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High Quality Foxboro0303440D/SY-0303440-AS Module New In Stock

Introduction

Redundant Valve Outputs are utilized to eliminate single point of failure vulnerabilities within the control application and improve reliability and robustness of the system and its ability to automatically control the plant over its full power range for the entire fuel cycle. The I/A Series Fieldbus Modules include the FBM218, which is capable of providing redundant, channel isolated outputs to field devices. If a failure is detected in one of the Fieldbus Modules, its output is driven to 0 mA and the corresponding channel in the tracking module automatically continues supplying the proper current to the output current loop.

Redundant Valve Outputs have been used for feedwater controls such as the Start-Up Bypass Feedwater Valve and the Main Feedwater Valve controls.

Traditionally, the feedwater control system operated in Single Element control at low power using only the Startup Bypass valve to maintain Steam Generator Level. Above ~25% power, a Three Element system was employed using only the Main Feedwater Regulating (MFWR) valve. Steam generator level is more robustly controlled using the three elements of steam flow, feedwater flow, and steam generator level. As reactor power increased from 20% to 25%, operators would perform a manual transfer from the Single Element Start-up Bypass valve to the Three Element MFWR valve. Similarly, as reactor power would decrease from 25 to 20%, operators manually transferred from the Three Element MFWR valve back to the Single Element Start-up Bypass valve. These manual transitions require intense operator involvement, and have been the cause of many unplanned unit trips.

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