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Reinforcement of Nuclear Safety Authorities.

Reinforcement of Nuclear Safety Authorities.


In July 1991, the Commission of the European Communities (CEC) instituted a Six Months Emergency Action Programme for Bulgaria under the PHARE regional nuclear safety programme. consisting of three parts :

  • an industrial emergency programme supporting the utility of the Kozloduy NPP
  • technical assistance for reinforcement of the Bulgarian Nuclear Safety Authority (BNSA).
    Based on the safety assessment of the design and of construction and control rules used for the mechanical equipment, and also on the review of corresponding operating experience, the Consortium concluded that the integrity of the pressurised components and piping that safe operation can only be supported by careful periodical material testing and inspection.
    The Consortium identified a certain number of deficiencies, some of which have already been identified by the IAEA. Among the conclusions of the Consortium on systems deficiencies, it is possible to point out following weak points:
    • insufficient scram signals,
    • possibility to inhibit scram signal,
    • safe operation of safety systems is not warranted under accidental environmental conditions,
    • automatic back-up of safety systems is not sufficient,
    • lack of protection against cold overpressurization exists,
    • inadequate means to identify ruptured steam generator tubes,
    • diesel generator capacity seems to be low.


    • internal floodings,
    • missiles and falls of heavy loads.


    • trains of safety systems are installed,
    • qualification of utilised lire retardant coating is not proved,
    • fire resistant separation of the turbine hall from adjacent buildings is insufficient,
    • Outage programme regarding design deficiencies
      As strict appliance of Western rules would require large-scale reconstruction of safety systems and even adding new ones, the analysis of the outage programme was performed under the basic assumption that time of operation is limited. Based on the conventional list of transients and accidents used in Western countries, on international operational experience and on Western completed PSA studies, the orientation of the action was as follows:
      • for the most probable events, to improve the systems in normal operation and the safety systems associated with these accidents in order to mitigate their consequences,
      • On this basis, for each particular point of the programme, this review has led the Consortium to generally confirm the actions proposed by the utility. In some cases, however, changes of priorities or explanation on determination of the actions have been requested. Finally, in few cases, new items have been added to the programme.
        • for core decay heat removal, investigate EFWS redundancy by another system and implement feed and bleed,
        • investigate the insufficient qualification of equipment (I&C transmitters located in the transmitter room, pumps in the boron room, ...) and define, if necessary compensatory measures.

        The analysis took into account the negative points, but also includes the positive points of the current design of these units. However, positive aspects of the installation cannot contribute to improvement of safety unless the equipment installed is reliable, available and is operated in correct conditions. This is why the Consortium considers that safety system analysis must be accompanied by decisive action by the utility to improve management, requalification, operation, maintenance and periodic tests of the systems. Consequent improvements in those fields must be shown by the utility before restarting.
        Recommendations made in the field of operation have short term as well as longer term objectives. The short term objectives, which require urgent attention are:

        • systematic application of the restoration methodology defined within the utility and checking results after implementation,
        • clear definition of responsibilities within the standing organisation of the NPP,
        • installation of a Nuclear Safety Review Committee at the NPP to examine nuclear safety aspects including the safety assessment of operational events and proposed modifications to the plant,
        • improved operational guidelines for normal and emergency operation,
        • For operational aspects, these requirements set minimum conditions under which the plant could be operated. Longer term objectives are:
          • setting up and implementation of a quality assurance programme and procedures,
          • achievement of an adequate working operation experience feedback mechanism,
          • Regulatory matters
            • improvements in the organisation and increased staffing of the regulatory body,
            • improvements in the training of inspectors and in their working methods and conditions.

            Beneficiary Organization Details

            Nuclear Regulatory Agency (Bulgaria)
            Project Aims
            The main objective of the project was to support the establishment of Nuclear Regulatory Agency in Bulgaria familiar with the Western European regulatory practices and procedures. The project aimed at transfer of initial knowledge in licensing procedures, safety assessment techniques and inspection practices. This was the first project to initiate the support provided to Bulgarian Regulatory Agency under further Phare projects.
            Project Results
            The project has been completed according to the specified Terms of references.
            Further Project Results
            Further information on the project results could be sought from the beneficiary organizations.

General Information

Reinforcement of Nuclear Safety Authorities.
Budget year: 
Types of activities: 
Regulatory Authorities
Installation types: 
VVER-440/230 + 1000
Duration (months): 
IRSN (Institut de Radioprotection et de Surete Nucleaire)
Old reference: 
Effective contract date: 
Closure date: