Global Deployment ofMitsubishi Standard APWR as
an Effective Countermeasure
Against Global Warming
SHIGEMITSU SUZUKI*1YOSHIKI OGATA*1

YUKIO NISHIHARA*1SHIRO FUJITA*1

With an increased requirement for nuclear power generation as an effective countermeasure against global warming, weestablished the APWR plant, a large-capacity Mitsubishi standard reactor combining our accumulated experience and technology as
an integrated PWR plant supplier. The APWR plant has accomplished high reliability, safety and enhanced economy based on thetechnology that has been developed with the support of the government and utilities through the improvement and standardization
programs of light water reactors. Currently, Tsuruga Units 3 and 4, the ﬁrst two APWRs, are undergoing licensing, while we aremaking efforts to obtain standard design certiﬁcation (DC) of US-APWR and preparing for the European Utility Requirements (EUR)
compliance assessment of EU-APWR. Mitsubishi Heavy Industries, Ltd. (MHI) positions the APWR as a core technology that willcontribute to the prevention of global warming and meet worldwide requirements.

Tsuruga Units 3 and 4, the ﬁrst two APWRs. As a result, thegovernment started the safety assessment of these units.
On the basis of these units, we are making efforts toestablish APWRs as a lineup of large-capacity standard PWR
plants with excellent enhanced economy. This includes 1,600
and 1,700 MWe class APWRs whose design certiﬁcation in
the US has already been applied for, with high-performancesteam generators and steam turbines. The APWRs haveaccomplished a large capacity increase of about 30% or more,compared with the current 4-loop PWRs (Fig. 1).
T he ma i n feat ures of A P W R pla nt components, asoutlined in Section 3, are as follows.

1. Introduction
I n t he m i ds t of t he u r ge nt ne c e s s i t y fo r v a r ious
countermeasures and technological development against
global warming, nuclear power generation is increasinglyrequired, being a technology with zero CO2 emissions. This
paper outlines the large-capacity Mitsubishi Standard APWR
(Advanced Pressurized Water Reactor) plant as an effective
countermeasure against global warming and our recent
efforts to disseminate the plant domestically and overseas.

2. APWR development and deployment
The development of the APWR was launched jointly by
the Japanese government, ﬁve utility companies (Hokkaido
Electric Power, Kansai Electric Power, Shikoku ElectricPower, Kyushu Electric Power and The Japan Atomic PowerCompany) and suppliers in the early 1980s, under the Third
Phase Improvement Standardization Program for Light
Water Reactors. The development was aimed at establishingan advanced standard light water reactor with f ur therenhanced reliability and safety, improved economy andsiting efﬁciency with increased power, based on the resultsof the First and Second Phase Improvement Standardization
Programs. This also involves our experience and techniques
obtained through the design, construction and operationof existing PWR plants. Even after the completion of thenational programs, the APWR design has been improvedt hrough up - rat i ng by redesig ni ng its core st r uct ure,
opt i m i z at ion of s a fet y syst ems by i nt roduc i ng h igh performance accumulator tanks and other improvements by
the continuous support of the utilities. Later, in March 2004,
the Japan Atomic Power Company applied for the approval ofchanges in the reactor installation related to the addition of

Increase of fuel assemblies
Upsizing of components

OutputIncreased number of loops

2-loop600 MWe
class
[121]

3-loop900 MWe
class
[157]

4-loop
APWR
1200 MWe 1 500-1700 MWe
class
class
[193]
[257]
[ ]: Number of fuel assemblies

Fig. 1 Trend of PWR plant capacity*1 Nuclear Energy Systems Headquarters

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 45 No. 3 (Sep. 2008)51

(1) Large reactor core and main components with large
capacit y (stea m generator, pr ima r y coolant pump,pressurizer, and turbine)(2) Advanced safety systems (four subsystems and refuelingwater storage pit installed in the reactor containment)(3) New instrumentation and control systems (advanced
digital main control board)

APWR
Neutron reflector block structure

Current 4-loop
baffle plate structure
ChannelholeBolt

Tie rodRingblock3. APWR technologies
3.1 Large capacity core
T he A P W R h a s a dop t e d a l a r ge c a p a c it y c or e t oaccomplish high thermal power, and has increased thenumber of fuel assemblies from 193 in the current 4-loop
type to 257 (Fig. 2). An advanced 17×17 fuel assembly has
been adopted as the fuel bundle, and also a zircaloy grid thatabsorbs less neutrons, already used in existing plants has
been incorporated for the effective use of uranium resources.
Furthermore, the APWR allows the number of control rods
to be set according to the quantity of loaded MOX fuel, sothat the requirement for diverse operations, such as the useof a MOX core and high burnup can be met ﬂexibly.

