MAIN RESULTS OF THE

TARGET ANPP SAFETY

ANALYSIS FOR EXTREME

EXTERNAL HAZARDS

Presented by

Khachik Poghosyan, ANPP Vienna, 25 – 29 August, 2013

ANPP

A R M E N I A N N P P

Armenian NPP is located in the west part of Ararat valley, 10 km north-

east from regional center Armavir, 28 km west from Yerevan and 16

km away from the Turkish border.

The ground zero level of the site corresponds to 934.5 m height above

the sea level.

ANPP site horizontal peak ground acceleration (PGA) is 0,28g for

mean and 0,32g for 85% confidence with excess probability once

per 10000 years (10-4).

The service and potable, as well as fire-fighting water supply of ANPP

is provided from reservoir located in the distance of 5-6 km at

860880 m level above the sea.

After Spitak`s earthquake in 1988 the two units were shutdown. Since

1995 only Unit 2 is in operation. Unit 1is in conservation state and

the reactor is unloaded.

Main Parameters of Unit 2

Parameter Value

Reactor heat power output 1375 MW

Primary coolant flow rate 42000 m3/h

Primary pressure 12.26 МPa

Coolant temperature at reactor input 267oС

Average heat-up of coolant in reactor 29.3oС

Boron acid concentration in coolant 12.00 g/kg

Main steam pressure 4.5 MPа

Steam flow rate 2700 t/hr

The limiting linear load per fuel cell 325 W/cm

Installed electrical capacity 407.5 MW

Safety analysis and estimation of ANPP

resistance against external hazards

Following the Fukushima accident in March 2011 there was held an

extraordinary meeting of the ANPP General Director’s safety council

in order to identify the needed actions resulting from that accident. A

group of ANPP experts was charged by the safety council to specify

the following, at the earliest possible date, based on the existing

information and engineering judgment:

Plant safety deficiencies in regard to external hazards;

Recommendations on compensation of these deficiencies in short

and long terms.

In compliance with the safety council decision the first draft of the report

was prepared in the second half-year 2011. Upon consideration and

approval of the offered actions by the technical council of ANPP, the

plant started implementation of the short-term (not demanding

capital expenditures) compensating measures.

Compensating measures implemented in

2011÷2012

Some of implemented compensating measures in 2011÷2012 which greatly

contributed improvement of ANPP resistance against extreme external

hazards are listed below:

Reevaluation of ANPP site seismic hazard with up-to-date methods;

Seismic qualification of ANPP main systems, components and structures

ensuring the plant safety at 0.35g seismic impact, defined for ANPP site.

Currently the plant seismic margin is approximately 1.5 times higher than

HCLPF (high reliability of low probability of failure), corresponding to 0.57g.

in ground acceleration terms;

Technical solution on cooling water supply from an alternative source to DG

of independent power supply system, in case of all cooling water sources

loss. This DG is designed for safety systems power supply in case of failure

of main and reserve power supplies;

Compensating measures implemented in

2011÷2012(continued)

Technical solution on accumulator batteries reliability improvement and

extension of their operating time up to 7÷8 hours;

Laying of cable from stationary 200kW DG to the AB charger, for emergency

recharge of AB, and development of its use procedure;

Unloading of AB board with transfer of a load part to all-unit DC board;

Construction of 50сm height and 50m length penetration through the output

channel wall, ensuring water discharge from NPP site in case of circulating

gate valve failure to close during water supply from the higher channel, via

condensers, to the lower channel. The plant site flooding due to overfill of the

lower channel is excluded;

Technical solution for remote filling of SG auxiliary make-up diesel pump tank

with diesel fuel;

Compensating measures implemented in

2011÷2012(continued)

Technical solution on creation of an alternative source of potable and fire

water supply to the plant. From three wells located outside the external

fencing of plant, three 45L/sec capacity depth pumps, in two legs (channels),

supply water to the potable and fire water system;

Technical solution on ensuring MCR habitability. Establishment of

Emergency Control Board is under implementation;

Additional thermohydraulic calculations of severe beyond design basis

accidents (BDBA). Currently the revision of Guidelines on BDBA

Management and development of severe accident management guidelines

(SAMGs) is under implementation;

Contract with Rosenergoatom (Russian Federation) crisis center for scientific

and technical support of plant in case of beyond design basis accident at

ANPP is concluded;

Intervals of emergency trainings of ANPP personnel focused on BDBA are

twice reduced.

EC support to ANPP

However performance of complete analysis based on "Stress tests“ methodology in compliance with ENSREG specification was beyond ANPP possibilities. In this regard EC provided ANPP with support in performance of "Stress test". The winner of tender invited by EC for ANPP support in "Stress test" performance was the consortium including:

Tractebel Engineering Company (CDF Suez), as a leader of consortium;

• Ustav jaderho vyzkumu Reza.z (UJV);

• Armenian scientific research institute of nuclear power plant operation(APMATOM);

• TsKTI - Vibroseism. Subcontractor.

"Stress test" activities for ANPP started in 08.2012г.

Currently the ANPP experts, supported by the consortium, prepared "The report on performance of "Stress test" at ANPP, for consideration and preparation of the national report and its presentation in EC" and submitted it to Armenia regulatory body.

Conclusion

The implemented analysis demonstrated that for the designed external natural and man-

induced hazards, the safety of ANPP is ensured and proved in safety analysis

documentation.

The implemented safety analysis of extreme external hazards (earthquakes, floods)

demonstrated that:

seismic stability of civil structures, systems and components of the Unit which were

entered into the SSEL for seismic impact, is approximately 1.5 times higher than the

designed SSE level;

the plant designed elevation is 60÷80m higher than the nearby reservoirs water level

and the flood of the plant site is excluded.

Conclusion (continued)

At the same time the plant safety analysis was carried out for the

following BDBAs:

• station blackout (total loss of all sources of alternating current,

including emergency ones);

• loss of the ultimate heat sink.

These analyses revealed a number of weaknesses which can lead to

situation deterioration at the nuclear power plant, up to occurrence of

severe beyond design basis accident.

Conclusion (continued) The main weaknesses include:

Due to the discharge of accumulator batteries there is a loss of key parameters control necessary for NPP transfer to safe condition and its maintaining in this condition;

In case of long-term station blackout there is a deficiency of power supply to safety systems due to insufficiency of diesel fuel stock;

There are no additional independent power supply systems for safety systems;

Insufficient water supply to steam generators, storage pools and primary circuit;

Lack of analyses of severe accidents late stages with radiation consequences assessment;

Lack of hydrogen explosion safety assessment for severe accidents;

Revision of emergency operating procedures (EOPs) and Guidelines is required;

Development of SAMGs, based on the results of severe accidents analysis for late stage, is required;

Development of emergency I&C available in severe accident conditions is required;

Seismic qualification of normal operation system components which can be used in severe accident management (for heat removal from spent fuel in storage pools) is required.

Conclusion (continued)

A list of activities for mitigation of the

abovementioned BDBAs was developed

aimed at ANPP safety improvement and

prevention of severe accidents.

Currently the ANPP waits for the RA

regulator decision on the plant conclusions

and suggestions that were presented in the

"Stress test“ report.

Thank you for attention!