PM-HIP Research for Pressure Retaining Applications Within the Electric Power Industry

For more than 60 years now, the nuclear power industry has relied on structural and pressure retaining materials generated via established manufacturing practices such as casting, plate rolling-and-welding, forging, drawing, and/or extrusion. During the past three years, EPRI has been leading the development and introduction of another established process, powder metallurgy and hot isostatic pressing (PM/HIP), for pressure retaining applications in the electric power industry. The research includes assessment of two primary alloys: 316L stainless steel and Grade 91 creep-strength enhanced ferritic steels, for introduction into the ASME Boiler and Pressure Vessel Code. Continuing DOE and EPRI research on other structural/pressure retaining alloys such as Alloy 690, SA 508 Class 1, Alloy 625, hard-facing materials, and others are also underway. This research will have a tremendous impact as we move forward over the next few decades on the selection of new alloys and components for advanced light water reactors and small modular reactors. Furthermore, fabrication of high alloy materials/components may require the use of new manufacturing processes to achieve acceptable properties for higher temperature applications such as those in Generation IV applications. Current research by EPRI and DOE will be reviewed and emphasis will be targeted at advanced applications where PM/HIP may be applied in the future.

Approaches to Process Monitoring in Small Modular Reactors

One of the advantages of small modular reactors (SMRs) is their possible deployment in remote locations and continued long-term operation with minimum downtime. In order to achieve this operational goal, the SMRs may require remote and continuous monitoring of process parameters. This feature is also important in monitoring critical parameters during severe accidents and for post-accident recovery. Small integral light water reactors have in-vessel space constraints and many of the traditional instrumentation are not practical in actual implementation. In order to resolve this issue, experiments were carried out on a flow test loop to characterize the relationship among process variables (flow rate, pressure, water level) and pump motor signatures. The paper presents the findings of this research with implications in relating electrical signatures to pump parameters.

Inservice Testing Program Improvements for New Reactors Small Modular Reactors (SMRs)

The nuclear industry is preparing for the licensing and construction of new nuclear power plants in the United States. Several new designs have been developed and approved, including the “traditional” reactor designs, the passive safe shutdown designs and the small modular reactors (SMRs). The American Society of Mechanical Engineers (ASME) provides specific Codes used to perform preservice inspection/testing and inservice inspection/testing for many of the components used in the new reactor designs. The U.S. Nuclear Regulatory Commission (NRC) reviews information provided by applicants related to inservice testing (IST) programs for Design Certifications and Combined Licenses (COLs) under Part 52, “Licenses, Certifications, and Approvals for Nuclear Power Plants,” in Title 10 of the Code of Federal Regulations (10 CFR Part 52) (Reference 1). The 2012 Edition of the ASME OM Code defines a post-2000 plant as a nuclear power plant that was issued (or will be issued) its construction permit, or combined license for construction and operation, by the applicable regulatory authority on or following January 1, 2000. The New Reactors OM Code (NROMC) Task Group (TG) of the ASME Code for Operation and Maintenance of Nuclear Power Plants (NROMC TG) is assigned the task of ensuring that the preservice testing (PST) and IST provisions in the ASME OM Code to address pumps, valves, and dynamic restraints (snubbers) in post-2000 nuclear power plants are adequate to provide reasonable assurance that the components will operate as needed when called upon. Currently, the NROMC TG is preparing proposed guidance for the treatment of active pumps, valves, and dynamic restraints with high safety significance in non-safety systems in passive post-2000 reactors including SMRs.

