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The Russian-designed PWR model VVER1000/V320 has four coolant loops with horizontal steam generators. For PCTRAN we model one single loop with the pressurizer at left and the remaining three loops combined at right.
The core thermal power is 3000 MW. Nominal full power hot leg temperature is 320ºC and cold leg is 290ºC. The primary pressure is 155 bar and steam generator secondary is 63 bar. The feedwater flow is each SG is 1480 t/h (411 kg/s).
PCTRAN-VVER/320 model has been prepared to benchmark the RELAP5 YR Line paper:
Note in the PCTRAN mimic above the reactor vessel head there is a YR off-gas vent line. After a total loss of feedwater (TLFW) event, the Bulgarian study concluded that opening the YR line prior to the reactor coolant saturation could prevent core damage. In the paper there are:
We have successfully benchmarked these four cases in high fidelity. The phenomena of SG inventory depletion, primary coolant over-heat to saturation, PORV lifts and cycling, RC inventory depletion through the PORV, venting via the YR line, etc. were not only reproduced, but also the key transient variables in numerical accuracy.
It proves PCTRAN/VVER-1000 to be a highly sophisticated simulation tool for severe accidents.
Upon successful installation of the PCTRAN PWR Severe Accident Module, clicking at “Run” will start a run. For LOCA without ECCS will lead to core melt and containment failure. Click “View” and “Dose will give you another view of the core and dose release configuration.
By going into “Restart” and choose other “Initial Conditions” you may observe the plant at various stages of degraded conditions. There is even one for hydrogen burn. You may also activate any mitigation devices such as ECCS, PORV, containment spray, SG PORV, AFW, etc. and witness their impact and consequences.
For the SAMG event, both trains of ECCS were assumed to run for maximum rate of depletion of the RWST. At about 1000 seconds after the double-ended break, recirculation from the sump was assumed to be lost. The core subsequently became uncovered, melt, collapsed and eventually debris penetrated the vessel. The degraded core mimic is shown below:
