ML18178A268
| ML18178A268 | |
| Person / Time | |
|---|---|
| Site: | 05200021 |
| Issue date: | 05/31/2018 |
| From: | Mitsubishi Heavy Industries, Ltd |
| To: | Office of New Reactors |
| References | |
| UAP-HF-18004 MUAP-07001-NP, Rev 7 | |
| Download: ML18178A268 (10) | |
Text
THE ADVANCED ACCUMULATOR MUAP-07001-NP (R7) 48/127 4.0 TESTING PROGRAM FOR THE ACC This section of the Topical Report; (1) describes the purpose and objectives of the confirmatory and qualification test program; (2) provides a detailed description of the tests and the test results.
4.1 Purpose of the ACC Testing Development of the ACC was conducted through confirmation tests using several scale models.
A qualification test was conducted in full-scale test facility to verify the overall design of the ACC.
During the development phase, the following items were tested to confirm the principles and characteristics of the flow damper:
(1) Confirmation of the principles of the flow damper:
Tests were conducted to observe the behavior of the flow in the vortex chamber of the flow damper during large flow injection, large/small flow switching, and small flow injection to confirm that their actual behavior was as expected.
(2) Confirmation of the anti-vortex function at the end of large flow injection:
As water level in the accumulator decreases after initiation of accumulator injection, it may be possible to form a vortex at the entrance to the standpipe and the nitrogen gas in the ACC gas space can be sucked into the standpipe when the water level is low. Therefore, an anti-vortex cap was designed for the large flow inlet. The tests were conducted to confirm that the anti-vortex cap prevented the vortex from forming at the standpipe inlet and that gas was not sucked into the standpipe.
A qualification test using a full-scale test facility was conducted to verify the following items:
(1) Verification of performance during large flow and small flow phases:
Tests were conducted to confirm that the performance of the flow damper, during large flow and small flow respectively, met the acceptance criteria (resistance coefficient for large and small flow injection)
(2) Verification of flow switching without need of any moving parts:
It was assumed that the injection flow rate shifts from large flow to small flow when the tank water level decreases to the lower edge of the standpipe anti-vortex cap. This design feature was verified by actual injection testing.
Moreover, the following item was confirmed by the full-scale testing:
(3) Confirmation of the effect of dissolved nitrogen gas:
Mitsubishi Heavy Industries, LTD.
4.1-1
THE ADVANCED ACCUMULATOR MUAP-07001-NP (R7) 49/127 Since the accumulator utilizes compressed nitrogen gas, nitrogen gas may dissolve in the water. If the water in the accumulator contains dissolved nitrogen gas, it is assumed that the gas comes out of solution and affects the flow characteristics of the flow damper.
Therefore, tests were conducted with nitrogen-rich water to confirm that the effect of nitrogen gas did not impact the ACC performance.
Mitsubishi Heavy Industries, LTD.
4.1-2
THE ADVANCED ACCUMULATOR MUAP-07001-NP (R7) 50/127 4.2 Detailed Description of the Test and Results 4.2.1 Confirmatory Testing During the development of the ACC, three types of scaled tests were performed: 1/8.4, 1/3.5 and 1/5-scale model tests. These tests used visualization to confirm flow rate switching, vortex formation, and the prevention of significant gas entrainment into the vortex chamber at the end of the large flow stage of injection.
4.2.1.1 1/8.4 Scale Test
- 1) Objectives A 1/8.4 scale flow visualization experiment was designed to examine the basis of operation of the ACC and to understand the injection flow characteristics. Items to be confirmed by this test are as follows:
Confirmation of operating principles of the flow damper Visualize the behavior of flow in the flow damper and the standpipe during large flow injection, large/small flow switching, and small flow injection. Confirm the behavior and stability of the flow in the vortex chamber and flow switching. From this test, it was confirmed that: (1) a vortex was not formed in the vortex chamber during large flow, (2) a vortex was formed and flow rate decreased during small flow, and (3) injection flow rate was sharply switched from large to small flow.
Confirmation of behavior of the water level in the standpipe at flow-switching Visualize the behavior of the water level in the standpipe at flow-switching and confirm the behavior of the flow.
- 2) Test Apparatus The visualization test of the operating principles of the flow damper was conducted using the test apparatus shown in Fig. 4.2.1.1-1 and Photo. 4.2.1.1-1. The test apparatus consisted of an ACC model, exhaust tank, and injection pipe. The scale of the flow damper was 1/8.4 and the vortex chamber is upright. One side of the vortex chamber and the standpipe was integrated into the front of the ACC model which was made of transparent acrylate so that the flow behavior inside of the ACC, the standpipe and the flow damper could be observed. The shape of each part of the apparatus was simplified while ensuring that the operating principle of the flow damper was not affected.
Mitsubishi Heavy Industries, LTD.
4.2.1-1
THE ADVANCED ACCUMULATOR MUAP-07001-NP (R7) 51/127 1/8.4 Scale Test Apparatus Fig. 4.2.1.1-1 Mitsubishi Heavy Industries, LTD.
4.2.1-2
THE ADVANCED ACCUMULATOR MUAP-07001-NP (R7) 52/127 Anti-vortex cap Stand pipe Vortex chamber Small flow inlet Photo. 4.2.1.1-1 1/8.4 Scale Test Apparatus The major specifications of the test facility are as follows:
(1) ACC Model Design Pressure : [ ]
Width : [ ]
Length : [ ]
Height : [ ]
Volume : [ ]
(2) Flow Damper and Standpipe Dimensions : 1/8.4 of actual tank (Flow damper inner diameter: [ ]) Simplified shape (3) Injection Piping Diameter : [ ]
Mitsubishi Heavy Industries, LTD.