Development of Operational Concepts for Advanced SMRs: The Role of Cognitive Systems Engineering

Advanced small modular reactors (AdvSMRs) will use advanced digital instrumentation and control systems, and make greater use of automation. These advances not only pose technical and operational challenges, but will inevitably have an effect on the operating and maintenance cost of new plants. However, there is much uncertainty about the impact of AdvSMR designs on operational and human factors considerations, such as workload, situation awareness, human reliability, staffing levels, and the appropriate allocation of functions between the crew and various automated plant systems. Existing human factors and systems engineering design standards and methodologies are not current in terms of human interaction requirements for dynamic automated systems and are no longer suitable for the analysis of evolving operational concepts. New models and guidance for operational concepts for complex socio-technical systems need to adopt a state-of-the-art approach such as Cognitive Systems Engineering (CSE) that gives due consideration to the role of personnel. The approach described here helps to identify and evaluate human challenges related to non-traditional operational concepts. A framework for defining operational strategies was developed based on an analysis of the Experimental Breeder Reactor-II (EBR-II), a small (20MWe) sodium-cooled reactor that was successfully operated for thirty years. Insights from the application of the systematic application of the methodology and its utility are reviewed and arguments for the formal adoption of CSE as a value-added part of the Systems Engineering process are presented.

Soil Structure and Fluid Interaction Assessment of New Modular Reactor: Part 1 — Numerical Simulation of Fluid Motion due to Seismic Waves

In recent years, the nuclear industry has proposed design of affordable small modular reactors (SMR), which will be installed below grade. A complex soil-structure-fluid interaction is expected to occur during a seismic event at such installation sites. A thorough understanding of this interaction is needed for the purpose of designing damping or isolation systems as well as to determine the adequacy and safety of these devices. A fully dynamically coupled analysis of the surrounding soil, reactor structure, and contained fluid within the reactor would provide the most accurate estimate of the forces acting on the SMR, but such an exercise is difficult to accomplish due to large discrepancies in length and time scales of each subsystem. It also would be computationally intensive to explicitly model all the detail physical features that affect system response in a single analysis framework. A sequential one-way explicit coupling between parts of the system, such as soil-structure or fluid-structure interaction in response to seismic ground motion, would provide some reasonable engineering information useful to designers and regulators. A two part study was conducted to understand the soil-structure and fluid-structure interaction in response to a seismic event for an SMR. The present paper describes the latter (fluid-structure interaction), where the containment fluid behavior during a seismic event is studied. A simplified two-dimensional computational fluid dynamics (CFD) model, representing a mockup structure based on the mPower reactor is developed in the study. It is used to simulate the sloshing motion of the fluid during a seismic event. A general volume of flow (VOF) approach is employed to simulate the sloshing motion and track the air-water interface. Ground acceleration calculated from a separate mechanical analysis is adopted in the study to specify the body forces experienced by the fluid. CFD simulations are performed for two different cases that correspond to two different input seismic waveforms. Simulated results highlight the movement of air-water interface due to sloshing within the containment building. The total horizontal and vertical forces on the structure, resulting from the sloshing motion were calculated. A Fourier analysis of the calculated fluid forces shows the dominant frequencies of the force, due to fluid sloshing, are different from that of the seismic acceleration. Similar dominant frequencies of the forces are predicted using two different input seismic waveforms. The magnitudes of the forces varied, depending on the magnitude of the seismic waveform input.

The U.S. Federal Market as an Early Adopter of SMRs

The Federal Government accounts for about 2% of energy usage within the United States, with electricity accounting for approximately one-fifth of this usage. The Department of Defense (DOD) is the largest energy consumer across all Federal Agencies, accounting for nearly half of total use and has implemented programs to assure sustainable energy supplies for meeting mission critical operations. As prototype systems of Small Modular Reactors mature during the remainder of this decade, there is growing interest at senior levels of government to use the secure confines of military bases for electricity generated with SMRs to service power requirements of the DOD base and possibly the surrounding communities. This paper explores the potential for using DOD as an early adopter of SMRs from perspectives of the size of the market and adaptability of the current procurement process for private ownership of SMRs on military bases. Such an approach is shown to be consistent with DOD Sustainability objectives, as well as ensuring a continuation of the projected erosion of diversity mix for prime power generation within the U.S. A review of contract types for energy services are evaluated from the perspective of including SMRs. Required modifications for SMRs to be a part of this energy mix for Federal Agencies are presented.

