Progress Report on OPG Heat Transport System Aging Safety Analysis

Transcription

1 ONTARIOFiiiiiER GENERATION 889 Brock Road pa2-sa 1 Pickering. Ontario L lw 3J2 W. M. (Mark) Elliott, P. Eng. Senior Vice President Nuclear Engineeri ng and Chief Nuclear Engineer Telephone: (905) x 5418 mark.elliott@opg.com August 15, 2013 CD#: N-CORR (P) MR. M. SANTtNI Director Pickering Regulatory Program Division MR. F. RINFRET Director Darlington Regulatory Program Division Canadian Nuclear Safety Commission 280 Slater Street Ottawa, Ontario K1P 5S9 Oear Messrs. Santini and Rinfret: Progress Report on OPG Heat Transport System Aging Safety Analysis Further to Ref. [1 ], the purpose of this leuer is to provide a progress report on Heat Transport System (HTS) Aging Safety Analysis and related activities and submit the analysis reports for Pickering A Small Break Loss of Coolant Accident (SBLOCA) and Loss of Flow (LOF) events. The Pickering A analysis results for SBLOCA and LOF demonstrate adequate shutdown system trip coverage with respect to maintaining fuel and fuel channel integrity for these accident scenarios and ensure continued safe operation for Pickering A to end of December 2017 (601 0 EFPD) for the lead unit. A summary of the enclosed analysis reports is provided in Table 1. Further discussion on these analyses is provided in Attachment 1 and full documentatio n of the analysis methodology and results are provided in the enclosed detailed analysis reports in Enclosure 1 (enclosed CO). Development of HTS models for Pickering B and Darlington aged conditions are currently underway and targeted for completion in A nalyses for Darlington and Pickering B SBLOCA and LOF will also be completed in alignment with the revised Ontario Power Generation Inc_ This documenl has been produced and distribuled for Ontario Power Generation Inc. purposes only. No part of this document may be reproduced, published, converted. or stored in any data retrieval system. or transmitted in any form by any means (electronic. mechanical, photocopying. recording. or otherwise) without the prior written I permission of Ontario Power Generation Inc.

2 Messrs. M. Santini and F. Rinfret August 15, 2013 CD # N-CORR validity periods in accordance with Ref. [2]. The current analyses continue to support the safe operation of Darlington and Pickering B units until December 15, 2013 and October 31, 2014 respectively. Updated analyses demonstrating sufficient margins for SBLOCA and LOF events for Darlington will be submitted in a standalone submission and will be tracked under a new regulatory management action as summarized in Table 2. As part of the HTS Aging Management Strategy (HTS-AMS) activities, Shutdown System trip setpoint modifications are being undertaken at Darlington and Pickering B to mitigate the effect of decreased safety margins. At Darlington, work is progressing into the detailed stages of the design change for the Heat Transport Low Pressure (HTLP) trip setpoint. The proposed Pickering B modifications to HTLP and Low Core Differential Pressure (LCDP) trip setpoints are currently in the preliminary stages of design change. The OPG HTS-AMS for site-specific and fleet-wide activities was updated and submitted in the previous progress report [1). Progress made since that report is reflected in the table in Attachment 2 of this letter. OPG has completed an impact assessment for two findings related to the modelling of reactivity effects of coolant void in safety analysis, which were reported to the CNSC in late 2012 [3, 4]. The scope of the impact assessment on coolant void includes impact on SBLOCA and LOF scenarios for Darlington and Pickering Band Large Break Loss of Coolant Accident (LBLOCA) for all stations. Impact on SBLOCA and LOF for Pickering A was assessed based on results for Pickering B. The results of these analyses indicate that fuel sheath integrity is maintained in the SBLOCA scenario and impact on LOF scenarios is very small. The impact on LBLOCA was assessed for all stations against the interim acceptance criterion for Hot Bundle Enthalpy (HBE) which was met at each station. The results of this impact assessment were presented to the CNSC in a meeting in Ottawa on June 28, At that meeting, the CNSC requested that the scope of the LBLOCA impact assessment be broadened to investigate additional parameters of interest, and the results be reported separately from the HTS aging progress report. A follow-up teleconference with the CNSC and Industry took place on July 22, 2013, and CNSC provided clarification on the additional scope required to address the findings. OPG is following up on the CNSC's request and work planning on increasing the LBLOCA impact assessment scope is currently underway. OPG will provide future updates on the impact assessment in separate correspondence. Per current practice, status updates for both Neutron Overpower Protection (NOP) analyses and 37M fuel implementation at Darlington will be reported separately. This submission completes regulatory management action AR to submit a progress report on OPG HTS Aging Safety Analysis. The next progress report will be provided to the CNSC by February 28, OPG will track this future submission under a new regulatory management action as summarized in Table 2. 2

