Page 247 - Dynamics and Control of Nuclear Reactors

248 APPENDIX B Advanced reactors

B.5.3 Pressurized heavy water reactors
Canada offers two advanced pressurized heavy water reactor designs. The reactors
differ in design and purpose. Brief descriptions follow:
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• Advanced CANDU Reactor (ACR): The ACR is a Generation III reactor,
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designed to compete with other Generation III reactors for service as large
central station power plants (Ref. [10]). The main difference from earlier
CANDU reactors in the use of light water coolant instead of heavy water. Heavy
water moderator in a calandria remains. The ACR employs the principles
described in Section B.1. However, the ACR has proved to be non-competitive
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compared to other Generation III designs and development has been stopped.
• Advanced Fuel CANDU Reactor (AFCR): The Generation III AFCR appears to
offer the CANDU reactor a new lease on life. It offers the options of using
recycled spent fuel from light water reactors and using low enriched uranium/
thorium (LEU//Th) fuel. The AFCR design is basically the same as the CANDU-
6, but with new fuel designs [11–13].

Spent fuel from light water reactors contains too little fissile material for continued
use in the LWR. But the LWR spent fuel contains enough fissile material for use in a
CANDU reactor because of CANDU’s better neutron economy (due to heavy water’s
small neutron absorption probability).
The LEU/Th fuel version enables use of the thorium resource for power produc-
tion. The AFCR fuel bundle is cylindrical with 43 concentric fuel rods. The recycled
spent fuel version uses 42 rods containing recycled spent fuel and one (centrally
located) rods containing a mixture of recycled spent fuel and dysprosium oxide.
The LEU/Th version uses eight inner rods containing thorium oxide and thirty-five
outer rods containing low enrichment uranium.

B.6 Large developmental reactors
Several large reactor designs in the developmental stage are potential options for
wide-spread implementation. Each design draws on experience with earlier proto-
types. Brief descriptions follow:

B.6.1 Gas-cooled reactors
Magnox, CO 2 cooled power reactors have been operating in Britain for many years,
but they were overshadowed by light water reactors developed in other countries. No
advanced gas-cooled reactors have been built, but technology development and pro-
totype reactor implementation has been pursued.
Advanced gas-cooled reactors include prismatic and pebble bed designs (Refs.
[14–17]) Prismatic designs have fuel particles embedded in graphite blocks and peb-
ble bed designs have fuel particles in graphite balls.