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Partial MSLB accident: effect of larger pressurizer vapor region

cf rtvunsym_2a.dat (download)

Data changes | reference case rtvunsym_2.dat
v2p= 32.5 | 18.355 for ref.
v2p is adjusted to position the water level just above the level of pressu heater and thus considered as a minimum .
Results
Faster pressu voiding (chart 02, chart 11) is responsible for slight boiling in dome (chart 03), downstream the pump of loop2 (hsl2: chart 05) and in the "warm" sector of the core" (x2ckl2(1:20) chart 04).
Boiling occurs only during the (100,200) period.
Average x2ck and cold sector x2ckl1(1:20) (remains however well below 0 (x2ck(1:20): chart 04).

Curiously, the general power trend is modified (chart 01, chart 06).
In the (100,200) period, after a short q2c peak, the system variables hec (chart 05), p3 (chart 07), tln1 (chart 08) (fluid temp in sg1), remain quasi constant.

q2c level is lower, (400 Mw vs 750) for ref case, but the peak u2c7 (chart 09) remains about the same (740 K) because q2c lowering is compensated by the deformation of fci profile (chart 10).
Now u2c7 peaks occurs later than the q2c peak.

This case highlights the limitations of the separated flow model: in the return to power period (100, 200 s): boiling, which appears firstly in the warmest parts of the primary system, is propagated in the "warm" core sector whilst no boiling at all is observed in the cold sector (l=1) where most of the power should develop.
Actually, if boiling does appear first at the bottom of hot sector, this should have the effect of pushing both flow and power towards the cold sector and enhance radial flow mixing.