3 Messrs. M. Santini and F. Rinfret August 15, 2013 CD # N-CORR If you require any further information, please contact Dr. YOksel Parlatan, Manager, Safety Analysis Improvement Project Department at (905) , extension Sincerely, " W. M. Elliott Senior Vice President, Nuclear Engineering and Chief Nuclear Engineer Ontario Power Generation CD Enc. cc: J. Jin G. McDougall Y. Z. Wang B. Finigan A Ling CNSC (Ottawa) CNSC (Ottawa) CNSC (Ottawa) CNSC Site Office - Pickering CNSC Site Office - Darlington 3

4 Messrs. M. Santini and F. Ri nfret August CD # N-CORR Table 1: Summary of Description of Enclosed Reports Report Title and Number Development of 4590 and 6010 EFPD TUF Aged Models for Pickering NGS A: Trending Analysis of HTS Operational Data and Creation of TUF Single Channel and Fun System Aged Input Data Sets N-REP R002 Description A thermalhydraulic model of the Pickering A Heat Transport System was developed for the projected aged conditions at 6010 EFPD. The model is produced using the computer code TUF, by tuning the relevant heat transport system and fuel channel parameters to produce the system conditions projected to occur at 6010 EFPD. The future aged conditions are projections based on the historical trends of station data including header pressures, flows, and temperatures. The result is a model for use in safety analysis such as small break. LOCA, LOF, and NOP EFPD corresponds approximately to the end of December 2017 for the lead unit, assuming continued full power operation and taking into account planned outage days. A previous revision of the report was submitted as an enclosure in the September 2012 HTS aging progress report (2]. The model has since been updated. Some of the modeling parameters incorporated into the previous revision (R001) have been rescinded in the most current revision fonowing an in depth review of TUF's treatment of momentum nux due to area change. The SBLOCA and LOF analyses enclosed in this leller were performed using the latest model associated with the ROO2 report enclosed in this letter. Pickering A Trip Effectiveness Assessment at This report documents the analysis examining shutdown 6010 EFPD following a Small Break Loss of system effectiveness for the limiting cases of a 100 kg/s break Coolant Accident and a guillotine break of the largest inlet feeder (GBUF) at end of December 2017 conditions for the lead unit. N-REP ROOO The analysis results indicate that SDSA is effective in maintaining fuel and fuel channel integrity following SBLOCA events. Although not a licensing requirement, SDSE is also examined and demonstrated to be effective. This analysis was performed with spatial kinetics through fully coupled TUF and RFSP reactor simulations. Pickering A Trip Effectiveness Assessment at This report documents the analysis examining shutdown 6010 EFPD following Loss of Flow Event system effectiveness for the limiting case of electrical failures resulting in the loss of eight heat transport system pumps at N-REP ROOO end of December 2017 conditions for the lead unit. The analysis results indicate that SDSA is effective in maintaining fuel and fuel channel integrity following LOF events. Although not a licensing requirement, SDSE is also examined and demonstrated to be effective. This analysis was performed with spatial kinetics through fully coupled TUF and RFSP reactor simulations. 4

5 Messrs. M. Santini and F. Rinfret August 15, 2013 CD # N-CORR Table 2: Summary of Regulatory Management Action Made Submission Title: Progress Report on Heat Transport System Aging Analysis Regulatory Management Actions (REGM): No, Commitment Description Completion Date 1 Provide CNSC with Darlinglon SBLOCA and LOF ana lyses 10 end of December 2017 for Ihe lead unit 13DEC Provide CNSC with a progress report on the OPG Heat Transport System Ag ing Safety Analysis. 28FEB2014 References 1. OPG Letter, W. M. Elliott to M. Santini and P. A. Webster, "Progress Report on OPG Heat Transport System Aging Safety Analysis," March 22, 2013, CD# N CORR OPG Letter, W. M. Elliott to M. Santini and P. A. Webster, "Progress Report on OPG Heat Transport System Aging Safety Analysis," September 25, 2012, CD# N CORR Reports, "Current TUF code version does not accurately model void fraction distribution in Fuel Channel," October 2012, CD# NA44-WER ROOO, NK30-WER ROOO, and NK38-WER ROOO. 4. Reports, "Review of Recent Study Suggests High Coolant Void Reactivity (CVR)," October 2012, CD# NA44-WER , NK30-WER ROOO, and NK38-WER