Current 4-loop(193)

Fig. 3 Neutron reﬂector

3.2 Neutron reﬂector
The APWR’s reactor internals employ a neutron reﬂector
around the core for the effective use of uranium resources(Fig. 3). The neutron reﬂector has a simple structure thatconsists of stacked stainless steel ring blocks without weldlines and with few bolt connections, whereas the previous
PWR has a baffle plate structure in which stainless steel
plates are connected with many bolts. The new structure
reduces neutron irradiation to the reactor vessel to about 1/3and improves the reliability of the vessel.

APWR(257)

Reactorvessel

3.3 Advanced safety systems: best mix of active andpassive systems

Core barrel

In the APWR, the emergency core cooling system (ECCS)
has a 4-train conﬁguration (4 × 50% capacity) instead of theconventional 2-train configuration (2 × 100% capacity) toimprove safety. The new conﬁguration increases the reliabilityof equipment operation in the case of an accident. Thesystems of each train are installed near the corresponding
loop to reduce the quantit y of piping and enhance theseparation and independence of each train (Fig. 4).

Fuelassembly

Neutron reflector
Fig. 2 Adoption of large core

APWR(4-train (4-subsystem) configuration)

Current 4-loop(2-train configuration)

SIPSH
SG

ACC

ACC
SG

LP: Low-pressure injection pump

RWSP

CSP: Containment spray pump

ReactorACC

CS/RHRP

HP: High-pressure injection pump

SG

ACC

SIP

CS/RHRP

SIP: Safety injection pumpSH

SG

CS/RHRP: Containment spray/
residual heat removal pump

SH
ACC
ACC

SG

SG

Reactor

SG: Steam generator
Sump

CSP LP HP

ACC: Accumulator tank/high-performance accumulator tank
HP LPCSPSHSGSG

SIP

SIP

SH
ACC
ACC

SH

RWSP: Refueling water storage pit
SH: Spray header
CS/RHRP

RWSP

CS/RHRP

Fig. 4 Emergency core cooling system

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 45 No. 3 (Sep. 2008)52

In addition, a refueling water storage pit, conventionallyinstalled outside the reactor containment vessel, is placedat the bottom of the containment vessel to serve as a water
source for the ECCS during an accident. With this design,cooling water injected into the core during an accident canbe automatically collected in the pit. This eliminates theswitching operation of the core cooling water source andenhances safety.
Furthermore, a high-performance accumulator tank, newtechnology with a passive concept, has been adopted. The
accumulator tank can change over from the large ﬂow rate
injection required for core cooling in the initial stage of a lossof coolant accident (LOCA) to the small ﬂow rate injection
required to maintain water level in the core in a passive
manner without using external power. This is achieved bya ﬂow dumper in the tank. The function of the conventional
low- pressu re i nject ion system is i nteg rated i nto t heaccumulator injection system. As a result, the low-pressure
injection pumps are eliminated and the configuration of
ECCS systems is simpliﬁed (Fig. 5).

Fig. 6 Advanced main control board (prototype board)various technologies to improve performance and reliability
are being adopted and verified. According to the lineup ofplant electricity output, a high-performance and compact
steam generator (SG) with a substantially larger heattransfer area than that of the conventional 4-loop type isemployed (Fig. 7). In order to minimize the increase of
the outer dimensions of the SG with increased capacity, thetube diameter has been decreased from 7/8 to 3/4 inches
to reduce the SG diameter, and an improved moistureseparator with reduced stages has been adopted to reduce
the SG height. This reduces the weight of the SG by about
10 % or more compared with the larger SG based on theconventional design concept. To improve reliability, thenumber of anti-vibration bars installed at U-bends has been
increased from 6 in the latest existing plants to 9 or more.
To provide high efﬁciency to the steam turbine, the laststage blades of the low-pressure turbine has been extended
by adopting 54 to 74 inch blades. The high-performance
perfect three-dimensional (3D) blades have been adopted toreduce blade loss by perfect 3D ﬂow design. Furthermore,Core injection mechanism
Nitrogen gas

