Fission Product Release from Fuel under Severe Accident Conditions

1993 ◽  
Vol 101 (3) ◽  
pp. 270-281 ◽  
Author(s):  
Richard R. Hobbins ◽  
David A. Petti ◽  
Donald L. Hagrman
2007 ◽  
Vol 44 (11) ◽  
pp. 1428-1435 ◽  
Author(s):  
Tamotsu KUDO ◽  
Mitsuko KIDA ◽  
Takehiko NAKAMURA ◽  
Fumihisa NAGASE ◽  
Toyoshi FUKETA

Author(s):  
Klaus Mueller ◽  
Moses Yeung ◽  
Justin Byard ◽  
Zhen Xun Peng ◽  
Jun Tao ◽  
...  

The behavior of the spent fuel pool and the fission product release and transport for the CPR1000 reactor under severe accident conditions was analyzed using the integral severe accident code MELCOR. In the investigated accident scenario a total failure of the pump of the spent fuel cooling system was assumed. Furthermore, it is assumed that accident management fails to bring water into the spent fuel pool using mobile pumps or due to the non-recovery of the cooling pump. The grace time available for measures in order to avoid significant fission product release to the environment is determined. The calculated hydrogen mass flow rate due to clad oxidation and the steam flow rate from the spent fuel pool to the compartment above the spent fuel pool serve as boundary conditions for the three dimensional fluid dynamics code GASFLOW to assess possible hydrogen combustion or detonation in the compartment. Using this spent fuel pool MELCOR model the dose submerged in air or water can be determined. The calculated gamma dose rate in a specific compartment can be used for equipment qualification and compartment accessibility assessment. It was found that after four days the fuel assemblies are significantly heated-up and ten hours later the fission products are released as well as a significant amount of hydrogen is produced. A preliminary GASFLOW analysis shows by assuming an air atmosphere in the fuel building, that the risk of a hydrogen combustion or detonation is high. In late state of the accident a convection flow of pure hydrogen is established in spent fuel pool region. It was shown, that the flow conditions strongly influence the fission product transport behavior and consequently the dose rates in the compartment above the spent fuel pool.


Author(s):  
T. Kanzleiter ◽  
G. Poss ◽  
F. Funke ◽  
H.-J. Allelein

The THAI experimental programme includes combined-effect investigations on thermal hydraulics, hydrogen, and fission product (iodine and aerosols) behaviour in LWR containments under severe accident conditions. An overview on the experiments performed up to now and on the future test program is presented, in combination with a selection of typical results to illustrate the versatility of the test facility and the broad variety of topics investigated.


Author(s):  
Karl Verfondern ◽  
Heinz Nabielek

Various countries engaged in the development and fabrication of modern fuel for the High Temperature Gas-Cooled Reactor (HTGR) have initiated activities of modeling the fuel and fission product release behavior with the aim of predicting the fuel performance under operating and accidental conditions of future HTGRs. Within the IAEA directed Coordinated Research Project CRP6 on “Advances in HTGR Fuel Technology Development” active since 2002, the 13 participating Member States have agreed upon benchmark studies on fuel performance during normal operation and under accident conditions. While the former has been completed in the meantime, the focus is now on the extension of the national code developments to become applicable to core heatup accident conditions. These activities are supported by the fact that core heatup simulation experiments have been resumed recently providing new, highly valuable data. Work on accident performance will be — similar to the normal operation benchmark — consisting of three essential parts comprising both code verification that establishes the correspondence of code work with the underlying physical, chemical and mathematical laws, and code validation that establishes reasonable agreement with the existing experimental data base, but including also predictive calculations for future heating tests and/or reactor concepts. The paper will describe the cases to be studied and the calculational results obtained with the German computer model FRESCO. Among the benchmark cases in consideration are tests which were most recently conducted in the new heating facility KUEFA. Therefore this study will also re-open the discussion and analysis of both the validity of diffusion models and the transport data of the principal fission product species in the HTGR fuel materials as essential input data for the codes.


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