6 Attached to OPG letter, W. M. Elliott to M. Santini and F. Rinfret,"Progress Report on OPG Heat Transport System Aging Safety Analysis," CD# N-CORR Attachment 1 Summary of Pickering A Heat Transport System Aging Safety Analysis Update Safety Analysis has been performed for Small Break Loss of Coolant Accident (SBLOCA) and Loss of Flow (LOF) scenarios using the limit of operating envelope methodology to determine the impact of Heat Transport System (HTS) Aging using the new Pickering A model at 6010 EFPO aged HTS conditions. The SBLOCA analysis was performed for the limiting cases of a 100 kg/s break and a Guillotine Break of the Largest Inlet Feeder (GBLlF) at end of December 2017 aged HTS conditions for the lead unit. For the same aged conditions, the LOF analysis was performed for the limiting case of an electrical failure resulting in the loss of eight HTS pumps. Both analyses were performed using the latest safety analysis toolsets including the use of fully coupled thermal hydraulics and ph ysics codes with spatial kinetics simulation, and both employed validated safety analysis models. The coupled code suite of TUF/RFSP/RRS_Em has been demonstrated to possess the appropriate models for simulating important phenomena and is applicable to both SBLOCA and LOF analyses. Each report contains appendices documenting the applicability and accuracy of TUF for use in the analyses. In addition, the analyses were performed with updated RFSP Reference Dataset (RDS). The RDS has been generated with improved incremental cross sections and irradiation distribution. The LOF analysis for Pickering A was performed using spatial kinetics reactor physics simulation unlike the previous analysis at 4590 EFPD which used point kinetics simulation [1]. The spatial kinetics simulation predicts a more significant bulk power transient than the point kinetics analysis, and results in the backup trip on SDSA NOP prior to HTLP, which was credited as the backup trip in the previous analysis. The impact of using spatial kinetics for Pickering A LOF was documented and reported to the CNSC [2]. Trip coverage was confirmed for this case through an impact assessment which predicted effectiveness of the NOP trip. Trip coverage has been reconfirmed through detailed analysis. Both the current and previous Pickering A SBLOCA analyses were performed using spatial kinetics, and therefore the finding described above does not affect the SBLOCA analysis. A comparison of the current analyses for both LOF and SBLOCA at 6010 EFPO aged conditions to the previous analyses at 4590 EFPD represent not only the effects of HTS aging, but also reflect several modeling improvements. For this reason, the 6010 EFPD analysis results are not directly comparable to the previous analysis results. The most notable improvements include the spatial kinetics simulation mentioned above, the updated RFSP ROS, and the simulation of transition boiling prior to film boiling which is more representative of Post-Dryout (PDO) behaviour of CANDU, consistent with full scale water Critical Heat Flux I PDO tests at Stern Lab, and results in a reduction of the rate of PD~ sheath temperature increase. Several other differences are documented in the analysis reports in further detail. Results from these analyses demonstrate Shutdown System (SDS) A effectiveness for both SBLOCA and LOF scenarios. For SBLOCA, both the primary and secondary SDSA trips are demonstrated to occur before the onset of fuel sheath dryout. For the LOF scenario the primary SOSA trip occurs before the onset of dryout and the secondary SOSA trip occurs less 6

7 Attached to OPG letter, W, M. Elliott to M. Santini and F. Rinfret,"Progress Report on OPG Heat Transport System Aging Safety Analysis," CO# N-CORR than a second after the onset of dryout. The maximum fuel sheath temperature at time of secondary trip is 351 "C, well below the 600"C target. It is also demonstrated in the analysis reports that SDSE is effective, however it should be noted that this was completed only to demonstrate additional protection from SDSE, since SBLOCA and LOF are not licensing basis events for SDSE trip coverage. Based on the analysis results presented above, it is concluded that continued safe operation for the Pickering A units can be demonstrated until at least 6010 EFPD, corresponding to at least the end of December 2017 for the lead unit. References 1. Report, "Pickering NGS A: Eva luation of Impact of HTS Aging Effects on Loss of Flow Events for Operation up to 4590 EFPO," June 30, 2010, CO# N-REP Report, "Research Finding: Prediction of Reactor Response Using Spatial Kinetics Simulation Model for Loss of Flow events is different than previously reported," February 2013, CO# NA44-WER

8 Attached to OPG letter, W. M. Elliott to M. Santini and F. Ri nfret,"progress Report on OPG Heat Transport System Ag ing Safety Analysis," CD# N-CORR Attachment 2 Updates on Activities associated with the HTS Aging Management Strategy Previously completed items are not shown in this update. A fu ll listing of items is available in Ref [1]. HTS Aging Management Strategy (HTS AMS) Current Activities Item # Station Description TCO Status 1 PA Update NOP analysis PA NOP Analysis for 2017 aged conditions is targeted for comptetion by September PA Evaluate and propose operational Complete Complete. and/or design modifications Pickering A SBLOCA and LOF analyses (N-CORR , this letter) determined that no operational changes were required to the maximum channel power limits and maximum bundle power limits for Pickering A. 3 PB Update NOP analysis PB NOP Analysis for 2017 aged conditions to be initiated after completion of PA NOP Analysis. TCD has been updated from to Q to reflect progress of analysis to date. 4 PA Complete Pickering A LOF and Complete Complete. SBLOCA analyses to end of 2017 Analyses to 6010 EFPD corresponding to end of 2017 submitted as enclosure to this letter (N-CORR ). Analyses demonstrate adequate margins for both LOF and SBLOCA cases to the end of ON Complete Darlington LOF and Q Analysis initiated in SBLOCA analyses 10 end of 2017 Analysis validity period was extended and is valid until at least December 15, 2013 [1). TCD updated to December PB Complete Pickering B lof and Analysis to be initiated in SBlOCA analyses to end of 2017 References 1. OPG Letter, W. M. Elliott to M. Santini and P. A. Webster, ~ Progress Report on OPG Heat Transport System Aging Safety Analysis," September 25, 2012, CD# N CORR