Measures taken in Brazil to license

the postponed project of Angra 3 NPP

JOSE A. B. CARVALHO

CNEN-Comissão Nacional de Energia Nuclear

Rio de Janeiro, Brazil

INTRODUCTION

ANGRA 2 NPP IMPROVEMENTS

ANGRA 3 NPP IMPROVEMENTS

POST FUKUSHIMA ACTIONS

CONCLUSIONS

INTRODUCTION

Brazilian electric power matrix

3 NPPs in one site – 2 in operation + 1 under construction

INTRODUCTION

Angra 2 and Angra 3 NPPs were ordered from KWU (later Siemens) in the mid-70s Angra 2 NPP construction started in 1976

Angra 3 NPP was scheduled to start in 1980

Financial constraints have postponed Angra 2 NPP and interrupted Angra 3 NPP

Angra 2 NPP followed slowly, finishing in 1998

A number of modifications could be introduced during this long term construction phase.

ANGRA 2 NPP IMPROVEMENTS

Regulatory Initiatives Joint seminars among Regulator, Germans TSOs, Operator and Designers

Adoption of the Standard Format and Content for Safety Analysis Report

Inclusion of the Chapter 18 - Human Factors in the FSAR Adoption of the break preclusion concept

Adoption of formal acceptance criteria for the commissioning tests

Adoption of emergency procedures

Adoption of a computer based system to monitor critical safety functions.

ANGRA 2 NPP IMPROVEMENTS

Design and Administrative Modifications Reliability increasing of safety systems: More stringent design criteria; The pressurizer safety valves equal to the Konvoi NPP’s (ATWS qualification ); Reactor Protection System more efficient; Three subsystems to cool the fuel pool; Isolation of the accumulators to prevent gas cloud in primary system; Controlled relief of the reactor vessel. Man-machine interface improvement: Level measurement in the reactor pressure vessel; Temperature measurement in the reactor pressure vessel head; Post-accident instrumentation; Position measurement of the pressurizer safety and relief valves; Technical Support Center.

ANGRA 2 NPP IMPROVEMENTS

Design and Administrative Modifications Preventing accidents: Preventive emergency procedures; Mitigative emergency procedures; Hydrogen monitoring, dispersion and reduction systems; Reduction of the corrosion products in the secondary circuit in order to preserve the efficiency and avoid flaws in the vapor generating tubes. Measures to reduce radiation exposure of operating and maintenance personnel: Constructive measures (shielding, lay out, better access for maintenance) ; Materials substitution in the primary circuit; Automating inspection processes of the components of the primary circuit.

ANGRA 3 NPP IMPROVEMENTS Angra 3 NPP resumption The operator resumed the Angra 3 NPP project in 2006 and presented the PSAR requesting the Construction License in late 2006

Angra 2 NPP is the reference plant for Angra 3 NPP

Discussions on the applicable standards and design bases occurred along 2007

CNEN asked for some revisions in the Preliminary Safety Analysis Report.

The safety evaluation started in 2008

Construction License was issued by CNEN in 2010

ANGRA 3 NPP IMPROVEMENTS Regulatory Initiatives Normative bases not older than 2003, except when otherwise stated

Calculation of civil structures, considering updating of the 2007 Brazilian rules, particularly for shear design

Update of the seismic threat curve and all the order external events studies

Inclusion of tornado as a design basis accident

Adoption of the KTA 2207 (Ed. 2004)3 flooding criteria Inclusion of the Chapter 19 - Severe Accidents in the SAR.

ANGRA 3 NPP IMPROVEMENTS

Main design Modifications Digital Control Room and Reactor Protection System

Extra diesel generator (9º diesel engine)

The Switchgear Building and The Emergency Diesel Generator Building designed against all external events

Emergency power supply to the pressurizer heaters

POST FUKUSHIMA ACTIONS Regulatory Initiatives CNEN requested to ETN: Identification of the main design differences between Fukushima and Angra NPPs

Possible extreme internal and external events causing a common mode failure

Hydrogen concentration control measures in the containment

Emergency power supply assurance in case of blackout

Cooling chain in case of loss of the usual cooling systems

Procedures for severe accidents

Access to the reactor buildings and the area controlled after occurrence of a severe accident

POST FUKUSHIMA ACTIONS Regulatory Initiatives CNEN as a part of the Ibero-American Forum of Radiological and Nuclear Regulators , requested the implementation of a Resistance Assessment, similar to Stress Test

Cross-review process among countries (Argentine, Brazil, Mexico and Spain)

There were not identified any relevant weakness that required the adoption of urgent measures

POST FUKUSHIMA ACTIONS Fukushima Response Plan Three major area of assessment Protection against extreme events Cooling capacity Limitations of the consequences

Each area has initiatives and for each one it was established Objective Responsibility Characterization as a study or project Priority Scope Deadlines Cost

POST FUKUSHIMA ACTIONS Fukushima Response Plan Areas for assessment and major initiatives Earthquake – Updating of seismic data,seismic threat and assessment of safety margins Slopes - Updating of geotechnical mapping, reassessment of the monitoring system and evaluation of an extreme landslide Sea Movements - Revaluation of maximum wave heights and jetty stability Floods - Flood revaluation, considering the blockage of the drainage channels and landslide. Internal flood revaluation in Angra 1 NPP Tornadoes and Hurricanes - Impact assessment of tornado in Angra 1 and 2 NPPs. Reassessment of the hurricane threat in the site

POST FUKUSHIMA ACTIONS Cooling Capacity Secondary circuit feed and bleed for design extended conditions

Primary circuit feed and bleed for design extended conditions

Determination of temperature increase in the fuel pools in case of loss of cooling

Alternatives for emergency power supply

Revaluation of the autonomy of batteries, manual interconnection buses and diesel oil supply

Development of PSA for low power and fire

Implementation de SAMG procedures in Angra 2 NPP

Accessibility to the working areas in the caseof loss of total power.

POST FUKUSHIMA ACTIONS Limitations of the consequences Containment integrity - Implementation of passive catalytic recombiners and filtered venting;

Post instrumentation accident - Implementation of sampling system for design extended conditions;

Emergency Plan - Improvements in emergency centers. Enlargement of the present docks for increasing people evacuation capacity.

CONCLUSIONS

Angra 3 NPP is not the same plant purchased in the 70s. Today we can say that it is a Pre-Konvoi plant Long-term constructions require reassessments of the project adequacy and is a time consuming task. A good practice would be to determine an expiration date for a Construction License (e.g. 8 to 10 years) Many reassessments resulting from Fukushima event – it is important to prioritize those most relevant to each plant. For instance, for Angra NPPs site slope stability is much more important than seismic reassessment.

Thank you