Fukushima Nuclear Power Plant Accident and Thereafter

Abstract

Many lessons can be learned from the Fukushima Daiichi Nuclear Power Plant (NPP) accident. First, if an isolation condenser (IC) had continued to operate, the accident would have been terminated soon. Reactor core isolation cooling (RCIC) steam turbines also stopped because loss of battery power in Units No. 2 and No. 3 and temperature and pressure in each primary containment vessel (PCV) were so high that the accident management water injection took too long. After the loss of emergency core cooling system (ECCS) and IC core cooling, fuels in the core melted down. Leak of fission product and hydrogen began because of high-temperature damage to the PCV packing. A hydrogen explosion occurred in the upper floor in the reactor building in Units 1, 3, and 4. The Nuclear Regulation Authority (NRA) enforcement of the New Regulatory Requirements was based on the concept of “defense in depth,” for commercial nuclear power reactors from July 8, 2013. It is hoped that the lessons learned from this accident will improve the safety of nuclear power plants worldwide.

List of Nomenclature

AC:

Alternating current

ALPS:

Advanced liquid processing system

AM:

Accident management

AO:

Air-operated valve

BWR:

Boiling water reactor

CRD:

Control rod drive

CV:

Containment vessel

DBA:

Design base accident

DC:

Direct current

DF:

Decontamination factor

DiD:

Defense in depth

DW:

Dry well

EDF:

Électricité de France

EDG:

Emergency diesel generator

ENSI:

National regulatory body with responsibility for the nuclear safety and security of Swiss nuclear facilities

FARN:

Nuclear rapid response force established by EDF

FCVS:

Filtered containment venting system

FP:

Fission product

GIS:

Gas-insulated switchgear

HSK:

Swiss Federal Office of Energy

HVAC:

Heating, ventilation, and air conditioning

IC:

Isolation condenser

JNES:

Japan Nuclear Energy Safety organization

M/C:

Metal clad switchgear

METI:

Ministry of Economy, Trade and Industry

MEXT:

Ministry of Education, Culture, Sports, Science and Technology

MO:

Motor-operated valve

NISA:

Nuclear and Industrial Safety Agency

NRA:

Nuclear Regulation Authority

P/C:

Power center

PAR:

Passive autocatalytic recombiner

PWR:

Pressurized water reactor

R/B:

Reactor building

RCIC:

Reactor core isolation cooling system

RPV:

Reactor pressure vessel

RV:

Reactor vessel

S/C:

Suppression chamber

S/P:

Suppression pool

SA:

Severe accident

SAM:

Severe accident management

SBO:

Station blackout

SEHR:

Special Emergency Heat Removal

SGTS:

Standby gas treatment system

SRV:

Safety relief valve

T/B:

Turbine building

TEPCO:

Tokyo Electric Power Company Inc.

TIP:

Traversing in-core neutron probe

WW:

Wet well