Parametric Investigation of Brayton Cycle for High Temperature Gas-Cooled Reactor Page: 3 of 7
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The HTR-10 was designed to be operated up to 9500C for
investigating diverse power generation systems (e.g., gas
turbine) and nuclear process heat applications [5].
In the mid-1950s, interest in gas-cooled reactors was revived in
the U.S., United Kingdom, France and Germany. Several of
these reactors were built. Recently countries including the U.S,
South Africa and the Netherlands [6,7] renewed their interest in
gas-cooled reactor technology, particularly the modular pebble
bed reactor concept.
The only commercial HTGR built in the US was the Fort St.
Vrain unit, located at the confluence of the St. Vrain Creek and
the South Platte River near Platteville, Colorado. In June 1968
construction began and the initial criticality was reached on
January 31 1974 [1]. This plant was operated with some
technical problems and eventually it was shut down due to
water loss in water-cooling bearing on the circulator, which
cannot be a problem now thanks to the improvement of the
circulator design.
Recently Eskom, a power company based in South Africa,
submitted a nuclear installation license application to the
National Nuclear Regulator (NNR). It is proposed to locate the
installation on Eskom property within the owner-controlled
boundary of Koeberg Nuclear Power Station located in the
Western Cape. In the U.S., the DOE plans to build a VHTR at
the INEEL site by 2016.
REFERENCE DESIGN
Figure 1 shows the reference design developed at MIT [8]
for the pebble bed reactor (PBR). An intermediate heat
exchanger (IHX) is used to couple a PBR to a Brayton cycle.
T= 879.4 C Intercooler
= 7.83 MPa 6 8
T 0 0P=7.73 MPa Tuibine MPC2 HPC
52.8 MW 26.1 MW 26.1 MW
Intercoler Itercoc
T= 225
- ..57MPa
L PPC Tu rbine LPC Itror - MPC1 7
= 52.8 MWW _ 26.1 MW T 3CP 2.1M
T = 22.5C C~
Power -- Gneao
Trie Pa136.9 M '
Circulator T = 8.9. C
T =4 8.9 C P=2 .75 M Pa
P=799 MPa 8 M
9 l'T=6.7 C
P= =8.0 MPaIn the primary system, the helium is heated to 9000C in the
pebble bed reactor and then enters the primary side of the IHX,
in which the heat is transferred to the power conversion unit.
The helium flowing out from the primary side of the
IHX is compressed in the circulator up to 7.89 MPa. Thereafter
most of the helium is delivered back to the channels of the side
reflector in the core while a small part is bled into the primary
side of the vessel cooling heat exchanger.
The helium in the primary side of the vessel cooling heat
exchanger is cooled to a low temperature, and then flows
upward through the annulus between the core barrel and reactor
pressure vessel (RPV) to cool the RPV. Finally, the helium
from the channels in the side reflector and RPV mix in the core
upper plenum, then flows into the core, completing a
circulation loop.
In the power conversion unit, the helium coming from the
secondary side of IHX enters the high-pressure turbine at a
temperature of 879.40C. After sequential expansion in the high-
pressure, medium-pressure, low-pressure, and power turbines,
the helium enters the low-pressure side of the recuperator and
transfers its heat to the high-pressure side helium. The helium
then rejects more heat to a precooler, exiting the precooler at
300C. The helium is then compressed in a low-pressure
compressor to an intermediate pressure, and then it flows
through intercoolers where it is again cooled to 300C. This
process is repeated several times until the helium stream exits
the high-pressure compressor at 8.0 MPa. Most of the helium
with a pressure of 8.0 MPa is discharged into the high-pressure
side of the recuperator, where it recovers the exhaust heat from
the power turbine. A small part of the helium is delivered to the
vessel cooling heat exchanger to cool the helium of the primary
system. The helium from the high-pressure side of the
recuperator and the helium from the primary side of vessel
cooling heat exchanger mix before they enter the secondary
side of the IHX, at which point the helium starts the next
circulation.
The reference design for a three- shaft turbomachinary as
shown in Figure 1 is based on a 250 MW thermal reactor with
helium circulated in both the primary and secondary side of the
HTGR. We made preliminary investigations on a single-shaft
vs. multiple-shaft turbomachinary however, in this paper we
will presents only results from three-shaft turbomachinary
arrangement.Figure 1. Schematic of Reference HTGR Design
Copyright 2004 by ASME
er
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Oh, Chang. Parametric Investigation of Brayton Cycle for High Temperature Gas-Cooled Reactor, article, July 1, 2004; [Idaho Falls, Idaho]. (https://digital.library.unt.edu/ark:/67531/metadc880441/m1/3/: accessed April 23, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.