Original scientific paper
On the Estimation and Reduction of the Frequency of the Loss of Offsite Power Event
Hrvoje Grganić
; Nuclear Power Plant Krško Vrbina 12, 8270 Krško, Slovenia
Zdenko Šimić
; Faculty of Electrical Engineering and Computing, University of Zagreb Unska 3, 10000 Zagreb, Croatia
Abstract
Loss of offsite power (LOOP) contributes significantly to the estimated core damage
frequency (CDF) for the majority of nuclear power plants (NPPs). Based on experience from some
near-miss events around the world and especially in Japan from Fukushima Daiichi accident and
several other NPPs it was proven the how important power supply is for nuclear safety. Therefore
comprehensive description of the LOOP initiating event is given in this paper. Specific experience
of the NPP Krško (NEK) related operation is also presented with comparison to the U.S. NPPs’
approaches and experience. Statistical data are given to explain main characteristics (frequency and
duration) of the LOOP event. Important historical trends are also identified.
LOOP event frequency is often calculated using generic data because of statistical data base.
Thereat, many important factors that influence LOOP are neglected, such as the specific power
network configuration, load profiles, climate conditions, and ageing of the equipment. Several
different approaches that take these factors into consideration are therefore presented and discussed.
Familiarity with the actual state of the NPP, power network and weather conditions helps in the
proper planning process of the test and maintenance (T&M) activities and reducing of the risk. This
is significant for better online risk estimate.
Due to the Fukushima accident, it is necessary to review the safety of the NPPs from new
different angles. This paper also shortly reviews planned modifications in NEK that will increase
the electric power supply availability (i.e., reduce LOOP event frequency. Other, worldwide
solutions that can help to avoid or mitigate LOOP effects are briefly presented.
Keywords
Hrčak ID:
199052
URI
Publication date:
31.7.2017.
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