Establishing Code Certification System

Within the framework of the TACIS programme, the EU has undertaken to fund a number of projects to provide assistance to the Ukrainian nuclear safety authority (NRA) and Ukrainian TSOs in enhancing their technical capabilities.

TACIS Project UK/TSO/09, Support to Ukrainian NRA in Establishing a Code Certification System addresses the preliminary actions to be taken by the NRA to prepare a code certification process.
Within the certification process special attention was paid to aspects relating to the adequacy of the codes for modelling physical phenomena, the suitability of numerical methods, field of application and range of validity, users of the code, user interfaces, documentation, quality control and assurance and computer aspects.

The collaboration was focused on the following technical areas which were selected as a pilot for the certification plan:

• RPV embrittlement (structural calculation)
• Core neutronic calculations
• Containment environmental conditions
• Thermal hydraulics

The first two areas were carried out by VTT and the last two by CIEMAT. The Ukrainian Organisation (Energorisk) has participated in all four areas.

The objectives of the project were to transfer Western practices for code verification, qualification and certification to Ukraine, and adapt Western methodology to Ukrainian circumstances and propose objectives and a work plan for future activities.

The proposed activities were aimed at covering the above-established objectives relating to a Code Certification and which were set out and interpreted below:

• Establish the basis for a certification system for Western codes used to prove the safety of Ukrainian nuclear facilities.
• Provide technical assistance to Ukrainian specialists in order to prepare pilot certification procedures for a selected sample of specific codes. This on-the-job training method is deemed appropriate to transfer in a practical manner Western methodologies and adapt them to the Ukrainian situation.
• Define the code certification procedure to be followed in Ukraine and the work plan containing future actions to be taken.

The first project milestone was the issue of the Quality Assurance Program and the detailed work Plan. A series of project organisational procedures were developed. These procedures, together with the OA Program, constituted the organisational framework for the project. The methodology applied to the different tasks was:

TASK 1: ANALYSIS OF THE UKRAINIAN SITUATION

The Task was cancelled in accordance with the amendments attached to the TOR in the invitation to tender.

TASK 2: INFORMATION OF WEST EUROPEAN

The activities included in this task cover the objectives established in the Terms of Reference for Task 2, Western Practices on Codes Verification and Validation to establish the basis for a certification system for Western codes used to demonstrate the safety of Ukrainian nuclear facilities.

The objective of this task was to supply to NRA and the counterpart Organisation a package of information on West European practices (mainly Finnish and Spanish) in the field of codes verification, qualification and certification. Western methodologies for code certification were explained in a workshop, held in Kiev, so that they could be assimilated and discussed by specialists from the Ukrainian NRA and other participating organisations (SSTC, Energorisk).

The subjects covered in the workshop included:

• Validation and verification general methodology
• Normal Western practices: Spanish
• Normal Western practices: Finnish
• Considerations for specific applications

The objectives for transfer of information about code certification methodology have been more than adequately achieved. These objectives included compilation, transmission, presentation of information and detailed discussion with the Ukrainian Regulatory Authority and other participating organisations. The purpose of these activities was to better understand their content and to compare the different methodologies used in Western European countries, to be able to begin defining possible objectives for the Ukrainian certification plan.

The transfer of general information on code verification practices was complemented with examples of code verification. The examples covered validation of Western codes that have been applied to environments with features different to those for which they were developed.

TASK 3: UKRAINIAN CODE CERTIFICATION OBJECTIVES

The activities developed in this task cover the objectives established in the Terms of Reference for Task 3, Ukrainian Code Certification Objectives, to assist the NRA in developing specific Ukrainian objectives for verification, qualification and certification of safety-related codes.

The work method was as follows:

• analyse current requirements and normal Ukrainian work procedures for the use of safety codes;
• comparison to identify the differences between the Ukrainian and Western practices;
• identify Ukrainian needs and define objectives for safety-related codes, paying special attention to VVER NPPs.

The goal should be a unified Code Certification System for western and original Russian and Ukrainian VVER codes. The plant license should be issued only for a certain period and the analyses should always be carried out with methods based on latest knowledge and most up-to-date calculation tools.

The accuracy and reliability of results cannot be better than the models and input data behind them. A code should be certified always only for a certain plant, analysis or task and user organisation, and not for unlimited periods of time.

