McNp-DSP Users Manual

Valentine, T.E.

doi:10.2172/777654

Cited by 17 publications

(8 citation statements)

References 21 publications

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“…The fitted equation is 2.6exp( À 1.0E)þ0.0028 (cps unit; all parameters were fitted). In [11], the fission g-ray distribution has been reported to be proportional to exp(À 1.10E) for 3 MeV-8 MeV. As shown in Fig.…”

Section: Detection Efficiencymentioning

confidence: 90%

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Neutron detection with a NaI spectrometer using high-energy photons

Holm

Perajärvi

Sihvonen

et al. 2013

Nuclear Instruments and Methods in Physics Research Section A:

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Section: Detection Efficiencymentioning

confidence: 90%

“…The solid line is an exponential fit and the dashed line shows the fission photon distribution according to Ref[11].…”

mentioning

confidence: 99%

Neutron detection with a NaI spectrometer using high-energy photons

Holm

Perajärvi

Sihvonen

et al. 2013

Nuclear Instruments and Methods in Physics Research Section A:

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“…induced fission in the Pu-239, which is the predominant fissile nuclide in the BeRP ball [37]. The forward intrinsic neutron source Q , calculated using Pu-240 Watt fission parameters [56], is plotted in Fig. 3…”

Section: Model Calibration Applied To Neutron Multiplicity Counting Omentioning

confidence: 99%

Application of Neutron Multiplicity Counting Experiments to Optimal Cross-Section Adjustments

Clark

Mattingly

Favorite

2020

Nuclear Science and Engineering

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CLARK, ALEXANDER RICH. Application of Neutron Multiplicity Counting Experiments to Optimal Cross Section Adjustments. (Under the direction of John Mattingly.) This dissertation presents the first application of model calibration to neutron multiplicity counting (NMC) experiments for cross section optimization that utilizes adjoint-based sensitivity analysis (SA) and first-order uncertainty quantification (UQ). We summarize previous work on SA applied to NMC and describe notable additions. We give the procedure for first-order UQ and Bayesian-inference-based parameter estimation (PE). We then discuss model calibration applied to NMC of a 4.5-kg sphere of weapons-grade, alpha-phase plutonium metal with a neutron multiplicity counter. For bare and polyethylene-reflected configurations of the plutonium sphere, we discuss the sensitivity of the first-and second-moment detector responses (i.e. first and second moments of the NMC distribution, respectively) to the cross sections. We describe the sources of uncertainty in the measured and simulated responses. Specifically, uncertainty in the measured responses is due to both random and systematic sources of uncertainty. Uncertainty in the simulated responses is due to cross section covariances. We describe in detail the adjustment to the cross sections and cross section covariances due to the optimization. Due to the contribution of systematic uncertainties to the measured response uncertainties, the adjustment to the cross sections is similar in trend but larger in magnitude compared to that recommended by previous work. We compare the measured responses to responses simulated with nominal and optimized cross sections, demonstrating that the best-estimate cross sections produce simulations of NMC experiments that are more accurate with reduced uncertainty. We verify that the response variance due to the cross sections computed with sampling-based uncertainty quantification (UQ) is well-approximated by that estimated with first-order UQ.

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“…During the past decade several code extensions have been developed that allow the modeling of correlations in fission. MCNP-DSP [5,11] and MCNPX-PoliMi [5,12] added angular correlations of fission neutrons by assuming the 252 Cf spontaneous fission distribution can be employed for all fissionable nuclides. Both codes also include detailed multiplicity and energy distributions for prompt fission photons time-correlated with the fission event.…”

Section: Introductionmentioning

confidence: 99%

Fission Reaction Event Yield Algorithm, FREYA — For event-by-event simulation of fission

Verbeke

Randrup

Vogt

2015

Computer Physics Communications

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From nuclear materials accountability to detection of special nuclear material, SNM, the need for better modeling of fission has grown over the past decades. Current radiation transport codes compute average quantities with great accuracy and performance, but performance and averaging come at the price of limited interaction-by-interaction modeling. For fission applications, these codes often lack the capability of modeling interactions exactly: energy is not conserved, energies of emitted particles are uncorrelated, prompt fission neutron and photon multiplicities are uncorrelated. Many modern applications require more exclusive quantities than averages, such as the fluctuations in certain observables (e.g. the neutron multiplicity) and correlations between neutrons and photons. The new computational model, FREYA (Fission Reaction Event Yield Algorithm), aims to meet this need by modeling complete fission events. Thus it automatically includes fluctuations as well as correlations resulting from conservation of energy and momentum. FREYA has been integrated into the LLNL Fission Library, and will soon be part of MCNPX2.7.0, MCNP6, TRIPOLI-4.9, and Geant4.10.

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McNp-DSP Users Manual

Abstract: Lines 12-17: These lines describe the detectors in the problem and are the same as those provided in Fig. 6.13.

Cited by 17 publications

References 21 publications

Neutron detection with a NaI spectrometer using high-energy photons

Neutron detection with a NaI spectrometer using high-energy photons

Application of Neutron Multiplicity Counting Experiments to Optimal Cross-Section Adjustments

Fission Reaction Event Yield Algorithm, FREYA — For event-by-event simulation of fission

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