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Development and application of diagnostic systems to achieve fault tolerance

Description: Much work is currently being done to develop and apply diagnostic systems that are tolerant to faulted conditions in the process being monitored and in the sensors that measure the critical parameters associated with the process. A fault-tolerant diagnostic system based on state-determination, pattern-recognition techniques is currently undergoing testing and evaluation in certain applications at the EBR-II reactor. Testing and operational experience with the system to date has shown a high degree of tolerance to sensor failures, while being sensitive to very slight changes in the plant operational state. This paper briefly mentions related work being done by others, and describes in more detail the pattern-recognition system and the results of the testing and operational experience with the system at EBR-II. 9 refs., 10 figs.
Date: January 1, 1989
Creator: King, R.W. & Singer, R.M.
Partner: UNT Libraries Government Documents Department

Studies related to protected loss of flow accidents in a fast breeder reactor

Description: Intrinsic to the design of liquid-metal-cooled fast-breeder-reactors (LMFBR) are a number of physical processes which inherently contribute to the safe operation and shutdown of the plant. Natural circulation cooling of the plant following a complete loss of all on-site electrical power is analyzed. The calculations which are presented demonstrate that the reactor core is adequately and stably cooled by natural circulation for a wide range of postulated initial operating conditions and plant design parameters.
Date: January 1, 1979
Creator: Singer, R.M.; Gillette, J.L. & Mohr, D.
Partner: UNT Libraries Government Documents Department

Use of a pattern recognition scheme to compensate for critical sensor failures

Description: A general mathematical approach (the SSA code) for embodying learned data from a complex system and combining it with a current observation to estimate the true current state of the system has been applied to a nuclear power plant (EBR-II). Sensor validation and generation of estimates signals based upon the plant operating state are used for replacement of signals from multiple faulted sensors on a near real-time basis. A direct experimental demonstration of the capability of the code to perform these tasks is presented in which multiple sensor faults in EBR-II are simulated. 2 refs., 4 figs.
Date: January 1, 1989
Creator: Singer, R.M.; King, R.W. & Mott, J.
Partner: UNT Libraries Government Documents Department

Transition from forced to natural convective flow in an LMFBR under adverse thermal conditions

Description: One of the most important aspects of the demonstration of the safety of liquid metal cooled fast reactors (LMFBR) is the assurance of adequate cooling of the reactor and critical structures during all potential or hypothetical events. To this end, a design philosophy has developed in which alternate heat removal systems are included in a plant in order to provide independent, diverse, and redundant cooling from the normal heat transport system. Recent studies have examined various aspects of natural convective flow in such systems and preliminary conclusions from these efforts have indicated that the basic phenomena are reasonably well understood and predictable in most cases. However, in certain situations where significant thermal stratification occurs, the resulting buoyancy-driven flow patterns can become quite complex and as a result, the confidence in computer simulations diminishes. The purpose of this paper is to present the results of an experimental and analytical study of one class of such problems in which the development of natural convective flow requires a transition through an unstably stratified condition. The experiments were conducted in the Experimental Breeder Reactor II (EBR-II) and the analytical tool used was the NATDEMO system simulation code.
Date: January 1, 1982
Creator: Singer, R.M.; Mohr, D. & Gillette, J.L.
Partner: UNT Libraries Government Documents Department

A pattern-recognition-based, fault-tolerant monitoring and diagnostic technique

Description: A properly designed monitoring and diagnostic system must be capable of detecting and distinguishing sensor and process malfunctions in the presence of signal noise, varying process states and multiple faults. The technique presented in this paper addresses these objectives through the implementation of a multivariate state estimation algorithm based upon pattern recognition methodology coupled with a statistically-based hypothesis test. Utilizing a residual signal vector generated from the difference between the estimated and measured current states of a process, disturbances are detected and identified with statistical hypothesis testing. Since the hypothesis testing utilizes the inherent noise on the signals to obtain a conclusion and the state estimation algorithm requires only a majority of the sensors to be functioning to ascertain the current state, this technique has proven to be quite robust and fault-tolerant. Several examples of its application are presented.
Date: June 1, 1995
Creator: Singer, R.M.; Gross, K.C. & King, R.W.
Partner: UNT Libraries Government Documents Department