Automaticchangeover ofinjection flow

Nitrogen gas

InjectionwaterInjection
water

Flow dumper

Flow dumper

Large flow injection

Small flow injection

Fig. 5 High-performance accumulator tank
Steam outlet nozzle

3.4 Advanced main control board and integrated
digital control and protection system

Secondary moistureseparator

Compact console panels are adopted in the advanced main
control board to accomplish all monitoring and operations
by touch screen displays. The operational switches of theplant components and the necessary operation information
are consolidated on the screen to improve the operators’
performance in monitoring and operating (Fig. 6). Whenan anomaly occurs in the plant, the panel’s rich supporting
functions automatically check the status of the plant andequipment operation and provide the necessary information.
Compared with the conventional type, the advanced main
control board is expected to reduce the operators’ burden by
about 30% and human error by about 50%.
3.5 Main components with increased capacity
Main components with increased capacity have beendeveloped to cope with the increased core output, andPrimary moistureseparator
Feed waterring

Feed water inlet nozzle
Improved
anti-vibration bar
TT690 alloy tube
Tube support plate
Partition plate

Reactor coolant inlet / outlet nozzles

Fig. 7 High-performance, compact steam generator

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 45 No. 3 (Sep. 2008)

53

Reheated stop valve
Low-pressure
turbine

In Europe, with a growing trend for demands for nuclear
power generation, MHI held a technical seminar on the EUAPWR, designed for European utilities, on March 13 and
14 in Brussels. The EU-APWR is aimed at compliance with
the European Utility Requirements (EUR) for Light Water
Reactors and will be reviewed as a 1,700 MWe class plant as
is the case with the US-APWR.
These global deployment efforts respond to overseas
safety regulations and power requirements on the basis of
the APWR technologies developed in Japan and are expected
to gain support globally from overseas utilities.

ExciterIntercept valve

High-pressure
turbineGenerator

Moisture separator reheater

5. Conclusion

Steam chest(Main stop valve and Governing valve)

We have presented the established lineup of large-capacity
Mitsubishi St andard A P W R plants and related ef for ts
domestically and overseas. The APWRs are standard plants
developed by the combination of our accumulated experienceand technology as a PWR manufacturer with support fromthe Japanese government and utility companies. We will
make efforts to disseminate the standard plant as a coretechnology to combat global warming, while meeting theneeds of overseas and domestic utilities.

Fig. 8 Large-capacity, high-performance turbine generator
systemintegral shroud blades (ISBs) aimed at reducing vibrationstress by forming an all-round stitch structure throughcontact with adjacent blades during revolution have also been
adopted to enhance reliability. The developed blades weretested under actual steam conditions at own world’s largest
class test facility to verify their performance and reliability(Fig. 8). These new technologies are also being appliedduring the replacement of turbines in existing domestic andoverseas plants.

References
1. Plans for Improvement and St andardization of L ight Water
Reactor—General Data, edit. by Nuclear Power Plant Division,
Ministry of International Trade and Industry (1985)
2. Aeba, Y., et. al., Feature of 1530MW Advanced PWR, Mitsubishi
Juko Giho Vol.35 No.4 (1998) p.246
3. Miyake Y., et. al., For the Long-Term Stable Supply of Electric
Energ y -Yesterday, Today, and Tomorrow of Nuclear Power
Generation-, Mitsubishi Heavy Industries Technical Review Vol.40
No.1 (2003) p.24
4. Kaneda M., et. al., US-APWR for Deployment in the United States,
Mitsubishi Heavy Industries Technical Review Vol.43 No.4 (2006)
p.15

4. Future efforts
4.1 Toward new domestic plants
As mentioned above, Tsuruga Units 3 and 4, as the first
A PW R units, are undergoing licensing, MHI will strive
to deploy standard A PW R plants with enhanced safet y,reliability and economy by meeting the requirements ofindividual domestic utilities.
4. 2 Toward global deployment of standard APWR
The construction of new nuclear power plants has beeninterrupted for a long period of time in the US, however
due to global warming and soaring oil prices, the need fornuclear power generation has been rising in recent years anddemand for dozens of new plants by around 2030 is expected.
On February 29, 2008, the Nuclear Regulatory Commission(NRC) accepted for docketing and started reviewing ourapplication for the standard design certiﬁcation (DC) of theUS-APWR, an APWR design customized for the US utilities.
Luminant Power, formerly T X U Power, headquar teredin Da llas, Texas, decided to int roduce t his desig n toCommanche Peak Units 3 and 4, and other US utilities arealso showing interest.

Shigemitsu Suzuki

Yoshiki Ogata

Yukio Nishihara

Shiro Fujita

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 45 No. 3 (Sep. 2008)

54