Military Vulnerabilities of Civilian Nuclear
Facilities: Case Studies for South Koreaand Japan
Jungmin Kang, PhD
Independent Consultant
Former Chairman of ROK’s Nuclear Safety and Security Commission
Virtual Seminar by REEPS
10 July 2021
1

April 1986 Chernobyl Accident(Ref: Alan Taylor, "The Chernobyl Disaster: 25 Years Ago," The Atlantic, Mar 23, 2011)(Ref: "Sources and Effects of Ionizing Radiation, United Nations Scientific Committee on theEffects of Atomic Radiation, UNSCEAR 2008 Report to the General Assembly with ScientificAnnexes," United Nations, New York, 2011)

 More than 100,000 residents evacuated.
 Area of radiation control zone was 10,000 km2 contaminated to levels greaterthan 0.5 MBq/m2 of Cs-137(Ref: Robert Alvarez et al., "Reducing the Hazards from Stored Spent Power-Reactor Fuel in the United States," Science and Global Security, 11:1–51, 2003)

Voluntary relocation: the area where the surface contamination concentration of Cs-137 exceeds 0.5 MBq/m2
Compulsory relocation: the area where the surface contamination concentration of Cs-137 exceeds 1.5 MBq/m2

March 2011 Fukushima Accident(Ref: What Went Wrong: Fukushima Nuclear Disaster(http://www.popularmechanics.com/science/energy/a6721/fukushima-nuclear-disaster-what-went-wrong-5508927/))(Ref: Masa Takubo, "Fukushima disaster today," Busan, Korea, 27 February 2017)

 More than 160,000 residents evacuated to areas of lower contamination lessthan 1 MBq/m2 of Cs-137.
 The mean total activity of Cs-137 was around 7–20 PBq.
Most of the releases were dispersed over the North Pacific Ocean.

(Ref: IAEA, "The Fukushima Daiichi Accident: Report by the Director General," 2015, p.107.)What if a nuclear power plant had been thetarget of missile attack?

(Ref: https://abcnews.go.com/International/north-korean-missile-testyear/story?id=46592733)

In this study, I perform technical analysis if a nuclear
power plant had been the target of missile attack, focusing
on nuclear reactors and spent fuel pools in Northeast Asia

(Ref: Google Earth Pro, 6 May 2020.)

5

Vulnerability of Nuclear Power Plant


The missile attack could damage onContainment building punctured or cracked partly or largely lose its confinement capability to contain the escape of radioactive gas

Cooling systems
 pumps and/or the main coolant piping breaks and thus the pumps cannot

circulate coolant through the core that could lead to the core meltdown
 results in a loss of cooling of spent fuel pool that could lead to the spent
fuel pool firePower systems
 cut off offsite power and get onsite emergency diesel generators to bemalfunctioned
 results in a loss of reactor coolant that could lead to the core meltdown
 results in a loss of cooling of spent fuel pool that could lead to the spent
6
fuel pool fireVulnerability of Nuclear Power Plant (cont)7

Cs-137, a dominant radioactive isotope released
from the nuclear accidents of core meltdown orspent fuel pool fireCs-137 (30-year half-life) is relatively volatile and is a potent land
contaminant because 95% of its decays are to an excited state of Ba137, which de-excites by emitting a penetrating (0.66-MeV) gamma ray.
The release of Cs-137 from the Chernobyl accident was about 85 PBq(petabecquerel, 1015 Bq).
The release of Cs-137 from the Fukushima accident was around 7–20PBq.
About 4 PBq of Cs-137 is contained in the 1 tHM of 10-year cooled PWR spent fuelwith burnup of 40 MWd/kgHM. About 80 PBq of Cs-137 is contained in 20 tHM of PWR
spent fuel which is annually discharged from the 1GWe PWR.

Zirconium Fire of Spent Nuclear Fuel

Zirconium fire“If cooling of the spent fuel were not reestablished, the fuel could heat up
to temperatures on the order of 1,000℃. At this temperature, the spentfuel’s zirconium cladding would begin to react with air in a highly
exothermic chemical reaction called a runaway zirconium oxidation
reaction or autocatalytic ignition. This accident scenario is often referred toas a “spent fuel pool zirconium fire.” Radioactive aerosols and vapors
released from the damaged spent fuel could be carried throughout thespent fuel pool building and into the surrounding environment.”

Hydrogen production


Hydrogen is produced by reaction of water vapor with hot zirconium
cladding of spent fuel:US NRC found less hydrogen with low-density pool storage and muchless likelihood of an explosion.

(Ref: US NRC, "Generic Environmental Impact Statement for Continued Storage of Spent Nuclear Fuel," NUREG-2157 Vol.1, September 2013, p.F-1.; Frank von Hippel,"Proposals for Reducing the Danger from Spent Fuel Pool Fires," Busan, South Korea, 27 February 2017)Low Density vs. High Density Spent Fuel PoolHigh density,
Low density,
air-coolingpossible

air-cooling notpossible –especially if
partial drainage
and bottom ofracks coveredwith water.

