We suggest that the CCP and its homologs constitute a new family of carotenoproteins within the NTF2-like superfamily found across all kingdoms of life.
59 BASIC BIOLOGICAL SCIENCES↗
Connected Building Challenge – Seattle Demonstration
PNNL's first-ever innovation challenge invited teams to leverage PNNL's VOLTTRON technology to create solutions that advance the growth of the smart building market. Five teams presented their solutions at Seattle's Smart Buildings Center in early August 2016. This video summarizes the event.
29 ENERGY PLANNING, POLICY, AND ECONOMY↗
A Study of BWR Mark I Station Blackout Accident with GOTHIC Modeling
The overall objective of this study is to develop a high-fidelity simulation capability for the analysis of accident progression during Station Black-Out (SBO) scenario in Boiling Water Reactor (BWR) Mark I plant. The motivation is on predicting the effectiveness of containment venting within accident mitigation strategy and how to avoid core melt by choosing a proper time to initiate primary system venting. In this work, a GOTHIC model has been developed to support characterization of reactor safety systems performance and evaluation of the venting strategy. The GOTHIC model provides a seamless coupled simulation of the reactor coolant system and the containment system based on the design of the Peach Bottom-2 plant system. Efforts are also taken on the analysis for the primary system venting strategy. The safe time intervals (so-called “safe venting window”) to initiate the primary system depressurization in order to optimize the early cooling strategy by adding fire water and avoid core melt are also studied based on the heat removal capability (HRC) of the reactor vessel coolant. This concept is instructive for the operation of the safety systems during the SBO accident mitigation.
22 GENERAL STUDIES OF NUCLEAR REACTORS↗