Numerical Investigations of a Turbulence Mixing Process Related to Thermal Striping Phenomena at a T-Junction of Liquid Metal Fast Reactor Piping Systems

2002 ◽  
Author(s):  
Toshiharu Muramatsu
Keyword(s):  
Liquid Metal ◽  
Fast Reactor ◽  
Evaluation System ◽  
Velocity Ratio ◽  
Piping System ◽  
Mixing Process ◽  
Downstream Region ◽  
Piping Systems ◽  
Turbulence Mixing ◽  
Thermal Striping

Fluid-structure thermal interaction phenomena characterized by stationary random temperature fluctuations, namely thermal striping are observed in the downstream region of a T-junction piping system of liquid metal fast reactor (LMFR). Therefore the piping walls located in the downstream region must be protected against the stationary random thermal process which might induced high-cycle fatigue. This paper describes the evaluation system based on numerical simulation methods for the thermal striping, and numerical results of the thermal striping at a T-junction piping system under the various parameters, i.e., velocity ratio and diameter ratio between both the pipes and Reynolds number. Then detailed turbulence mixing process at the T-junction piping region due to arched vortexes generating lower frequency fluctuations are evaluated through a separate numerical analysis of a fundamental water experiment.

Numerical Investigations of Arched Vortex Characteristics Generated at T-Junction Piping Systems

2004 ◽  
Author(s):  
Toshiharu Muramatsu
Keyword(s):  
Stokes Equations ◽  
Velocity Ratio ◽  
Navier Stokes ◽  
Fluid Temperature ◽  
Simulation Code ◽  
Navier Stokes Equations ◽  
Downstream Region ◽  
Piping Systems ◽  
Frequency Components ◽  
Thermal Striping

Thermohydraulic analyses for a fundamental water experiment simulating thermal striping phenomena at T-junction piping systems were carried out using a quasi-direct numerical simulation code DINUS-3, which is represented by instantaneous Navier-Stokes equations and deals with a modified third-order upwind scheme for convection terms. Calculated results were compared with experimental results on the flow patterns in the downstream region of the systems, the arched vortex structures under a deflecting jet condition, the generation frequency of the arched vortex, etc. in the various conditions; i.e., diameter ratio α, flow velocity ratio β and Reynolds number Re. From the comparisons, it was confirmed that (1) the DINUS-3 code is applicable to the flow pattern classifications in the downstream region of the T-junction piping systems, (2) the arched vortex characteristics with lower frequency components and their generation possibilities can be estimated numerically by the DINUS-3 code, and (3) special attentions should be paid to the arched vortex generations with lower frequency components of fluid temperature fluctuations in the design of T-junction systems from the viewpoints of the avoidances for the thermal striping.

Non-Linear Design Verification of Nuclear Power Piping According to ASME III NB/NC

2008 ◽  
Author(s):  
Lingfu Zeng ◽  
Lennart G. Jansson
Keyword(s):  
Nuclear Power ◽  
Design Evaluation ◽  
Piping System ◽  
Design Verification ◽  
Intensive Study ◽  
Non Linear ◽  
Piping Systems ◽  
Design Requirements

A nuclear piping system which is found to be disqualified, i.e. overstressed, in design evaluation in accordance with ASME III, can still be qualified if further non-linear design requirements can be satisfied in refined non-linear analyses in which material plasticity and other non-linear conditions are taken into account. This paper attempts first to categorize the design verification according to ASME III into the linear design and non-linear design verifications. Thereafter, the corresponding design requirements, in particular, those non-linear design requirements, are reviewed and examined in detail. The emphasis is placed on our view on several formulations and design requirements in ASME III when applied to nuclear power piping systems that are currently under intensive study in Sweden.

