This paper presents the results of the statistical analysis of the loss of offsite power events (LOOP) registered in four reviewed databases. The reviewed databases include the IRSN (Institut de Radioprotection et de Sûreté Nucléaire) SAPIDE database and the GRS (Gesellschaft für Anlagen- und Reaktorsicherheit mbH) VERA database reviewed over the period from 1992 to 2011. The US NRC (Nuclear Regulatory Commission) Licensee Event Reports (LERs) database and the IAEA International Reporting System (IRS) database were screened for relevant events registered over the period from 1990 to 2013. The number of LOOP events in each year in the analysed period and mode of operation are assessed during the screening. The LOOP frequencies obtained for the French and German nuclear power plants (NPPs) during critical operation are of the same order of magnitude with the plant related events as a dominant contributor. A frequency of one LOOP event per shutdown year is obtained for German NPPs in shutdown mode of operation. For the US NPPs, the obtained LOOP frequency for critical and shutdown mode is comparable to the one assessed in NUREG/CR-6890. Decreasing trend is obtained for the LOOP events registered in three databases (IRSN, GRS, and NRC).

No abstract

This paper presents the results of the trend analysis of Loss of Offsite Power (LOOP) events registered in two reviewed databases. The reviewed databases include the Nuclear Regulatory Commission (NRC) Licensee Event Reports (LERs) database and the IAEA International Reporting System (IRS). Both databases were screened for the relevant events registered in period 1990 to 2012. The statistical analysis of the identified relevant LOOP events is done. The analysis includes assessment of the LOOP initiating event frequency, distribution of the events per year in the analysed period and trend analysis of the identified events. The LOOP frequency is calculated for LOOP events registered in NRC LERs subdivided into four types by cause or location: plant centered, switchyard centered, grid related, and weather related. These four LOOP categories are assessed for two modes of operation (critical and shutdown operation). The number of LOOP events in each year over the analysed period and distribution of events per unit in given year were assessed from the reviewed databases. Trend analysis of the identified events is performed with the utilization of four trend measures. Analysis is done for events registered during power and shutdown operation and their sum. The obtained LOOP frequency for events registered NRC LERs for critical and shutdown mode is comparable to the one assessed in NUREG/CR-6890. Decreasing trend is obtained for the LOOP events registered for events in NRC LER database. Different trends are identified during critical and shutdown modes of operation for the events registered in the IAEA database. The sum of the LOOP events reported during critical and shutdown modes in IAEA IRS show no trend.

An overview of the Spanish reactor pressure vessel surveillance programs is presented. This overview includes a description of the surveillance capsules that have been analyzed in the operating reactors to date. Several important considerations regarding the long-term operation of the Spanish reactors are discussed, including the use of reconstituted Charpy specimens and the implementation of ex-vessel dosimetry in the Spanish reactors.

This paper presents the results of statistical and engineering analysis of Loss of Offsite Power (LOOP) events registered in four reviewed databases. The paper includes events registered in IRSN (Institut de Radioprotection et de Sûreté Nucléaire) SAPIDE and GRS (Gesellschaft für Anlagen- und Reaktorsicherheit mbH) VERA database in time period 1992 to 2011. The Nuclear Regulatory Commission (NRC) Licensee Event Reports (LERs) database and the IAEA International Reporting System (IRS) database are screened for the relevant events registered in period 1990 to 2013. In total, 228 relevant events were identified in the IRSN database, 190 in GRS, 120 in LER and 52 in IRS. The data include events registered both during the critical (at power) and shutdown operation of the plants. The identified events were classified considering nine different categories. In the three databases (SAPIDE, VERA, IAEA-IRS) the largest numbers of events are registered for the plant centered category. The largest number of the events in the NRC-LER database is found for switchyard centered events. According to the mode of operation, most events were reported during critical power operation, in all four databases. The “Partial loss of external power” events are the most frequent type of event found in the IRSN and NRC databases while the “Physical loss of electrical busbars” is the main type in the GRS and IAEA databases. The largest number of events in all databases is identified for the switchyard failures followed by the interconnections failures (both lines and transformers). Mainly LOOP event are identified by the fault report in the control room. Electrical deficiency is detected as the main direct cause of events. Environment is registered as the main contributor for the electrical grid deficiency in the French and NRC databases. Electrical failures are dominant contributor to the electrical grid deficiency in the German and IAEA databases. The principal root cause for the LOOP events are human failures with the human errors during test, inspection and maintenance as the largest sub-group. The largest number of the LOOP events resulted in reactor trip followed by the Emergency Diesel Generator (EDG) start. The majority of the reported LOOP events lasted for more than 2 minutes. Main lessons learned from the analysed events and potential actions for decrease of the number of LOOP events are presented.