ACR- 1000 nuclear reactor

ACR-Nuclear  reactors

After several decades of slow growth of nuclear power capacity, governments  and public are again thinking seriously thinking about new nuclear power plants (NPPs) as a source of clean, safe economic base load electricity. During  this period Atomic Energy of Canada Limited ( AECL)continued to build CANDU plants around the world and recent new  build CANDU 6 projects have shown have shown record delivery performance, allowing the industry to over come public perception that nuclear power projects often exceed their budget and  schedule.

CANDU nuclear reactors currently produce about 16 per cent of Canada’s electricity and more than 50 per cent of province of Ontario’s electricity generation mix. Canada has abundant supplies of uranium ,a strong nuclear power industry  and high-performing , home grown reactor technology in the form of the successful CANDU  power reactor and a new product the advanced CANDU  reactor ACR-1000 can meet demands for safe , clean electricity in Canada and other countries

ACR - 1000 advanced CANDU  reactor

AECL is developing the advanced CANDU reactor (ACR) to meet customer requirements for emerging nuclear market over 20 years of sale. The ACR -1000 is an evolution generation 111+, 1200 Mwe class heavy water reactor designed to meet industry and public expectations for safe reliable, environmentally friendly, low cost nuclear power generation . The ACR-1000 the only generation 111+ reactor in the world to have completed phase 2 of the Canadian nuclear safety commission (CNSC) pre license review. In September 2009 CNSC released the results of this review and concluded that there were no fundamental barriers to licensing the ACR-1000 for new build construction in Canada .

ACR -1000 designed to meet market needs

. Evolutionary design
. Competitive economics
. Short construction duration
. Low and stable operating cost.
. Passive safety
. Hardened against external threats
. Enhanced  performance and operatability
. Clear , straight  forward  licensing
. Combined best aspects  of  CANDU  and light water reactor (LWR) technology

Evolved on experience of decades of successful CANDU  nuclear technology operation, AECL developed , ACR -1000 on principles and characteristics of proven  CANDU design but several enhancements.

ACR -1000 enhance include

. A compact core design with improved stability and higher out put.

. Light water coolant, which reduces heavy water inventory by two-thirds

. CANFLEX-ACR fuel bundles that use low-enriched uranium (LEU fuel to achieve higher burn up and negative void reactivity.
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. Improved passive safety

. Superior accident resistance and core damage prevention features, including steel -lined hardened containment.

. Optimized plant layout

. Designed in operatability and maintainability

 Improved operation ,performance and economics

Reduction  in heavy water  inventory by approximately  60 per cent over traditional CANDU  reactors, cutting costs and improving environmental  performance and occupational safety.

. Ability to burn alternative fuel, such as  mixed oxides (MOX) and thorium

. Less  re fuel's and lower spent fuel volume Mwh ,through use of  low -enriched  uranium in a complex-ACR  fuel bundles, as a result increased burn up.

. Simplified reactor control resulting from reduced pressure tube lattice pitch and use 0f LEU fuel for high stable, more compact core. Further simplification achieved with mechanical zone control rods and eliminating the liquid zone control systems.
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 . Improved on -power maintenance and testing, additional redundancy in actuating signals for tripped channels, reduced risk of spurious trips and overall increased reliability, though use of quadrant-based layout for safety and heat sink system.

. Enhanced power maneuvering ability due to  lower xenon load after shut down than traditional CANDU plants.

. Higher overall thermal cycle efficiency, resulting from increased coolant and steam supply pressure and temperature

The basic design and ACR -1000 program is in full project mode AECL ’s commercial operation group. The  basic features- including a modular, horizontal core with fuel channels, simple fuel bundle design , separate low -temperature and low pressure heavy water moderator and passive safety features-are retained and innovations enhance safety, performance  and economics.

Major changes to the design include using light water (instead of heavy water ) as a  coolant and introduction of low-enrich (instead of natural uranium fuel, in advanced ‘CANFLEX ‘ bundles. However 80 per cent of plant features, equipment and specification are still based on candu 6 reference plant, giving high degree of confidence that initial new build project will be completed successfully.

ACR-1000 evolving and enhancing safety

In ACR -1000 designs have increased safety and operating margins, enhanced accident resistance and core damage prevention features , provided a thicker steel -lined containment and improved fire protection. The thicker containment is designed to with stand external events such as earth quakes, tornadoes, floods, air craft crashes and malevolent acts. Each corner of reactor auxiliary building houses redundant safety equipment in a four quadrant design, with quadrant separated by three-hour fire barriers.

The ACR -1000 design combines CANDU s  passive safety features with engineered safety -technology. Central to the safety system are two fast acting, fully capable ,diverse and separate shutter down systems. These are physically and functionally dependent of each other and also from reactor regulating systems and are optimized for reliability.

Additional defense in depth is derived from the inherent passive safety of CANDU core including heat sink redundancy for potential accident conditions. These passive features have been enhanced still further in the ACR-1000 design to mitigate, prevent or significantly delay severe accidents. As well as  the ACR-1000 core is designed for a  the ACR -1000 core is designed for a small negative void coefficient.  This provides inherent protection against transients with any inadvertent   increase in power.

ACR -1000 meeting grid requirements

A focused effort was also made to ensure the ACR-1000 flexible enough to meet grid requirements. The ACR-1000’s enhanced power maneuvering capability simplifies reactor operation and  makes the reactor inherently more responsive to grid.