Massachusetts Institute of Technology Department of Nuclear Science and Engineering 22.06 Engineering of Nuclear Systems Dynamic Behavior of PWR 1PRISM Simulator Quick Reference Guide Accessing PRISM On the Desktop open (double click) ‘My Computer’ Open (double click) the c:\ drive Open (double click) the PRISM folder You will see a number of files, the following of which are the most important: PRISM.EXE - PRISM executable file needed to run the code PRISM.DAT - File of input data of initial conditions based on a four loop Westinghouse PWR PRISM.OUT - Output file of data of last run of PRISM.EXE PGRAPH.EXE - Graphing program which reads PRISM.OUT Initiate (double click) the PRISM.EXE file to run PRISM. Initial PRISM Input When entering PRISM you are presented with eight questions. For the first three questions, the default values are sufficient. For the number of loops, enter <4> for the reactor power enter 100% Choose the units with which you are most familiar. Finally, use the plant default data. As you become more familiar with the program you may want to alter these inputs later. Definitions and Acronyms The PRISM code is littered with shortened terminology and reactor specific nomenclature. To eliminate confusion, the following list is supplied from the Manual, with some additions: The NSSS View Screen NSSS stands for “Nuclear Steam Supply System”. The NSSS View screen will appear first after the TITLE screen (See Figure #2 in Appendix A). This screen provides a dynamic graphic mimic of the NSSS including the Reactor Coolant System (RCS) and steam generators. In addition, the following parameters are displayed: - FW Feedwater flow rate in kg/s or lbm/s 2- FL RCS loop flow rate in % of rated flow - HTR Pressurizer Control (P) and Backup Heaters (B) - L Pressurizer level in % - MWTH RCS thermal power in MW - NL Steam generator narrow-range level in % - P Steam generator or pressurizer pressure in MPa or psig - RXPWR Reactor power (fission power plus decay heat) in % of full power - SI Flow Safety Injection flow in kg/s or lbm/s - SPRY Pressurizer spray flow rate in kg/s or lbm/s - ST Steamline flow rate in kg/s or lbm/s - SUBCL RCS subcooling margin in degrees C or F - SURG Pressurizer in-surge flow rate in kg/s or lbm/s - TAVG RCS average temperature in degrees C or F - TC RCS cold leg temperature in degrees C or F - TFW Feedwater temperature in degrees C or F - TH RCS hot leg temperature in degrees C or F - TL Pressurizer liquid temperature in degrees C or F - TS Pressurizer saturation temperature in degrees C or F - TV Pressurizer vapor temperature in degrees C or F - VL Reactor vessel level in % - WL Steam generator wide-range level in % In the upper right-hand corner of the title menu bar, the current simulation time is displayed in “hours:minutes:seconds”. To the left of the simulation time, one of the following simulation statuses is displayed: - REAL This indicates that the simulation is running in real time - FAST This indicates that the simulation is in fast time: the simulation will progress as fast as the microprocessor can calculate - FREEZE This indicates that the simulation is frozen To the left of the simulation status the word ALARM will appear when an alarm condition exists. The alarms can be viewed on the ALARM PANEL screen discussed later in this chapter. 3OPERATIONAL TRANSIENTS Exercise 1: Approach to Criticality Objective Use PRISM simulator to verify the principles of subcritical reactor response and criticality approach: - Steady state subcritical multiplication count rate / Reactivity relationship (count rate doubling) - Identification of criticality Theory review Show N (neutron population) vs. t for the following 5 cases: 1) Critical reactor, no neutron sources 2) Supercritical reactor, no neutron sources 3) Subcritical reactor, no neutron sources 4) Subcritical reactor with neutron sources 5) Critical reactor with neutron sources Subcritical multiplication at steady-state (asymptotic values): N  S/(1-Keff) N1/N2  (1-K2)/(1-K1)  (-2)/(-1) S is the intensity of the neutron sources (e.g., Pu-Be, Pu-Ra). Why do we need neutron sources to start up? This equation also shows that if the distance to criticality is halved, the count rate is doubled. Show plot for K vs. t and N vs. t for approach to criticality. 4Set up PRISM as follows: 1. Start the program and enter initial and control parameters as follows: Total simulation time = 150 min. Accept (Y=return / N=No)? <ENTER> Time interval for hardcopy data = 60 sec. Accept (Y=return / N=No)? <ENTER> Time interval for screen data display = 1 sec. Accept (Y=return / N=No)? <ENTER> Enter number of RCS loops simulated (1 to 4): <1> Enter reactor power (HFP=100;HZP=0): <0> Select display units (0=SI;1=British): <0> Use default plant data. Accept (Y=return / N=No)? <ENTER> Are all input correct. Accept (Y=return / N=No)? <ENTER> 2. Silence PRISM alarms for exercise <d> 3. Select primary indications screen <F3> We will focus on the following four indicators on this page: “Source Range (SR) Power”, “Step” (in the Control Rod Drive panel), “Startup Rate”, “Net Reactivity”. 4. Record initial count rate from Source Range instrument Record initial control rod height (bank and steps) Record reactivity value 5. Shift to fast time <F9> 6. Pull control rods <UP cursor arrow> until negative reactivity is half of the value recorded in item 4. Record reactivity __________ 7. Wait until steady-state is achieved, then record count rate from Source Range instrument Record change in count rate (Item 7 – Item 4) Record control rod height (bank and steps) Compare count rates in Items 4 and 7. You should note that the count rate has doubled, in accordance with the theory. 58 Switch to Fast Time. Again pull control rods <UP cursor arrow> until negative reactivity is half of the value recorded in item 6. Record reactivity __________ 9. Wait until steady-state is achieved, then switch to real time, then record count rate from Source Range instrument Record change in count rate (Item 9 – Item 7) Record control rod height (bank and steps) Compare count rates in Items 7 and 9. You should note that the count rate has again doubled. 10. Final pull to, and recognition of, criticality. a. Place a small piece of opaque tape