**1. Introduction**

Nuclear power plants (NPPs) have negligible cradle-to-grave environmental impacts. In spite of this fact, nuclear power plants (NPPs) are potentially highrisk facilities, since the consequences of a severe accident at a nuclear power plant can be enormous. Severe accidents of NPPs affect large area and have environmentally regional and economically global character [1]. The accident at the Chernobyl NPP shows the extent and severity and long-term consequences of the nuclear disasters. Natural hazard safety of nuclear power plants became an eminent importance after the Great Tohoku earthquake on the 11th of March 2011 and subsequent disaster of the Fukushima Daiichi NPP. The case of the Fukushima Daiichi NPP demonstrated the tragic outcome of the interaction between severe natural phenomena and nuclear power plant, that is, the severe natural phenomena are a great threat per itself, but their damaging effects could be multiplied when a natural phenomenon damages a hazardous facility like a

**28**

*Natural Hazards - Risk, Exposure, Response, and Resilience*

In: Preprints, 15th Conference on Numerical Weather Prediction, American Meteorological Society, San Antonio, TX. 2002. pp. 280-283

[9] Janjic ZI. The surface layer in the NCEP eta model. In: 11th Conf. on NWP. American Meteorological Society,

[10] Weiss SJ, Bright DR, Kain JS, et al. Complementary use of short-range ensemble and 455?KM WRF-NMM model guidance for severe weather forecasting at the storm prediction Centre. In: Proceedings of the 23rd Conference on Severe Local Storms, American Meteorological Society. 2006

[11] Litta AJ, Mohanty UC, Bhan SC. Numerical simulation of a tornado over Ludhiana (India) using WRF-NMM model. Meteorological Applications.

[12] Litta J, Mohanty UC, Kiran Prasad S,

Mohapatra M, Tyagi A, Sahu SC. Simulation of tornado over Orissa (India) on March 31, 2009, using WRF-

NMM model. Natural Hazards.

[13] Betts AK. Thermodynamic classification of tropical convective soundings. Monthly Weather Review.

[14] Janjic ZI. A nonhydrostatic model based on a new approach. Meteorology and Atmospheric Physics.

[15] Skamarock WC, Klemp JB, Dudhia J, Gill DO, Barker DM, Duda MG et al. A description of the advanced research WRF version 3; NCAR technical note: NCAR/TN–475+STR. 2008. Available from: http://www.mmm.ucar.edu/wrf/ users/docs/arw\_v3.pdf [Accessed: 4 Feb

2009;**61**(3):1219-1242

1974;**102**:760-764

2003;**82**:271-285

2010]

2010;**17**(1):64-75

Norfolk, VA. 1996. pp. 354-355

[1] Franchito SH, Gan MA, Rao VB, Santo CME, Conforte JC, Pinto O Jr. Impacts of rainstorms during austral winter in Sao Paulo state, Brazil: A case study. Journal of Geography and Natural Disasters. 2016;**6**:162. DOI:

[2] Franchito SH, Gan MA, Fernandez JPR, Rao VB, Santo CME. Rainstorms during spring in Sao Paulo state, Brazil: A case study of 27-28 September 2015. IIARD International Journal of Geography and Environmental Management. 2017;**3**:12-24

[3] Janjic ZI, Gerrity JP Jr, Nickovic S. An alternative approach to nonhydrostatic modeling. Monthly Weather Review.

[4] Schwarzkopf MD, Fels SB. The simplified exchange method revisited:

computations of infrared cooling rates and fluxes. Journal of Geophysical Research. 1991;**96**:9075-9096

[5] Lacis AA, Hansen JE. A parameterization for the absorption of solar radiation in the earth's atmosphere. Journal of the Atmospheric Sciences.

An accurate, rapid method for

[6] Ek MB, Mitchell KE, Lin Y, Rogers E, Grunmann P, Koren V, et al. Implementation of NOAH land surface model advances in the NCEP operational mesoscale Eta model. Journal of Geophysical Research.

