Support to the Nuclear Safety Regulator of Brazil - Project BR3.01/12

The overall objective of the project was the enhancement and strengthening of a nuclear safety regulatory regime in Brazil in compliance with internationally used criteria and practices. More specifically, the areas covered were Probabilistic Safety Analysis (PSA) assessment, deterministic safety analysis, ageing management and long term operation, emergency preparedness, severe accident management and digital I&C systems licensing. Some of these areas had been already partially covered by the previous project BR3.01/09. The project started with the inception meeting held in Rio de Janeiro, Brazil from 9 to 10 June 2015. The planned project duration was 36 months; the final project meeting took place on 15 March 2018 in Brussels, Belgium.

Task 1 - Probabilistic Safety Analysis (PSA)

This task aimed at supporting the National Nuclear Energy Commission in Brazil (Comissão Nacional de Energia Nuclear, CNEN) in the strengthening of Probabilistic Safety Assessment capabilities. It had three goals:

1. To support CNEN in PSA regulatory issues, including the development of a guide for regulatory applications of PSA.
2. To support CNEN in the review of PSA documentation submitted to CNEN by Brazilian NPPs (Angra 1, 2 and 3) within the 2013/16 period.
3. To provide guidance on the first steps in PSA Level 3 in Brazil.

Four workshops were held to discuss the different regulatory issues faced by CNEN in regard to PSA, and training sessions on PSA-related topics such as fire risk, Level 2 assessments, low power and shut down PSA and external hazards were provided. The project team completed a draft regulation for the development, application and use of PSA for Brazilian nuclear installations. Some parts of the guide could not be finalized within the project as they rely on CNEN’s overall regulatory positions which will be defined later (as for example regarding the probabilistic safety goals or the requirement to include the spent fuel pool in the required Level 2 PSA scope). A guide for the review of PSA documentation was also prepared and was ready to be used by CNEN staff in future PSA submittals' reviews. The Contractor supported CNEN's review of the Angra 2 PSA by doing a preliminary review of the following specific areas: Fire PSA, Low Power & Shutdown PSA, Level 2 PSA, Seismic PSA and External Events PSA. The detailed and final review of these chapters will be accomplished by CNEN in the future, taking into account the results of the preliminary review. Finally, the Contractor gave general guidance and practical advice regarding the review of PSA models conversion from one computer code to another one. This guidance allowed CNEN to perform the preliminary review of the PSA models conversion from CAFTA to RiskSpectrum done by AREVA. This preliminary review will be the basis for CNEN to make recommendations for the Brazilian utility and to carry out a detailed analysis.

Task 2 - Deterministic Safety Assessment

The first objective was to support the uncertainty and sensitivity analysis performed by CNEN on the Angra-2 Loss of Coolant Accident (LOCA) evaluation model with a best estimate code, as part of the licensing process of power upgrade and new fuel design. Another objective was to support the safety evaluations of fuel design, using different fuel analysis codes like FRAPCON or FRAPTRAN. The project team reviewed the large LOCA simulations at Angra-2 prepared by CNEN based on SUSA and RELAP5 codes. Through a number of meetings and workshops, the reactor nodalisation and the uncertainty and sensitivity analyses of the LOCA simulations were improved. The project team also developed an interface software to generate automatically a FRAPCON input file from other codes outputs. the source code of the interfacing software was delivered to CNEN, together with associated training.

Task 3 - Ageing Management and Long Term Operation

In the field of Ageing Management Program Assessment, there is a need of transfer of knowledge and know-how to identify the appropriate parts which must be evaluated in the Periodic Safety Review (PSR) as far as long term operation is concerned, and on the way to carry out such evaluation.

Previous to this project, CNEN had already developed a state-of-the-art general regulatory guide to evaluate ageing management programs, and was envisaging the development and the application of specific requirements for Brazilian NPPs based on guidance developed by the Forum IberoAmericano de Organismos Reguladores Radiológicos y Nucleares (FORO) and by other countries.

