Feedwater Pump Trip Research Articles

Assessing the SCRRI and RIP runback performances of TRACE/PARCS for Lungmen ABWR

The TRACE/PARCS model is conventionally adopted as a best-estimate calculation approach for the Lungmen advanced boiling water reactor (ABWR). This study assesses the performance of SCRRI and RIP runback simulated by TRACE/PARCS featuring three-dimensional evaluation. The effectiveness of TRACE/PARCS is demonstrated by selecting the two transients in the startup test prediction, feedwater pump trip and loss of feedwater heater, which are involved with the initiation of both SCRRI and RIP runback. Calculation results indicate that SCRRI is a slower measure than the runback mechanism in mitigating the steam flow dumped into the main condenser, subsequently reducing the power to another state. Additionally, RIP runback is alternative approach to diminishing the power by reducing the core flow. Moreover, sensitivity studies involving different settings for RIP runback and SCRRI are also performed to determine the SCRRI and RIP runback delay times, as well as RIP runback rate. Sensitivity studies reveal that the operational settings of SCRRI and RIP runback influence the process during transients. Nevertheless, the setting does not significantly impact the final state of the transient.

ABWR power tests simulation by using a dual RELAP5 nuclear power plant simulation platform

Lungmen nuclear power plant is the first advanced boiling water reactor (ABWR) plant in Taiwan. According to the most up-to-date schedule, Lungmen Plant will begin its power tests in later 2011. The tests contain (1) loss of feedwater heater test, (2) one feedwater pump trip test, (3) one reactor internal pump trip test, (4) three reactor internal pumps trip test, (5) loss of offsite power and turbine/generator trip test, (6) turbine trip test, (7) load rejection test, (8) fast load winddown test, and (9) reactor full isolation test. The acceptable values of the plant major parameters in all test criteria of each plant power test have been provided by the plant vendor's analysis results. Thus, the verification of the correctness of the vendor results is important. A dual RELAP5 advanced Lungmen Plant specific simulation platform (ALPS) has been used to simulate the plant power tests. ALPS is developed based on two independent RELAP5 modules: one for the reactor system modeling and the other one for the balance of plant system modeling. All plant systems simulation models are synchronized on a PC-based commercial simulation platform, namely 3KeyMaster. The plant major control systems and the emergency core cooling system are simulated in great detail with the built-in modeling tools of 3KeyMaster. ALPS calculation results have been compared with the plant vendor's preliminary power tests analysis results. The comparison results have been delivered to the plant vendee for references. In this article some typical power tests simulation and comparison results are presented for (1) one feedwater pump trip test, (2) one reactor internal pump trip test, (3) load rejection test, and (4) reactor full isolation test.

RETRAN analysis results of feedwater pump trip transient for Lungmen ABWR Plant

The RETRAN model of Lungmen ABWR was used to simulate one feedwater pump trip (FWPT) transient of the Lungmen start-up test program. The purpose of this test is to verify the capability of one surviving Turbine Driven Reactor Feedwater Pump (TDRFP) plus a Motor Driven Feedwater Pump (MDRFP) to continue operating the reactor stably following the incident. There are three major control systems implanted in Lungmen RETRAN model (LRM), which include Recirculation Flow Control System (RFCS), Steam Bypass and Pressure Control System (SBPCS), and Feedwater Control System (FWCS). The reactor water level margin with respect to the low level scram setpoint in the transient is monitored to confirm whether the acceptance criteria has been satisfied, which depends on the responses of the control systems to the FWPT transient. The analysis result of base case at 100% rated power/100% rated core flow with automatic start of MDRFP demonstrates that the acceptance criteria are met, which shows that the water level still sustains ample margin of 30 cm above the low level setpoint, and the reactor does not scram. To get more insight into the function of MDRFP, a set of sensitivity studies with the assumption of unavailable MDRFP, and with a different initial condition which extended to the maximum allowable core flow of 111% rated at rated power, was conducted to verify the superior capability of power coastdown due to the RIPs runback logic under the lowest load line, and also the delay time of the Reactor Internal Pumps (RIPs). Finally, it is concluded that FWPT transient without start of MDRFP eventually actuates the low level scram signal, even with the lowest load line at rated power as the initial condition.

ICONE19-43755 Investigation of Feedwater Pump Trip Transients of Lungmen Nuclear Power Plant

TRACE (TRAC/RELAP Advanced Computational Engine) model of Lungmen Nuclear Power Plant (NPP) was used to analyze the feedwater pump trip transient as defined in Lungmen startup test procedure. The transient will lead to low water level and accordingly the Recirculation Flow Control System (RFC) will trigger the RIPs runback to reduce the reactor power with another Turbine Driven Reactor Feedwater Pump (TDRFP) and the Motor Driven Reactor Feedwater Pump (MDRFP) remain operational. For the purpose of investigating characteristics of the transients, it is very important to identify and evaluate the parametric sensitivity under certain ranges of study. It was observed in parametric sensitivity studies of one feedwater pump trip that the water level will fluctuate between L3 and L8, having reliable safety margins to avoid either low or high water level reactor trip setpoints.

