Use of TRACE best estimate code to analyze spent fuel storage pools safety

Abstract

Nuclear policies have experienced an important change since Fukushima Daiichi nuclear plant accident and the safety of spent fuels has been in the spot issue among all the safety concerns. At many countries, the spent fuel of nuclear power plants is not reprocessed so it has to be stored inside the facilities, normally in pools. As nuclear power plants use best estimate codes to perform safety analysis, it is interesting to assess the capacity of such codes to simulate spent fuel pools behavior. This paper uses TRACE thermal-hydraulic code to simulate steady state and transient conditions of spent fuel pools. The steady state results are compared with plant measurements of Maine Yankee with a good agreement between the calculations and the measurements. The transient simulated is a loss of cooling together with a loss of coolant through the transfer channel. TRACE heat transfer radiation model has been activated using the parameters obtained from COBRA thermal-hydraulic code.

Zero-dimensional transient model of large-scale cooling ponds using well-mixed approach

“…TRACE data for the accident scenario in terms of water temperature and drop of pond water 453 level respectively. In Figure 5, for up to one hour the same linear trend is observed, but a clear 454 shift of 1.8 o C is recorded, the reason for which is not obvious from the original paper [18]. 455 Figure 6 shows a sudden drop in water level over a very short time (something similar to 456 purging), but the reason for such behaviour was also not explained.…”

“…The Maine Yankee spent fuel pool is a relatively small cooling pond located at the reactor site, 410 with dimensions of 12.6 m long, 11.3 m wide and 11.1 m deep. Carlos et al [18] used TRACE 411 best estimate code to analyse the response of the cooling pond in different scenarios. During 412 their calculations, no heat loss was considered at the free water surface except when the water 413 has reached its saturation temperature (100 o C) with the initiation of boiling.…”

“…The Z-D model is used to perform calculations on the Maine Yankee spent fuel pool, Wiscasset, 418 USA [18] and the results obtained are compared against the published data for this pool. These 419 calculations are developed for three cases: (a) steady-state, (b) licensing, and (c) accident 420 scenarios.…”

“…In the paper reported by Carlos et al [18], the temperature data were available for the steady-422 state case in the form of actual temperature measurements collected from the Maine Yankee 423 spent fuel pool. For the licensing case, the temperature data were calculated by GFLOW 424 software [31], while the TRACE best estimate code was used for the pool temperature under 425 the accident scenarios.…”

“…On the other hand, most of the studies adopting the system codes were concerned about 95 investigating accident scenarios and their consequences. Carlos et al [18] Some investigations concern accident mitigation options using thermal-hydraulic codes. Chen [23] conducted an analysis of the loss of cooling accident scenarios for a spent fuel pool at the 107 CPR1000 NPP using the MAAP5 code.…”