Transient Simulations
Selection of a transient is menu-driven that includes all possible disturbances to a plant such as:
• Normal operation control - startup, shutdown, power ramp
• Loss-of-coolant-accident (LOCA) or steamline break
• Loss of flow, single or two-phase natural circulation
• Turbine trip with or with bypass, station blackout
• Steam generator tube rupture (PWR)
• Feedwater transients
• Anticipated transient without scram (ATWS)
• Damage to containment or spent fuel storage facility (for example, caused by airplane crash)
Intentional sabotage by terrorist group to cause a reactivity event, fire or loss of diesel
• Any combination of above
Severe Accident Model
The core is modeled into six vertical nodes. Each one will generate a portion of the decay heat. When the boundary heat removal rate is less than the core heat, the core node is heated up to the point of melting. Molten fuel may collapse into the bottom of the vessel. The vessel lower head may then heat up to the melting point, too. The molten debris may drop into the containment cavity floor. During the fuel damage process, first the fission gas in the clad may leak out. Later if the fuel and cladding continue their degradation, fuel isotopes will release also. In addition to iodine and noble gases, there are alkali metals, tellurium, barium, cerium, lanthanides, etc. The elevated concentration of these radioactive isotopes would find their ways through the vessel break, relief valves, and containment leakage into the environment.
PCTRAN is most powerful in its versatile and interactive control. The user can at any time manually trip the reactor or the pumps, open or close a relief valve, override the ECCS or change the set points for a number of the control systems. All transient parameters are available for trending during execution or printed after the run. The data can be saved in Access or Excel files for later usage. The restart capability can virtually extend a transient simulation to indefinite time period.
RMS Source Term & Area Dose Projection
Available as an option, the extended simulation model keeps track of fission product transport along the major release pathways. Normal and accident condition readings of major area, effluent, and process radiation monitors throughout the plant are displayed in a separate mimic. Iodine, noble gases and other fission products based on Regulatory Guide 1.183 Revised Source Terms are calculated periodically. Plume or puff release is then projected for variable wind speed and stability factors in the Emergency Planning Zone.
Available Plant Models
MST has completed the following models in Windows:
• GE BWR 2 (Oyster Creek), 4 (Peach Bottom), 5 ( La Salle ), 6 (River Bend) and ABWR (Lungmen) with Mark I, II, III or advanced containment
• Westinghouse 2-loop ( Point Beach ), 3-loop (Turkey Point) and 4-loop ( Salem ) PWR dry containment or ice condenser containment (Sequoyah)
• Westinghouse AP1000
• C-E PWR's of 2x4 hot/cold loops (St Lucie and Fort Calhoun ), System 80+, Korean Advanced PWR
• B&W (now Areva) PWR's of once through steam generators (TMI)
• Framatome PWR's ( Guangdong ) or Areva EPR 1600
• ABB BWR's (TVO)
• Russian VVER-440 and 1000 of horizontal steam generators