Development and diversity and defense-in-depth application of ABWR feedwater pump and controller model

This work developed an advanced boiling water reactor (ABWR) feedwater pump and controller model, which was incorporated into Personal Computer Transient Analyzer (PCTran)-ABWR, a nuclear power plant simulation code. The feedwater pump model includes three turbine-driven feedwater pumps and one motor-driven feedwater pump. The feedwater controller includes a one-element/three-element water level controller and a specific feedwater speed controller for each feedwater pump. The performance tests, including step change of dome pressure, feedwater pumps transfer, inadvertent closure of all turbine control valves, and one feedwater pump trip at 100% power, demonstrate the feasibility of dynamic response of stand-alone model and incorporated model. Furthermore, a diversity and defense-in-depth analysis is performed to demonstrate the feasibility for motor-driven feedwater pump as an emergency core cooling system (ECCS) automatic diverse back-up. In Lungmen nuclear power plant (NPP), a diverse manual initiation means for the high pressure core flooder (HPCF) loop C is designed as the back-up of digitalized engineered safety features actuation system (ESFAS). If the motor-driven feedwater pump (MDFWP) can be an automatic digital diverse back-up for ESFAS, Lungmen NPP would be more robust to defend against software common-cause failure (CCF).

Safety design of Pb–Bi-cooled direct contact boiling water fast reactor (PBWFR)

In Pb–Bi-cooled direct contact boiling water small fast reactor (PBWFR), steam is generated by direct contact of feedwater with primary Pb–Bi coolant above the core, and Pb–Bi coolant is circulated by steam lift pump in chimneys. Safety design has been developed to show safety features of PBWFR. Negative void reactivity is inserted even if whole of the core and upper plenum are voided hypothetically by steam intrusion from above. The control rod ejection due to coolant pressure is prevented using in-vessel type control rod driving mechanism. At coolant leak from reactor vessel and feedwater pipes, Pb–Bi coolant level in the reactor vessel required for decay heat removal is kept using closed guard vessel. Dual pipes for feedwater are employed to avoid leak of water. Although there is no concern of loss of flow accident due to primary pump trip, feedwater pump trip initiates loss of coolant flow (LOF). Injection of high pressure water slows down the flow coast down of feedwater at the LOF event. The unprotected loss of flow and heat sink (ATWS) has been evaluated, which shows that the fuel temperatures are kept lower than the safety limits.

Analysis of the Leibstadt power plant condensate and feedwater systems during selected operational transients

This paper presents a selection of plant analyses that were carried out by PSI in support of the Leibstadt Nuclear Power Plant (Swiss boiling water reactor). The analyses were performed as part of a collaboration between Leibstadt and PSI, to help resolve some operational problems that were experienced during the power uprate beginning in 1998. The issues under investigation were related to the behavior of the condensate and feedwater systems during transients initiated by a turbine trip, load rejection and a single feedwater pump trip, all of which increased the risk of an inadvertent reactor shutdown by reaching reactor pressure vessel water level limits. The possibility of a reactor shutdown was related to perturbations in the feedwater flow caused by transitory pump cavitation of the feedwater pumps, due to a rapid depressurization in the feedwater tank. In addition to a direct analysis of plant measurement provided by Leibstadt, steady-state and transient simulations of the events were performed at PSI using the system codes TRAC-BF1 and TRACE. Through a combination of the analysis of the plant measurements, the code simulations and an analysis of the whole plant behavior using the Leibstadt plant-simulator appropriate modifications of the plant hardware, control system and operational set points were proposed. The implementation and success of these changes were verified by a number of plant tests. Finally, the original designed plant capability not to shutdown during the aforementioned transients was demonstrated.

Empirical Steam Generator Water-Level Modeling Using Neural Networks

Neural networks such as the radial basis function network, adaptive neuro-fuzzy inference systems, and the multilayer feedforward neural network were adopted to model the steam generator water level, which was intended to be the analytic redundancy in the signal validation system. The training data were the simulation results of the small-demand turbine power variations around the steady state. The test data were from two small-load maneuvers: the load reduction from 100 to 50% of the rated power, and one feedwater pump trip event. The network training required only a short time, and the simulation results show that the neural networks are suitable for the modeling of steam generator water level.

96/04998 Neutron scattering from elemental uranium and thorium

The RETRAN model of Lungmen ABWR was used to simulate one feedwater pump trip (FWPT) transient of the Lungmen start-up test program. The purpose of this test is to verify the capability of one surviving Turbine Driven Reactor Feedwater Pump (TDRFP) plus a Motor Driven Feedwater Pump (MDRFP) to continue operating the reactor stably following the incident. There are three major control systems implanted in Lungmen RETRAN model (LRM), which include Recirculation Flow Control System (RFCS), Steam Bypass and Pressure Control System (SBPCS), and Feedwater Control System (FWCS). The reactor water level margin with respect to the low level scram setpoint in the transient is monitored to confirm whether the acceptance criteria has been satisfied, which depends on the responses of the control systems to the FWPT transient.The analysis result of base case at 100% rated power/100% rated core flow with automatic start of MDRFP demonstrates that the acceptance criteria are met, which shows that the water level still sustains ample margin of 30 cm above the low level setpoint, and the reactor does not scram. To get more insight into the function of MDRFP, a set of sensitivity studies with the assumption of unavailable MDRFP, and with a different initial condition which extended to the maximum allowable core flow of 111% rated at rated power, was conducted to verify the superior capability of power coastdown due to the RIPs runback logic under the lowest load line, and also the delay time of the Reactor Internal Pumps (RIPs). Finally, it is concluded that FWPT transient without start of MDRFP eventually actuates the low level scram signal, even with the lowest load line at rated power as the initial condition.