3. DESCRIPTION OF PROGRAM OR FUNCTION
Restricted to the benchmark participants.
Oskarshamn-2 Nuclear Power Plant (Sweden, 1800 MW external loop BWR) experienced stability event on February 25, 1999. A loss of feed-water pre-heaters and control system logic failure resulted in a condition with a high feed-water flow and low feed-water temperature without reactor scram. In addition to the initiating event, an interaction of the automatic power and flow control system caused the plant to move into low flow – high power regime. Combination of above events culminated in diverging power oscillations which triggered automatic scram at high power.
The benchmark is based on the February 25, 1999 feed-water transient event. In addition, to increase the confidence on the codes’ and models’ performance, 5 linear stability measurements before the event and 5 linear stability measurements after the event are included in the benchmark. This benchmark defines a coupled code problem for further validation of thermal-hydraulics system codes for application to BWR stability based on actual plant data from the Oskarshamn-2 Nuclear Power Plant.
Phase 1: 1999 Event Analysis – model the Oskarshamn-2 feed-water transient which occurred on February 25, 1999
-Exercise 1.1: Plant system model initialization
-Exercise 1.2: 3D core model initialization
-Exercise 1.3: Coupled plant system/3-D core simulation
-Exercise 1.4: Sub-channel T/H evaluations (optional)
Phase 2: Analysis of Extreme Scenarios – challenge codes to the limits of their capabilities
-Exercise 2.1: Limit cycle for global instability
-Exercise 2.2: Limit cycle for regional instability
Phase 3: Blind Model Validation – BWR stability measurements, uncertainty analysis
-Exercise 3.1: Stability test decay ratio evaluation
-Exercise 3.2: Uncertainty analysis