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Assessment of the safety upgrading for Unit 2 of Armenian NPP IC related issues

Regional Workshop on Modernization Projects of NPP Instrumentation and Control Systems Related to Power Uprates and Licence Renewals Project (RER/4/027)Portoroz, Slovenia14-18 April 2008. Introduction. Performed modernizations for I

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Assessment of the safety upgrading for Unit 2 of Armenian NPP IC related issues

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    1. Assessment of the safety upgrading for Unit 2 of Armenian NPP I&C related issues Tsolak Malakyan, Nuclear & Radiation Safety Centre (NRSC) Gagik Matnishyan, Armenian Nuclear Regulatory Authority (ANRA)

    2. Regional Workshop on Modernization Projects of NPP Instrumentation and Control Systems Related to Power Uprates and Licence Renewals Project (RER/4/027) Portoroz, Slovenia 14-18 April 2008

    3. Regional Workshop on Modernization Projects of NPP Instrumentation and Control Systems Related to Power Uprates and Licence Renewals Project (RER/4/027) Portoroz, Slovenia 14-18 April 2008 Task A: Adaptation and completion of safety issues list related of I&C 16 safety related issues for I&C were assessed 12 safety related issues from IAEA TECDOC-649 3 additional safety related issues proposed by GRS/Riskaudit experts

    4. Regional Workshop on Modernization Projects of NPP Instrumentation and Control Systems Related to Power Uprates and Licence Renewals Project (RER/4/027) Portoroz, Slovenia 14-18 April 2008 Task A: Adaptation and completion of safety issues list related of I&C Conclusion of this stage are that all considering issues escape of 1 are relevant for ANPP initial design

    5. Regional Workshop on Modernization Projects of NPP Instrumentation and Control Systems Related to Power Uprates and Licence Renewals Project (RER/4/027) Portoroz, Slovenia 14-18 April 2008 Task B: Detailed analysis safety issues list related of I&C The goals of task B2 is development of technical report with assessment of technical solutions completeness for elimination of safety deficiencies. Here only information related safety issues of categories IV and III are presented Reliability of I&C Equipment (III) I&C Redundancy, Separation and Independence (IV) I&C / Electrical Equipment Qualification (III) Control Room Habitability/Shutdown Panel (III)

    6. Regional Workshop on Modernization Projects of NPP Instrumentation and Control Systems Related to Power Uprates and Licence Renewals Project (RER/4/027) Portoroz, Slovenia 14-18 April 2008 Task B: Detailed analysis safety issues list related of I&C Reliability of I&C Equipment (III) Issue description: I&C equipment still used is very old fashioned (e.g. electrochemical switches, relays) and its reliability is questionable. The causes include deterioration with age, difficulty of maintenance and testing and the need for frequent attention. Modernisation: The replacement of non-seismic relays in emergency protections and interlocks circuits was performed with seismic relays at ANPP. The non-seismic sensors and secondary instruments operated in protection and interlock circuits were replaced with seismic ones. New digital instruments were installed at MCR of Unit 2: “network frequency”, current frequency on 28NA, 29NA buses; “Unit total electrical output”; measuring sets of TG-3,4 revolutions; electrical capacity of TG-3,4. The instrumentation stock of ANPP main and auxiliary systems was significantly renewed; Additional “P” measuring instruments were installed in SG-RCP compartment and in this connection new interlocks on confinement ventilation systems were implemented. The number of “H” measuring channels in 2SG-1?6 was significantly increased. Additional “?P” measuring sets (two sets for every RCP) were installed on 2RCP-1?6 and in this connection the EP-III actuation logic was modified by 2 out of 3 logic.

