Results of thermal mixing tests at the HDR-facility and comparisons with best-estimate and simple codes

Wolf, L.; Schygulla, U.; Häffner, W.; Fischer, K.; Baumann, W.

doi:10.1016/0029-5493(87)90128-2

Cited by 7 publications

(2 citation statements)

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“…The results of the previous study [4,5], from mixing and temperature fluctuation tests on the feedwater sparger [2,3] which feeds the water to the reactor pressure vessel, have been used to predict crack propagation of materials. We have investigated the improvement of the thermal mixing performance [6] based on flow visualization at the mixing tee junction between hot and cold fluids.…”

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Flashing characteristics in a pipe downstream from a depressurizing tank and temperature fluctuation characteristics at a mixing tee junction with cold water injection

Shiina

Takahashi

Asada

2003

Heat Trans. Asian Res.

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The flashing characteristics in a pipe downstream from a depressurizing tank were experimentally and analytically investigated on the basis of the transient test and two-phase flow analysis. The following conclusions were obtained. (1) When the pressure margin of the pump inlet side and the distance to obtain an isothermal condition were sufficient, flashing phenomena did not occur in spite of the decreasing pressure. (2) When the ratio of the cold water injection flow rate to the hot water flow rate Mc/Mh increased, the peak distance of the water temperature fluctuation moved from L/D = 1 to 0, and the maximum water temperature fluctuation ratio was about 40% of the temperature difference between hot and cold water near the mixing tee junction. Because no problem occurred regarding the pipe material thermal fatigue, reliability of the mixing tee junction was assured. (3) Due to suppression of flashing phenomena of the mixing pipe system, the decision diagram on the flashing occurrence was obtained from the test and the analytical results, taking into consideration three factors: the depressurizing ratio in the tank; the cold water injection flow rate due to remaining subcooling; and the delay time of thermal mixing. The simplified analytical equation was used to decrease the cold water injection flow rate by the optimized pipe length between the mixing tee junction and the drain pump. The cold water injection flow rate was minimized when the pipe length was about 15 to 20 times the pipe inner diameter.

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confidence: 99%

Flashing characteristics in a pipe downstream from a depressurizing tank and temperature fluctuation characteristics at a mixing tee junction with cold water injection

Shiina

Takahashi

Asada

2003

Heat Trans. Asian Res.

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“…The onset of interfacial mixing that leads to thermal striping can approximately be correlated with the initiation of a Kelvin-Helmholtz instability, which occurs when inertial forces overcome stratifying density differences between the fluid layers (Hafner and Spurk 1990). Wolf et al (1987) conducted thermal stratification experiments in horizontal feedwater lines at the HDR test facility in Germany. The experiments were performed at several different flow rates with thermocouples mounted on the inside pipe surface to measure metal temperatures.…”

Section: Thermal Striping and Turbulent Mixingmentioning

confidence: 99%

Review of industry efforts to manage pressurized water reactor feedwater nozzle, piping, and feedring cracking and wall thinning

Shah¹,

Ware²,

Porter³

1997

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Attached for your information and use is a copy of the report, "Review of Industry Efforts t o Manage Pressurized Water Reactor Feedwater Nozzle, Piping, and Feedring Cracking and Wall Thinning," NUREG/CR-6456. The study objective was t o provide a comprehensive overview document discussing pressurized-water reactor (PWR) feedwater nozzle, piping, and feedring cracking and wall thinning; safety aspects; and industry actions taken t o manage these issues. The report should be useful in identifying, assessing, and evaluating program options t o manage these issues. The time frame spans from initial discovery of feedwater nozzle cracking in 1979 through 1996.The review and assessment effort covers relevant field experience with PWR feedwater systems, the factors causing the damage, design modifications, operating procedure changes, augmented inspection programs, and repair and replacement activities carried out because of the degradation that occurred. The effort focused on the feedwater system adjacent t o the feedwater nozzle where fatigue cracking and wall thinning had been reported. This includes the main and auxiliary feedwater piping adjacent t o the feedwater nozzle, and the thermal sleeve, feedring, and J-tubes. The principal areas reviewed were (1 ) feedwater system design, (2) safety significance of feedwater line rupture, (3) fatigue cracking experience, (4) f low-accelerated corrosion-induced wall thinning experience, (5) steam generator water hammer damage experience, (6) degradation mechanisms, (7) inservice inspection methods, and (8) mitigation, monitoring, and replacement activities.This effort emphasized understanding the technical aspects for each area in order t o assess the impact on managing (establish confidence that limits for safe operation are maintained) degradation of these components. In this context, the study concentrates on causes, mechanisms, conditions (temperature, pressure, environment, etc.), inspections, procedures, and corrective actions from the perspective of capability t o assess a specific aspect such as crack characterization. Thus, the report is directed toward determining whether current technology is sufficient t o "manage the problem".The operating experience review addressed feedwater nozzle cracking caused by thermal fatigue; flow-accelerated corrosion wall thinning of carbon steel J-tubes, feedrings, and thermal sleeves in top-feed steam generators, and auxiliary feedwater lines in preheat steam generators; and water hammer damage in both types of steam generators.Feedwater nozzle cracking was detected in 18 PWRs from 1979 through 1983. These were found as a result of IE Bulletin 79-13, "Cracking in Feedwater System Piping," 1979. -2-There was approximately one event per year from 1983 until bulletin closure in 1991. The nozzle cracking event frequency increased t o six per year for 1992 and 1993 but no additional events were detected from then through 1996. It appears that licensee action has been sufficient t o minimize flow-accelerated wall thinning in J-tubes a...

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Results of HDR-experiments for pipe loads under thermally stratified flow conditions

Wolf

Häfner

Geiss

et al. 1992

Nuclear Engineering and Design

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Results of thermal mixing tests at the HDR-facility and comparisons with best-estimate and simple codes

Cited by 7 publications

References 1 publication

Flashing characteristics in a pipe downstream from a depressurizing tank and temperature fluctuation characteristics at a mixing tee junction with cold water injection

Flashing characteristics in a pipe downstream from a depressurizing tank and temperature fluctuation characteristics at a mixing tee junction with cold water injection

Review of industry efforts to manage pressurized water reactor feedwater nozzle, piping, and feedring cracking and wall thinning

Results of HDR-experiments for pipe loads under thermally stratified flow conditions

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