Eletronuclear ( Brazil) Fukushima Response Plan
Edmundo Selvatici
Site Manager
Mario de Mello Ferreira Junior
Manager, Materials Engineering
Technical Meeting on Operational Experience with
Implementation of Post-Fukushima Actions in Nuclear
Power Plants
25 - 27 march 2017
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Angra Nuclear Power Station (single NPP site in Brazil)
ANGRA 1 PWR
Power: 640 MW
Technology: Westinghouse
Operation start: Jan. 1985
ANGRA 2 PWR
Power: 1,350 MW
Technology: KWU/ Siemens
Operation start: Jan. 2001
ANGRA 3 PWR
Power: 1,405 MW
Technology: KWU/ Siemens/ Areva
Under construction
Planned start of operation: 2022
(illustrative view)
ANGRA 1
RADIOACTIVE
WASTE STORAGE
CENTER
ANGRA 2
500kV Switchyard
2
Plan in Full Integration with Nuclear Industry Brazilian Nuclear Authority
Initiatives
3
Response to Fukushima – Main Safety Goals 29
6
4
Response to Fukushima – Evaluation of ST Report
Basis: WENRA
Specification for
Stress Test Report
FORO Angra 1 and Angra 2 NPPs Stress Test
Report Evaluation
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Protection from Hazard Events
External Events
Earthquakes;
Rainfalls;
Landslides;
Tidal Waves;
Tornadoes.
• Assessment of existing DB external
event scope and design criteria for
completeness and updating
• Assessment of safety margins of
existing design in case of BD
external events
– 1st step: simplified calculations,
engineering/expert judgement
– 2nd step: detailed deterministic and
probabilistic analyses.
Internal Events
Fire;
Internal Flooding.
• Reevaluation considering
up-to-date safety requirements;
• Identification of design gaps.
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Protection from Hazard Events - Results
Earthquakes
Evaluation of margins
•
estimated safety margins relative to
Design PGA by expert walkdown and
judgement : 2 - 2.5 for Angra 1 and 2.5 3.0 for Angra 2;
•
Extensive updating of geological and
seismological database (three-years
program completed);
•
PGMRS( Probabilistic Ground Motion
Response Spectrum) determined for use
in the Seismic PSA;
Plants Seismic Design
Low seismicity site (intraplaque
region). Largest recorded
•
earthquake 5.2 Richter scale at 300
km (PGA 0.002g at site);
Design PGA for SSE: 0.1g (p< 104/yr) based on deterministic seismic
response spectrum.
Seismic PSA for Angra 2 completed
(safety margin: up to 4xDesign PGA)
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Protection from Hazard Events - Results
Rainfall and Landslides
Evaluation of margins
Studies considering heavy rains
and consequential or seismic
induced landslides concluded.
Extreme case of full rupture of
slope covering material
evaluated.
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Slopes very steep around the site
Residual and colluvial soils
High rainfall rates
Station protected by slope stabilization
works and slope monitoring system
Results:
For worst case switchyard and
discharge channels may be
affected however no impact on
Plants buildings;
Recommendation for
enlargement of slope drainage
system and reinforcement of
some stabilization works
(ongoing)
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Protection from Hazard Events - Results
External Flooding
plant construction level
access to safety
buildings
Angra
1 and 2
+ 5.15m + 5.60m
0 CNG
Evaluation of margins: Reevaluation of flooding level under more severe
conditions concluded (rainfall rate higher than 10,000 years rainfall,
blockage of site drainage channels and circulating water discharge tunnel
due to landslides, highest sea level).
Results:
Current design flooding level includes sufficient safety margin (up to 75.000
years rainfall); Recommendation for checking and reinforcement of
existing flooding barriers (finished).
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Protection from Hazard Events - Results
Tidal Waves
•
calculation of tidal waves for severe metereological conditions( sea
storms and hurricanes) at Ilha Grande Bay concluded; largest waves>
maximum design wave for wave breaker design
•
evaluation of wave breaker stability through physical model by
international lab being contracted;
•
Results may lead to recommendation of breaker structural reinforcement
Angra NP
Station
Ilha Grande Bay
Bay area, natural protection
from Atlantic Ocean
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Protection from Hazard Events - Results
Tornadoes
Tornadoes were not originally considered for
Angra 1 and 2 due to low probability
(~10-7/y);
Tornado hazard study developed for Angra 3;
Impact on Angra 1 and 2 evaluated and
actions plans issued for further evaluation
and/or protection of selected structures
and components.
