Gateway for:

Member Countries

Fission Products Release from Heated Fuel


Investigation of Fission Products Release from Uranium Dioxide at Heat up Under Oxidizing and Reducing Media. VERONIKA Project.

Tech Area / Field

  • FIR-NSS/Nuclear Safety and Safeguarding/Fission Reactors

3 Approved without Funding

Registration date

Leading Institute
NIIAR (Atomic Reactors), Russia, Ulianovsk reg., Dimitrovgrad

Supporting institutes

  • Nuclear Safety Institute, Russia, Moscow


  • Gesellschaft für Anlagen und Reaktorsicherheit mbH, Germany, Köln\nEuropean Commission / Joint Research Center / Institute for Transuranium Elements, Germany, Karlsruhe\nForschungszentrum Karlsruhe GmbH, Germany, Karlsruhe\nHungarian Academy of Sciences / KFKI Atomic Energy Research Institute, Hungary, Budapest\nCEA / Institut de Radioprotection et de Surete Nucleaire, France, Saint-Paul-lez-Durance

Project summary

At present, one of the urgent tasks solved in the frame of the VVER safety justification is the development of a calculation code for fission products (FP) release and high-burnup fuel degradation under the beyond the design-basis accident. To solve this task, a vast program should be implemented, including numerous experiments on FP release and calculated simulation. The beyond the design-basis accident conditions are characterized by a wide range of changes of external parameters (temperature, oxygen potential of the gas medium, pressure) that causes complexity and variety of processes determining the FP release and fuel degradation. A high cost and laboriousness of experiments make it practically impossible for a single country to justify the work safety and thus, require joint efforts.

The proposed Project is aimed at the investigation of the FP release behavior, including short-lived ones, from highly irradiated uranium dioxide pellets under annealing at temperature up to 2200°С in various oxidizing and reducing media. The obtained data will be used for the development and validation of a calculation code to simulate FP release from uranium dioxide under the beyond the design-basis accident.

RIAR has more than 40-year experience in investigation of irradiated VVER-type fuel. For this purpose, there are several research reactors to irradiate materials and up-to-date material testing complex for post-irradiation examinations, where the whole scope of work under this Project can be performed. During the last ten years, IBRAE specialists, including the project participants, in cooperation with IRSN (Cadarache, France) have been developing a detailed mechanistic code MFPR to simulate FP release from uranium dioxide under the PWR and VVER accident conditions.

The specialists involved in this work are very experienced in the implementation of large-scale projects on reactor material science. Many of them are well known both in Russia and abroad. Their integration in the international community will contribute to the mutual understanding between scientists from different countries. The implementation of this project allows weapon specialists to re-orient their capabilities to peaceful activities. Besides, the Project work will be performed at unique facilities and with unique devices and tools, including remote controlled ones, that will allow the experimental base of the Institute to be involved both into the peaceful research in the field of nuclear power engineering and in solving of fundamental tasks of radiation damage of nuclear fuel.

The Project provides the following scope of work:

  1. Development of a facility to study FP release from irradiated uranium dioxide heated up to 2200°С in different gas media.
  2. Selection of samples from high burnup VVER fuel rods and their preparation for additional irradiation.
  3. Additional irradiation of samples in the RBT-6 reactor to accumulate short-lived FP in the samples.
  4. Preparation of the samples for testing at the facility. Examination of the samples.
  5. Testing of the samples at the test facility.
  6. Material science examinations of the samples.
  7. Improvement of the MFPR code physical models describing the FP behavior in the crystalline lattice and verification of the calculation results.
  8. Modification of the MFPR code on the basis of the obtained experimental data.

This Project will results in the development of reliable physical models and calculation codes able to describe the FP behavior in the uranium dioxide matrix and their release to the containment under high temperatures and wide range of environments (different steam concentration, H presence). These results are necessary to assess the radiation risk, to develop measures to prevent the FP release from the containment and thus, to increase the NPP safety.


The International Science and Technology Center (ISTC) is an intergovernmental organization connecting scientists from Kazakhstan, Armenia, Tajikistan, Kyrgyzstan, and Georgia with their peers and research organizations in the EU, Japan, Republic of Korea, Norway and the United States.


ISTC facilitates international science projects and assists the global scientific and business community to source and engage with CIS and Georgian institutes that develop or possess an excellence of scientific know-how.

Promotional Material

Значимы проект

See ISTC's new Promotional video view