Regional Basic Professional Training Course in Korea

❙ 541 ❙
8-B. Deterministic Accident Analysis (LOCA)
The CEFLASH‐4AS code was one of the version of CEFLASH‐4A used for LBLOCA
analysis. The code simulates Nuclear Steam Supply System (NSSS) by number of
volumes and flow paths and solves conservation equations of mass and energy and
determine pressure using the equation of state with assuming the thermodynamic
equilibrium at each volume. The momentum equations are solved assuming the
homogeneous and thermodynamic equilibrium at each flow path which links volume to
volume.
The major features of CEFLASH‐4AS are:
(1) Non‐homogeous node and path
(2) Variable area of reactor core volumes and pths
(3) SBLOCA specific heat transfer model at the core
(4) SG heat transfer dependent on water level
(5) Neglecting the momentum flux term of momentum equation
(6) Neglecting the terms of potential energy and kinetic energy
(7) Two‐phase pump performance model
The CEFLASH‐4AS code has additional SBLOCA‐specific models such as phase
separation model, liquid entrainment model at loop seal, etc. The code and the associated
methodology was approved to conform with the requirements in Appendix K to 10 CFR
50.
The descriptions of other codes that are used in SBLOCA analysis, STRIKIN‐II,
COMPERC‐II and PARCH are the same as the LBLOCA.
Table 8.8‐1 shows the result from SBLOCA Break Spectrum analysis of Ulchin Units 5
and 6. Pump discharge pipe breaks ranging 0.02 ~ 0.5 ft 2 were calculated and 0.3 ft 2 hot