Abstract
In response to a station blackout accident similar to the Fukushima nuclear accident, China’s Generation III nuclear power HPR1000 designed and developed a passive residual heat removal system connected to the secondary side of the steam generator. Based on the two-phase natural circulation principle, the system is designed to bring out long-term core residual heat after an accident to ensure that the reactor is in a safe state. The steady-state characteristic test and transient start and run test of the PRS were carried out on the integrated experiment bench named ESPRIT. The experiment results show that the PRS can establish natural circulation and discharge residual heat of the first loop. China’s Fuqing no. 5 nuclear power plant completed the installation of the PRS in September 2019 and carried out commissioning work in October. This debugging is the first real-world debugging of the new design. This paper introduces the design process of the PRS debugging scheme.
Highlights
Introduction to the passive residual heat removal system (PRS) ePRS [1] consists of three trains associated to the RCS loops
E PRS emergency heat exchanger is located in the accident cooling tank, which provides the heat sink for the PRS emergency heat exchanger. e PRS emergency heat exchanger consists of a bank of C-tubes, connected to a top tube sheet and bottom tube sheet. e PRS emergency heat exchanger is connected to the steam line through the inlet line and to the condensate line through the outlet line
(2) e reactor system is controlled as the following initial state: (a) e three main pumps remain operational (b) To prevent the pressurizer heater from being exposed, the initial level of the regulator is controlled at 50% of the span (c) In order to provide sufficient heat capacity, the initial average temperature of the primary circuit is controlled at 291.7°C (d) To ensure adequate subcooling, the initial pressure of the pressurizer is controlled at 15.5 MPa (e) e initial level of the steam generator is controlled at 50% of the range, and the secondary side pressure is automatically controlled at 7.6 MPa through the steam bypass valves to atmosphere
Summary
Steam line penetrates through the containment and splits into two branches outer containment: one branch connects to the emergency heat exchanger and another one connects to the emergency make-up tanks. e emergency heat exchanger is seated on the bottom of the heat transfer tank and submerged in it, while the emergency make-up tanks are seated on the same level with the heat exchanger. e condensate line equipped with two parallel connected isolation valves from the heat exchanger combined with the one from make-up tanks, which is equipped with two parallel connected isolation valves, penetrates back the containment and connects to the feedwater line of the steam generator. ere is a check valve on the condensate line inner containment so as to avoid back flow of feedwater during normal operation. E PRS emergency heat exchanger is connected to the steam line through the inlet line and to the condensate line through the outlet line. (ii) e elevation of the loop and the altitude difference between the cold core and the hot core are equaled to the prototype (iii) e same working fluid is used (iv) Working fluid, pressure, and temperature are the same with the prototype (v) e same friction coefficient is used for the steam line and condensate line (vi) e tube of SG is with the same outer diameter and spacing (vii) e same tubes and tube spacing are used, and the number ratio is 1/62.5 e test facility consists of the following systems: steamwater natural circulation system, pool heat removal system, steam emission branch, and auxiliary systems. During the first 800 s, steam has not entered the tubes, the depressurization rate of the transient test is greater than the value calculated by the RELAP5 program, and the times GCT-a valves open are less than results of RELAP5 as shown in Figure 3. is is because RELAP5 lacks the ability to simulate the steam direct contact condensation in the makeup tank. e larger direct contact condensation rate at the top of the make-up tank will reduce the top pressure and cause the smaller flow at the outlet of the make-up tank
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