Development of a Lumped Parameter Dynamic Degassing Model for Spray-Heating Degasser and Its Application in the Pressurizer of a Pressurized Water Reactor

The pressurizer of a pressurized water reactor (PWR), as a spray-heating degasser, has been widely used to remove dissolved gas in the primary coolant of PWRs. In the real degassing process, the boundary conditions of the pressurizer may change, causing fluctuations in the degassing state and affecting the efficiency of degassing. However, open-published studies have focused mainly on the steady-state degassing characteristics of the pressurizer. This paper studies the dynamic characteristics of a spray-heating degasser as applied to the pressurizer of a PWR. First, a lumped parameter dynamic degassing model for the spray-heating degasser is proposed based on basic gas dissolution and transport theory. Second, this model is extended, and a dynamic degassing model for the pressurizer is obtained. Third, two sets of numerical hydrogen degassing tests are carried out using the pressurizer dynamic degassing model. These two sets of numerical tests take the Shippingport pressurizer as the research object and integrate the structure and operating parameters of the Shippingport pressurizer with the system parameters of a Bettis Atomic Power Laboratory hydrogen degassing test as the numerical test condition.

The spray-heating degasser degassing model is universal and applicable to this pressurizer as well as other devices with similar structures. The first set of numerical tests carried out reveals the physical mechanism of degassing with the spray-heating degasser. The pressurizer degassing model can be used for transient degassing analysis, and it also provides a basis for the subsequent design of the control system of pressurizer degassing.