An experimental evaluation of the instrumented flux synthesis method for the real-time estimation of reactivity. Final report

Technical Report · Mon Jan 01 04:00:00 EST 1996

DOI:https://doi.org/10.2172/167217· OSTI ID:167217

Hughes, J C; Henry, A F; Lanning, D D; Bernard, J A

One method of determining the flux density is flux synthesis which approximates the flux in the core by linear combinations of precomputed shape functions. In traditional flux synthesis, the unknown mixing coefficients are determined using a weighted residual method of solving the diffusion equation. In the instrumented synthesis method, the mixing coefficients are determined using count rates from neutron detectors in the core. In this way the mixing coefficients are linked to conditions in the reactor. Using the synthesized flux, kinetics parameters, notably reactivity, can be calculated in real time. An experimental evaluation has been performed in the Massachusetts Institute of Technology Reactor, MITR-II. Detector measurements have been collected using fission chambers placed at the periphery of the core. The reactor was put into a number of various conditions, both static and transient, and data were collected using a digital acquisition system for later combination with shape functions. Transients included increasing power, decreasing power, and a reactor scram. The shape functions were generated using Version 3.0 of the QUARTZ code, a quadratic nodal diffusion theory code in triangular-Z geometry. Supernodal analysis algorithms have been added to the original program, along with subroutines to guarantee diagonal dominance of the leakage matrix in the finite difference or quadratic current approximations in the coarse mesh. The agreement between coarse mesh and fine mesh in all cases is excellent, with finite difference coarse mesh solutions generally slightly better. The synthesis method has been shown to accurately reflect the changes from an initial condition by combining representative flux shapes. It can be concluded that, with proper calibration of the measurement system and inclusion of representative flux shapes, the instrumented synthesis method will properly predict the flux in the core under a number of conditions.

• Research Organization: Massachusetts Inst. of Tech., Cambridge, MA (United States). Nuclear Reactor Lab.
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: FG02-92ER75710
• OSTI ID: 167217
• Report Number(s): DOE/ER/75710--T1; ON: DE96004078
• Country of Publication: United States
• Language: English

Related Subjects

22 GENERAL STUDIES OF NUCLEAR REACTORS
44 INSTRUMENTATION
INCLUDING NUCLEAR AND PARTICLE DETECTORS
CALCULATION METHODS
DIAGRAMS
EXPERIMENTAL DATA
FLUX DENSITY
FLUX SYNTHESIS
MITR REACTOR
Q CODES
REACTIVITY
REACTORS