DIGITAL SIMULATION OF XENON INSTABILITY IN REACTORS

Technical Report · Wed Mar 01 04:00:00 EST 1961

OSTI ID:4074459

Barss, W M

A digital computer was made to simulate the behavior of a reactor by computing alternately a one-group twodimensional neutron flux distribution for a buckling dependent on the instanthneous xenon distrinution and a new xenon distribution. assuming that the flux remains unchanged for an interval of the order of 1 hr. Oscillations in these dis- . tributions may be induced. if they do not occur spontaneously. and the threshold for undamped oscillations may be predicted from the rates of growth or decay of oscillations produced under two or more sets of conditions. The oscillation threshold determined in this way for a uniform rectangular reactor was compared with the threshold determined analytically by a linearized perturbation method. The computer method has some advantages for simuiating arbitrary spatial variations in the fission yield of xenon and in the buckling in both core and reflector. and for portraying local flux disturbances due to fuel changes. Computing time was reduced by exciting an oscillation free of higher modes and by calcuiating the xenon distribution at intervals of about three times the xenon relaxation time. then correcting the apparent oscillation decay constant for the flnite interval. For a 100-point mesh. a decay consthnt determination requires about 45 minutes on the Dathtron computer. The computer method was used to predict the behnvior of the CANDU power reactor. as a check on earlier analytical studies. This reactor. which uses natural uranium oxide fuel with heavy water as both moderator and primary coolant. is designed for a thermal power output of approximately 700 MW. The results indicated that xenon instability would be an operating problem if the reactor were not stabilized by the power coefficient of reactivity: this coefficient is negative for CANDU because the low thermal conductivity of the oxide leads to high fuel temperatures at which the Doppler effect is predominant. (auth)

• Research Organization: Atomic Energy of Canada Ltd., Chalk River, Ont.
• NSA Number: NSA-15-020322
• OSTI ID: 4074459
• Report Number(s): CRRP-1002; AECL-1226
• Country of Publication: Canada
• Language: English

Related Subjects

ANALOG SYSTEMS
BUCKLING
CANDU
COMPUTERS
DECAY
DISTRIBUTION
EQUATIONS
FISSION
GROUP THEORY
HEAVY WATER COOLANT
HEAVY WATER MODERATOR
HIGH TEMPERATURE
NATURAL URANIUM FUEL
NEUTRON FLUX
OPERATION
OSCILLATIONS
PERTURBATION THEORY
POWER
REACTIVITY
REACTOR CORE
REACTOR TECHNOLOGY
REACTORS
REFLECTORS
SPECTRAL SHIFT
STABILITY
THERMAL CONDUCTIVITY
URANIUM DIOXIDE
VARIATIONS
XENON