Davis-Besse Nuclear Power StationReactor Vessel Incore Nozzles 1 Davis-Besse DavisNuclear Power Station November 26, 2002 Opening Remarks . . . . . . . . . . ……….……...Gary Leidich Reactor Vessel Incore Nozzles……………. Bob Schrauder • Incore Nozzle Configuration • Recent Inspection and Evaluation at Davis-Besse • Actions Prior to Returning the Plant to Service • Contingency Repair Concept • FLÜS Online Leak Monitoring System Closing Comments………………………….. Gary Leidich 2 Davis-Besse DavisNuclear Power Station November 26, 2002 Gary Leidich Executive Vice President - FENOC 3 Davis-Besse DavisNuclear Power Station November 26, 2002 • Brief the NRC Staff on the status of the DavisBesse Reactor Vessel Incore Monitoring Instrumentation Nozzles and future plans • Obtain NRC comments on Davis-Besse approach 4 Davis-Besse DavisNuclear Power Station November 26, 2002 CEO of FirstEnergy has set the standard of returning Davis-Besse back to service in a safe and reliable manner. We must do the job right the first time and regain the confidence of our customers, regulators, and investors in our nuclear program. We are committed to meeting this challenge. 5 Davis-Besse DavisNuclear Power Station November 26, 2002 Return to Service Plan Restart Overview Panel Reactor Head Resolution Plan Bob Schrauder Program Compliance Plan Jim Powers Containment Health Assurance Plan Randy Fast 6 Davis-Besse DavisNuclear Power Station System Health Assurance Plan Jim Powers Restart Test Plan Randy Fast Restart Action Plan Lew Myers Management and Human Performance Excellence Plan Lew Myers November 26, 2002 Inspection of the Incore Nozzles is part of the Containment Health Assurance Building Block in the Davis-Besse Return to Service Plan 7 Davis-Besse DavisNuclear Power Station November 26, 2002 Bob Schrauder Director - Support Services 8 Davis-Besse DavisNuclear Power Station November 26, 2002 Configuration • Babcock & Wilcox reactor vessel has 52 Incore Nozzles • Incore nozzles are ~ 1 inch in diameter • Original incore nozzles fabricated from Alloy 600 material • Welds - Alloy 182 (stress relieved) • Incore nozzles modified following Oconee 1 1972 Hot Functional Testing Failure 9 Davis-Besse DavisNuclear Power Station Incore Nozzles at Bottom of Reactor Vessel (Post-cleaning) November 26, 2002 Repair in Process Davis-Besse DavisNuclear Power Station 1 0 November 26, 2002 Completed Repair Incore Nozzles • Incore nozzles are exposed to lower temperature (558oF) than Control Rod Drive Mechanism nozzles (605oF) and are less susceptible to stress corrosion cracking • Visual inspections of the incore nozzles have not been routinely conducted in United States plants • Inspections/testing of incore nozzles at 13 French plants have not discovered cracking or leaking Davis-Besse DavisNuclear Power Station 1 1 November 26, 2002 Original Configuration EDF Nozzle Configuration Davis-Besse DavisNuclear Power Station 1 2 November 26, 2002 B&W Current Nozzle Configuration • Visual Inspections performed as part of the Extent of Condition Program Inspection of Bottom of Reactor Vessel Davis-Besse DavisNuclear Power Station 1 3 November 26, 2002 Bottom of Reactor Vessel Davis-Besse DavisNuclear Power Station 1 4 November 26, 2002 Inspection results: – Boron and rust deposit trails were observed on the sides and bottom of the reactor vessel – Similar deposits observed on several incore nozzles – Tape remnants and residue observed on incore nozzles – No build-up of boric acid or corrosion products on top of insulation – No evidence of wastage on bottom of reactor vessel Incore Nozzle #42 Incore Nozzle #45 Davis-Besse DavisNuclear Power Station 1 5 November 26, 2002 AREAS: • Reactor vessel flow trail and incore nozzle deposits OBJECTIVE: • Determine through chemical analysis whether flow trails and incore nozzle deposits had common source SAMPLE POPULATION: • 2 from flow trails observed on under reactor vessel sides • 12 from incore nozzles • Analysis by Framatome-ANP Davis-Besse DavisNuclear Power Station Bottom of Reactor Vessel 1 6 November 26, 2002 Incore Nozzle #45 35 45 14 13 1 3 7 46 18 27 • Sample locations ( ) chosen were nozzles 48 23 Davis-Besse DavisNuclear Power Station 1 7 November 26, 2002 • Boron and Lithium were higher at several incore nozzle locations than in flow trails and more comparable with previously analyzed upper head deposit samples (shown next slide) • Minor species (Uranium, Barium, Thorium, Strontium, & Zirconium) were higher at several incore nozzle locations than in the flow trails. However, the lack of activity associated with these species did not support reactor coolant as the source • Cobalt (Co60) and Iron (Fe59) were higher in the flow trails than at the incore nozzle locations • Inconsistent concentration gradients along possible flow trail