Steam Generator Tube Rupture Event Research Articles

Frequency and Consequences Associated with a Steam Generator Tube Rupture Event

The results of a study into the frequency of steam generator tube rupture (SGTR) events are presented, including estimates on the upper and lower bound frequencies for U-tube and once-through steam generator plants and single- and multiple-tube ruptures. In addition, commercial pressurized water reactor operational data have been researched and iodine spiking data used to develop data bases of maximum resultant iodine concentrations and release rates. The frequencies and iodine spiking magnitudes are compared with other studies, and conclusions are drawn regarding current guidelines for analysis of this design-basis transient.

A Guillotine Tube Rupture Modeling Technique Using RETRAN-02

A method allowing individual representation of a ruptured steam generator tube without including it explicitly in the RETRAN-02 nodalization was investigated. The resulting methodology allows accurate representation of flow through a single ruptured tube without incurring prohibitive computing costs.The study considered a wide variety of fluid conditions at the rupture ranging from subcooled liquid to two-phase fluid and from choked to unchoked rupture flow. Although only one tube rupture geometry was considered, this study provides the groundwork from which methods specific to other geometries can be easily developed. Portions of this method were compared with RELAP5 calculations and good agreement was shown.This methodology was incorporated in a RETRAN-03 analysis of a steam generator tube rupture event in a Westinghouse two-loop plant. This included a case with a tube rupture accompanied by loss of off-site power as well as a case incorporating procedures for operator actions during a tube rupture event. The results indicate both the impact and the necessity of appropriate operator actions in such an event.The RETRAN-03 computer code was found to perform satisfactorily when this tube rupture modeling technique was incorporated. Faster than “realtime” computational speed was demonstrated on a Cyber 176 computer when using a fairly detailed RETRAN plant model (54 volumes, 82 junctions).

The Development and Application of System Analysis at Kansas Gas and Electric Company

The U.S. Nuclear Regulatory Commission (NRC) has encouraged utilities to perform their own safety analyses to support reload applications, technical specification amendments, etc., to significantly improve their understanding of plant behavior. During the meetings of the Advisory Committee on Reactor Safeguards on the Wolf Creek project, Kansas Gas and Electric Company (KGandE) was urged to develop ''a strong in-house capability for analyzing and understanding the nuclear-thermal-hydraulic behavior and systems performance.'' KGandE fully intends to develop a strong in-house analytical capability and responded as such to the NRC. Part of this in-house analytical capability will be provided through the Safety Analysis Section. The development and application of system analysis is an integral part of the Safety Analysis Section. The development phases of achieving in-house system analysis capability are discussed. They include intermediate and long-term goals, a technical review of all non-loss-of-coolant accident transients performed by Westinghouse in Chap. 15 of the Final Safety Analysis Report, and the development of RETRAN system analysis models. Applications of system analysis are also discussed. Applications include an analysis of the plant loss-of-flow startup test to relax the acceptance criteria and a joint effort with Union Electric to reanalyze the steam generator tube rupture event formore » the NRC licensing commitment.« less

Potential Radiological Consequences of a Multiple Steam Generator Tube Rupture

The range of radiological consequences that could result from a multiple steam generator tube rupture event has been examined. Efforts to obtain thermal hydraulic data for the multiple tube rupture event were only partially successful. Lacking a detailed knowledge of the thermal-hydraulic characteristics of a multiple tube rupture event, a three-variable parametric study was performed. Both thyroid and whole-body exposures were determined as a function of integrated primary to secondary flow and integrated secondary relief valve flow. For all cases considered, calculated exposures were below guidelines specified in 10CFR100 and far below a level where injury might be expected. On this basis and considering the conservatism employed in the exposure estimates, it was concluded that a multiple tube rupture event would not endanger the health and safety of the public. Furthermore, it would be overly conservative, in view of the significantly lower likelihood of a multiple tube rupture event, to base primary coolant technical specifications for iodine on a multiple tube rupture event and a limit of a 1.5-rem thyroid exposure at the site boundary.