    7. Regional Workshop on Modernization Projects of NPP Instrumentation and Control Systems Related to Power Uprates and Licence Renewals Project (RER/4/027) Portoroz, Slovenia 14-18 April 2008 Task B: Detailed analysis safety issues list related of I&C Reliability of I&C Equipment (III) Modernisation: Additional “?P between SG and MSH” and “P” instrument sets were installed in MSH (to provide channelling principle). The differential transformer sensors and transmitters were replaced with 0?5mA standard output sensors. All I&C sensors and instruments were replaced on DG-3, 4, 5, 6. All protection removal keys were eliminated from reactor protection generation circuits. “Safety parameters display system were implemented at Unit 2 with their individual sensors qualified for operation in environmental and seismic conditions. Physical and galvanic isolation of measuring channels was performed though there are still common circuits left.The whole instrumentation stock is subjected to departmental and laboratory tests in compliance with annual test schedule. Modernization of SG level regulators (performed during 2006 outage)

    8. Regional Workshop on Modernization Projects of NPP Instrumentation and Control Systems Related to Power Uprates and Licence Renewals Project (RER/4/027) Portoroz, Slovenia 14-18 April 2008 Task B: Detailed analysis safety issues list related of I&C Reliability of I&C Equipment (III) Modernisation: Replacement of source range neutron flux monitoring instrumentation (performed during 2006 outage) There were installed four sets for level controlling and four sets of four-meter level controllers on each SG. Upon the installation of these instruments the interlock and protection set-points were isolated though there are still some common circuits. Modernization of old automatic reactor power regulation (ARM) system Effectiveness of modernization It is necessary to identify those I&C which have significant influence on NPP safety and perform measures to increase their reliability. This analysis could be done using PSA model developed for ANPP.

    9. Regional Workshop on Modernization Projects of NPP Instrumentation and Control Systems Related to Power Uprates and Licence Renewals Project (RER/4/027) Portoroz, Slovenia 14-18 April 2008 Task B: Detailed analysis safety issues list related of I&C I&C Redundancy, Separation and Independence (IV) Issue description: There are numerous instances where redundancy, physical and electrical separation and independence of safety related instrumentation channels are not adequately provided Modernisation: The type of activation logic is that all the channels of emergency protection system are designed with logic 2 out of 3 (or 2 out of 6 for the steam generator protection for all 6 loops). They mainly use de energize-to actuate technique. Only one channel (delta pressure on reactor coolant pump) use energize-to actuate technique. All protections and interlocks of reactor are powered from six buses of –220V DC (3 bushings from 2BAB-1 and 3 bushings from BAB-2), the loss of even 4 corresponding bus won’t effect the safety system operation. The Unit 2 MCR, the process alarm circuits are powered from two I category reliability buses (according to Automatic Stand-by Start-up circuit) of 28NA and 29NA AC buses. Modernization is foreseen in 2008 aimed to separation (physically and electrically) of emergency protection system’s channels as possible (during implementation of modernization ANPP will fully follow and respect the international design rules (diversity, redundancy, physical separation etc.)) Effectiveness of modernization Foreseen modernizations will increase independence of the existing safety related instrumentation, however modernization needs to include measurements which will assure total independency between A and B channels of emergency protection system. Otherwise planned modernization only partially will cover this issue.

    10. Regional Workshop on Modernization Projects of NPP Instrumentation and Control Systems Related to Power Uprates and Licence Renewals Project (RER/4/027) Portoroz, Slovenia 14-18 April 2008 Task B: Detailed analysis safety issues list related of I&C I&C / Electrical Equipment Qualification (III) Issue description: At the time the design was made, the environmental and seismic qualification of instrumentation and electrical equipment was not addressed, and there was no backfitting program developed in that field up to now. Modernisation: Measures are foreseen aimed to safety-related equipment qualification. It is planned to perform this work in 2008 based on current international qualification standards The Engineered Seismic Protection System is replaced with a new Engineered Seismic Protection System-2, interlocking logic is simplified for the functioning of ESPS. Cable lines, supply systems, protections, interlocks and other consumers of safety systems and safety related systems are reconstructed in the form of two divergent category I and II power supply systems. Seismic non-qualified relay, detectors and gauges are replaced with seismic-resistant ones. ANPP put into operation new diagnostic systems: acoustic primary leak detection system (ALUS); primary loose object detection system (KUS).

