Development of nodal diffusion code RAST-V for Vodo–Vodyanoi Energetichesky reactor analysis

• Published in: Nuclear engineering and technology 2022, 54(9), , pp.3494-3515
• Main Authors: Jang, Jaerim, Dzianisau, Siarhei, Lee, Deokjung
• Format: Article
• Language: English
• Subjects: PWR; TPEN; Validation; VVER-1000; 원자력공학
• ISSN: 1738-5733; 2234-358X
• DOI: 10.1016/j.net.2022.04.007

This paper presents the development of a nodal diffusion code, RAST-V, and its verification and validation for VVER (vodo–vodyanoi energetichesky reactor) analysis. A VVER analytic solver has been implemented in an in-house nodal diffusion code, RAST-K. The new RAST-K version, RAST-V, uses the triangle-based polynomial expansion nodal method. The RAST-K code provides stand-alone and two-step computation modes for steady-state and transient calculations. An in-house lattice code (STREAM) with updated features for VVER analysis is also utilized in the two-step method for cross-section generation. To assess the calculation capability of the formulated analysis module, various verification and validation studies have been performed with Rostov-II, and X2 multicycles, Novovoronezh-4, and the Atomic Energy Research benchmarks. In comparing the multicycle operation, rod worth, and integrated temperature coefficients, RAST-V is found to agree with measurements with high accuracy which RMS differences of each cycle are within ±47 ppm in multicycle operations, and ±81 pcm of the rod worth of the X2 reactor. Transient calculations were also performed considering two different rod ejection scenarios. The accuracy of RAST-V was observed to be comparable to that of conventional nodal diffusion codes (DYN3D, BIPR8, and PARCS).