COMPONENTE 5 FORTALECIMIENTO INSTITUCIONAL, CREACIÓN DE UNA UNIDAD EJECUTORA
S. A DE C.V JULIO CESAR LOPEZ MOLINA SERVICIOS DE CONSTRUCCION, DISENO Y SUPERVICION DE OBRAS DE INGENIERIA CIVIL,
STUK assessed the operating experience feedback on the basis of reports, inspection visits and inspec- tions within the periodic inspection programme. During the year, there were no events classified as INES 1 or higher.
Three root cause analyses were performed at the Loviisa power plant in 2011. Their subjects were the problems related to ventilation and cool- ing systems, management of component isolations and the modification process. The related events
and observations are described in more detail in Appendix 3. The root cause analyses also con- sidered several events with similar features of underlying factors. The analysis tool used was the AcciMap method, which the power company has used for seven root cause analyses since 2008.
The different steps of the root cause analyses brought up various observations concerning the technical solutions of systems or the operations of the organisation that can be deemed to be of particular importance. The analyses have been used as the basis for developing the procedures for nuclear fuel handling, risk assessment of work operations and the technical planning of projects. Factors leading to the events were identified in several areas, such as instructions, competence, observance of instructions or established practices, flow of information and lack of systems or tools supporting isolation management. The proposed actions related, among other things, to kick-off meeting practices, isolations carried out during daytime, qualification requirements regarding pro- cess chemistry and to recording observations.
The Loviisa power plant provided STUK with special reports regarding the omission of the hydro- gen analysis required in the Operating Limits and Conditions and regarding the initiation of main- tenance operations on the DC systems of a diesel generator while still in power operation. The events are described in closer detail in Appendix 3. STUK was provided with 12 event reports. A total of 52 un- expected operation-related events were recorded at the Loviisa power plant. The most significant events were processed at the Loviisa power plant, and the reports were completed on time. The reports related, for example, to water and other leaks, component isolation problems, modification works, component failures and methods of operation.
The follow-up procedures regarding the imple- mentation and success of corrective actions decided following operational events at the Loviisa power plant are currently insufficient. The areas in need of improvement include the setting of priorities regarding action decisions and the timely imple- mentation of actions. The Loviisa power plant has participated in the corporation-led development of a new follow-up system for observations, opera- tional events and risk management. Organisation of the operating experience feedback activities as a separate group was being planned during the year.
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The Loviisa power plant also intends to expand the group of people dealing with operating experience feedback.
The procedures for utilising international op- erating experience feedback function well at the Loviisa power plant. Foreign event reports are comprehensively analysed, and the corrective ac- tions decided on their basis are justified and trace- able. Fortum itself conducts pre-screening of the reports coming from various sources, mainly via WANO and the IRS system maintained by IAEA/ NEA. The selection criterion for events to be taken to the International operating experience team is their safety significance for the Loviisa power plant. The operating experience feedback activi- ties and the monitoring of their impact could be further enhanced and improved using a uniform operating experience feedback database covering the company’s internal and external operating ex- perience. The fire that occurred in connection with the containment leak tightness test performed in connection with the 2011 maintenance outage of
Ringhals 2, and the protective plastic sheet that burned, releasing a lot of corrosive chlorides, was also identified as an issue to be investigated at Loviisa. Fortum investigated the amount of plastic materials in the reactor hall in order to assess the fire load and risk. During the cleaning operations following the fire, a possible operational risk was discovered in the containment spraying system at Ringhals, caused by foreign material found in the pipelines. The foreign material possibly consisted of plugs and welding debris dating back to the modification work carried out in 1988, and it had not been detected in the periodic tests performed using air. No similar blockage of the containment spraying system has been identified as a problem at Loviisa.
The IRS reports dealing with the connecting rod bearing problems of EDGs in Germany and France had significant information for Finnish plants because the Loviisa power plant has emergency diesel generators of a similar size. The investiga- tions performed by the power company revealed
Loviisa µSv 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
Figure 9. Annual radiation doses to the critical groups since the start of operation of the Loviisa nuclear power plant. Over the recent years, the doses to the critical groups have remained below one percent of the set limit, 0.1 milliSv. Loviisa manSv 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
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that bearings of the subject type, proven to be sus- ceptible to damage, had been installed in one of the EDGs at the Loviisa power plant in the summer 2009. The bearings were changed back to the origi- nal type in January 2011. It transpired during the basic overhaul of another EDG at Loviisa in the summer 2011 that the situation in spare bearings for the EDGs is worrying and an extensive problem because the supplier does not yet have a new, ap- proved replacement bearing, and the old type bear- ings are no longer available. Fortum commissioned VTT to investigate the reasons behind the bearing damage. STUK reported the bearing problems in- ternationally.
Following the results of the root cause analysis, STUK supplemented its report submitted in 2010 to the operating experience database maintained by the IAEA regarding an event at the Loviisa power plant where radioactive resin escaped into the ventilation channel from the mixing tank of a liquid waste solidification plant in trial operation.