(Ref: KHNP, "Status of Spent Fuel Management," Feb 2014 (Korean))(Ref: Frank von Hippel, "Proposals for Reducing the Danger from Spent Fuel Pool Fires," Busan, South Korea, 27 February 2017)

A Dense-Racked Spent Fuel Pool

(Ref: Frank von Hippel, "Proposals for Reducing the Danger from Spent Fuel Pool Fires," Busan, South Korea, 27 February 2017)

Cs-137 Inventory Release from SFPF
SFP loading

Low case

Base caseHigh caseHigh-density

10%

75%90%

Low-density

0.5%

3%5%

(Ref: USNRC, "COMSECY-13-0030 - Staff Evaluation and Recommendation for Japan Lessons-Learned Tier 3 Issue on Expedited Transfer of Spent Fuel,"
November 25, 2013)

Devil’s Scenario of Fukushima
Spent Fuel Pool #4
Science journal
“Japan’s chief cabinet secretary called it “the devil’s scenario.” Two weeks
after the 11 March 2011 earthquake and tsunami devastated theFukushima Daiichi Nuclear Power Plant, causing three nuclear reactors tomelt down and release radioactive plumes, officials were bracing for evenworse. They feared that spent fuel stored in pools in the reactor halls
would catch fire and send radioactive smoke across a much wider swathof eastern Japan, including Tokyo. Thanks to a lucky break detailed in areport released last week by the U.S. National Academies of Sciences,Engineering, and Medicine, Japan dodged that bullet.”(Ref: Richard Stone, "Near miss at Fukushima is a warning for U.S.: Panel says spent reactor fuel in a storage pool could have boiled dry and caught on fire,"
Science 27 May 2016, Vol. 352, Issue 6289, pp. 1039-1040)

Devil’s Scenario of Fukushima
Spent Fuel Pool #4 (cont)
Leakage into the pool from the adjacent reactor pit saved Fukushima
Spent Fuel Pool #4 from dryout(Ref: Frank von Hippel, "Proposals for Reducing the Danger from Spent Fuel Pool Fires," Busan, South Korea, 27 February 2017)

Devil’s Scenario of Fukushima
Spent Fuel Pool #4 (cont)Source of water that kept the spent fuel in pool #4 covered(Ref: "Lessons Learned from the Fukushima Accident for Improving Safety and Security of U.S. Nuclear Plants: Phase 2," National Academy of Sciences, 2016, p.23)

Devil’s Scenario of Fukushima
Spent Fuel Pool #4 (cont)

Sequence of events postulated by TEPCO for water inflow to the spent fuelpool from the reactor well. (DS Pit = dryer-separator pit; RPV = reactor pressurevessel; SFP = spent fuel pool; FPC = fuel pool cooling and cleanup)(Ref: "Lessons Learned from the Fukushima Accident for Improving Safety and Security of U.S. Nuclear Plants: Phase 2," National Academy of Sciences, 2016, p.45)

Devil’s Scenario of Fukushima
Spent Fuel Pool #4 (cont)If no water added, would have had fire in 30 days. If pool leaked, muchsooner.

(Ref: Frank von Hippel, "Proposals for Reducing the Danger from Spent Fuel Pool Fires," Busan, South Korea, 27 February 2017)

(Ref: (Ref: Frank von Hippel, Msafumi Takubo, Jungmin Kang "Plutonium: How Nuclear Power’s Dream Fuel Became a Nightmare," Springer Nature, 2019))

Assumptions of this studyThe radioactivity of the Cs-137 release from the nuclear accident ofcore meltdown of 1GWe NPP is assumed about 258 PBq which is
75% of core inventory of Cs-137. The containment building isassumed to be punctured or cracked largely from the missile attack.
For a fire in the Kori-3 pool, that would correspond to a release ofabout 2,240 PBq while about 6,470 PBq for a fire in the Rokkasho
reprocessing plant’s spent fuel pool. Kori-3 pool is dense-packed with
about 910 tons of spent fuel. The Rokkasho reprocessing plant’s poolcontains 2,968 tons of spent fuel as of January 31, 2019.

Assumptions of this study (Cont)• Atmospheric transport simulations of hypothetical radiological release
were conducted to assess the impact on population and land area
– Using Hysplit model by NOAA with GDAS meteorological data (3-hour and 1degree resolution) and population database (NASA)– 12 simulations were conducted for each scenario, one for the first day of eachmonth in 2019 to cover seasonal variations.
– Release was assumed to last 32 hours from a vertical line source of 0-300m.
– Plume and fallout were simulated for one week, including dry and wetdeposition.

