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Mitigation of an ATWS using the fine motion control rod system of the simplified boiling water reactor

Book ·
OSTI ID:438866
; ;  [1]
  1. Brookhaven National Lab., Upton, NY (United States)
The present study focuses on the ATWS event for the loss of feedwater heater, and the consequent shutdown with the Fine-Motion-Control-Rod (FMCRD) system assuming the normal shutdown system of the reactor is not available. The analysis tool is the detailed best estimate code RAMONA-4B with 3D neutron kinetics and non-equilibrium thermal-hydraulics with drift flux model. The reactivity feedbacks on power due to void fraction, moderator and fuel temperature are used to couple the neutronics results to thermal hydraulics calculations. Due to the negative void-reactivity feedback, loss of feedwater heating is accompanied by an increase in reactor power. The fission power is found to increase by 16% due to increase in core inlet subcooling from 10.1 C to 17.5 C. A gradual peaking of power in the lower part of the core is observed due to a lower void fraction in this region. A second transient has been initiated by slow insertion of the FMCRD at 80 seconds. According to the prediction of RAMONA-4B, the FMCRD system is found to shut down the reactor within 200 seconds from the initiation of the transient, in the absence of the normal scram system of the reactor.
Sponsoring Organization:
Nuclear Regulatory Commission, Washington, DC (United States)
OSTI ID:
438866
Report Number(s):
CONF-950828--; ISBN 0-7918-1715-6
Country of Publication:
United States
Language:
English