Comparison of Failure Modes of Piping Systems With Wall Thinning Subjected to In-Plane, Out-of-Plane, and Mixed Mode Bending Under Seismic Load: An Experimental Approach

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
Izumi Nakamura ◽  
Akihito Otani ◽  
Masaki Shiratori
Keyword(s):  
Dynamic Behavior ◽  
Failure Modes ◽  
Seismic Load ◽  
Piping System ◽  
Shake Table ◽  
Shake Table Tests ◽  
Wall Thinning ◽  
Piping Systems ◽  
Out Of Plane ◽  
Plane Bending

Pressurized piping systems used for an extended period may develop degradations such as wall thinning or cracks due to aging. It is important to estimate the effects of degradation on the dynamic behavior and to ascertain the failure modes and remaining strength of the piping systems with degradation through experiments and analyses to ensure the seismic safety of degraded piping systems under destructive seismic events. In order to investigate the influence of degradation on the dynamic behavior and failure modes of piping systems with local wall thinning, shake table tests using 3D piping system models were conducted. About 50% full circumferential wall thinning at elbows was considered in the test. Three types of models were used in the shake table tests. The difference of the models was the applied bending direction to the thinned-wall elbow. The bending direction considered in the tests was either of the in-plane bending, out-of-plane bending, or mixed bending of the in-plane and out-of-plane. These models were excited under the same input acceleration until failure occurred. Through these tests, the vibration characteristic and failure modes of the piping models with wall thinning under seismic load were obtained. The test results showed that the out-of-plane bending is not significant for a sound elbow, but should be considered for a thinned-wall elbow, because the life of the piping models with wall thinning subjected to out-of-plane bending may reduce significantly.

The Influence of Support Hardware and Piping System Seismic Response on Snubber Support Damping

1997 ◽  
Vol 119 (4) ◽  
pp. 451-456 ◽  
Author(s):  
C. Lay ◽  
O. A. Abu-Yasein ◽  
M. A. Pickett ◽  
J. Madia ◽  
S. K. Sinha
Keyword(s):  
Seismic Response ◽  
Fundamental Frequency ◽  
Damping Ratio ◽  
Damping Coefficient ◽  
Piping System ◽  
Nodal Displacement ◽  
Damping Coefficients ◽  
Fundamental Frequencies ◽  
Piping Systems

The damping coefficients and ratios of piping system snubber supports were found to vary logarithmically with pipe support nodal displacement. For piping systems with fundamental frequencies in the range of 0.6 to 6.6 Hz, the support damping ratio for snubber supports was found to increase with increasing fundamental frequency. For 3-kip snubbers, damping coefficient and damping ratio decreased logarithmically with nodal displacement, indicating that the 3-kip snubbers studied behaved essentially as coulomb dampers; while for the 10-kip snubbers studied, damping coefficient and damping ratio increased logarithmically with nodal displacement.

Experimental Study on Fluid Mixing for Evaluation of Thermal Striping in T-Pipe Junction

2002 ◽  
Author(s):  
Minoru Igarashi ◽  
Masaaki Tanaka ◽  
Shigeyo Kawashima ◽  
Hideki Kamide
Keyword(s):  
Temperature Fluctuation ◽  
Velocity Ratio ◽  
Impinging Jet ◽  
Fluid Mixing ◽  
Cold Spot ◽  
Wall Jet ◽  
Fluid Temperature ◽  
Thermochromic Liquid Crystal ◽  
Inflow Condition ◽  
Thermal Striping

A water experiment is performed to investigate thermal striping phenomena in a T-pipe junction which is a typical geometry of fluid mixing. The flow velocity ratio and temperature difference were experimental parameters. The jet form was classified into four patterns; (1) impinging jet, (2) deflecting jet, (3) re-attachment jet and (4) wall jet according to the inflow condition. The parameter experiments showed that the jet form could be predicted by a momentum ratio between the two pipes. The thermochromic liquid crystal sheet showed that a cold spot was formed at the wall surface in the main pipe in the cases of the impinging jet and the wall jet. From the temperature measurement in the fluid, temperature fluctuation intensity was high along the edge of the jet exiting from branch piping. A database of temperature fluctuation and frequency characteristics was established for an evaluation rule of thermal striping in a T-pipe junction.