paths Davis-Besse DavisNuclear Power Station 1 8 November 26, 2002 Comparison of Normalized Boron and Lithium Concentrations (Flow trails at bottom of reactor head and incore nozzle deposits) 40,000 35,000 30,000 25,000 ppm 20,000 15,000 10,000 5,000 0 Li B Tr ai l Tr ai l #1 Ru st #3 ci d #7 le No zz #1 3 le No zz #1 4 le No zz NW #1 8 A Bo ric #2 3 le No zz #2 7 le No zz #3 5 le No zz #4 5 le le No zz SE #4 6 le le No zz No zz No zz No zz Davis-Besse DavisNuclear Power Station 1 9 November 26, 2002 No zz le #4 8 le Conclusion From the results of the analysis, it is inconclusive whether the flow trails at the bottom of the reactor head and nozzle deposits had a common source Davis-Besse DavisNuclear Power Station 2 0 November 26, 2002 • FENOC and Framatome-ANP developed inspection plan • Bottom of reactor vessel thoroughly cleaned 9/2002 • Planned visual inspections prior to startup: – Raise Reactor Coolant System to normal operating pressure and temperature (hold for 3-7 days) – Potential use of hot optics (visual inspection aid) – Lower temperature and pressure – Perform bare metal reactor vessel visual inspection – Perform bare metal reactor vessel visual inspection during the next scheduled outage Davis-Besse DavisNuclear Power Station 2 1 November 26, 2002 Boron Deposit Rate For 2000 ppm Boron Reactor Coolant Leakage (Unchoked Flow) 100% Deposition Rate For a Given Number of Days 1000.000 35 Day 28 Day 21 Day 14 Day 10 Day 7 Day 3 Day 1 Day 100.000 Boric Acid Deposits (in3) 10.000 1.000 0.100 0.010 FLUES OPTION 1 ? 0.001 1.00E-06 FLUES OPTION 2 1.00E-05 1.00E-04 1.00E-03 1.00E-02 Leakage Rate (gpm) Davis-Besse DavisNuclear Power Station 2 2 November 26, 2002 • Inspections will be sufficient to detect leakage • Absence of boric acid will confirm that the deposits found in in 2002 were not from incore nozzle leaks Davis-Besse DavisNuclear Power Station 2 3 November 26, 2002 • Program Objectives – Measure leak rate as a function of simulated and/or actual flaw geometry • Benchmark analytical models for bounding leak rate calculations • Identify residue deposit chemistry and any volatile chemicals that exit the crevice • Investigate effect of annulus on leakage rates – Verify methods for detecting very small leaks • Visible evidence of boron residue • In-situ monitoring techniques Davis-Besse DavisNuclear Power Station 2 4 November 26, 2002 • Framatome-ANP Hot Leak Test Facility will be used to provide primary fluid: – Tc = 558º F; p = 2200 psig – Primary chemistry (boron & lithium concentration) • Mockup assembly will be connected to existing high temperature/ high pressure supply system • Leak rates measured from 10-6 to 0.25 gpm 2 5 November 26, 2002 Davis-Besse DavisNuclear Power Station • Mockup is being designed and built to measure leak rates through simulated (SCC) flaws • Leak rate bounding tests will be conducted for 8 hours each • Final test with a selected leak rate will be run for 5 days Davis-Besse DavisNuclear Power Station 2 6 November 26, 2002 • Insert mechanical plug and cut existing incore nozzle • Deposit 1/2” - 5/8” weld pad • Bore out incore nozzle remnant into reactor vessel to 1” maximum depth • Fit-up replacement nozzle and complete new weld • Remove mechanical plug PT 1/16" - 1/8" prior to welding New Alloy 690 Nozzle New SST Safe End Davis-Besse DavisNuclear Power Station 2 7 November 26, 2002 • If repairs are necessary, a meeting to discuss final design will be held with the NRC • 10CFR50.55a alternative code (ASME Code Section XI) requests will be necessary to permit implementation of repairs • Alternative code request will be similar to those submitted to NRC for the repair of Control Rod Drive Mechanism nozzles at other plants Davis-Besse DavisNuclear Power Station 2 8 November 26, 2002 • Davis-Besse plans to install FLÜS Online Leak Monitoring System • Ability to detect and locate leakage with significantly higher sensitivity than other available systems • Leak detection system measures the moisture penetrating a sensor tube • Installed or being installed in 12 units in a variety of European countries and Canada • Operational history of 10 years Davis-Besse DavisNuclear Power Station 2 9 November 26, 2002 Non-Sensitive Tubing Sensor Element Davis-Besse DavisNuclear Power Station 3 0 November 26, 2002 FLÜS SENSORS RV Insulation • Install sensor tube between the reactor vessel insulation and reactor vessel • Simple installation • Expected sensitivity of approximately 4E-3 to 2E2 gpm • System sensitivity is dependent on the air tightness of reactor vessel insulation 3 1 November 26, 2002 Davis-Besse DavisNuclear Power Station Gary Leidich Executive Vice President - FENOC Davis-Besse DavisNuclear Power Station 3 2 November 26, 2002
Report "Davis-Besse Nuclear Power Station Reactor Vessel Incore Nozzles"