Expert system for online surveillance of nuclear reactor coolant pumps

Description: This report describes an expert system for online surveillance of nuclear reactor coolant pumps. This system provides a means for early detection of pump or sensor degradation. Degradation is determined through the use of a statistical analysis technique, sequential probability ratio test, applied to information from several sensors which are responsive to differing physical parameters. The results of sequential testing of the data provide the operator with an early warning of possible sensor or pump failure.
Date: December 31, 1992
Creator: Gross, K.C.; Singer, R.M. & Humenik, K.E.
Partner: UNT Libraries Government Documents Department

Experimental study of the transition from forced to natural circulation in EBR-II at low power and flow

Description: A series of tests have been conducted in EBR-II which studied the dynamics of the transition from forced to natural circulation flow in a liquid-metal-cooled fast breeder reactor (LMFBR). Each test was initiated by abruptly tripping an electromagnetic pump which supplies 5 to 6% of the normal full operational primary flow rate. The ensuing flow coast-down reached a minimum value after which the flow increased as natural circulation was established. The effects of secondary system flow through the intermediate heat exchanger and reactor decay power level on the minimum in-core flow rates and maximum in-core temperatures were examined.
Date: January 1, 1979
Creator: Gillette, J L; Singer, R M; Tokar, J V & Sullivan, J E
Partner: UNT Libraries Government Documents Department

Analytical enhancement of automotive sensory system reliability

Description: The technical issues that must be addressed to assure reliable sensor systems include the following: validation (is the sensor properly functioning and/or has the component/system deteriorated); failure accommodation (can the system adequately function with a degraded sensor); and system diagnostics (what has failed, what probabilities of missed positives and false positives are acceptable and is real-time on-board response needed). Clearly, the essential activity is the development of sensors to meet the accuracy and reliability requirements in the anticipated operational environment of a vehicle over it`s useful life. However, it is equally important that the data generated by these sensors be processed to extract the information needed to assure that the sensors and the systems they are monitoring and/or controlling remain within their intended operating specifications. The purpose of this paper is to report on an analytical method used to address the above technical issues and to illustrate particular applications of this method.
Date: June 1, 1994
Creator: Singer, R. M.; Gross, K. C. & King, R. W.
Partner: UNT Libraries Government Documents Department

Non-isotropic thermal behavior of an MHTGR fuel block: Impact upon reactivity feedback

Description: This report discusses lumped parameter and detailed multi-dimensional thermal analyses of a New Production Modular High Temperature Gas Cooled Reactor (NP-MHTGR) fuel block were conducted that indicated that during a power transient, the target temperature would rise significantly later than the fuel temperature. This behavior, which is due to radiative, convective and conductive heat transport phenomena within the fuel block coupled with the significantly different thermal physical properties of the fuel block materials, leads to the potential for a delayed positive contribution to the temperature coefficient of reactivity of the NP-MHTGR core during TOP events. These results have indicated the need for additional experimental and analytical studies in order to more fully assess the design, operational and safety implications of this phenomenon. In addition, experiments in the TREAT facility are planned to provide additional data to assist in the capabilities to predict the reactivity feedback characteristics of the NP-MHTGR core. These studies will be the subject of a future paper.
Date: September 1, 1992
Creator: Delpech, M.; Singer, R. M. & Finck, P. J.
Partner: UNT Libraries Government Documents Department