Internal Fire
Internal
Flooding
Fire Hazard of Angra 1 revised by EPRI
(risk based evaluation); design
modification packages under
evaluation.
Reevaluation of Angra 1 design against
internal flooding; Recommendation to
increase the safety margins under
evaluation
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Evaluation of Station Blackout Scenarios (SBO)
Existing power supply
conditions for
Angra 1 and Angra 2
(Design or backfit)
Angra 1:
2x100% DG ( Plant Design) +
2x100% DG (backfit)
Same cooling system for all DG
Angra 2:
4x50% EDG +
4x50% EFDG in dedicated
bunkered building with
independent cooling system.
Cachoeira
Paulista
São
José
Santa
Cruz
SE
500kV
SE
138kV
A2 A1
A2 A1
Angra 2
Angra 1
4 x 50%
2 x 100%
4x
M G
2x
M G
UBP – D1
EDE – 3/4
4x
M G
2x
2x
M G
ULB – D2
EAS – 1A/1B
2,5h
4,0h
Minimum batery duration
Zona
Oeste
Off site
Power
Emergency
Diesels
1st Emergency
Power System
2nd Emergency
Power System
both meet NRC
requirements for
exclusion of SBO
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Existing SBO Emergency Procedures
•
SG feeding through steam turbine driven pumps (Auxiliary
Feedwater Turbine Pumps) in Angra 1 and Diesel Driven Emergency
Feedwater Pumps in Angra 2);
•
at least 20 hours in Angra 1 and 33 hours in Angra 2 of feeding
from, respectively, Auxiliary Feedwater Tank - AFT and Demineralized
Water Pools - DWP;
•
possibility of AFT and DWP refilling from Fire Fighting Water
Supply System - FFWS (5,000 m3 reservoir, located on an elevation
110 m above the site level);
•
possibility of full passive secondary B&F from the FFWS reservoir
(connection before SG becomes empty, in case AF-2 or LAS pump
fails, about 50 minutes).
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Evaluation of Loss of Main Heat Sink
Existing design conditions:
• water intake structures protected from open sea hazards (Ilha Grande
Bay);
• water intake structures protected by wave breaker 8.0 m high above
average seawater level;
• Availability of alternative heat sink by means of Fire Fighting Water
Supply System - FFWS (5,000 m3 reservoir, located on an elevation
110 m above the site level); alternative already incorporated in
Emergency procedures for both Plants. Not designed for earthquake..
Main implications for the plants:
• Angra 1: failure of both Emergency Diesel Generator Systems (failure
of common cooling system);
• Angra 2: Only EDG fail. Bunkered Emergency Feedwater Diesels (EFDG)
not dependent of Service Water;
• impossibility of operating the RHR chain.
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Provision of Cooling Capacity – extreme conditions
Deterministic evaluation approach (WENRA/FORO guidelines)
• no credit given to special design features or former backfits at the
Angra plants
• no possibility of external support within 72h after the accident onset;
Event Initial Conditions
• Loss of Offsite and Onsite Power (SBO) and Loss of Ultimate Heat
Sink (LUHS)
Plant in Power Operation
• 100% reactor power;
Plant at Refueling (worst condition for fuel pool temperature)
• full core transferred to fuel pool;
• full loading of fuel pool storage racks;
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Stress Test results
•Based on the Stress Tests results mobile equipment to
provide additional means to supply power and cooling
capacity for the core and the fuel pools were identified,
specified and purchased, comprising
– different sizes of Diesel Generators, Diesel driven pumps
and associated connection fixtures.
•General Concept adopted for Mobile equipment
– Equipment stored on site in location that is not affected
by the external events that would affect the site,
housed in a light tent-like structure commercial grade
equipment;
– Mobile equipment connections specified in accordance
to the Requirement Category of the systems where the
connection is applied.
– Mobile equipment incorporated to the decision trees of
the EOPs;
– Mobile equipment have specific procedures; not
incorporated to the Tec Specs.
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Stress Test results
• Design modification processes have been developed for
the short and medium term strategies, in case of loss of all
AC power and/or UHS, as follows:
Short term (1 to 3 hours): recharging of batteries and Steam
Generator feed.