[7] Janjic ZI. Nonsingular implementation of the Mellor–Yamada level 2.5 scheme in the NCEP Meso model. NCEP Office Note. 2002;**437**:61

[8] Ferrier BS, Lin Y, Black T, Rogers E, DiMego G. Implementation of a new grid-scale cloud and precipitation scheme in the NCEP Eta model.

10.4172/2167-0587.1000162

**References**

2001;**129**:1164-1178

1974;**31**:118-133

2003;**108**(22):8851

nuclear power plant. The importance of the preparedness to the natural hazards at NPPs has recently been demonstrated when the Hurricane Florence September 2018 endangered the NPPs in North and South Carolinas.

Majority of the existing nuclear power plants will be operated during the twenty-first century, and there are ongoing new construction projects. There are prestigious institutions and authors justifying that the nuclear power is needed for sustainable power supply (e.g., [2]). There are good enough reasons for continuous efforts to ensure and enhance the nuclear safety.

Protection of NPPs against natural hazard effects has been required since earlier times of industrial deployment of nuclear power. Related design requirements were getting more and more stringent with accumulated knowledge on hazards, with their consequences, as well with the development of design methodologies and supporting empirical evidences. All probable at the site natural hazards should be accounted for in the design of NPPs.

The risk due to NPPs is controlled and reduced by design means ensuring very low annual probability of a large release of radioactive substances. The acceptable annual probability limit for large release is ≤10<sup>−</sup><sup>6</sup> . The concept of defense in depth (DiD) is applied for protection of the people and environment [3, 4]. According to this, a hierarchy of protective means and procedures should be designed and implemented for preventing the escalation of a failure to accidents and to maintain the integrity of physical barriers between the radioactive substances and environment, even if a protective feature fails. There are a series of physical barriers nested inside one another for separation of the radioactive substances from the environment: the fuel matrix, the fuel cladding, the primary pressure boundary, and the containment. The effectiveness of barriers should be maintained in every operational state, and the last barrier, the containment, should perform its retaining function as long as possible during accident sequences.

In this chapter, a brief insight into the actual issues of natural hazard safety and related scientific challenges is provided. The state of the art of ensuring safety of NPPs with respect to natural hazard is briefly presented with focus on the preparedness to the accident sequences caused by rare natural phenomena. The safety relevance of different hazards and vulnerability of NPPs to different hazards are discussed. Specific attention is made to the non-predictable phenomena with sudden devastating effects like earthquakes and fault ruptures. Post-event conditions that affect the on-site and off-site accident management activities are also considered. The "specific-to-nuclear" aspects of the characterization of hazards are discussed. Design and severe accident management require characterization of very rare events with annual probability 10<sup>−</sup><sup>4</sup> –10<sup>−</sup><sup>5</sup> for the design basis and up to 10<sup>−</sup><sup>7</sup> for the safety analysis. This is a great challenge for the sciences dealing with hazard characterization. There might be epistemic limitations, and a positivist approach to the possibility of learning the phenomena is questionable. The epistemic issues of natural hazard characterization and management are also briefly considered.

The approach followed in the chapter is a typical positivist, engineering approach. The hazards accounted for in the design of conventional, potentially high-risk industrial facilities, are about hundred times more likely and far less dangerous than the design-basis hazards for the nuclear power plants; apart from this cardinal difference, the development and design of nuclear power plants are carried out according to the same logic as any other technical objects, that is, the design shall be based on evidences, verified knowledge, and experimentally proven methods. The design requirements and safety analysis procedures are briefly presented with the main focus on the rare and unpredictable phenomena.

The statement of the head of the Fukushima Nuclear Accident Independent Investigation Commission should be understood, which recognized the Fukushima

**31**

*Natural Hazards and Nuclear Power Plant Safety DOI: http://dx.doi.org/10.5772/intechopen.83492*

by the shock of the Fukushima catastrophe.

aspects of vulnerability are briefly considered.

recent practice of the nuclear industry.

