ANALYSIS OF WNP-2 SINGLE-LOOP OPERATION USING RETRAN-02

A limiting transient under single-loop operation (SLO) conditions was analyzed to establish the analytical capability to support SLO for Was hington Public Power Supply System's WNP-2. In the WNP-2 RETRAN model, each of the two recirculation loops is simulated separately. Under th e SLO condition, the unaffected loop provides similar to 50% core flow with a power of similar to 72%. Two steady-state cases were run using actual plant data under single-loop conditions to show that the model initializes correctly. The plant data were collected from the cycle 2 SLO. An additional benchmark was performed using the single-recircula tion-pump test data collected during the power ascension test in the i nitial startup phase of WNP-2. The calculated reverse flow of the idle loop compared well with the measured data from the single recirculati on pump trip test. After the benchmarking, a limiting transient, i.e., generator load rejection without bypass, tvas analyzed for cycle 8. T he resulting power, flow and pressure histories were compared with the fuel supplier's results. The Supply System results for the limiting t ransient showed reasonably good comparison with the fuel supplier's re sults, with the Supply System model yielding more conservative results . In addition, hot-channel analyses indicate that the SLO thermal limi ts are bounded by those from the two-loop operations.