The NRA should clarify its position concerning the requirements for licensing analyses and safety related analyses, and the type of calculation code that supports them.

As regards the certification effort for international software presently in use in the Ukraine, the number of codes that would initially have to be subjected to the process does not seem excessively large. An initial estimate is that there would be some two international codes for each field of application. The validation of the calculation models would probably be of prime importance in the process.

The work procedures currently used in the Ukraine are comparable to those used in the West. International guides and recommendations should be progressively replaced by National Regulations.

TASK 4: REQUIREMENTS, CRITERIA AND PROCEDURES OF THE UKRAINIAN CODE CERTIFICATION SYSTEM

The purpose of this task was to assist in the preparation of requirements, criteria and procedures for a national code verification, qualification and certification system The methodology used for this purpose was the development of pilot procedures for each code of the proposed areas (RELAP, CONTAIN, HEXTRAN and ABAQUS codes).

The sub-tasks were identified as in the following:

1. General aspects

1.1 Description of the code, classification

1.1.1 Description of the code, origin

1.1.2 Safety-related classification

1.1.3 Verification and Validation Class

1.2 Safety-related code applications in Ukraine

1.2.1 Licensing applications

1.2.2 Best-estimate applications

1.3 Reasons for Verification and Validation

1.4 Scope and objectives for the level of Verification and Validation selected

1.5 Development products to be used for the review

1.6 Developer channel information

1.7 Availability and use of user experience

2. Verification and validation review plan

2.1 Review Team: Organisation and responsibilities

2.2 Review activity description

3. Validation requirements

3.1 General Code Requirements

3.1.1 Class of problems

3.1.2 Physical phenomena involved

3.1.3 Mathematical model

3.1.4 Solution algorithms

3.1.5 Program range

3.1.6 Auxiliary codes

3.1.7 User environment

3.2 Program Design

3.2.1 Design Specification

3.2.2 Source Code

3.3 Software Assurance Applicability (SAA)

3.3.1 Ukrainian NPPs specific phenomenology

3.3.2 Covered and uncovered phenomena identification

3.3.3 Scenarios and phenomenology range validation

3.4 Software Quality Assurance (SQA)

3.4.1 Developer Quality Assurance Scope

3.4.2 Code Quality Assurance Organisation

3.4.3 Code Maintenance

3.4.4 Configuration Management

3.4.4.1 Baseline Version

3.4.4.2 Revision Release

4. Test coverage

4.1 Developer tests

4.1.1 Testing objectives

4.1.2 Testing conventions

4.1.3 Testing levels

4.1.4 Independent testing

4.1.5 Tests planning

4.1.6 Test implementation

4.1.7 Test documentation

4.2 User tests

4.2.1 International Standard Problems

4.2.2 Documented experiences

4.2.3 Ukrainian experiences

4.3 Evaluation and applicability of tests results

4.4 Additional tests to be performed

5. Validation state

5.1 Validation criteria

5.2 Code accomplishment with the validation criteria

5.3 Validation scope

6. Validation conclusions

TASK 5: WORK PLAN FOR FUTURE ACTIVITIES

The objective of the task was to identify problems to be solved in the future and to propose work plans for future activities. The activities proposed took into account the conclusions of the tasks performed during this project, basically, the conclusions of Task 3 on the needs and objectives of a code certification system. The proposed activities were discussed with the Ukrainian NRA and the Scientific Technical Centre (STC).

Comments

(quality of the results, lesson learnt, recommendations for follow-up)

The following general activities have been identified for the future development and follow-up of a national certification system:

• Specific Objectives of a Code Certification System: this analysis will result in a clear identification of the main goals of the Ukrainian Code Certification System.
• Computer Codes And Application Fields Selection: a detailed list of computer codes to be certified should be prepared and the fields of application of these codes clearly identified.
• Identification of Priorities And Needs: since all codes cannot be certified at the same time, some priorities should be established to ensure a detailed planning of the different steps of the code certification system.
• Software Management Procedure: the objective of this item is to regulate and standardise activities involved in the reception and control of the different code versions for the validation/certification process.
• Assisting in the Application of Certification of one or Several Codes: this item implies a specific application of the certification process, starting from the procedures developed in the project.