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1. Gas cooled Reactors

2. For more help contact me
Muhammad Umair
Bukhari
Engr.umair.bukhari@gmail.com
http://onlinemetallurgy.com

3. History of Gas Cooling
• CP1 was first reactor without coolant in
Chicago and structure was made up of wood
and bricks

4. First Gas Cooled Reactor
• For the first time coolant was used in
November 1943 at Oak Ridge
• And first coolant was air
• X10 was first air cooled reactor
• Wind scale in UK and G1 also used air as
coolant

5. X10 Air Cooled Reactor

6. Purpose of Coolant
• The real task of a coolant is not to cool the
fuel but to transport heat from the reactor
core to the boilers to produce steam for
electricity generation or to generate process
heat.

7. Why Gas as Coolant?
Gases exhibit interesting qualities such as
– The density of a gas is variable, its operating
temperature can be chosen independently of
the operating pressure. Thus a high gas
temperature can be used, limited only by the
core and circuit materials, to give good steam
conditions from the boiler and thus good
conversion of heat to electrical energy through
the resulting high turbine efficiency

8. Why Gas as Coolant?
• Gases also has certain intrinsic safety
advantages e.g.
– They don’t undergo any phase change as a result
of rising temperature or falling pressure,
resulting
• Cooling continuity
• Continuous flow
• Ease of temperature calculation

9. Why Gas as Coolant?
• On-load refueling is more easily achieved with
a gas
• There is no risk of a fuel-coolant interaction of
the kind that in certain circumstances could
result from the dispersion of melted fuel in a
liquid coolant.

10. Why Gas as Coolant?
• A gas carries a relatively low burden of
activated corrosion products
• And low neutron absorption cross section

11. Limitations
Some limitation associated with gases are
• low specific heat of gases, and requires large
volume flows to transport the heat results in
– large circulator sizes and powers

12. Some gases of choice

13. Gas cooled reactor
• Natural uranium, graphite-moderated reactors
were developed in the United States during
World War II for the conversion of 238U to
239pu for military purposes.
• Most “first generation” gas-cooled power
plants were designed and built in the UK– the
Magnox series – and in France – the NUGG.

14. Features of First Generation Reactor
• Natural uranium (in metallic) fueled reactor
• Fuel was in form of bars cladded in Mg-alloy
• Graphite moderator
• CO2 gas as coolant
• Their ability to unload the fuel without having
to shut down the reactor made it possible to
produce almost pure 239Pu for military
applications by short irradiation.

15. Cont….
• Ealier Magnox has efficiency 22% and after
development it reached to peak of 33.6%
• Gas pressure of a typical reactor was 6.9 bar
and temperature was limited to 340oC
• Boiler was integrated with core
• NUGG used the pressure of CO2 29 bar

16. 300 MWe Magnox reactor Oldbury A1
(Marshall W 1981)

17. CO2 Characteristics
• CO2 has following characteristics
– Easily available, cheap
– Good heat transfer rate
– Good chemical compatibility with core materials(
e.g graphite moderator, cladding material & fuel)
– Compatible neutronic properties with graphite
moderator

18. AGR
( Advance Gas Cooled Reactor)
• Magnox were predecessor of AGR
• AGR differs from latest Magnox in fuel
elements
• They can operate on low enriched uranium
oxide fuel in form of small dia. Pins
• Cladding material was stainless steel

19. AGR features
• UO2 and CO2 compatibility made the high
temp 650oC possible
• And efficiency reached at 42%
• Methane was used in coolant to avoid
corrosion

20. Components of AGR

21. Fuel element features of AGR

22. High temperature Reactor
• In 1970 and 1980 in Germany and USA
• They differ from AGR with use of He as
coolant and different type of fuel
• Fuel element was 1mm diameter particles or
6cm dia. spheroid
• Used dual coating of pyrocarbon and SiC
• Operating temperature achieved was 750-
850oC and pushed at the limit of 1050oC

24. Gen IV GFR
(Gas Cooled Fast reactor)
• Mostly paper work or lab scale
• Modified form of HTR’s
• Some modification are made in flow cycle of
helium
• They are also known as high efficiency
reactors

25. • Gen IV introduced the “twofold” concept
– combining high thermodynamic efficiency through
high temperatures, and high neutronic efficiency
(with significant economization of resources in the
case of the uranium-plutonium cycle) through fast
spectrum conditions.

26. Flow sheet of Gen IV GFR

27. Gen IV Concept
• Gen IV concept mainly focus on
– High efficiency
– Safety and environment friendly