The Contractor prepared a state-of-the-art report on ageing management & LTO practices and reviewed existing Brazilian standards related to ageing management and LTO. Based on these inputs, CNEN drafted the Brazilian Regulatory Requirements for Ageing Management and LTO in NPP, which were also reviewed by the project team.

Task 4 - Emergency Preparedness.

CNEN intended to make available in its emergency room the operating parameters from NPPs. This information would also be helpful for operational supervision and for event analysis. The parameters were already available at the NPP's main control rooms through a dedicated information system (SICA, developed by the University of Rio de Janeiro).

The project team supported CNEN in this area by giving guidance on how to select the parameters that are relevant for emergencies, and on the hardware and software systems needed for the interface with SICA and the display of the data at the emergency room. The role of the Finnish (STUK) and Spanish (CSN) regulators in emergency preparedness were discussed with CNEN staff, and a visit to the Spanish SALEM emergency room. During the visit, CNEN staff could discuss about the maintenance of the equipment and the role of the room during drills and other exercises. The project team proposed a complete set of parameters needed for emergency management applicable to KWU-type reactors. It was confirmed that the SICA system could provide all required information. CNEN was also seeking support to enhance the functionalities of the ARGOS-BR code in order to deal with Brazilian Emergency Planning Zones (EPZs). A subcontractor with specialized knowledge on the ARGOS project was hired to develop the additional features required by CNEN. With the enhanced software, CNEN can now define the zones on ARGOS maps, and use this software to calculate the doses projected and issue warnings when thresholds are exceeded. These results can then be used to support emergency actions (sheltering, evacuation, etc.). This has allowed CNEN to reduce the time needed to issue the warnings from 30 minutes to almost instantly.

Task 5 - Severe Accident Management

The objective of this task was to enhance the assessment capabilities of CNEN for Severe Accident Management. The results of CNEN's calculation of scenarios for Emergency Operation Procedure assessment was discussed with the project's experts during the 1st workshop. Then, the Contractor reviewed also the documentation related to the hydrogen recombiners and the independent accident analysis for station blackout and small LOCA. Project experts provided guidance on the implementation of severe accident management systems based on the Finnish and Spanish practice. They also supported CNEN in developing the "Regulatory evaluation report of the Angra 2 Severe Accident Management Programs (SAMPs)" and the "Technical report on the MELCOR plant simulation model used for implementation/evaluation of the severe accident analysis of Angra 2". The works carried out within the task were presented at the Eurosafe Conference 2017 in Paris.

Task 6 - Safety of digital instrumentation and control (I&C) systems

Prior to this project, CNEN was preparing for the regulatory review of the Angra 3 I&C systems chapters of the Final Safety Study, as well as the inspections and reviews associated to the I&C hardware & software life cycle (including factory acceptance tests and site acceptance tests). The project experts discussed with CNEN the safety classification of I&C systems, explaining the European practice in this area, particularly in Finland. The CNEN's internal guide "Review and Assessment of Digital I&C systems" was reviewed by the project, and comments for improvement provided. The chapters of the Angra 3 Preliminary Safety Analysis Report (PSAR), submitted by the licensee, covering the I&C systems were reviewed by the project team, who provided their comments to CNEN (issues concerning unidirectional vs. bidirectional communication in the Reactor Protection System (RPS), independency issues of the RPS, security aspects on USB ports of service computers, etc.).

Furthermore, the project team supported CNEN to develop the regulatory framework for the acceptance of foreign suppliers of digital I&C systems, taking into account the latest German safety standards. The construction of the Angra 3 NPP was interrupted during the execution of the project, so that parts of the originally planned scope, like the preparation of commissioning procedures, had to be modified or cancelled, as the licensee did not send the required documentation. The activities completed within the task were also presented at the Eurosafe Conference 2017 in Paris.