PROGRESS IN NUCLEAR ENERGY; FEEDBACK FROM FUKUSHIMA ACCIDENT

Hydrogen Generation
June 14, 2021
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PROGRESS IN NUCLEAR ENERGY; FEEDBACK FROM FUKUSHIMA ACCIDENT

Abstract

The use of nuclear energy for electricity generation began in the late 1950s and went through
several phases over the subsequent half-century. Today, nuclear energy contributes 11% of the world’s
electricity, with over 443 power reactors in 31 countries. The designs of nuclear power plants (NPPs)
are categorized by “generation.” The three historical commercial NPP accidents (i.e., Three Mile
Island, Chernobyl, and Fukushima) have promoted higher safety standards. Hence, the safe shutdown
of the reactor under all probable circumstances is an important requirement to ensure the prevention of
core melt accidents and provide safe controlled shutdown behavior in all situations. Maintaining safe
and reliable operation can lead to: Increased use of inherent safety features, more robust designs,
Enhancing public confidence in the safe operation and production of nuclear energy.

Graphical Abstract

Figure 1. Four generation of nuclear reactors

Keywords: HPR100, Heat Pipe, Accident, Passive cooling

Introduction

Nuclear energy is an important contributor to the global objective of developing low-carbon energy
technologies for current and future generations. The use of nuclear energy for electricity generation
began in the late 1950s and went through several phases over the subsequent half-century. Today,
nuclear energy contributes 11% of the world’s electricity, with over 443 power reactors in 31 countries
[1, 2]. The designs of nuclear power plants (NPPs) are categorized by “generation.” After the prototype
reactors of Generation-I and the commercial reactors of Generation-II, Generation-III light water
reactors (LWRs) incorporate state-of-the-art improvements in the areas of fuel technology, thermal
efficiency, and safety systems [3, 4].
The three historical commercial NPP accidents (i.e., Three Mile Island, Chernobyl, and
Fukushima) have promoted higher safety standards on inherent safety and probabilistic safety
objectives, stricter requirements for the prevention and mitigation of severe accidents, and the
implementation of the passive safety concept. Operational experiences and industrial capability
improvements have brought technologies with longer lifetimes, higher burnup, higher reliability,
higher availability, modularization and standardization, design simplification, and digital
instrumentation and control (I&C) systems into NPPs [4].

2.Design Philosophy

The Generation-III nuclear technologies such as AP1000, EPR, HPR1000, etc., claimed to be safer,
more economic, and more advanced, and have become the mainstream of the nuclear power industry.
For instance, the China National Nuclear Corporation (CNNC) developed the evolutionary advanced
pressurized water reactor known as HPR1000. The concept makes full use of proven technology from
the design, construction, and operation experience of the large PWR fleet in China. HPR1000 as shown
in figure 1 introduces several advanced design features to meet the latest safety requirements and
address the feedback from the Fukushima accident.

Figure 2. Active and passive systems of HPR1000. Red line—active systems; green line—passive systems;
IRWST—in-containment refueling water storage tank. [4]

In April 2013, the basic design of HPR1000 was reviewed by an expert group organized by the
China Nuclear Energy Association (CNEA). The first deployment of HPR1000 is at units 5 and 6 of
Fuqing NPP, located in Fujian Province. Construction started on May 7, 2015, after the preliminary
safety analysis report (PSAR) was reviewed and a construction license was granted by the National
Nuclear Safety Administration (NNSA) [5]. The concept of HPR1000 was proposed as the final
solution for the Generation-III PWR. Today, the most advanced reactor designs are under development
in the United States and are expected to deploy in 2030. They range from advanced light-water-cooled
small modular reactors to new designs that use molten salts and high-temperature gases to flexibly
operate at even higher temperatures and lower pressures. Furthermore, in HPR1000, both active and
passive features are employed to guarantee the safety functions of emergency core cooling, residual
heat removal, etc.

The passive safety systems serve as the backup for the active systems in case of a
loss of alternate current (AC) power. The passive systems can operate for 72 hours with a sufficient
inventory of storage water and dedicated batteries, which significantly extends the plant autonomy
period (figures 2-4). In addition, the reactor core is designed with negative reactivity coefficient
feedbacks; the control rods are inserted into the reactor by gravity in case of a power cut-off; natural
circulation can be established in the reactor coolant system (RCS) as long as the integrity of the RCS
is maintained and heat is removed by the secondary side of steam generators [4, 6]. Finally, the
operational performance and economic goals of HPR1000 are in line with the requirements in Utility
Requirements Document (URD) and European Utility Requirements (EUR), such as plant availability,
design lifetime, and refueling cycle [7]

2.1 Fukushima Feedback – Portable Equipment and Interfaces

Figure 5. Mobile water makeup for spent fuel cooling

Heat Pipe (or Hybrid Heat Pipe)

The safe shutdown of the reactor under all probable circumstances is an important requirement to
ensure the prevention of core meltdown and provide safe controlled shutdown behavior in all
situations. The most recent development of heat pipes has been the application within the nuclear
sector. The hybrid heat pipe (see figures 5 and 6) is used for two main purposes. First, to shut down
the reactor in case of an accident, and second, to remove the decay heat generated during the reaction
from the core after shutdown. A passive device that combines the functions of the current control rod
assembly and the passive cooling systems could avoid such accidents in the future [8]. The cooling of
the Spent Fuel Pool (SFP) has not been taken into full consideration.

Figure 6. Systematic design of hybrid heat pipe as a Passive IN-core Cooling system [8
Figure 7. Schematics of the design candidates of hybrid heat pipe as Passive IN-core Cooling system [8

Conclusion

The Generation-III nuclear technologies claimed to be safer, more economic, and more advanced,
and have become the mainstream of the nuclear power industry. The passive safety systems serve as
the backup for the active systems in case of a loss of AC power. Further, the passive systems can
operate for 72 hours with a sufficient inventory of storage water and dedicated batteries, which
significantly extends the plant autonomy period. In the HPR1000, both active and passive features are
employed to guarantee the safety functions of emergency core cooling, residual heat removal, etc.
Maintaining safe and reliable operation can lead to: Increased use of inherent safety features, more
robust designs, Enhancing public confidence in the safe operation and production of nuclear energy.

References

  1. Agency., I.A.E., Nuclear power reactors in the world 2015: Vienna: IAEA. p. 86.
  2. Buckthorpe, D., Introduction to Generation IV nuclear reactors, in Structural Materials for
    Generation IV Nuclear Reactors. 2017. p. 1-22.
  3. International Atomic Energy Agency [Internet], V. 50 years of nuclear energy. [cited 2015 Aug
    13];Availablefrom: https://www.iaea.org/About/Policy/GC/GC48/Documents/gc48inf-4_ftn3.pdf.
  4. Xing, J., D. Song, and Y. Wu, HPR1000: Advanced Pressurized Water Reactor with Active and
    Passive Safety. Engineering, 2016. 2(1): p. 79-87.
  5. King, A. and M.V. Ramana, The China Syndrome? Nuclear Power Growth and Safety After
    Fukushima. Asian Perspective, 2015. 39(4): p. 607-636.
  6. International Atomic Energy Agency [Internet], V., Passive Safety Systems and Natural
    Circulation in Water Cooled Nuclear Power Plants. 2009.
  7. organization, E., European utility requirements for LWR nuclear power plants. . 2001.
  8. Jeong, Y.S., et al.,, Hybrid heat pipe based passive in-core cooling system for advanced nuclear
    power plant. Applied Thermal Engineering, 2015

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