• Output is the average and maximum number of affected people andland area according to the following thresholds– The contamination levels for compulsory evacuation are shown in orange andred and those for voluntary evacuation in yellow. The yellow area is great than
0.5 MBq/m2 less than 1.5 MBq/m2. The orange area is great than 1.5 MBq/m2
less than 4.5 MBq/m2. The red area is great than 4.5 MBq/m2
 [The Hysplit calculations were done by Dr. Michael Schoeppner, IndependentConsultant]Hypothetical nuclear accident atthe Genkai 3 reactor in Japan
Relocation areas for hypothetical nuclear accident at the Genkai 3
reactor on 1 October and 1 December 2019(258 PBq of Cs-137 release)Hypothetical nuclear accident at theGenkai 3 reactor in Japan (cont)Country

Relocated populations

Interdicted areas (km2)

Average

Maximum

Average

Maximum

1.3 million

9.5 million

5,800

18,400(2.6 million)(12.4 million)(14,300)(40,500)

400

5,000

50

600

(0.7 million)(8.6 million)(14,300)(40,500)

China

(500)

(6,000)

(50)

(600)

Taiwan(71,000)(0.8 million)(1,500)(18,400)

JapanSouth Korea(The numbers of the parenthesis are total numbers when the voluntary evacuation is added.)Hypothetical nuclear accident at
the Kori 3 reactor in South Korea
Relocation areas for hypothetical nuclear accident at the Kori 3
reactor on 1 August and 1 December 2019(258 PBq of Cs-137 release)Hypothetical nuclear accident at theKori 3 reactor in South Korea (cont)Country

Relocated populations

Interdicted areas (km2)

Average

Maximum

Average

Maximum

2.3 million

12.9 million

4,500

20,300(6.3 million)(46.6 million)(14,900)(72,200)

North Korea(28,000)(0.3 million)

(50)

(600)

Japan

47,000459,000

400

2,500

(0.5 million)(3.0 million)(4,900)(20,900)(43,000)(0.5 million)(200)(2,500)South Korea

Taiwan(The numbers of the parenthesis are total numbers when the voluntary evacuation is added.)Hypothetical nuclear accident at theKori 3 spent fuel pool in South Korea
Relocation areas for hypothetical nuclear accident at the Kori 3
spent fuel pool on 1 May and 1 August 2019(2,240 PBq of Cs-137 release)Hypothetical nuclear accident at the Kori 3
spent fuel pool in South Korea (cont)Country

Relocated populations

Interdicted areas (km2)

Average

Maximum

Average

Maximum

8.5 million

50.0 million

26,700117,100(10.0 million)(52.0 million)(34,800)(100,200)

0.2 million

2.6 million

1,400

16,500(2.0 million)(21.5 million)(12,900)(124,100)

5.1 million

40.0 million

36,700201,900(17.5 million)(118.6 million)(111,100)(467,200)

China(2.0 million)(17.4 million)(19,000)(199,400)

Russia1,000

17,000700

8,900(0.1 million)(1.1 million)(10,400)(91,800)

0.9 million

11.0 million

2,100

24,700(1.7 million)(20.1 million)(3,900)(44,300)(38,000)(0.4 million)(1,700)(12,000)

South Korea
North Korea
JapanTaiwan
Philippine

Hypothetical nuclear accident at the Rokkasho
reprocessing plant’s spent fuel pool in Japan
Relocation areas for hypothetical nuclear accident at the Rokkasho
reprocessing plant’s spent fuel pool on 1 October and 1 December 2019
(6,470 PBq of Cs-137 release)Hypothetical nuclear accident at the Rokkasho
reprocessing plant’s spent fuel pool in Japan (cont)CountryJapan
RussiaRelocated populations

Interdicted areas (km2)

Average

Maximum

Average

Maximum

6.4 million

62.1 million

51,700312,700(8.9 million)(89.2 million)(65,900)(391,800)

5,000

31,00012,10070,300(20,000)(0.2 million)(24,300)(151,300)(The numbers of the parenthesis are total numbers when the voluntary evacuation is added.)

Conclusions






The nuclear power plants are vulnerable from military attack,including missile attacks in war conditions.
The missile attack could make containment building punctured or
cracked to lose its confinement capability to contain the escape ofradioactive gas. The missile attack also could damage on coolingsystems/power systems that could lead to the core meltdown
and/or the spent fuel pool fire.
The hypothetical reactor core meltdown and/or spent fuel pool fireoccurred by the missile attack could have major impacts inadjoining countries.
Although it may not be possible to prevent these attacks, theirconsequences can be mitigated to some extent by moving spent
fuel from the pools after five years of cooling into dry cask storage.

Pool Storage vs. Dry Cask Storage
Debris on top of fuel racks in Unit 4 pool

(Ref: "Lessons Learned from the Fukushima Accident for Improving Safety andSecurity of U.S. Nuclear Plants: Phase 2," National Academy of Sciences, 2016, p.23)

Spent fuel storage casks at Fukashima
after the tsunami(Ref: http://cryptome.org/eyeball/daiichi090911/daiichi090911.htm)