**2. Hazards and their severity**

accident as a typical "man-made disaster" that could be foreseen and prevented [5]. In spite of the truth of this statement, the extreme natural phenomena can cause enormous consequences at NPPs. The question is how frequent can an extreme event happen that can trigger a nuclear catastrophe, and whether the risk due to

Nuclear power plants are stigmatized by two severe accidents, Chernobyl accident, and by the Fukushima NPP accident caused by extreme natural phenomena. However, the operation of nuclear power plants is characterized not only by these accidents but also by more than 10,000 reactor years of positive experience. There are studies predicting 50% of chances for occurrence of a Fukushima-type accident within every 60–100 years [6] and auguring decreasing the frequency but increasing the severity of nuclear accidents. The lessons learned from the Fukushima accident changed the paradigm of the design; preparedness to extreme improbable situations became a great importance. In this chapter the availability of proven technical means against natural hazards is demonstrated on the practical examples. The presentation of the manageability of natural hazard effects should not relativize the safety issues, just providing realistic insights compared to those determined

Natural hazards can also cause economic impact due to inability of being operated at 100% level, and/or restoration is needed for the restart of the plant. These aspects will gain more importance due to increasing severity, frequency, and duration of some hazards, for example, extremes due to climate change that affect the efficiency of nuclear power plants especially those with freshwater cooling. These

An overall presentation of the state of the art of hazard evaluation and natural hazard risk management is not intended in the chapter. The focus is limited to the

Nuclear power plant can be constructed and operated at a particular site without undue risk to the health and safety of the public by ensuring the confinement of radioactive substances. From the technical point of view, this means that some fundamental safety functions should be ensured during and after the natural phenomena: the reactor should be shut-down, subcriticality of the reactor core and the spent fuel pool should be ensured, and the fuel in the reactor core and the spent fuel pool should be cooled. The most important function is the retaining capability of the reactor containment that should be kept leak-tight as long as possible. Plants are designed per principle of defense in depth (DiD) [3, 4], applying overlapping provisions (design, operational, etc.), so that, if a failure were to occur, it would be detected and compensated for or corrected by appropriate measures returning the plant to the normal operational conditions. In case this is not succeeding, a hierarchy of protective means and procedures are designed in preventing the escalation of a failure to accidental event, even if a protective measure fails. These protective means are redundant safety systems that are conservatively designed to withstand even effects of natural hazards beyond those accounted for in the design. The effects of natural hazards selected for the basis of design are loads defined conservatively and used in the design calculations according to codes and standards. Therefore, in deterministic sense, the effects of natural hazards within the basis of design should not cause accidents, or any failures, called initiating events, leading to accident sequences. Off course, the probability of failure of some systems or structures is not equal to zero, but the adequate design ensures low probability of

these events can be reduced to an acceptable for the society level?

#### *Natural Hazards and Nuclear Power Plant Safety DOI: http://dx.doi.org/10.5772/intechopen.83492*

*Natural Hazards - Risk, Exposure, Response, and Resilience*

efforts to ensure and enhance the nuclear safety.

annual probability limit for large release is ≤10<sup>−</sup><sup>6</sup>

accounted for in the design of NPPs.

as possible during accident sequences.

rare events with annual probability 10<sup>−</sup><sup>4</sup>

2018 endangered the NPPs in North and South Carolinas.

nuclear power plant. The importance of the preparedness to the natural hazards at NPPs has recently been demonstrated when the Hurricane Florence September

Majority of the existing nuclear power plants will be operated during the twenty-first century, and there are ongoing new construction projects. There are prestigious institutions and authors justifying that the nuclear power is needed for sustainable power supply (e.g., [2]). There are good enough reasons for continuous

Protection of NPPs against natural hazard effects has been required since earlier times of industrial deployment of nuclear power. Related design requirements were getting more and more stringent with accumulated knowledge on hazards, with their consequences, as well with the development of design methodologies and supporting empirical evidences. All probable at the site natural hazards should be

