Fission Reactors: Common Designs

Some common designs for fission reactors include:


Boiling water reactors(BWR)
: Operate around 7 MPa and 573 K with regular water as the moderator and coolant. Water boils at the top of the core and provides steam to turbines directly. These reactors use slightly enriched UO2. [5]


Pressurized water reactors(PWR): Operate around 14 MPa and 573 K with regular water as the moderator and coolant. Heat is transferred from the core of the reactor to steam generators via intermediate heat exchangers. These reactors also use slightly enriched UO2. [5]


Heavy-water moderated reactors (CANDU): Operate around 15 MPa and 573K with regular water as the coolant, and heavy water as the moderator. The heavy water is contained within a calandria through which the coolant circulates, transferring heat to steam generators. These reactors use natural UO2. [5]


Magnox/advanced gas cooled reactors(AGR)
: These reactors use carbon dioxide gas as their coolant, and graphite as their moderator. The Magnox reactors were retired in favor of advanced gas-cooled reactors (AGR) which use stainless steel clad slightly enriched UO2 fuel rods, as opposed to the natural uranium and magnesium alloy clad fuel rods used in Magnox reactors. AGR reactors can operate at higher temperatures than Magnox reactors. Both reactors follow the same concept as the other reactors of circulating the coolant to transfer heat to steam generators. [5]


High-temperature helium cooled reactors (HTGR): Operate between 973 K and 1273K between 5 MPa and 8 MPa.These reactors use helium gas the coolant and graphite as the moderator. These reactors use coated-particle oxide or carbide fuel. Like the other reactors the helium is circulated through to transfer heat to steam generators. [5]


Liquid-metal cooled fast breeder reactors (LMFBR): Fast reactors do not need moderation since their chain reaction is sustained entirely by fast neutrons. Fast reactors are smaller since they do not need moderation components and thus are common on submarines where space is limited. In these reactors liquid-metal is used as the coolant, which circulates through transferring heat to steam generators. UO2 or PuO2 pellets clad in steel are used to fuel these reactors. [5]

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