Abstract
An experimental study was conducted on the characteristics of high pressure vessel water level systems at both fast and slow depressurization states. The swollen and collapsed water levels were observed experimentally. The test results show that the swollen water level has a relatively fixed difference compared to the collapsed one for the transient of both high and low depressurization rates. Under the conditions of steady and heat up, the differences between the swollen and collapsed water levels are acceptable. For the transients of depressurization, the outputs from the three channels of the inside vessel double-reference-tube water level system have a great deal of differences between each other because of the thermal inertia of the two reference tubes and the water levels in the cistern. In view of nuclear power plant safety and operation, the outside vessel single-reference-tube water level system used in the current pressurizer is adequate and the inside vessel double-reference-tube water level system is suggested as an additional reference to monitor the water level in the steam generator.
Highlights
The water level is a very important parameter in the energy and chemical industry especially for the boiler drum (Maslovaric et al, 2014)
For the third-generation nuclear power plant (NPP) like AP1000 (Schulz, 2006), there are no penetrations through the lower head of the reactor pressure vessel (RPV) which highlights the importance of PZR water level
Loss of coolant accident (LOCA) and main steam line break (MSLB) accident are characterized by fast depressurization which results in the formation of bubbles and water levels swollen at the free surface (Hardy and Richter, 1986; Kmetyk, 1994; Boesmans and Berghmans, 1995; Boesmans and Berghmans, 1996; Chen et al, 2013; Hatamura et al, 2014)
Summary
The water level is a very important parameter in the energy and chemical industry especially for the boiler drum (Maslovaric et al, 2014). The leaks and cracks in the reactor coolant pressure boundary and primary steam system cannot be avoided, resulting in the slow depressurization of PZR and SG (Sanda and Veira, 2014). The experimental vessel has three types of water level measurement systems such as the outside vessel singlereference-tube water level measurement system, the inside vessel double-reference-tube water level system, and the magnetic flap water level sensor with a maximum absolute deviation of 10 mm. The experimental PZR steam pressure is measured by a sensor with a range of 0–6 MPa and the maximum relative deviation is 0.075%. The pressure differences used by the outside vessel single-reference-tube and inside vessel double-reference-tube water level systems are measured by the sensors with a range of 0–30kPa and a maximum relative deviation of 0.075%. The characteristics of different high pressure vessel water level measurements were conducted experimentally at both fast and slow depressurization states
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