The neutron–gamma Feynman variance to mean approach: Gamma detection and total neutron–gamma detection (theory and practice)

Chernikova, Dina; Axell, Kåre; Avdic, Senada; Pázsit, Imre; Nordlund, Anders; Allard, Stefan

doi:10.1016/j.nima.2015.01.104

Cited by 10 publications

(5 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The sufficient similarity of the noise information from gamma and neutron detectors in terms of measuring has been shown experimentally in CROCUS with in-core detectors 17 , 18 . Theoretical considerations for VTM/CTM equations using gamma detectors were explored by Chernikova et al 26 . This existing literature led to the hypothesis of gamma noise measurements being potentially superior to neutron noise measurements regarding precision and observable distances, alleviating the above-mentioned limitations of noise measurements.…”

Section: Resultsmentioning

confidence: 99%

“…1 d, as also affects the amplitude of the excess variance. The amplitude term of gamma noise VTM/CTM curves is however a more complex expression that includes gamma multiplicities, delayed gamma rays, and the gamma ray absorption 26 . Future work would therefore be needed to investigate whether the gamma-ray induced terms are significant, and to quantify whether a relevant signal can be detectable for a given fuel composition change scenario.…”

Section: Discussionmentioning

confidence: 99%

“…The theoretical reasoning as to why gamma noise follows approximately the neutron induced correlations has been explored by other authors 26 . They found that the VTM and CTM expressions for a gamma detector signal will take the following shape: We find two terms: one is governed by the excess variance due to the fission chain propagation and thus has the shape factor .…”

Section: Methodsmentioning

confidence: 99%

See 2 more Smart Citations

Gamma noise to non-invasively monitor nuclear research reactors

Pakari,

Mager,

Frajtag

et al. 2024

Sci Rep

View full text Add to dashboard Cite

Autonomous nuclear reactor monitoring is a key aspect of the International Atomic Energy Agency’s strategy to ensure nonproliferation treaty compliance. From the rise of small modular reactor technology, decentralized nuclear reactor fleets may strain the capacities of such monitoring and requires new approaches. We demonstrate the superior capabilities of a gamma detection system to monitor the criticality of a zero power nuclear reactor from beyond typical vessel boundaries, offering a powerful alternative to neutron-based systems by providing direct information on fission chain propagation. Using the case example of the research reactor CROCUS, we demonstrate how two bismuth germanate scintillators placed outside the reactor vessel can precisely observe reactor criticality using so called noise methods and provide core status information in seconds. Our results indicate a wide range of applications due to the newly gained geometric flexibility that could find use in fields beyond nuclear safety.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Gamma noise to non-invasively monitor nuclear research reactors

Pakari,

Mager,

Frajtag

et al. 2024

Sci Rep

View full text Add to dashboard Cite

show abstract

“…In order to distinguish time-correlated particles induced by a non-fission source from those emitted by a fission source, the use of more parameters such as energy, lifetime, joint neutron-gamma-ray multiplicity, Feynman variance to mean ratio for neutrons and gamma photons [7], etc. can be significantly useful for identifying the presence of SNM.…”

Section: The Simulated Results and Discussionmentioning

confidence: 99%

Joint probability of density functions of energy-lifetime distributions for neutrons and gamma-rays from 252Cf source

Avdic¹,

Gazdic²,

Pehlivanovic³

et al. 2017

Sci Publ State Univ Novi Pazar Ser A

Self Cite

View full text Add to dashboard Cite

In contrast to some traditional neutron detectors, liquid scintillators are suitable for measuring spontaneous fission produced on the nanosecond time-scales. The high multiplicity events in a short period of time are signatures for fissile materials. The neutron and gamma multiplicities have potential to enable extraction of the fissile material attributes. The simulations presented in this paper were done using the MCNPX-PoliMi radiation transport code based on the Monte Carlo method. It was demonstrated that the energy and time information depending on the number of neutrons and gamma-rays emitted in spontaneous fission events of 252 Cf contribute additionally to characterize a fission source.

show abstract

“…The assemblies were measured with an organic scintillator array (OSCAR [12]). Previous works have also used organic scintillators to perform Feynman-alpha measurements [30,31,32], although 3 He detectors are traditionally used. The OSCAR comprised 12, cylindrical, 5.08-cm thick × 5.08-cm diameter trans-stilbene organic scintillators (C 14 H 12 ) wrapped in polytetrafluoroethylene tape and housed in aluminum [33,34], coupled to photomultiplier tubes (PMTs), and arranged in a 3×4 matrix.…”

Section: Methodsmentioning

confidence: 99%

On the Feynman-alpha Method for Reflected Fissile Assemblies

Hua¹,

Hutchinson²,

McKenzie³

et al. 2020

Preprint

View full text Add to dashboard Cite

The Feynman-alpha method is a neutron noise technique that is used to estimate the prompt neutron period of fissile assemblies. The method and quantity are of widespread interest including in applications such as nuclear criticality safety, safeguards and nonproliferation, and stockpile stewardship; the prompt neutron period may also be used to infer the k eff multiplication factor. The Feynman-alpha method is predicated on time-correlated neutron detections that deviate from a Poisson random variable due to multiplication. Traditionally, such measurements are diagnosed with one-region point kinetics, but two-region models are required when the fissile assembly is reflected. This paper presents a derivation of the two-region point kinetics Feynman-alpha equations based on a double integration of the Rossi-alpha equations, develops novel propagation of measurement uncertainty, and validates the theory. Validation is achieved with organic scintillator measurements of weapons-grade plutonium reflected by various amounts of copper to achieve k eff values of 0.83-0.94 and prompt periods of 5-75 ns. The results demonstrate that Feynman-alpha measurements should use the two-region model instead of the one-region model. The simplified one-region model deviates from the validated two-region models by as much as 10% in the estimate of the prompt neutron period, and the two-region model reduces to the one-region model for small amounts of reflector. The Feynman-alpha estimates of the prompt neutron period are compared to those of the Rossi-alpha approach. The comparative results demonstrate that the Feynman-alpha method is more precise than the Rossi-alpha method and more accurate for k eff < 0.92, whereas the Rossi-alpha method is generally more accurate for higher multiplications. The uncertainty propagation developed in this work should be used for all Feynman-alpha measurements and will therein improve fitting accuracy and appropriate precision estimates.

show abstract

The neutron–gamma Feynman variance to mean approach: Gamma detection and total neutron–gamma detection (theory and practice)

Cited by 10 publications

References 12 publications

Gamma noise to non-invasively monitor nuclear research reactors

Gamma noise to non-invasively monitor nuclear research reactors

Joint probability of density functions of energy-lifetime distributions for neutrons and gamma-rays from 252Cf source

On the Feynman-alpha Method for Reflected Fissile Assemblies

Contact Info

Product

Resources

About