Page 45 - AERB Bulletin English

Safety Statistics

Significant Events

Major Accident
7
AERB requires NPPs to report certain events that
occur in the plant which have or may have impact on IDENT 6 Serious Accident
operational safety. The reporting criteria is provided in 5 Accident with wider
the Technical Specification for operations. These reports C C consequences
A Accident with local
are reviewed and categorized based on International 4 consequences
Nuclear & Radiological Event Scale (INES). Serious incidents
INES Rating IDENT 3 Incidents

The INES system of the International Atomic Energy INIC 2 Anomaly
Agency (IAEA) rates events at seven levels (1 to 7) 1
Below Scale/ Level 0
depending on their safety significance.
The accidents at Chernobyl NPP in former USSR (now in No Safety Significance
Ukraine) in April 1986 and Fukushima NPPs in Japan in
March 2011 were rated at level 7 on INES. These accidents
involved core meltdown with the consequences of off-
site radioactivity release to environment.

• No significant event was reported in NPP under INES Rating of Events
construction. NPPs
INES-0 INES-1
• A total of 45 significant events were reported from
TAPS-1 & 2 2 0
the operating NPPs in 2019. Of these, one significant
TAPS-3 & 4 3 0
event at RAPS-2 was rated at level-1 on INES, while
40 significant events were rated at level-0 on INES. RAPS-1 & 2 7 1
• One event at TAPS-3&4 is currently under review for RAPS-3 & 4 3 0
finalising the INES rating. RAPS-5 & 6 6 0

• Three industrial safety events, one each at RAPS-5&6, MAPS-1& 2 3 0
KGS-1 ad KKNPP-1&2 were not rated on INES (as they
NAPS-1 & 2 1 0
are amenable for rating in INES).
KAPS-1 & 2 2 0
KGS-1 & 2 8 0
All these significant events were reviewed in detail
KGS- 3 & 4 1 0
to identify and implement corrective actions as
KKNPP-1&2 4 0
required.
Total 40 1
The events reported were categorized as per the IAEA-
IRS coding system. The classification of systems failed /
affected in the significant events is as shown.
I & C
Systems Primary RAPS-2 Event
Systems
Feedwater,
15%
Steam and
RAPS-2 was shut down due to water leakage
Power
Conversion from secondary side of multiple boiler hairpins.
Systems The investigation revealed that leakage was
17% 44%
due to generic phenomenon (i.e. under deposit
corrosion) which had led to wall thinning and
pinholes in the boiler hairpins, near the weld
19%
Electrical joint between tube-sheet and boiler hairpin
Systems 5%
shell.
Essential
Auxiliary
Systems
43
AERB BULLETIN 2019
AERB BULLETIN 2019