Safety Analysis

Deterministic Analyses

Risk Engineering Ltd. is one of the leading companies in Bulgaria in the field of deterministic analyses using thermal-hydraulic software products.

The company is licensed to perform thermal-hydraulic analyses using RELAP5 / MOD3.3, MELCOR 1.8.5 / 1.8.6 / 2.1 and RELAP5 / SCDAP / MOD3.4.

Extensive experience has been gained in the field of deterministic analyses for structures and components evaluation, as well as in mechanical strength analyses using the following software products.   SOLVIA, NISA, ALGOR and “PIPE PLUS”.

The main activities include:

  •  Design and engineering of pipelines of high risk sites subject to monitoring as perParagraph 35 of the Technical Requirements to the Product Act.
  •  Inspections of equipment and pipelines, residual lifetime assessment, design solutions analysis and hanger-support systems adjustment
  •  Strength analyses for static and dynamic loads of pipelines and equipment

Probabilistic Safety Analyses

Probabilistic Safety Analyses are very important and integral part of the documentation required for reactor installations licensing. With the aid of this type of analyses various objectives are achieved with safety assurance of the studied site being the most important.

The main purpose of PSA Level 1 is to obtain qualitative and quantitative evaluations of the systems reliability and technological site safety, taking into account both design characteristics and particular characteristics of operational practice and operating personnel actions.  PSA provides a comprehensive model of nuclear unit behavior and determines the most essential to safety factors and provides basis for decision making related to nuclear safety.

Our team has performed probabilistic safety analyses, level 1 of all Units at Kozloduy NPP, Zaporozhye NPP and Armenian NPP. The Company’s experts are engaged by the International Atomic Energy Agency for participation in independent inspections (IPSART review missions) of analyses performed by other companies of European and Asian Nuclear Power Plants.

PSA, Level 2 is an analysis, on the basis of which power unit’s response under severe accident conditions is evaluated (i.e. after fuel failure) and is a natural continuation of the PSA, Level 1. The other main task of this type of analyses is to assess the radiological consequences, which includes analysis of the possible mechanisms of radioactive fission product release, their composition, quantity and energy. In this sense, PSA, Level 2 is also a necessary precondition for development of PSA, Level 3, whose main task is to assess the consequences on the environment and the population (in particular the personnel) resulting from a potential severe accident.

What is specific about the application of PSA, Level 2 and Level 3 is that, based on these outcomes, both guidelines for severe accidents management and emergency plans for the respective site can be developed.

Risk Engineering Ltd. has independently developed several PSA, Level 2 projects with different scope for power plants in Bulgaria and abroad for VVER-440 and VVER-1000 reactors. Analyses performed for our clients include reactor installations response at full power, low power and shutdown.  Additionally, within the projects related to PSA applications, we have developed simplified models for evaluation of the frequency of large early radioactive releases.  When developing a project, the latest practices and results from various experiments are used. In this sense, the deterministic and probabilistic models developed by us reflect the latest internationally recognized practices.

All Services