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Note to this table

CRD: control rod drive RHR: residual heat removal system

RCIC: reactor core isolation cooling system HPCS: high pressure core spray

HPCF: high pressure core flooder system LPCS: low pressure core spray

LPCF: low pressure core flooder system LPCI: low pressure core injection

RCIC

LPFL (RHR)

HPCF

automatic depressurization system

RCIC

(reactor core isolation cooling)

LPFL / RHR

HPCF HPCF

(high pressure core flooder)

LPFL (RHR)

LPFL (RHR)

note : Legend

LPFL/RHR LPFL/RHR

(emergency diesel generator)

Figure 2.12.10 abwr eccs (three divisions)

NSRA, Japan

2 126

Chapter 2 Systems of BWR Nuclear Power Plants

  1. Enhanced Operability and Maneuverability

  1. Improved monitoring and maneuverability

In order to improve the monitoring and maneuverability, the ABWR main control console has been newly developed by advancing the second generation main control console. New features of the ABWR main control benchboards are compared below with the second generation type.

  1. Centralized monitoring and maneuvering

In the second generation control benchboards, monitoring information was centralized by the extensive use of CRTs. However, the control benchboards were still large sized, since all maneuvering devices consisted of hardware switches. The new ABWR main control benchboards reduce the operator’s monitoring and maneuvering area by using software switches (touch screen operation) and other advanced technologies.

  1. Prevention of faulty operation and misjudgment The second generation main control

benchboards optimized the classification of importance of hardware monitoring instruments (alarm windows, indicators, recorders) and the mounting layout of switches. The new ABWR main control benchboards further reduce human errors, using features of flexible display locations and variable display colors coupled with advanced human-machine interface devices and digital technologies.

  1. Simple and sure monitoring

The alarm system of the second generation benchboards had more than 1,000 hardware alarm windows, The new ABWR central control benchboards have been improved by reducing the number of alarm windows and applying a hierarchy alarm indication method on the CRT

In addition, the relevant information is arranged to be shared by all operators in the main control room for their cooperative work in a crew.

  1. Simple and sure maneuverability

In the second generation benchboards, main operation processes during the startup and shutdown were automated. But, investigations showed that the operator workloads were significant immediately after a plant trip for corrective actions and control rod maneuvering.

Therefore, the new ABWR main control benchboards automate these operation processes.

The configuration (Figure 2.6.13) and functions of the ABWR main control benchboards are described next. It consists of the main control console and a wide display panel.

The wide display panel has three areas: the important alarm display area on the left; the fixed mimic display in the center; and a large screen display on the right. The information displayed on these panels covers key information to be monitored during normal operations and in accidents. Display characters and symbols are enlarged for easy identification by the shift supervisor and all crew members in the main control room from their individual seats.

The main control console is designed more compactly compared with the second generation control console to allow monitoring and maneuvering from the operators’ seats. Hardware switches and flat displays (FDs) are arranged on the main control console in addition to the CRTs. Each FD is an integrated display device driven by a microprocessor. Its screen size and the quantity of processing information per unit are limited as compared with the process computer driven CRT, but the FDs are deployed as the backup monitoring devices to prepare for process computer sudden shutdown failures. This is possible because the risk of simultaneous failures of all FDs is made negligible by decentralizing the microprocessors. Maneuvering can be done by either hardware switches or touch operations of the CRT and FDs. The hardware switches serve as the “mode switches” to execute a series of standard system operations mostly by a single maneuvering, both during the plant startup or shutdown and during a failure occurrence. When a single specific device needs to be operated for tests or inspections, it can be maneuvered by the touch operations on the CRT or FDs.

The basic items of the operation support functions newly introduced in the ABWR main control benchboards have been selected based on the work load analysis of conventional BWR-5 operators.

The operator work load analyses found the following points.

2- 127

NSRA, Japan