Applications of nuclear physics

Hayes, A. C.

doi:10.1088/1361-6633/80/2/026301

Cited by 23 publications

(11 citation statements)

References 113 publications

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“…Let us finally emphasize that the knowledge of the reactor antineutrino fluxes is useful not only for applications in fundamental physics research, but also for practical applications as antineutrino monitoring of reactors (see Refs. [35][36][37]). …”

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confidence: 99%

Improved determination of the U235 and Pu239<

Giunti

2017

Phys. Rev. D

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We present the results of a combined fit of the reactor antineutrino rates and the Daya Bay measurement of σ f,235 and σ f,239 . The combined fit leads to a better determination of the two cross sections per fission: σ f,235 = 6.29 ± 0.08 and σ f,239 = 4.24 ± 0.21 in units of 10 −43 cm 2 /fission, with respective uncertainties of about 1.2% and 4.9%. Since the respective deviations from the theoretical cross sections per fission are 2.5σ and 0.7σ, we conclude that, if the reactor antineutrino anomaly is not due to active-sterile neutrino oscillations, it is likely that it can be solved with a revaluation of the 235 U reactor antineutrino flux. However, the 238 U, 239 Pu, and 241 Pu fluxes, which have larger uncertainties, could also be significantly different from the theoretical predictions.The flux of electron antineutrinos produced in nuclear reactors is generated by the β decays of the fission products of 235 U, 238 U, 239 Pu, and 241 Pu. The 2011 recalculation [1, 2] of the four fluxes led to the discovery of the reactor antineutrino anomaly [3], which is a deficit of the rate of electron antineutrinos measured in several reactor neutrino experiments. There are two known possible explanations of the reactor antineutrino anomaly: 1) a miscalculation of one or more of the four electron antineutrino fluxes [4,5] and 2) active-sterile neutrino oscillations (see Ref.[6] and references therein). In this paper we consider the first possibility and we present an improvement of the results presented in Refs. [4,5] The cross section per fission σ f,235 of the 235 U electron antineutrino flux was determined in Ref.[4] with a fit of the reactor rates by taking into account the different fuel compositions. Recently the Daya Bay Collaboration presented a determination of σ f,235 and σ f,239 obtained by measuring the correlations between the reactor core fuel evolution and the changes in the reactor antineutrino flux and energy spectrum [5]. In this paper we present a combined fit of the reactor rates and the Daya Bay measurement of σ f,235 and σ f,239 which leads to a better determination of both cross sections per fission.In the analysis of the reactor rates, we consider the theoretical ratios [4]where f a k is the antineutrino flux fraction from the fission of the isotope with atomic mass k and the coefficient r k is the corresponding correction of the theoretical cross section per fission σ SH f,k which is needed to fit the data (k = 235, 238, 239, 241, denotes, respectively We analyze the data of the reactor rates with the leastsquares statisticwhere R exp a are the measured reactor rates listed in Table 1 of Ref. [6] and V R is the covariance matrix constructed with the corresponding uncertainties. The second term in Eq. (2) serves to keep under control the variation of the rates of the minor fissionable isotopes 238 U and 241 Pu, which are not well determined by the fit [4]. We consider ∆r 238 = 15% and ∆r 241 = 10%, which are significantly larger than the nominal theoretical uncertainties (respectively, 8.15% and...

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confidence: 99%

Improved determination of the U235 and Pu239<

Giunti

2017

Phys. Rev. D

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“…At low energies (E ex ≤ 3 MeV), typical values for σ 2 C are 7-10 in the Zr region and 12-16 in the Gd region [48]. As E ex increases from a few MeV to about 20 MeV, σ 2 C can increase by a factor 4 or more for these mass regions [43]. If we then assume that the spins populated in the residual nucleus are small compared to the σ C , the level density can be written as…”

Section: Acknowledgementsmentioning

confidence: 99%

“…Nuclear reaction data is required for many applications in both basic and applied science, whether it be for modeling the origin of elements in the universe, the safe operation of a next-generation reactors, or for nationalsecurity applications [1,2]. Nuclear reaction libraries provide evaluated reaction data for many such applications [3].…”

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confidence: 99%

Cross Sections for Neutron-Induced Reactions from Surrogate Data: Assessing the Use of the Weisskopf-Ewing Approximation for (n,n') and (n,2n) Reactions

Gorton

Escher

2020

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Background: Modeling nuclear reaction networks for nuclear science applications and for simulations of astrophysical environments relies on cross section data for a vast number of reactions, many of which have never been measured. Cross sections for neutron-induced reactions on unstable nuclei are particularly scarce, since they are the most difficult to measure. Consequently, we must rely on theoretical predictions or indirect measurements to obtain the requisite reaction data. For compound nuclear reactions, the surrogate reaction method can be used to determine many cross sections of interest. Purpose: Earlier work has demonstrated that cross sections for neutron-induced fission and radiative neutron capture can be determined from a combination of surrogate reaction data and theory. For the fission case, it was shown that Weisskopf-Ewing approximation, which significantly simplifies the implementation of the surrogate method, can be employed. Capture cross sections cannot be obtained, and require a detailed description of the surrogate reaction process. In this paper we examine the validity of the Weisskopf-Ewing approximation for determining unknown (n, n) and (n, 2n) cross sections from surrogate data. Methods: Using statistical reaction calculations with realistic parametrizations, we investigate first whether the assumptions underlying the Weisskopf-Ewing approximation are valid for (n, n) and (n, 2n) reactions on representative target nuclei. We then produce simulated surrogate reaction data and assess the impact of applying the Weisskopf-Ewing approximation when extracting (n, n) and (n, 2n) cross sections in situations where the approximation is not strictly justified. Results: We find that peak cross sections can be estimated using the Weisskopf-Ewing approximation, but the shape of the (n, n) and (n, 2n) cross sections, especially for low neutron energies, cannot be reliably determined without accounting for the angular-momentum differences between the neutron-induced and surrogate reaction. Conclusions: To obtain reliable (n, n) and (n, 2n) cross sections from surrogate reaction data, a detailed description of the surrogate reaction mechanisms is required. To do so for the compound-nucleus energies and decay channels relevant to these reactions, it becomes necessary to extend current modeling capabilities. I. BACKGROUND AND NEED

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“…Nuclear physics has seen continuous application in many fields of science [1]. The fields span from energy to the environment, geophysics, materials research, astrophysics, and, of course, biology and medicine.…”

Section: Applied Nuclear Physics At Acceleratorsmentioning

confidence: 99%