Experimental observation of adverse and beneficial effects of nitrogen on reactor core cooling

Riikonen, Vesa; Kouhia, Virpi; Kauppinen, Otso-Pekka; Sjövall, H.; Hyvärinen, Juhani

doi:10.1016/j.nucengdes.2018.03.027

Cited by 4 publications

(1 citation statement)

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“…At LUT University, the effect of the accumulator nitrogen release on the core cooling during a lossof-coolant-accident (LOCA) situation was studied with the PWR PACTEL test facility (Riikonen et al, 2016(Riikonen et al, , 2018. The aim of these experiments was to study nitrogen release effects on cooling conditions during LOCA situation and to generate data for the development and validation of the thermal-hydraulic system codes.…”

Section: Introductionmentioning

confidence: 99%

System code analysis of accumulator nitrogen discharge during LOCA experiment at PWR PACTEL test facility

Kauppinen

Kouhia

Riikonen

et al. 2019

Nuclear Engineering and Design

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The hydroaccumulators in pressurized water reactors can inject nitrogen into the reactor system. In the primary system, nitrogen affects core cooling and accident management, both adversely and beneficially. The PWR PACTEL experiment NCG-13 have shown that during a hot leg SB LOCA, nitrogen in the primary side can block the primary to secondary heat transfer and thereby prevent the primary depressurization to the point needed for the long-term accident management. This paper presents the APROS and TRACE calculations of the PWR PACTEL NCG-13 experiment. Both codes calculate the transient progression and the timing of the main events satisfactorily, once the suitable options are selected and adjustments made. There is, however, one big discrepancy between the code simulations and the experiment: in the simulations, much more nitrogen is needed to get qualitatively the same behaviour. The difference is a factor of 2.5 by mass for stopping the depressurization and 4-6 to cause a core heat-up. This is of concern regarding the confidence in the codes, as the simulations underestimate the adverse effect of nitrogen on the core coolability. HIGHLIGHTS: Codes predict the transient behaviour and timing of the main events satisfactory  In the simulations, nitrogen stops the primary side depressurization  Amount of released nitrogen is larger in the simulations than in the experiment *Highlights (for review)

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Section: Introductionmentioning

confidence: 99%