Nuclear Street - Nuclear Power Plant News, Jobs, and Careers

For the Toshiba ABWR fact sheet, click here. 

In the News: Toshiba ABWR

Features:

Easy to Operate, Environmentally Friendly

• Centralized monitoring and control system
• Operation mostly automated
•  Improved water quality
•  Low-cobalt material

Utilizes Proven Technology

Inherent Safety

• Negative feedback
• Void feedback
• Doppler feedback

Entranced Reliability

• Plant components proven in practice
• Optical multiplexing transmission
• Integrated digital control

High Operating Performance

• Stable power control over a wide range ensured by recirculation flow
• Daily load-following operation

Superior Cost Efficiency

• Simplified system configuration with direct cycle
• Shorter construction period
• High plant efficiency

Reactor Pressure Vessel and Its Internals

In an ABWR, coolant water is recirculated inside the reactor pressure vessel (RPV) by reactor internal pumps installed within the vessel itself. The RPV contains the fuel assemblies, control rods and the reactor's internals. It is made of low-alloy steel and its inner surface is clad with corrosion- resistant materials.
The internal elements it houses include the steam separator and dryer and the core support structures.

 Control Rods and Control Rod Drive

The material in the control rods absorb neutrons and so restrain and control the reactor's nuclear fission chain reaction. The rods themselves have a cruciform cross section.
They are inserted upwards, from the base of the RPV, into the rod spaces in fuel assemblies.
In the ABWR, the position of each rod is regulated by its Fine Motion Control Rod Drive (FMCRD), which is actuated by an inverter drive system during normal operation.
It also applies hydraulic scram.

 Emergency Core Cooling System

Any accident resulting in a loss of reactor coolant automatically sets off the Emergency Core Cooling System (ECCS).
Made up of multiple safety systems, each one functioning independently, ECCS also has its own diesel-driven standby generators that take over if external power is lost.

High Pressure Core Flooder (HPCF) and Reactor Core Isolation Cooling (RCIC) Systems
These systems inject water into the core to cool it and reduce reactor pressure.

Low Pressure Flooder (LPFL) System
Once pressure in the reactor vessel is reduced, this system injects water into the reactor vessel. The reactor core is then cooled safely.

Automatic-Depressurization System
Should the high-pressure injection system fails, this system lowers the reactor vessel pressure to a level where the LPFL system can function.

Control and Instrumentation

Spectacular advances in the computerization of Control and Instrumentation (C&I) and power electronics now make possible functions that were once little more than an engineer's dream. These advances are utilized to the full in the Nuclear Power Station, enhancing overall operability and assuring highly user-friendly man-machine interface.
All required operating information is brought to the main control room. Here, A-PODIA (Advanced Plant Operation by Displayed Information & Automation) supports the operator in overseeing the proper functioning of the plant, with information from all monitoring and control devices shown on large display panel and at the operator console.

Reactor Internal Pump

BWR utilize a forced circulation system for the reactor coolant that intensifies steam generation at the reactor core.
ABWR further enhances plant reliability, safety and operating economy by use of reactor internal pumps (RIP). The reactor coolant is circulated by 10 RIP installed in the RPV.
Each is driven by a wet stator motor mounted in a motor casing. The speed of the pump controls the coolant flow rate, which enables control of the reactor output.

 Reactor Core and Nuclear Fuel

The reactor core comprises fuel assemblies and control rods.
Each fuel rod in fuel assemblies contains sintered pellets of low-enriched uranium within a zirconium-lined cladding.
They are brought together in fuel assemblies, 8x8 arrays of control rods held in place by upper and lower tie plates and spacers.

Primary Containment Vessel

The primary containment vessel encloses the reactor pressure vessel, other primary components and piping. In the highly unlikely event of an accident, this shielding prevents the release of radioactive substances.
The ABWR uses a Reinforced Concrete Containment Vessel (RCCV).
Its reinforced concrete outer shell is designed to resist pressure, while the internal steel liner ensures the RCCV is leak-proof.
The compact cylindrical RCCV integrated into the reactor building enjoys the advantages of earthquake-resistant design and economic construction cost.