Sensitivity Analyses for a PWR SCC Case Using the Probabilistic Loss-of-Coolant-Accident (Pro-LOCA) Software

2016 ◽  
Author(s):  
Bruce A. Young ◽  
Sang-Min Lee ◽  
Paul M. Scott
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
The United States ◽  
Design Criterion ◽  
Mitigation Strategies ◽  
Sensitivity Analyses ◽  
Base Case ◽  
Piping System ◽  
Loss Of Coolant Accident ◽  
Piping Systems

As a means of demonstrating compliance with the United States Code of Federal Regulations 10CFR50 Appendix A, General Design Criterion 4 (GDC-4) requirement that primary piping systems for nuclear power plants exhibit an extremely low probability of rupture, probabilistic fracture mechanics (PFM) software has become increasingly popular. One of these PFM codes for nuclear piping is Pro-LOCA which has been under development over the last decade. Currently, Pro-LOCA is being enhanced under an international cooperative program entitled PARTRIDGE-II (Probabilistic Analysis as a Regulatory Tool for Risk-Informed Decision GuidancE - Phase II). This paper focuses on the use of a pre-defined set of base-case inputs along with prescribed variation in some of those inputs to determine a comparative set of sensitivity analyses results. The benchmarking case was a circumferential Primary Water Stress Corrosion Crack (PWSCC) in a typical PWR primary piping system. The effects of normal operating loads, temperature, leak detection, inspection frequency and quality, and mitigation strategies on the rupture probability were studied. The results of this study will be compared to the results of other PFM codes using the same base-case and variations in inputs. This study was conducted using Pro-LOCA version 4.1.9.

Effects on Pipe Vibrations of Cavitation in an Orifice and in Globe-Style Valves

2006 ◽  
Author(s):  
Se´bastien Caillaud ◽  
Rene´-Jean Gibert ◽  
Pierre Moussou ◽  
Joe¨l Cohen ◽  
Fabien Millet
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Low Frequency ◽  
Flow Regimes ◽  
Piping System ◽  
Low Frequencies ◽  
Choked Flow ◽  
Single Hole ◽  
Piping Systems ◽  
Large Amplitude Vibrations

A piping system of French nuclear power plants displays large amplitude vibrations in particular flow regimes. These troubles are attributed to cavitation generated by single-hole orifices in depressurized flow regimes. Real scale experiments on high pressure test rigs and on-site tests are then conducted to explain the observed phenomenon and to find a solution to reduce pipe vibrations. The first objective of the present paper is to analyze cavitation-induced vibrations in the single-hole orifice. It is then shown that the orifice operates in choked flow with supercavitation, which is characterized by a large unstable vapor pocket. One way to reduce pipe vibrations consists in suppressing the orifices and in modifying the control valves. Three technologies involving a standard trim and anti-cavitation trims are tested. The second objective of the paper is to analyze cavitation-induced vibrations in globe-style valves. Cavitating valves operate in choked flow as the orifice. Nevertheless, no vapor pocket appears inside the pipe and no unstable phenomenon is observed. The comparison with an anti-cavitation solution shows that cavitation reduction has no impact on low frequency excitation. The effect of cavitation reduction on pipe vibrations, which involve essentially low frequencies, is then limited and the first solution, which is the standard globe-style valve installed on-site, leads to acceptable pipe vibrations. Finally, this case study may have consequences on the design of piping systems. First, cavitation in orifices must be limited. Choked flow in orifices may lead to supercavitation, which is here a damaging and unstable phenomenon. The second conclusion is that the reduction of cavitation in globe-style valve in choked flow does not reduce pipe vibrations. The issue is then to limit cavitation erosion of valve trims.

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