The risk due to NPPs is controlled and reduced by design means ensuring very low annual probability of a large release of radioactive substances. The acceptable

(DiD) is applied for protection of the people and environment [3, 4]. According to this, a hierarchy of protective means and procedures should be designed and implemented for preventing the escalation of a failure to accidents and to maintain the integrity of physical barriers between the radioactive substances and environment, even if a protective feature fails. There are a series of physical barriers nested inside one another for separation of the radioactive substances from the environment: the fuel matrix, the fuel cladding, the primary pressure boundary, and the containment. The effectiveness of barriers should be maintained in every operational state, and the last barrier, the containment, should perform its retaining function as long

In this chapter, a brief insight into the actual issues of natural hazard safety and related scientific challenges is provided. The state of the art of ensuring safety of NPPs with respect to natural hazard is briefly presented with focus on the preparedness to the accident sequences caused by rare natural phenomena. The safety relevance of different hazards and vulnerability of NPPs to different hazards are discussed. Specific attention is made to the non-predictable phenomena with sudden devastating effects like earthquakes and fault ruptures. Post-event conditions that affect the on-site and off-site accident management activities are also considered. The "specific-to-nuclear" aspects of the characterization of hazards are discussed. Design and severe accident management require characterization of very

–10<sup>−</sup><sup>5</sup>

for the safety analysis. This is a great challenge for the sciences dealing with hazard characterization. There might be epistemic limitations, and a positivist approach to the possibility of learning the phenomena is questionable. The epistemic issues of natural hazard characterization and management are also briefly considered. The approach followed in the chapter is a typical positivist, engineering approach. The hazards accounted for in the design of conventional, potentially high-risk industrial facilities, are about hundred times more likely and far less dangerous than the design-basis hazards for the nuclear power plants; apart from this cardinal difference, the development and design of nuclear power plants are carried out according to the same logic as any other technical objects, that is, the design shall be based on evidences, verified knowledge, and experimentally proven methods. The design requirements and safety analysis procedures are briefly presented with the main focus on the rare and unpredictable phenomena.

The statement of the head of the Fukushima Nuclear Accident Independent Investigation Commission should be understood, which recognized the Fukushima

. The concept of defense in depth

for the design basis and up to 10<sup>−</sup><sup>7</sup>

**30**

accident as a typical "man-made disaster" that could be foreseen and prevented [5]. In spite of the truth of this statement, the extreme natural phenomena can cause enormous consequences at NPPs. The question is how frequent can an extreme event happen that can trigger a nuclear catastrophe, and whether the risk due to these events can be reduced to an acceptable for the society level?

Nuclear power plants are stigmatized by two severe accidents, Chernobyl accident, and by the Fukushima NPP accident caused by extreme natural phenomena. However, the operation of nuclear power plants is characterized not only by these accidents but also by more than 10,000 reactor years of positive experience. There are studies predicting 50% of chances for occurrence of a Fukushima-type accident within every 60–100 years [6] and auguring decreasing the frequency but increasing the severity of nuclear accidents. The lessons learned from the Fukushima accident changed the paradigm of the design; preparedness to extreme improbable situations became a great importance. In this chapter the availability of proven technical means against natural hazards is demonstrated on the practical examples. The presentation of the manageability of natural hazard effects should not relativize the safety issues, just providing realistic insights compared to those determined by the shock of the Fukushima catastrophe.

Natural hazards can also cause economic impact due to inability of being operated at 100% level, and/or restoration is needed for the restart of the plant. These aspects will gain more importance due to increasing severity, frequency, and duration of some hazards, for example, extremes due to climate change that affect the efficiency of nuclear power plants especially those with freshwater cooling. These aspects of vulnerability are briefly considered.

An overall presentation of the state of the art of hazard evaluation and natural hazard risk management is not intended in the chapter. The focus is limited to the recent practice of the nuclear industry.
