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You searched for subject:(FW CADIS). Showing records 1 – 2 of 2 total matches.

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University of California – Berkeley

1. Munk, Madicken. FW/CADIS-Ω: An Angle-Informed Hybrid Method for Neutron Transport.

Degree: Nuclear Engineering, 2017, University of California – Berkeley

The development of methods for deep-penetration radiation transport is of continued importance for radiation shielding, nonproliferation, nuclear threat reduction, and medical applications. As these applications become more ubiquitous, the need for transport methods that can accurately and reliably model the systems’ behavior will persist. For these types of systems, hybrid methods are often the best choice to obtain a reliable answer in a short amount of time. Hybrid methods leverage the speed and uniform uncertainty distribution of a deterministic solution to bias Monte Carlo transport to reduce the variance in the solution. At present, the Consistent Adjoint-Driven Importance Sampling (CADIS) and Forward-Weighted CADIS (FW-CADIS) hybrid methods are the gold standard by which to model systems that have deeply-penetrating radiation. They use an adjoint scalar flux to generate variance reduction parameters for Monte Carlo. However, in problems where there exists strong anisotropy in the flux, CADIS and FW-CADIS are not as effective at reducing the problem variance as isotropic problems.This dissertation covers the theoretical background, implementation of, and characteri- zation of a set of angle-informed hybrid methods that can be applied to strongly anisotropic deep-penetration radiation transport problems. These methods use a forward-weighted adjoint angular flux to generate variance reduction parameters for Monte Carlo. As a result, they leverage both adjoint and contributon theory for variance reduction. They have been named CADIS-Ω and FW-CADIS-Ω.To characterize CADIS-Ω, several characterization problems with flux anisotropies were devised. These problems contain different physical mechanisms by which flux anisotropy is induced. Additionally, a series of novel anisotropy metrics by which to quantify flux anisotropy are used to characterize the methods beyond standard Figure of Merit (FOM) and relative error metrics. As a result, a more thorough investigation into the effects of anisotropy and the degree of anisotropy on Monte Carlo convergence is possible.The results from the characterization of CADIS-Ω show that it performs best in strongly anisotropic problems that have preferential particle flowpaths, but only if the flowpaths are not comprised of air. Further, the characterization of the method’s sensitivity to deterministic angular discretization showed that CADIS-Ω has less sensitivity to discretization than CADIS for both quadrature order and PN order. However, more variation in the results were observed in response to changing quadrature order than PN order. Further, as a result of the forward-normalization in the Ω-methods, ray effect mitigation was observed in many of the characterization problems.The characterization of the CADIS-Ω-method in this dissertation serves to outline a path forward for further hybrid methods development. In particular, the response that the Ω- method has with changes in quadrature order, PN order, and on ray effect mitigation are strong indicators that the method is more…

Subjects/Keywords: Nuclear engineering; Anisotropy; CADIS; FW-CADIS; Hybrid Methods; Radiation Shielding; Radiation Transport

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Munk, M. (2017). FW/CADIS-Ω: An Angle-Informed Hybrid Method for Neutron Transport. (Thesis). University of California – Berkeley. Retrieved from http://www.escholarship.org/uc/item/26c5k0tq

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Munk, Madicken. “FW/CADIS-Ω: An Angle-Informed Hybrid Method for Neutron Transport.” 2017. Thesis, University of California – Berkeley. Accessed March 19, 2019. http://www.escholarship.org/uc/item/26c5k0tq.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Munk, Madicken. “FW/CADIS-Ω: An Angle-Informed Hybrid Method for Neutron Transport.” 2017. Web. 19 Mar 2019.

Vancouver:

Munk M. FW/CADIS-Ω: An Angle-Informed Hybrid Method for Neutron Transport. [Internet] [Thesis]. University of California – Berkeley; 2017. [cited 2019 Mar 19]. Available from: http://www.escholarship.org/uc/item/26c5k0tq.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Munk M. FW/CADIS-Ω: An Angle-Informed Hybrid Method for Neutron Transport. [Thesis]. University of California – Berkeley; 2017. Available from: http://www.escholarship.org/uc/item/26c5k0tq

