On-line Generation of Three-Dimensional Core Power Distribution Using Incore Detector Signals to Monitor Safety Limits

  • Published : 2004.12.01

Abstract

It is essential in commercial reactors that the safety limits imposed on the fuel pellets and fuel clad barriers, such as the linear power density (LPD) and the departure from nucleate boiling ratio (DNBR), are not violated during reactor operations. In order to accurately monitor the safety limits of current reactor states, a detailed three-dimensional (3D) core power distribution should be estimated from the in-core detector signals. In this paper, we propose a calculation methodology for detailed 3D core power distribution, using in-core detector signals and core monitoring constants such as the 3D Coupling Coefficients (3DCC), node power fraction, and pin-to-node factors. Also, the calculation method for several core safety parameters is introduced. The core monitoring constants for the real core state are promptly provided by the core design code and on-line MASTER (Multi-purpose Analyzer for Static and Transient Effects of Reactors), coupled with the core monitoring program. through the plant computer, core state variables, which include reactor thermal power, control rod bank position, boron concentration, inlet moderator temperature, and flow rate, are supplied as input data for MASTER. MASTER performs the core calculation based on the neutron balance equation and generates several core monitoring constants corresponding to the real core state in addition to the expected core power distribution. The accuracy of the developed method is verified through a comparison with the current CECOR method. Because in all the verification calculation cases the proposed method shows a more conservative value than the best estimated value and a less conservative one than the current CECOR and COLSS methods, it is also confirmed that this method secures a greater operating margin through the simulation of the YGN-3 Cycle-1 core from the viewpoint of the power peaking factor for the LPD and the pseudo hot pin axial power distribution for the DNBR calculation.

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References

  1. Final Safety Analysis Report for YGN Unit 3 & 4, Korea Electric Power Company
  2. W. B. Terney, J. L. Biffer, C. O. Dechand, A. Josson, and R. M. Versluis, 'The C-E CECOR Fixed In-core Detector Analysis System,' Trans. Am. Nucl. Soc. 44, 542 (1983)
  3. 'Overview Description of the Core Operation Limit Supervisory System (COLSS),' CEN-312-P, Revision 01-P, .ABB Combustion Engineering Inc, Nov. 1986
  4. Final Safety Analysis Report for Wolsung Unit 1, Korea Electric Power Company
  5. Tang, T. L., et al., 'Analytical Design of the CANDU-600 On-line Flux Mapping System,' TDAI-152, Atomic Energy of Canada Limited (1978)
  6. B. G. Kim, 'Core Simulations Using Actual Detector Readings for CANDU Reactors', Ph.D. Thesis, Korea Advanced Institute of Science and Technology (1991)
  7. Charles F. Karlson, 'Continuing Advancements in In-core Power Distribution Measurement Methods Using SIMULATE-3 and CECOR 3.4,' Nucl. Sci. Eng., 121, pp.57-66 (1995) https://doi.org/10.13182/NSE95-A24129
  8. Raymond J. Webb and James C. Brittingham, 'Comparison of CECOR Algorithm to Lagrange Multiplier Method to Estimate Reactor Power Distributions,' Nuclear Technology, Vol. 132, pp. 206-213, (2000) https://doi.org/10.13182/NT00-A3139
  9. P. S. W. Chan, 'The Application of Advancements in Computer Technology to the Control and Safety Systems of CANDU Reactors,' The 7th KAIF/KNS Joint Annual Conference, Seoul, Korea, April 21-23, 1992
  10. Eun Ki Lee, Chang Hyo Kim, and Geun-Sun Auh, 'Feasibility Study for Improved Power Distribution Monitoring Program Development in PWRs,' Trans. Am. Nucl. Soc., Vol. 72, pp. 322-324 (June 1995)
  11. L. R. Pogosbekyan and D. A. Lysov, 'Quasi Solution of Radiation Transport Equation,' Nucl. Sci. Eng., 121, pp. 345-351 (1995) https://doi.org/10.13182/NSE95-A28570
  12. Byung-Oh Cho et. aI., 'Development of the Integrated Core On-line Monitoring and Protection Aid Surveillance System,' Proceedings of the Korean Nuclear Society Fall Meeting, Seoul Korea (October 1998)
  13. Kibog Lee and Chang Hyo Kim, 'The Least-Squares Method for Three-Dimensional Core Power Distribution Monitoring in Pressurized Water Reactors,' Nucl. Sci. Eng., 143, pp. 268-280 (2003) https://doi.org/10.13182/NSE03-A2335
  14. Byung-Oh Cho et. aI., 'MASTER: Reactor Core Design and Analysis Code,' Proceedings of PHYSOR 2002, Seoul Korea (October 2002)