In the present, various testing programs are being performed or planned to consolidate their feasibilities and to find further room for improvements. ABWR-II results are planed to reflect the new next generation light water reactor development program sponsored by the government.

FIG. I-3. Example of containment pressure transient following typical low pressure core melt scenario.

ANNEX II. ACR-1000
Atomic Energy of Canada Ltd, Canada

I — 1. Introduction

The Advanced CANDU Reactor ™ (ACR™) is a Generation III+ pressure tube reactor designed by Atomic Energy of Canada (AECL). The ACR-1000 is an evolution of the proven CANDU reactor design. It is a light-water-cooled reactor that incorporates features of both pressurized heavy water reactors (PHWRs) and advanced light-water PWRs. It incorporates multiple and diverse passive systems, wherever necessary, for mitigation of any postulated accident scenarios, including severe accidents. The ACR-1000 uses passive design elements to complement active features, thus enhancing reliability and improving safety margins.

The ACR retains the core features of previous CANDU designs, such as horizontal fuel channels surrounded by a heavy water moderator. The major innovation in the ACR is the use of low enriched uranium fuel and light water as the coolant.

The overall layout of an ACR-1000 reactor and its primary components are shown in Fig. II-1 and Fig. II-2. The ACR-1000 reactor is designed by Atomic Energy of Canada Ltd to produce a nominal gross output of 1165 MW(e). The reactor employs active as well as passive safety features, the latter relying on gravity, compressed gas or natural circulation (thermosyphoning). As with all CANDU reactors, the high pressure, (11.1 MPa) heat transport system (HTS) and the low pressure and low temperature moderator are separate systems.

The low pressure, low-temperature moderator is contained in a tank called the Calandria. The primary coolant system consists of fuel channels, stainless steel feeders, four inlet headers, four outlet headers, four steam generators, four electrically driven heat transport pumps, and the interconnecting piping. There are 520 fuel channels and each fuel channel contains 12 nuclear fuel bundles (approximately 50 cm long x 10 cm in diameter). The primary coolant system is arranged in a two ‘figure of eight’ loop configuration. The pumps circulate the water in the two loops in opposite directions.

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In normal operation heat is generated in the reactor fuel bundles and exchanged with the fast-flowing coolant. The heated water is transported through the feeder pipes to the headers and into the U tubes inside the steam generators (SGs). The heat is then transferred to the water on the secondary side to produce steam, driving the turbine to generate electricity. The cooled water leaving the steam generator is pumped by four HTS pumps through two separate HTS loops connected to a common pressurizer, which maintains the HTS at a constant pressure.