Application of Statistical Correlation Techniques for Measurement of the Keff of Highly Subcritical Systems

  • S. B. Degweker
  • M. Srinivasan
  • K. K. Rasheed
  • C. S. Pasupathy


The possibility of measurement of the Keff of highly subcritical (0.4 < Keff < 0.8) systems by statistical correlation techniques is demonstrated. Measurements were carried out using three different techniques on the storage tank of the U-233 uranyl nitrate solution reactor PURNIMA II at Trombay. The first of these is an adaptation of the neutron coincidence counting technique familiar in passive assay of plutonium for safeguards applications. An equation relating the system Keff and the coincidence counts obtained using a shift register has been derived along the lines of Bonnels 1985 paper. The second technique is the so called Dead Time a (first moment) method. Here the loss in count rate measured following introduction of an artificial dead time in the pulse path is related to the kinetic parameters of the subcritical assembly. The complimentarity of these two techniques is pointed out. The third technique adopted is the well known Asymptotic Prompt Variance method of Feynman. In all these techniques it is shown that the subcritical reactivity [(1-Keff)/Keff)] is inversely proportional to a directly measurable quantity characteristic of the technique such as the real coincidence probability or the V/m ratio. The results of the three experiments with the storage tank filled up to maximum solution height as well as those of the shift register coincidence experiment spanning a Keff range of 0.4 to 0.8 are found to be in good agreement with Monte Carlo calculations.


Storage Tank Dead Time Uranyl Nitrate Spontaneous Fission Coincidence Count Rate 
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  1. 1.
    N. Pacilio, Reactor Noise Anaylysis in the Time Domain, USAEC Technical Monograph No. TID 24512 (1969)CrossRefGoogle Scholar
  2. 2.
    R. E. Uhring. Random Noise Techniques in Nuclear Reactor Systems, Ronald Press, New York (1970)Google Scholar
  3. 3.
    M. S. Krickand J. C. Swansen, Neutron Multiplicity and Multiplication Measurements, Nucl. Instr. Method 219, 384 (1984)CrossRefGoogle Scholar
  4. 4.
    M.S. Krick and H. O. Menlove, The High Level Neutron Coincidence Counter (HLNCC): Users Manual, Report LA-7779-M (1979)CrossRefGoogle Scholar
  5. 5.
    K. Bohnel, Die Plutoniumbestimmung in Kernbrennstoffen mit der Neutronenkoinzidenzmethode, Report KFK-2203 (1975)Google Scholar
  6. 6.
    R. Dierckx and W. Hage, Neutron Signal Multiplet Analysis for the Mass Determination of Spontaneous Fission Isotopes, Nucl. Sci.Engg. 85, 325, (1983)Google Scholar
  7. 7.
    K. Bohnel, The Effect of Multiplication on the Quantitative Determination of Spontaneously Fissioning Isotopes by Neutron Correlation Analysis, Nucl.Sci. and Engg. 90, 75 (1985)Google Scholar
  8. 8.
    M. Srinivasan, On the Measurement of by a simple dead time method, Nucleonik, 10, 224 (1967)Google Scholar
  9. 9.
    M. Srinivasan and D.C. Sahni, a Modified Statistical Technique for the Measurement of a in Fast Intermediate Reactor Assemblies, Nucleonik, 9, 155 (1967)Google Scholar
  10. 10.
    Huanquiao et al, The average Number of Prompt Neutrons and the Distribution of Prompt Neutrons and the Distribution of Prompt Neutron Number for spontaneous Fission of Pu-240, Cu-242 and Cu-244. Nucl. Sci. Eng. 86, 315 (1984)Google Scholar
  11. 11.
    M. M. R. Williams, Random Processes in Nuclear Reactors, Pergamon Press, 1974Google Scholar
  12. 12.
    M. Srinivasan, K.K. Rasheed, C.S. Psapathy and S. B. Degweker, Experimental Determination of the Keff of Highly Subcritical Enriched Fissile Units by a Statistical Correlation Technique, Int. Sem. Criticality Safety, Tokyo, 1987Google Scholar
  13. 13.
    Anil Kumar, M. Srinivasan and K. Subba Rao, Characterisation of Neutron Leakage Probability, Keff and Critical Core Surface Mass Density of Small Reactor Assemblies through the Trombay Criticality Formulae, Nucl. Sci. Engg. 84, 155 (1983)Google Scholar
  14. 14.
    M. Edelmann, et. al., Investigations of the Two Detector Covariance Method for the Measurement of Coupled Reactor Kinetics Parameters, Ann. of Nuclear Energy. 2, 207 (1975)CrossRefGoogle Scholar

Copyright information

© Plenum Press, New York 1989

Authors and Affiliations

  • S. B. Degweker
    • 1
  • M. Srinivasan
    • 2
  • K. K. Rasheed
    • 2
  • C. S. Pasupathy
  1. 1.Reactor Analysis and Systems DivisionBhabha Atomic Research CentreTrombayIndia
  2. 2.Neutron Physics DivisionBhabha Atomic Research CentreTrombayIndia

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