Applications of pattern recognition techniques to online fault detection

Description: A common problem to operators of complex industrial systems is the early detection of incipient degradation of sensors and components in order to avoid unplanned outages, to orderly plan for anticipated maintenance activities and to assure continued safe operation. In such systems, there usually are a large number of sensors (upwards of several thousand is not uncommon) serving many functions, ranging from input to control systems, monitoring of safety parameters and component performance limits, system environmental conditions, etc. Although sensors deemed to measure important process conditions are generally alarmed, the alarm set points usually are just high-low limits and the operator`s response to such alarms is based on written procedures and his or her experience and training. In many systems this approach has been successful, but in situations where the cost of a forced outage is high an improved method is needed. In such cases it is desirable, if not necessary, to detect disturbances in either sensors or the process prior to any actual failure that could either shut down the process or challenge any safety system that is present. Recent advances in various artificial intelligence techniques have provided the opportunity to perform such functions of early detection and diagnosis. In this paper, the experience gained through the application of several pattern-recognition techniques to the on-line monitoring and incipient disturbance detection of several coolant pumps and numerous sensors at the Experimental Breeder Reactor-II (EBR-II) which is located at the Idaho National Engineering Laboratory is presented.
Date: November 1, 1993
Creator: Singer, R. M.; Gross, K. C. & King, R. W.
Partner: UNT Libraries Government Documents Department

Experimental Breeder Reactor II inherent shutdown and heat removal tests - test results and analysis

Description: A test program is being conducted to demonstrate that a power producing Liquid Metal Reactor (LMR) can passively remove shutdown heat by natural convection; passively reduce power in response to a loss of reactor flow and passively reduce power in response to a loss of the balance of plant heat sink. Measurements and pretest predictions confirm that natural convection is a reliable, predictable method of shutdown heat removal and suggest that safety-related pumps or pony motors are not necessary for safe, shutdown heat removal in a LMR. Measurements from tests in which reactor flow and heat rejection to the balance of plant were perturbed show that reactivity feedbacks can passively control power and temperature. This data is a basis for additional tests including a complete loss-of-flow without scram and a complete loss of heat sink without scram.
Date: January 1, 1985
Creator: Planchon, H.P.; Singer, R.M.; Mohr, D.; Feldman, E.E.; Chang, L.K. & Betten, P.R.
Partner: UNT Libraries Government Documents Department

Decay heat removal and dynamic plant testing at EBR-II

Description: The complete testing program at EBR-II directed towards transient thermal-hydraulic performance is described. The program, which was initially directed towards an understanding of the dynamics of natural convective flow and the validation of related computer codes, has evolved into studies of unprotected transients. These later tests are intended to provide experimental data as well as to directly demonstrate the inherently safe response of an LMR to transients which in the recent past were thought to lead to core disruption. Tpical results and conclusions from the series of protected natural circulation tests are also presented.
Date: January 1, 1985
Creator: Singer, R.M.; Planchon, H.P.; Betten, P.R.; Chang, L.K.; Feldman, E.E. & Mohr, D.
Partner: UNT Libraries Government Documents Department

EBR-II inherent shutdown and heat removal tests: a survey of test results

Description: An experimental study of inherently safe characteristics of LMFBR systems is being conducted in EBR-II. Experiments have been conducted which show (1) capabilities of heat removal without the aid of active safety systems and (2) capabilities to mitigate a reduction in-core cooling flow or heat rejection to the balance of plant (BOP) without aid of active control or protection systems. Experiments involving loss of forced reactor cooling flow and loss of all heat rejection to the BOP are planned to be conducted. Purpose of this paper is to summarize the result of the test program by presenting representative test data.
Date: January 1, 1985
Creator: Planchon, H.P.; Singer, R.M.; Mohr, D.; Feldman, E.E.; Chang, L.K. & Betten, P.R.
Partner: UNT Libraries Government Documents Department

Response of EBR-II to a complete loss of primary forced flow during power operation

Description: Detailed measurements of the thermal, hydraulic, and neutronic response of EBR-II to a complete loss of primary forced flow followed by a PPS-activated scram are presented. The experimental results clearly indicate a smooth transition to natural convective flow with a quite modest incore temperature transient. The accompanying calculations using the NATDEMO code agree quite well with the measured temperatures and flow rates throughout the primary system. The only region of the plant where a significant discrepancy between the measurements and calculations occurred was in the IHX. The reasons for this result could not be definitively determined, but it is speculated that the one-dimensional assumptions used in the modeling may not be valid in the IHX during buoyancy driver flows.
Date: January 1, 1980
Creator: Singer, R.M.; Gillette, J.L.; Mohr, D.; Tokar, J.V.; Sullivan, J.E. & Dean, E.M.
Partner: UNT Libraries Government Documents Department