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

2. Flaspoehler, Timothy Michael. FW-CADIS variance reduction in MAVRIC shielding analysis of the VHTR.

Degree: MS, Nuclear and Radiological Engineering, 2012, Georgia Tech

In the following work, the MAVRIC sequence of the Scale6.1 code package was tested for its efficacy in calculating a wide range of shielding parameters with respect to HTGRs. One of the NGNP designs that has gained large support internationally is the VHTR. The development of the Scale6.1 code package at ORNL has been primarily directed towards supporting the current United States' reactor fleet of LWR technology. Since plans have been made to build a prototype VHTR, it is important to verify that the MAVRIC sequence can adequately meet the simulation needs of a different reactor technology. This was accomplished by creating a detailed model of the VHTR power plant; identifying important, relevant radiation indicators; and implementing methods using MAVRIC to simulate those indicators in the VHTR model. The graphite moderator used in the design shapes a different flux spectrum than water-moderated reactors. The different flux spectrum could lead to new considerations when quantifying shielding characteristics and possibly a different gamma-ray spectrum escaping the core and surrounding components. One key portion of this study was obtaining personnel dose rates in accessible areas within the power plant from both neutron and gamma sources. Additionally, building from professional and regulatory standards a surveillance capsule monitoring program was designed to mimic those used in the nuclear industry. The high temperatures were designed to supply heat for industrial purposes and not just for power production. Since tritium, a heavier radioactive isotope of hydrogen, is produced in the reactor it is important to know the distribution of tritium production and the subsequent diffusion from the core to secondary systems to prevent contamination outside of the nuclear island. Accurately modeling indicators using MAVRIC is the main goal. However, it is almost equally as important for simulations to be carried out in a timely manner. MAVRIC uses the discrete ordinates method to solve the fixed-source transport equation for both neutron and gamma rays on a crude geometric representation of the detailed model. This deterministic forward solution is used to solve an adjoint equation with the adjoint source specified by the user. The adjoint solution is then used to create an importance map that can weight particles in a stochastic Monte Carlo simulation. The goal of using this hybrid methodology is to provide complete accuracy with high precision while decreasing overall simulation times by orders of magnitude. The MAVRIC sequence provides a platform to quickly alter inputs so that vastly different shielding studies can be simulated using one model with minimal effort by the user. Each separate shielding study required unique strategies while looking at different regions in the VHTR plant. MAVRIC proved to be effective for each case. Advisors/Committee Members: Petrovic, Bojan (Committee Chair), Deo, Chaitanya (Committee Member), Hertel, Nolan (Committee Member), Peplow, Douglas (Committee Member).

Subjects/Keywords: Tritium; Reaction rate; Neutral particle; SINBAD; HTGR; VENUS; PCA; Variance reduction; FW-CADIS; MAVRIC; Shielding; Dosimetry; Surveillance capsule monitoring; Dose; Photon; Gamma; Neutron; Radiation; Transport; Shielding (Radiation); Nuclear engineering Safety measures; Radioactivity Safety measures

…rate used to define the adjoint source for FW-CADIS… …122 Figure 84. The FW-CADIS weighted MC flux (Left) with relative uncertainty… …134 Figure 95. The 3He (n, p) 3H reaction distribution when using FW-CADIS with an… …136 Figure 96. The 3He (n, p) 3H reaction distribution when using FW-CADIS with an… …The MAVRIC sequence implements the CADIS and FW-CADIS methodologies developed by J.C. Wagner… 

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Flaspoehler, T. M. (2012). FW-CADIS variance reduction in MAVRIC shielding analysis of the VHTR. (Masters Thesis). Georgia Tech. Retrieved from http://hdl.handle.net/1853/45743

Chicago Manual of Style (16th Edition):

Flaspoehler, Timothy Michael. “FW-CADIS variance reduction in MAVRIC shielding analysis of the VHTR.” 2012. Masters Thesis, Georgia Tech. Accessed March 19, 2019. http://hdl.handle.net/1853/45743.

MLA Handbook (7th Edition):

Flaspoehler, Timothy Michael. “FW-CADIS variance reduction in MAVRIC shielding analysis of the VHTR.” 2012. Web. 19 Mar 2019.

Vancouver:

Flaspoehler TM. FW-CADIS variance reduction in MAVRIC shielding analysis of the VHTR. [Internet] [Masters thesis]. Georgia Tech; 2012. [cited 2019 Mar 19]. Available from: http://hdl.handle.net/1853/45743.

Council of Science Editors:

Flaspoehler TM. FW-CADIS variance reduction in MAVRIC shielding analysis of the VHTR. [Masters Thesis]. Georgia Tech; 2012. Available from: http://hdl.handle.net/1853/45743

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