Initiators and Triggering Conditions for Adaptive Automation in Advanced Small Modular Reactors

It is anticipated that Advanced Small Modular Reactors (AdvSMRs) will employ high degrees of automation. High levels of automation can enhance system performance, but often at the cost of reduced human performance. Automation can lead to human out-of the loop issues, unbalanced workload, complacency, and other problems if it is not designed properly. Researchers have proposed adaptive automation (defined as dynamic or flexible allocation of functions) as a way to get the benefits of higher levels of automation without the human performance costs. Adaptive automation has the potential to balance operator workload and enhance operator situation awareness by allocating functions to the operators in a way that is sensitive to overall workload and capabilities at the time of operation. However, there still a number of questions regarding how to effectively design adaptive automation to achieve that potential. One of those questions is related to how to initiate (or trigger) a shift in automation in order to provide maximal sensitivity to operator needs without introducing undesirable consequences (such as unpredictable mode changes). Several triggering mechanisms for shifts in adaptive automation have been proposed including: operator initiated, critical events, performance-based, physiological measurement, model-based, and hybrid methods. As part of a larger project to develop design guidance for human-automation collaboration in AdvSMRs, researchers at Idaho National Laboratory have investigated the effectiveness and applicability of each of these triggering mechanisms in the context of AdvSMR. Researchers reviewed the empirical literature on adaptive automation and assessed each triggering mechanism based on the human-system performance consequences of employing that mechanism. Researchers also assessed the practicality and feasibility of using the mechanism in the context of an AdvSMR control room. Results indicate that there are tradeoffs associated with each mechanism, but that some are more applicable to the AdvSMR domain than others. The two mechanisms that consistently improve performance in laboratory studies are operator initiated adaptive automation based on hierarchical task delegation and the Electroencephalogram (EEG)–based measure of engagement. Current EEG methods are intrusive and require intensive analysis; therefore it is not recommended for an AdvSMR control rooms at this time. Researchers also discuss limitations in the existing empirical literature and make recommendations for further research.

The Mitsubishi Small Module High Temperature Gas-Cooled Reactor “MHR-50/100is” — Present Design Status and Its Prospect for Commercialization

Mitsubishi Heavy Industries, Ltd. (MHI) has been carrying on development of a SMR for global strategic business and a conceptual design study of HTGR, namely MHR-50/100is having a high inherent safety and a high economical advantage for commercialization with supporting by Japan Atomic Energy Agency (JAEA). To begin with, a design philosophy of the MHR-50/100is had been set and the next phase, a conceptual design including plant dynamics analysis to investigate operational function and plant controllable performance had been carried out. It has been improved to establish higher safety level to meet the safety requirements after TEPCO’s Fukushima Daiichi Accident on March 11, 2011 in Japan. A market research and a financial analysis to review a feasibility of nuclear business have been studied. Consequently, it has concluded that the large market and the business potential will be prospected. We envisioned that it is effective for acceleration of MHR-50/100is utilization to show wider application of the nuclear energy in general industry as well as electricity generation. In the study cooperative with these users, we have studied on a practical applicability of MHR-50/100is in a typical general industry. A concept of the heat utilization plant consisting of the MHR-50/100is and hydrogen production plant has been developed; a safety concern has been evaluated. This paper reports a summary of a series of the conceptual design studies, and the various evaluation analyses in which we investigated a technical feasibility and a business potential of MHR-50/100is.

The Flow Characteristics of a New Microchannel Heat Exchanger

Cooling technology is very important for the safe operation of nuclear power plant. Microchannel heat exchangers have been treated as one of the most potential cooling technologies. Flow characteristics of microchannels (hydraulic diameter is 100 μm) with a new structure, with which obstructions were placed along channels walls, have been investigated under the consideration of the effect of compressibility and viscosity heating. The influences of the Reynolds number, obstruction height, pitch, and geometry and width height ratio on the flow characteristics are investigated. It indicated that Poiseuille number increased with the increasing of Reynolds number and second order increasing with obstruction height. It was observed that the obstruction pitch is an important design parameter for flow characteristics, the pressure drop decreased with the increase of the obstruction pitch. The Poiseuille number reaches maximum for triangular obstruction and minimum for semicircle obstruction. It is also found that width height Ratio of obstruction plays an important role, Poiseuille number will obviously increase when width height Ratio of obstruction is bigger than 1.