– Mobile equipment : one 250 KVA DG and 2 Diesel Driven pumps
per Plant;
– Countermeasure: Bleed and Feed through the secondary side.
Medium term (1 to 2 days): in case of available UHS.
– Countermeasure: repowering one RHR cooling train
– Mobile equipment: 3 large DG, of 600 KVA each for Angra 1; 2
large DG, of 600 KVA each for Angra 2.
Medium term (1 to 2 days): in case UHS is unavailable
– Countermeasure: continue Secondary B&F and replenish source of
water for SG cooling (tank/pool) with sea water;
– Mobile equipment: 2 submergible Diesel powered pumps
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Stress Test results
• The implementation of a new water reservoir of 4000 m3
meeting seismic requirements located at a height able to
provide means of feeding the steam generators in a totally
passive way, is in phase of design completion.
• An alternative means of cooling the Diesel Groups in Angra
1, in case of loss of the Service Water System (SWS), was
developed by installing a connection in the SWS piping for sea
water injection with a mobile Diesel powered pump.
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Overview of Additional Emergency Supply Alternatives
Mobile DG
(Emergency Power
Supply for essential
Safety Systems)
2017 status
(completed)
2017 status
(completed)
Mobile DG
(Emergency Power
Supply for essential
Safety Systems)
Interconnection of Diesel
Systems D1 and D2 (intended)
2017 status
(design
concluded)
ANGRA 1
ANGRA 2
Mobile DG
(extension of
batteries autonomy)
2017 status
(final
implementation)
Alternative cooling
chain for Angra 1
Emergency Power DG
2017 status
(final
implementation)
Mobile DG
(extension of
batteries autonomy)
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Additional Alternatives for Reactor Cooling
Alternatives for Reactor Cooling Via Steam Generators
Angra 1 and Angra 2: Secondary side “bleed-and-feed” through the Steam
Generators. (2017 status – final implementation)
Alternatives for Direct Reactor Cooling
Angra 2 Primary side“bleed-and-feed”: Installation of additional valves in the
Pressurizer valve station with dedicated power supply and I&C. (2017
status – completed). Ensures depressurization of Primary System(bleed).
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Additional Alternatives for Reactor Cooling
Mobile Pumps for SG Feeding
Mobile Pumps for Refilling Water
Reservoirs
Mobile Ar
Compressor
for Remote
Valve
Actuation
(Angra 1)
Fire Hoses
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Mobile Equipment maintenance and storage
Testing and Maintenance activities:
- All tests and maintenance are being performed according the equipment
supplier manuals;
- Weekly sequence of DG performance tests, mobile pumps and mobile air
compressor;
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Loss of Fuel Pool Cooling
Fuel Pool Temperature Increase after Loss of Cooling
Unit
Angra 1
Angra 2
Plant condition
Time until start
boiling
Time until fuel
element exposure
Power Operation
28 h
179 h
Refueling (*)
9h
56 h
Power Operation
23 h
136 h
Refueling (*)
5h
31 h
(*) Full core unloaded and full occupation of pool racks
Fuel Pool Cooling alternatives :
• Angra 1 (SFP in external Fuel Building): Feed
to the SFP from outside – fire fighting FF)
water reservoir or FF truck. (2017)
• Angra 2( SFP inside Containment): fuel pool
cooling using fire fighting water – 2018)
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Mitigation of Radiological Consequences
Containment Protection:
Passive H2
catalytic
recombiners
(PARs) already
installed in Angra 1
and 2 (completed)
Containment Filtered Venting (CFV):
• AREVA CFV (wet option) under
design for Angra 2. Implementation
in steps due to budget limitations
• Not yet decided for Angra 1.
Severe Accident Management Guidelines (SAMGs):
•Angra 1: WOG SAMGs have been implemented and integrated with the
Emergency Planning (EP) procedures.
• Angra 2: AREVA SAMGs have been developed, implemented and integrated with
the Emergency planning procedures.
Other improvements of the infrastructure for Emergency
Planning
• Implementation of trails in emergency planning zones (completed)
• Improvements in Emergency Centers (underway)
• Improvements in radiological protection controls for Severe accident situations(
underway)
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Thank you for
your
attention.
[email protected]
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