Large Scale PWR Passive Containment Cooling System Wind Tunnel Test

CAP1400 is a large passive pressurized water reactor nuclear power plant, which relies on engineering safety features such as passive containment cooling system (PCS) to remove the decay heat in the containment and mitigate accident consequences. PCS is designed to perform passive containment cooling which is mainly dependent on natural convection inside the containment and inner wall condensation heat transfer, outer containment surface water film coverage and evaporation heat transfer and external air flow path cooling performance, etc. Among them, the key factors that affect the performance of the external air flow path include the flow resistance characteristics of the air flow path and the wind-direction neutrality characteristics. The relevant performance will be the important design input of the accident analysis, which will directly affect the safety of the power plant. During the normal operation of power plant, the PCS air flow path is influenced by the external environment, and its internal flow is very complicated. Designers are often lack of data support, and can’t fully consider the impact of environmental flow. In order to fully study the performance of PCS air flow path, it is necessary to perform PCS integrated scaled wind tunnel test. According to the original design of CAP1400 PCS system, the model scale research is developed and CAP1400 PCS wind tunnel test scaled model is established and the scale is 1:100. The test model includes shield building model and the surrounding plant model, which contain pressure measuring points uniformly distributed in 6 horizontal cross sections of the shield building. The pressure measuring point arrangement does not affect air flow in the air flow path. The following wind tunnel tests are simulated in different wind speed including 15m/s, 20m/s, 10m/s, 25m/s. The air flow pressure, wind velocity at the inlet and outlet of air flow path and the pressure distribution of inner annulus and outer annulus are measured in order to study the air flow pressure drop and wind-direction neutrality characteristics, and the wind tunnel test also considers the different wind direction angle, with and without the surrounding buildings and the effects of different landforms. The test results show that the flow rate of inlet and outlet of air flow path is balanced and the wind velocity at the upwind and central area of the flow path outlet is larger than other area, and a large vortex comes on the leeward side near the wall. The local uneven flow phenomenon exists in the outer annulus of the air flow path, but the wind pressure distribution of inner annulus is not affected by environment wind speed, wind direction angle, landforms and the surrounding buildings. So CAP1400 PCS air flow path has the characteristics of wind direction neutrality, and the natural convection of the air flow path will not be adversely affected by the environment wind.

Decomposing full-waveform borehole acoustic data with application to data from a North Sea well

The objective of this study is to establish whether sonic data acquired in a cased hole can be used to estimate the material behind a second casing when the annulus between the two sets of casings is fluid filled. We have analyzed full-waveform data acquired using the Schlumberger tool Sonic Scanner for a double casing with a fluid between them, and where the outer annulus, outside the outer casing, might be cement filled or fluid filled. The sonic tool uses a cylindrical array of 104 omnidirectional receivers. The cylindrical array — approximately 4 in. in diameter and 1.8 m (6 ft) long — allows a formal decomposition of the acquired data into quasi-plane waves. Analyzing these plane waves, we have identified subtle but distinct changes in the waveforms. These changes appear to be dependent on the material filling the outer annulus, allowing for the determination of the fill material. The most significant changes relate to the propagating Stoneley waves. The identifications made are confirmed by cement bond log (CBL) analysis done on the exposed outer pipe after pulling the inner pipe. In one instance, for single-casing logging and a clean top-of-cement, like with conventional CBL analysis, we were able to confidently and accurately identify the cement/fluid boundary. In another instance, we were able to identify it as a nondistinct/smooth transition zone. For double-casing logging, we could confidently and accurately identify the cement/fluid boundary behind the second casing. For one case, we have substantiated that this zone has a longer interval of smooth transition from cement to consolidated/unconsolidated barite to a fluid-filled annulus.