PARAMETRIC STUDY OF THE STEADY-STATE OPERATIONAL CHARACTERISTICS OF THE OHIO-STATE-UNIVERSITY NATURAL CIRCULATION, INDIRECT-CYCLE, INHERENTLY SAFE BOILING WATER-REACTOR

The Ohio State University Inherently Safe Reactor (OS U-ISR) is a conc eptual design for a 340-MW(electric) [1000-MW(thermal)] natural circul ation, indirect-cycle, small boiling water reactor. Ah the OSU-ISR pri mary loop components are housed within a prestressed concrete reactor vessel (PCRV). The OSU-ISR performance has been investigated as a func tion of several design parameters in an attempt to better understand t he interdependency among the system variables and hence to establish a knowledge base for the refinement of the conceptual design. The compu tational tool used in the study is a Dynamic Simulation for Nuclear Po wer Plants (DSNP) code whose predictions for the steady-state OSU-ISR performance compare favorably with RELAP5/MOD3 results for most of the operational characteristics of interest. The results show that (a) th e key quantity that governs the OSU-ISR steady-state performance is th e pressure difference between the primary and the secondary loops, (b) the magnitude of water-level swell (which occurs due to void formatio n in the core during operation and which affects the size of the steam separators that need to be used) can be more effectively controlled b y varying the PCRV water level at cold shutdown rather than by varying the infernal PCRV dimensions, (c) turbine inlet steam quality can be controlled without substantially affecting the other operational param eters by varying the secondary mass flow rate, and (d) the PCRV pressu re and core exit steam quality are most sensitive to changes in the se condary loop pressure. The results also show that if there is a large drop in the secondary loop pressure (e.g., due to a steam line break), then although this pressure drop may induce a large drop in the PCRV pressure, the core flow, and hence core cooling capability, will not b e appreciably affected.