SARWUT- Safety Analysis Report  at Warsaw University of Technology

Grant Issued by National Center for Research and Development (NCBiR) in the field of reactor safety

  • National Center for Research and Development (NCBiR) is a state body that provides funding for research and development, especially ones that are focused on industrial applications.
  • Topic of a grant: Elaboration of methods for the safety analysis of PWRs and BWRs in case of disturbances in coolant system (SBLOCA, LBLOCA) and serious accidents. Codes: RELAP5, TRACE, MELCOR.
  • Grant Awarded
  • Project started October 3rd 2012
  • Duration Oct 2012 – August 2014


SARWUT – Project Description

  1. Description of the analysis methods with a full modeling of primary and secondary coolant loops in a PWR and primary coolant loop in a BWR.
  2. Preparation of a model data set to conduct the above analysis, including cases such as: changes in the amount of coolant in the primary coolant loop, partial loss of integrity of the primary coolant loop, loss of coolant accidents, reactivity transients and disturbances of heat removal in the secondary coolant loop.
  3. Perform calculations using the codes provided by the nuclear regulatory body (RELAP, TRACE, ASTEC) for the scenarios agreed by the nuclear regulatory body.
  4. The development of simplified calculation methods for application in simulators of PWRs and BWRs that are intended for training of operational staff.
  5. Undertake tasks concerning the validation of applied analysis methods in the scope agreed by the nuclear regulatory body.

SARWUT Project – Developing reactor models

The development of reactor models is a time consuming process and requires a a lot efforts and good understanding of the phenomena that occur in many reactor components / systems.


Nodalization of loop #1 of the primary side of the generic model of PWR 900 MWe in RELAP5.

For the analysis of the processes that take part in the primary side of the reactor, analyzing thermohydraulic processes, SARWUT Team is applying following calculation codes:

RELAP5 – Reactor Excursion and Leak Analysis Program, American code for reactor safety analysis

TRACE – TRAC/RELAP Advanced Computational Engine (TRACE), American reactor analysis code.SARWUT Team wants to increase its capability in reactor modeling, better understand the processes in the reactor components/systems. Therefore SARWUT Team started to apply French code.

CATHARE – le Code Avançé de THermohydraulique pour les Accidents sur les Reacteurs à Eau, French reactor analysis code


SARWUT Team has developed following reactor models:


Nodalization of the ABWR Reactor Pressure Vessel in RELAP5.


  • Generic PWR, 3-loop
  • Zion, PWR, 4-loop
  • ABWR model


  • Generic, PWR, 3-loop
  • EPR


  • BWR, Peach Bottom
  • Generic 3-loop



The development of reactor models for the analysis the severe accidents, that take into considerations reactor core meltdown, hydrogen production, transport of radioactive substances in the reactor containment and into environment.


Nodalization scheme of reactor pressure vessel in MELCOR code.

SARWUT Team is applying following calculation code:

MELCOR – American code for severe accident analysis.

SARWUT Team has developed following models:


  • Peach Bottom, BWR
  • Zion, PWR, 4-loop





SARWUT Team has developed EPR models using:

  • the documents published at US Nuclear Regulatory Comission and UK Nuclear Regulators
  • Comments and guides from AREVA

Some data cannot be transmitted to WUT due to prioprietary reasons. In many cases SARWUT Team has applied a scaling of the drawing to obtain all necessary dimensions.

SARWUT Team has analyzed EPR in 3 different codes:

  • RELAP5

Nodalization of primary side loop. Scaling performed by AutoCAD.

SARWUT Project – Accident modeling


LBLOCA: mass flow rate through the break, 112 from RPV side , 111 from SG side.

SARWUT Team has modeled following accident using thermohydraulic codes: RELAP5, TRACE , CATHARE:

  • Small break loss of coolant accident (SBLOCA)
  • Large break loss of coolant accident (LBLOCA)
  • Main steam line break (MSLB)
  • Steam Generator tube rupture (SGTR)

The methodology for these accidents have been created.




SARWUT Team is modeling the following severe accidents using MELCOR:

  • Core meltdown accidents


    Core meltdown accident, reactor type of Peach Bottom.
    5049 s: large core degredation, lower bottom of RPV is begining to break

  • Loss of offsite power
  • Station blackouts
  • Large radioactive releases

The methodology for these accidents have been created.