4.2.1-3
THE ADVANCED ACCUMULATOR MUAP-07001-NP (R7) 53/127 (4) Exhaust Tank Design Pressure : [ ]
Width : [ ]
Length : [ ]
Height : [ ]
Volume : [ ]
- 3) Test Conditions The pressure of the gas space is [ ] (Max pressure of test facility)
- 4) Parameters to be Measured The behavior of flow in the standpipe and the flow damper was observed. Also, flow-switching was observed on a CRT as shown in Fig. 4.2.1.1-1.
- 5) Measuring Equipment The behavior of flow in the standpipe and the flow damper was confirmed by visual inspection.
Flow switching was confirmed by visual tracking of flow rate using the flow meter as shown in Fig. 4.2.1.1-1.
- 6) Test Results and Considerations The behavior of the flow and the flow transient in the standpipe and the vortex chamber during flow switching are shown in Photos. 4.2.1.1-2 to 4.2.1.1-7, respectively. The following items were confirmed from the test:
(1) The behavior of the flow in the vortex chamber during large flow conditions is shown in Photo. 4.2.1.1-3. It was confirmed that a vortex was not formed in the vortex chamber since the air, which was injected as a flow tracer, directly drifted from the point where the flow from the inlet of standpipe and the flow from small flow pipe collided to the outlet.
(2) By comparing the water level in the standpipe shortly after the flow switching (Photo.
4.2.1.1-5) and during the small flow condition (Photo. 4.2.1.1-6), it was found that the water level during small flow is higher than the water level during flow switching. This observation confirmed that the water level in the standpipe was temporarily reduced and then recovered.
(3) It was confirmed that the flow switched sharply from large to small flow in a short period of time as shown in Photo. 4.2.1.1-6.
(4) It was confirmed that following the initiation of small flow, the stable vortex was formed since the air that was injected as a flow tracer was swirling into the outlet as shown in Photo. 4.2.1.1-7.
From the test results above, the basic principle of the flow damper was confirmed as follows:
Mitsubishi Heavy Industries, LTD.
4.2.1-4
THE ADVANCED ACCUMULATOR MUAP-07001-NP (R7) 54/127 (1) When the water level in the accumulator is above the upper end of the standpipe, the flow from the standpipe and the small flow inlet collide in the vortex chamber and flow directly to the outlet. A vortex is not formed in the vortex chamber. Therefore, the resistance is small and the large flow rate is available.
(2) When the water level in the tank is reduced below the upper end of the standpipe, the flow from the standpipe almost stops and only the flow from the small inlet flows into the vortex chamber. A strong vortex is formed. Therefore, the flow resistance is large and the injection flow rate becomes small. No cavitation was observed at the center of the vortex.
(3) When the water level is close to the flow switching level, it was confirmed that the anti-vortex cap on the standpipe prevents a vortex from being drawn into the standpipe.
The lower end of the anti-vortex cap is almost at the same level as the upper end of the standpipe. If the water level in the tank is reduced below the lower end of the anti-vortex cap, the flow from the standpipe almost rapidly comes to a near-stop.
(4) During the flow switching, the water level in the standpipe is temporarily reduced by inertial force. However the water level recovers quickly, the flow in the standpipe comes to a near-stop, and the water level in the standpipe is maintained. Therefore, gas does not enter into the vortex chamber from the standpipe.
Mitsubishi Heavy Industries, LTD.
4.2.1-5
THE ADVANCED ACCUMULATOR MUAP-07001-NP (R7) 55/127 Flow rate 3.37 seconds after initiation of the test time Large Flow Photo. 4.2.1.1-2 Flow in the Standpipe and the Vortex Chamber during Large Flow Flow rate 12.48 seconds after initiation of the test Air injection into the time Flow rate vortex chamber (This Photo. shows that Large Flow the vortex is not formed in the vortex chamber.)
Photo. 4.2.1.1-3 Flow in the Vortex Chamber during Large Flow Mitsubishi Heavy Industries, LTD.
4.2.1-6
THE ADVANCED ACCUMULATOR MUAP-07001-NP (R7) 56/127 Flow rate 23.37 seconds after initiation of the test Inlet of Standpipe time Flow Switching Photo. 4.2.1.1-4 Flow Just before Large/Small Flow Switching Flow rate 24.10 seconds after Inlet of Standpipe initiation of the test Water Level time Flow Switching Photo. 4.2.1.1-5 Flow Shortly after Large/Small Flow Switching Mitsubishi Heavy Industries, LTD.
4.2.1-7
THE ADVANCED ACCUMULATOR MUAP-07001-NP (R7) 57/127 Inlet of Standpipe Flow rate 27.81 seconds after initiation of the test Water Level time Small Flow Photo. 4.2.1.1-6 Flow during Small Flow Flow rate 34.13 seconds after initiation of the test Air injection into the vortex chamber (This Photo. shows that time the vortex is formed in the vortex chamber.)
Small Flow Photo. 4.2.1.1-7 Flow in the Vortex Chamber during Small Flow Mitsubishi Heavy Industries, LTD.
4.2.1-8