| After a severe accident,the rupture of the primary circuit boundary would lead to the rise of temperature and pressure in the containment,which may damage its integrity and release radioactive gas.Therefore,the nuclear power plant uses the Filtered Containment Venting System(FCVS)to relieve the pressure of containment and remove radioactive material in the gas.The scrubbing of radionuclides contained in submerged gas jet is the critical process of the FCVS,which could efficiently remove radioactive aerosol.Based on the background of filter,this paper made an experimental study on the thermal-hydraulic characteristics of hightemperature and high-pressure gas discharged into the pool.The pressure oscillation signal and the pool’s temperature signal are recorded using high-frequency pressure sensor and highprecision thermocouple,respectively.According to the experimental results,the effects of different discharge conditions on the behavior of pressure oscillation and temperature rise are analyzed.It is expected to provide a basis for the optimal filter device.The main research results obtained in this paper are as follows:(1)The characteristics of pressure oscillation intensity are studied.It is found that the increase of discharge flow and pool temperature significantly improves the oscillation intensity,while the oscillation intensity first decreases and then increases with the increase of noncondensable gas fraction.The condensation region is divided according to the oscillation amplitude based on the above conclusions.Finally,three condensation regions are obtained:oscillation condensation region,stable condensation region,and transition condensation region.(2)The empirical equation is given between the dominant frequency of single hole jet oscillation in different states.There are two dominant frequencies for the steam jet.The first dominant frequency is inversely proportional to the dimension of the gas plume,and the second dominant frequency is inversely proportional to the dimension of the separated bubble.According to this theory and experimental results,the prediction relationship of the second dominant frequency is fitted in this paper.At the same time,it is found that there is only one dominant frequency for the mixed gas jet,which is caused by the reduction of condensation capacity caused by the introduction of non-condensable gas.Therefore,it could introduce the non-condensable gas fraction variable and propose a prediction equation of the dominant frequency.(3)In the case of double jets,the two plumes would affect each other,even converge and coalescence at high-temperature conditions,and condense and oscillate in a large volume,resulting in the change of dominant frequency.The research shows that hole pitch is an essential factor affecting coalescence.Based on the research results of the dominant frequency,this paper introduces the variable of hole pitch and puts forward the empirical equation of the dominant frequency of the double jets.(4)Under the condition of high-pressure discharge,the water temperature increases evenly.Under the condition of upward jet,the strong secondary flow in the pool is caused by highpressure discharge,resulting in uniform mixing of the pool.The gas discharge pressure affects the secondary flow velocity;if the discharge pressure decreases,the secondary flow weakens,and thermal stratification could occur. |
