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Accessible Unlicensed Requires Authentication Published by De Gruyter August 18, 2017

New engineering safety factors for Loviisa NPP core calculations

Neue Engineering-Sicherheitsfaktoren für Kernberechnungen für das KKW Loviisa
J. Kuopanportti, S. Saarinen, T. Lahtinen and K. Ekström
From the journal Kerntechnik

Abstract

In Loviisa NPP, there are two limiting thermal margins called the enthalpy rise margin and the linear heat rate margin that are monitored during normal operation. Engineering safety factors are applied in determination of both of these factors. The factors take into account the effect of various manufacturing tolerances, impact of the irradiation and simulation uncertainties on the local heat rate and on the enthalpy of the coolant. The engineering factors were re-evaluated during 2015 and the factors were approved by the Finnish radiation and nuclear safety authority in 2016. The re-evaluation was performed by considering all of the identified phenomena that affect the local heat rate or the enthalpy of the coolant. This paper summarizes the work that was performed during the re-evaluation of the engineering safety factors and presents the results for each uncertainty component. The new engineering safety factors are 1.115 for the linear heat rate and 1.100 for the enthalpy rise margin when the old factors were 1.12 and 1.16, respectively. The new factors improve the fuel economy by about 1%.

Kurzfassung

Im KKW Loviisa gibt es zwei limitierende thermische Sicherheitsabstände, den des Anstiegs der Enthalpie und den der linearen Stableistung. Beide werden während des Betriebs überwacht. Bei der Ermittlung dieser beiden Sicherheitsabstände werden Sicherheitsfaktoren berücksichtigt. Diese Faktoren berücksichtigen die Wirkung verschiedener Fertigungstoleranzen, Auswirkungen der Bestrahlung und der Simulationsunsicherheit auf die lokale Stableistung und auf die Enthalpie des Kühlmittels. Im Jahr 2015 wurden diese Sicherheitsfaktoren neu bewertet und im Jahr 2016 von der Aufsichtsbehörde genehmigt. Die Neubewertung wurde unter Berücksichtigung aller identifizierten Phänomene, die die lokale Stableistung oder die Enthalpie des Kühlmittels beeinflussen, durchgeführt. Dieser Beitrag beschreibt die Arbeitsschritte der Neubewertung und stellt die Ergebnisse für jeden Einflussparameter vor. Die neuen Engineering-Sicherheitsfaktoren betragen 1.115 (vorher 1,12) für die lineare Stableistung und 1.100 (vorher 1,16) für den Anstieg der Enthalpie. Durch die neuen Faktoren verringert sich der Brennstoffverbrauch um etwa 1%.


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Received: 2017-01-27
Published Online: 2017-08-18
Published in Print: 2017-09-01

© 2017, Carl Hanser Verlag, München