An effective numerical algorithm for intra-granular fission gas release during non-equilibrium trapping and resolution

Journal Article · Wed Jul 18 00:00:00 EDT 2018 · Journal of Nuclear Materials

DOI:https://doi.org/10.1016/j.jnucmat.2018.07.030· OSTI ID:1557658

Pastore, Giovanni  ^[1]; Pizzocri, Davide  ^[2]; Rabiti, Cristian  ^[3]; Barani, Tommaso  ^[2]; Van Uffelen, Paul ^[4]; Luzzi, Lelio  ^[2]

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1. Idaho National Lab. (INL), Idaho Falls, ID (United States); Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
2. Politecnico di Milano, Milano (Italy)
3. Idaho National Lab. (INL), Idaho Falls, ID (United States)
4. European Commission, Joint Research Centre, Karlsruhe (Germany)

Both fission gas release and gaseous swelling in nuclear fuel are driven by the transport of fission gas from within the fuel grains to grain boundaries (intra-granular fission gas release). The process involves gas atom diffusion in conjunction with trapping in and resolution from intra-granular bubbles, and is described mathematically by a system of two partial differential equations (PDE). Following Speight, under the assumption of equilibrium between trapping and resolution (quasi-stationary approximation) the system can be reduced to a single diffusion equation with an effective diffusion coefficient. Numerical solutions used in engineering fuel performance calculations invariably rely on this simplification. First, we investigate the validity of the quasi-stationary approximation compared to the solution of the general system of PDEs. Results demonstrate that the approximation is valid under most conditions of practical interest, but is inadequate to model intra-granular fission gas release during rapid transients to relatively high temperatures such as postulated reactivity initiated accidents (RIA). Then, we develop a novel numerical algorithm for the solution of the general problem in time-varying conditions. We verify the PolyPole-2 algorithm against a reference finite difference solution for a large number of randomly generated operation histories including prototypical RIA transients. Results demonstrate that PolyPole-2 captures the solution of the general PDE system with a high accuracy and a low computational cost. As a result, the PolyPole-2 algorithm overcomes the quasi-stationary approximation and the concept of an effective diffusion coefficient for the solution of the intra-granular fission gas release problem in nuclear fuel analysis.

• Research Organization: Idaho National Lab. (INL), Idaho Falls, ID (United States)
• Sponsoring Organization: USDOE Office of Nuclear Energy (NE)
• Grant/Contract Number: AC07-05ID14517; 198236
• OSTI ID: 1557658
• Alternate ID(s): OSTI ID: 1702414
• Report Number(s): INL/JOU-18-44865-Rev000
• Journal Information: Journal of Nuclear Materials, Vol. 509, Issue C; ISSN 0022-3115
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
Fission gas release
Nuclear fuel modeling
Diffusion algorithm