    11. Regional Workshop on Modernization Projects of NPP Instrumentation and Control Systems Related to Power Uprates and Licence Renewals Project (RER/4/027) Portoroz, Slovenia 14-18 April 2008 Task B: Detailed analysis safety issues list related of I&C I&C / Electrical Equipment Qualification (III) Modernisation: Feasibility study has been done for replacement of an old ??-500?? information computing system with an advanced complete set that meets the current seismic requirements. Cables and communication instrumentation of the unit were analysed in the view of their resistance to short circuits, recommendations were developed on improvement of reliability and thermal resistance of cables and instrumentation: automatic fire alarm for switchboard rooms, intake air-ducts of MCR, ECB implemented on the basis of seismic qualified components was documented; documentation was developed and ANPP reconstructed the snubber displacement control system; rooms containing I&C and safety related electric equipment are seismic qualified against current requirements; up to 1976 both I&C, electric equipment and switchboards were tested against seismic resistance.

    12. Regional Workshop on Modernization Projects of NPP Instrumentation and Control Systems Related to Power Uprates and Licence Renewals Project (RER/4/027) Portoroz, Slovenia 14-18 April 2008 Task B: Detailed analysis safety issues list related of I&C I&C / Electrical Equipment Qualification (III) Modernisation: The tests were performed on vibration stand in the frequency range of 0?30Hz and peak ground acceleration (0.4g and 1.08g). In 1976-1977 the second phase of tests was performed on vibration stand for seismic resistance of I&C, electric equipment and switchboard devices with due consideration of their reinforcement and anchoring which demonstrated their seismic resistance. seismic tests resulted in replacement of CK-40 type batteries with seismic resistant “VARTA” type, mounted on seismic resistant stacks. In 1998 motors on all Main Stop Valves were replaced with impermeable motors. Effectiveness of modernization A performed modernization allows qualifying seismically I&C/Electrical equipment at ANPP. However other environmental hazards were not considered.

    13. Regional Workshop on Modernization Projects of NPP Instrumentation and Control Systems Related to Power Uprates and Licence Renewals Project (RER/4/027) Portoroz, Slovenia 14-18 April 2008 Task B: Detailed analysis safety issues list related of I&C Control Room Habitability/Shutdown Panel Issue description: There is insufficient provision to maintain control room habitability. In case of main control room inhabitability or unavailability, there is no other centralized location from where a safe shutdown can be performed . Modernisation: In case of shut down and MCR unavailable, it is possible for the operators to monitor the plant with following parameters: Level in SG-1-6, Primary pressure, Level in Prz, Temperature in cold and hot legs, Temperature difference between hot and cold legs, Temperature in Prz. Neutron flux could be monitored from reactor building central hall (Shelter room - reserve emergency cooldown panel’s I&C is qualified as safety-related equipment), from the shelter room, which is located in the reactor building. These parameters are displayed in MCR during normal operation (same sensors used for MCR and reserve emergency cooldown panel) Implementation of adequate air filtering, supplied to MCR is foreseen in 2009 as well as flying objects protection installation Implementation of reserve control panel is foreseen in 2009

    14. Regional Workshop on Modernization Projects of NPP Instrumentation and Control Systems Related to Power Uprates and Licence Renewals Project (RER/4/027) Portoroz, Slovenia 14-18 April 2008 Task B: Detailed analysis safety issues list related of I&C Control Room Habitability/Shutdown Panel Modernisation: By design following measures were implemented to address this issue: Separation of scram buttons - MCR, SUZ-2 panel and Central control panel. Measures are taken for rooms and buildings seismic stability increase. Replacement of single-wing doors in cable tunnels and in turbine hall on the door with 90 min. fire-resistance is performed. Gas masks, air bottles, and communication are existing at MCR. Emergency personnel protection procedures are developed related Effectiveness of modernization The original design of MCR at ANPP provides sufficient base to maintain control room habitability in case of main control room inhabitability or unavailability. Implementation of reserve control panel will allows performing safe shutdown in case of unavailability of MCR.

    15. Regional Workshop on Modernization Projects of NPP Instrumentation and Control Systems Related to Power Uprates and Licence Renewals Project (RER/4/027) Portoroz, Slovenia 14-18 April 2008 Conclusion Performed modernizations for I&C improvement for ANPP were based on recommendations coming from IAEA-TECDOC-640 Most of recommendations for III and IV category issues were addressed Implementation of the rest recommendations is included in modernization program for 2006-2016 Further modernizations on I&C will be developed based on safety assessments (SAR and PSA results)

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