Re-evaluation of Savannah River reactor transient reactivity coefficient tests: The effect of delayed neutron constants and spatial variations

Transient reactivity test conducted in one of the Savannah River production reactors in 1962 have been re-evaluated. A significantly lower (more negative) coolant temperature coefficient is now ascribed to that test; {minus}1 pcm/Deg-C vs the previously obtained +2 pcm/Deg-C. The change from the previous value is because of revisions to delayed neutron constants and accounting for spatial effects. The new value is in reasonable agreement with the currently calculated value of {minus}2 pcm/Deg-C, considering measurements and calculational uncertainties. Therefore, we conclude that the current analytic models for physics and transient analysis are fully consistent with the 1962 test observation, and that there is no basis for assigning a calculational bias or increasing uncertainty allowances. 2 refs

Reliability evaluation of the Savannah River reactor leak detection system

The Savannah River Reactors have been in operation since the mid-1950's. The primary degradation mode for the primary coolant loop piping is intergranular stress corrosion cracking. The leak-before-break (LBB) capability of the primary system piping has been demonstrated as part of an overall structural integrity evaluation. One element of the LBB analyses is a reliability evaluation of the leak detection system. The most sensitive element of the leak detection system is the airborne tritium monitors. The presence of small amounts of tritium in the heavy water coolant provide the basis for a very sensitive system of leak detection. The reliability of the tritium monitors to properly identify a crack leaking at a rate of either 50 or 300 lb/day (0.004 or 0.023 gpm, respectively) has been characterized. These leak rates correspond to action points for which specific operator actions are required. High reliability has been demonstrated using standard fault tree techniques. The probability of not detecting a leak within an assumed mission time of 24 hours is estimated to be approximately 5 {times} 10{sup {minus}5} per demand. This result is obtained for both leak rates considered. The methodology and assumptions used to obtain this result are described in this paper. 3 refs., 1 fig., 1 tab

Westinghouse PAFC program update

Objective was to develop and demonstrate the air-cooled phosphoric acid fuel cell performance and economics. Completion of cell technology and manufacturing process developments and the supporting cell/stack engineering effort have culminated in the end product module. Two modules were built and tested: the Engineering Model Module and the Demonstration Module. 2 tabs, 3 figs, 2 refs. (DLC

Fracture assessment of Savannah River Reactor carbon steel piping

The Savannah River Site (SRS) production reactors have been in operation since the mid-1950's. One postulated failure mechanism for the reactor piping is brittle fracture of the original A285 and A53 carbon steel piping. Material testing of archival piping determined (1) the static and dynamic tensile properties; (2) Charpy impact toughness; and (3) the static and dynamic compact tension fracture toughness properties. The nil-ductility transition temperature (NDTT), determined by Charpy impact test, is above the minimum operating temperature for some of the piping materials. A fracture assessment was performed to demonstrate that potential flaws are stable under upset loading conditions and minimum operating temperatures. A review of potential degradation mechanisms and plant operating history identified weld defects as the most likely crack initiation site for brittle fracture. Piping weld defects, as characterized by radiographic and metallographic examination, and low fracture toughness material properties were postulated at high stress locations in the piping. Normal operating loads, upset loads, and residual stresses were assumed to act on the postulated flaws. Calculated allowable flaw lengths exceed the size of observed weld defects, indicating adequate margins of safety against brittle fracture. Thus, a detailed fracture assessment was able to demonstrate that the piping systems will not fail by brittle fracture, even though the NDTT for some of the piping is above the minimum system operating temperature

Westinghouse independent safety review of Savannah River production reactors

Westinghouse Electric Corporation has performed a safety assessment of the Savannah River production reactors (K,L, and P) as requested by the US Department of Energy. This assessment was performed between November 1, 1988, and April 1, 1989, under the transition contract for the Westinghouse Savannah River Company's preparations to succeed E.I. du Pont de Nemours Company as the US Department of Energy contractor for the Savannah River Project. The reviewers were drawn from several Westinghouse nuclear energy organizations, embody a combination of commercial and government reactor experience, and have backgrounds covering the range of technologies relevant to assessing nuclear safety. The report presents the rationale from which the overall judgment was drawn and the basis for the committee's opinion on the phased restart strategy proposed by E.I. du Pont de Nemours Company, Westinghouse, and the US Department of Energy-Savannah River. The committee concluded that it could recommend restart of one reactor at partial power upon completion of a list of recommended upgrades both to systems and their supporting analyses and after demonstration that the organization had assimilated the massive changes it will have undergone

Sensor-based material tagging system

Electronic identification tags are being developed for tracking material and personnel. In applying electronic identification tags to radioactive materials safeguards, it is important to measure attributes of the material to ensure that the tag remains with the material. The addition of a microcontroller with an on-board analog-to-digital converter to an electronic identification tag application-specific integrated-circuit has been demonstrated as means to provide the tag with sensor data. Each tag is assembled into a housing, which serves as a scale for measuring the weight of a paint-can-sized container and its contents. Temperature rise of the can above ambient is also measured, and a piezoelectric detector detects disturbances and immediately puts the tag into its alarm and beacon mode. Radiation measurement was also considered, but the background from nearby containers was found to be excessive. The sensor-based tagging system allows tracking of the material in cans as it is stored in vaults or is moved through the manufacturing process. The paper presents details of the sensor-based material tagging system and describes a demonstration system

Dynamics analyses of space power systems using the salt code

The dynamic behavior of large space power systems has been identified as a significant technical issue. To date several analyses of reactor kinetics have been reported in the literature, but there have been few (if any) studies of the dynamic response of the entire space power system. The problem is complex and required analytical methods are not generally available. Furthermore, given the conceptual state of current MMW space power systems designs, dynamic models of components are not generally available. We have used the SALT code to perform preliminary analyses of the startup and shutdown transients of several proposed MMW system designs. In this paper we will provide a description of the code methodology and present results of the analyses performed for the NERVA derivative reactor (NDR) system. 3 refs., 3 figs

Prediction of instability using the KR-curve approach

SIGLEReprint from ASTM Special Technical Publication 912 (1986) p. 99-113 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Simulating operator decision processes at Savannah River

Cognitive Environment Simulation (CES) is both a methodology and an AI tool. As a methodology, it denotes a technique that models human operators' cognitive processes to either (1) aid in designing the interface to a complex system (such as nuclear reactor control room), or (2) assess the cognitive causality that affects the likelihood of human error in specific accident scenarios. As an AI tool, CES is an expert system that models human operators' reasoning and decision processes. In this application, both the methodology and the tool were focused on modeling human intention formation and errors in a problem-solving context. The CES tool consist of an inference engine and knowledge base that are object-oriented at a level of analysis to facilitate the modeling of human decision-making. While descended from the early AI successes of Internist and Caduceus in the arena of medical diagnosis (Pople, 1985), CES has been restructured and enhanced to deal with additional knowledge requirements encountered in real-time control of complex systems. This version of CES receives its input from a virtual display, a file of several hundred plant parameters whose values are sampled every five seconds. Analogously to a crew observing control room displays, CES reads the virtual display file and evaluates what it sees.'' CES' evaluation is based on the changes it observes in relation to its prior knowledge of operational goals, plant structure, event history, and operator procedures that are represented in its knowledge base. Its output is an English-like protocol of observations, explanations, and declarations of recommended action (intent) that it would take if it could. These last also represent actions that human operator(s) could take if they so decide. Through manipulation of its knowledge base, CES can also be caused to make mistakes for human-like reasons