Validation of Effective Models for Simulation of Thermal Stratification and Mixing Induced by Steam Injection into a Large Pool of Water

Hua Li,Markku Puustinen,Walter Villanueva,Pavel Kudinov,Jani Laine

doi:10.1155/2014/752597

Abstract

The Effective Heat Source (EHS) and Effective Momentum Source (EMS) models have been proposed to predict the development of thermal stratification and mixing during a steam injection into a large pool of water. These effective models are implemented in GOTHIC software and validated against the POOLEX STB-20 and STB-21 tests and the PPOOLEX MIX-01 test. First, the EHS model is validated against STB-20 test which shows the development of thermal stratification. Different numerical schemes and grid resolutions have been tested. A48×114grid with second order scheme is sufficient to capture the vertical temperature distribution in the pool. Next, the EHS and EMS models are validated against STB-21 test. Effective momentum is estimated based on the water level oscillations in the blowdown pipe. An effective momentum selected within the experimental measurement uncertainty can reproduce the mixing details. Finally, the EHS-EMS models are validated against MIX-01 test which has improved space and time resolution of temperature measurements inside the blowdown pipe. Excellent agreement in averaged pool temperature and water level in the pool between the experiment and simulation has been achieved. The development of thermal stratification in the pool is also well captured in the simulation as well as the thermal behavior of the pool during the mixing phase.

Highlights

A pressure suppression pool (PSP) is an important element of a passive safety system in BWRs
0.1 m/s (c) t = 1600 s in GOTHIC and validated against the POOLEX STB-20 and STB-21 tests and the PPOOLEX MIX-01 test on thermal stratification and mixing induced by steam injection into a large pool of water
The Effective Heat Source (EHS) model is validated against the STB-20 test which shows the development of thermal stratification only

Summary

Introduction

A pressure suppression pool (PSP) is an important element of a passive safety system in BWRs. In [12, 13], two effective models, namely, Effective Heat Source (EHS) and Effective Momentum Source (EMS) models, have been proposed and discussed in detail These models can be utilized to predict thermal stratification or mixing during steam injection into a large pool of water. The EMS model (Figure 1) provides time averaged momentum source induced by steam injection This momentum creates large scale circulation in the pool which can lead to erosion of thermally stratified layer and mixing of the pool. More thermocouples installed inside the blowdown pipe are necessary in order to provide more accurate assessment of the amplitude and frequency of oscillation We discuss application of EHS-EMS models which yield even better predictions when experimental measurement uncertainties are significantly reduced

Validation of EHS and EMS Models against PPOOLEX MIX-01 Test

Findings

Summary and Conclusions