Theory of Correlation Measurement in Time and Frequency Domains with ²⁵²Cf

Abstract

A new method of reactivity determination is proposed which avoids some of the difficulties of the present methods, such as dependence on detection efficiency and inherent source strength, and the requirement for a calibration near delayed criticality.

Multivariate High Order Statistics of Measurements of the Temporal Evolution of Fission Chain-Reactions

“…Subsequently, the covariance between the detector and active source signals is This is the quantity measured by a pulsed neutron experiment; it is the distribution of detector counts chain-related to some detected active source emission over the delay between initial source emission and the subsequent count. [9] Neutronnoise analysis experiments often represent this distribution as a harmonic spectrum [10] Subsequently, the marginal probability of a count chain-related to a detected active source emission is However, some detector counts may instead be chain-related to an undetected active source emission with probability…”

“…There is no reason to consider permutations under which the source emission does not occur first; the probability 10 of a chain-related correlated pair of counts under such a permutation is zero because the source emission must initiate the chain-reaction. …”

“…[10] Subsequently the Laplace transform of a covariance (not a total coincidence distribution ) shall be simply termed a spectrum ; the context of use will clearly distinguish this harmonic spectrum from an energy spectrum, e.g., a fission neutron spectrum. The Laplace-domain representation shall be used exclusive of the Fourier representation; the latter is simply a special case (i.e., ) of the former.…”

Subcriticality Measurement by Neutron Source Multiplication Method Swith a Fundamental Mode Extraction

“…There are several methods for measurement of subcriticality, such as neutron source multiplication (NSM) method, pulse neutron method, exponential experiment method and stochastic methods such as Feynman-α, Rossi-α 1) and a frequency analysis method proposed by Mihalczo. 2) Normally, in nuclear facilities such as nuclear reactors, a neutron source is placed intentionally for a nuclear criticality safety or inherently contains due to (γ −n) nuclear reactions or nuclear fissions from self-fissionable isotopes. In such facilities, the NSM method is the simplest and cheapest method for measurement of subcriticality, without any expensive devices such as an accelerator or sophisticated measuring theories.…”

Technique for Reduction of Coherence Function Bias Error

“…However, in reactivity aeaaurtoent applications [3], the coherence function* to be quantified have values on the order of 10~°, Thus, using standard techniques, one alllion data blocks would have to be averaged to obtain results with 100% bias error, ten million data blocks for results with JO* bias error, and one hundred million data blocks for results with 1J bias error. In practical terms, the implication is that to achieve 1J bias error, 142 hours of real-time data would have to be processed (assuming a blockslze of 512 and a sampling rate of too kHz).…”