Three systems have been proposed for advanced high-temperature gas-cooled reactors: a supercritical carbon dioxide $(S-CO2)$ gas turbine power conversion system, a new microchannel heat exchanger (MCHE), and a once-through-then-out (OTTO) refueling scheme with burnable poison (BP) loading. A $S-CO2$ gas turbine cycle attains higher cycle efficiency than a He gas turbine cycle because of reduced compression work around the critical point of $CO2$. Considering temperature reduction at the turbine inlet by $30°C$ through intermediate heat exchange, the $S-CO2$ indirect cycle achieves an efficiency of 53.8% at a turbine inlet temperature of $820°C$ and a turbine inlet pressure of 20 MPa. This cycle efficiency value is higher by 4.5% than that (49.3%) of a He direct cycle at a turbine inlet temperature of $850°C$ and 7 MPa. A new MCHE has been proposed as an intermediate heat exchanger between the primary cooling He loop and the secondary $S-CO2$ gas turbine power conversion system and as recuperators of the $S-CO2$ gas turbine power conversion system. This MCHE has discontinuous “S-shaped” fins providing flow channels resembling sine curves. Its pressure drop is one-sixth that of a conventional MCHE with a zigzag flow channel configuration, but it has the same high heat transfer performance. The pressure drop reduction is ascribed to suppression of recirculation flows and eddies that appear around bend corners of the zigzag flow channels in the conventional MCHE. An optimal BP loading in an OTTO refueling scheme eliminates the shortcoming of its excessively high axial power peaking factor, reducing the power peaking factor from 4.44 to about 1.7, and inheriting advantages over the multipass scheme because it obviates reloading in addition to fuel handling and integrity checking systems. Because of the power peaking factor reduction, the maximum fuel temperatures are lower than the maximum permissible values of $1250°C$ for normal operation and $1600°C$ during a depressurization accident.

1.
Kato
,
Y.
,
Nitawaki
,
T.
, and
Muto
,
Y.
, 2004, “
Medium Temperature Carbon Dioxide Gas Turbine Reactor
,”
Nucl. Eng. Des.
0029-5493,
230
, pp.
195
207
.
2.
Muto
,
Y.
, and
Kato
,
Y.
, 2006, “
Turbomachinery Design of Supercritical CO2 Gas Turbine Fast Reactor
,”
Proceedings of the 2006 International Congress on Advances in Nuclear Power Plants (ICAPP‘06)
, Reno, NV, Jun. 4–8, Paper No. 6094.
3.
Hesselgreaves
,
J. E.
, 2001, “
Compact Heat Exchangers, Selection, Design and Operation
,”
Pergamon
,
New York
, pp.
126
128
and pp. 35–38.
4.
Tsuzuki
,
T.
,
Kato
,
Y.
, and
Ishizuka
,
T.
, 2007, “
High Performance Printed Circuit Heat Exchangers
,”
Appl. Therm. Eng.
,
27
, pp.
1702
1707
. 1359-4311
5.
Fluent, Inc.
, 2003,
Fluent 6.1 User’s Guide
,
Fluent Inc.
,
Lebanon, NH
.
6.
Ngo
,
T. L.
,
Kato
,
Y.
,
Nikitin
,
K.
, and
Tsuzuki
,
N.
, 2007, “
Heat Transfer and Pressure Drop Correlations of Microchannel Heat Exchangers With S-Shaped and Zigzag Fins for Carbon Dioxide Cycles
,”
Exp. Therm. Fluid Sci.
0894-1777,
32
, pp.
560
570
.
7.
Hansen
,
U.
,
Schulten
,
R.
, and
Teuchert
,
E.
, 1972, “
Physical Properties of the “Once Through Then Out” Pebble-Bed Reactor
,”
Nucl. Sci. Eng.
,
47
, pp.
132
139
. 0029-5639
8.
Tran
,
H. N.
, and
Kato
,
Y.
, 2008, “
,”
Nucl. Sci. Eng.
,
158
, pp.
264
271
. 0029-5639
9.
Ito
,
T.
(representative), and
PROPATH Group
, 1990,
PROPATH: A Program Package for Thermo-Physical Properties of Fluids, Version 10.2
,
Corona
,
Tokyo, Japan
.
10.
Nagaya
,
Y.
,
Okumura
,
K.
,
Mori
,
T.
, and
Nakagawa
,
M.
, 2005, “
MVP/GMVP II: General Purpose Monte Carlo Codes for Neutron and Photon Transport Calculations Based on Continuous Energy and Multigroup Methods
,” Report No. JAERI-1348.
11.
Shibata
,
K.
,
Kawano
,
T.
,
Nakagawa
,
T.
,
Iwamoto
,
O.
,
Katakura
,
J.
,
Fukahori
,
T.
,
Chiba
,
S.
,
Hasegawa
,
A.
,
Murata
,
T.
,
Matsunobu
,
H.
,
Ohsawa
,
T.
,
Nakajima
,
Y.
,
Yoshida
,
T.
,
Zukeran
,
A.
,
Kawai
,
M.
,
Baba
,
M.
,
Ishikawa
,
M.
,
Asami
,
T.
,
Watanabe
,
T.
,
Watanabe
,
Y.
,
Igashira
,
M.
,
Yamamuro
,
N.
,
Kitazawa
,
H.
,
Yamano
,
N.
, and
Takano
,
H.
, 2002, “
Japanese Evaluated Nuclear Data Library Version 3 Revision-3: JENDL-3.3
,”
J. Nucl. Sci. Technol.
0022-3131,
39
, pp.
1125
1136
.
12.
Nabielek
,
H.
,
Kuhnlein
,
W.
, and
Schenk
,
W.
, 1990, “
Development of Advanced HTR Fuel Elements
,”
Nucl. Eng. Des.
,
121
, pp.
199
210
. 0029-5493
13.
Minato
,
K.
,
Sawa
,
K.
,
Koya
,
T.
,
Tomita
,
T.
,
Ishikawa
,
A.
,
Baldwin
,
C. A.
,
Gabbard
,
W. A.
, and
Malone
,
C. M.
, 2000, “
Fission Product Release Behavior of Individual Coated Fuel Particles for High-Temperature Gas-Cooled Reactors
,”
Nucl. Technol.
,
131
, pp.
36
47
. 0029-5493