ML033490234
| ML033490234 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 04/04/2003 |
| From: | FirstEnergy Nuclear Operating Co |
| To: | Office of Nuclear Reactor Regulation |
| Hopkins J , NRR/DLPM, 301-415-3027 | |
| Shared Package | |
| ML033490221 | List: |
| References | |
| Download: ML033490234 (31) | |
Text
Davis-Besse Davis-Besse Nuclear Power Station Nuclear Power Station April 4, 2003 1
Reactor Vessel Incore Monitoring Instrumentation Nozzle Leakage Simulation Results Davis-Besse Nuclear Power Station
Davis-Besse Davis-Besse Nuclear Power Station Nuclear Power Station April 4, 2003 2
Agenda Opening Remarks............ Gary Leidich
- Background on Reactor Vessel IMI Nozzles.. Jim Powers
- Simulation of Reactor Vessel IMI Nozzle LeakageCraig Hengge Closing Comments..... Gary Leidich
Davis-Besse Davis-Besse Nuclear Power Station Nuclear Power Station April 4, 2003 3
Gary Leidich Executive Vice President - FENOC Opening Remarks
Davis-Besse Davis-Besse Nuclear Power Station Nuclear Power Station April 4, 2003 4
Desired Outcome
- Brief the NRC Staff on the Incore Monitoring Instrumentation (IMI) Nozzle Leakage Simulation Configuration and the Test Results
- Address the Plant Normal Operating Pressure Inspection Plan
Davis-Besse Davis-Besse Nuclear Power Station Nuclear Power Station April 4, 2003 5
Return to Service Plan
- Inspection of the IMI Nozzles is part of the Containment Health Assurance Building Block in the Davis-Besse Return to Service Plan Restart Overview Panel Restart Overview Panel Return to Service Plan Return to Service Plan Containment Health Containment Health Assurance Plan Assurance Plan Randy Fast Randy Fast Program Compliance Plan Program Compliance Plan Jim Powers Jim Powers Restart Action Plan Restart Action Plan Lew Lew Myers Myers Reactor Head Reactor Head Resolution Plan Resolution Plan Bob Bob Schrauder Schrauder System Health System Health Assurance Plan Assurance Plan Jim Powers Jim Powers Restart Test Plan Restart Test Plan Randy Fast Randy Fast Management and Human Management and Human Performance Excellence Performance Excellence Plan Plan Lew Lew Myers Myers
Davis-Besse Davis-Besse Nuclear Power Station Nuclear Power Station April 4, 2003 6
Jim Powers Director - Davis-Besse Engineering Background on Reactor Vessel Incore Monitoring Instrumentation (IMI) Nozzles
Davis-Besse Davis-Besse Nuclear Power Station Nuclear Power Station April 4, 2003 7
- Babcock & Wilcox reactor vessel has 52 IMI nozzles
- IMI nozzles are ~ 1 inch in diameter
- Original IMI nozzles fabricated from Alloy 600 material
- J-Groove welds - Alloy 182 (stress relieved)
- IMI nozzles modified (not stressed relieved) following Oconee 1-1972 Hot Functional Testing Failure IMI Nozzles Configuration B&W Nozzle Configuration Modified IMI nozzle (inside of reactor vessel)
Davis-Besse Davis-Besse Nuclear Power Station Nuclear Power Station April 4, 2003 8
IMI Nozzles Industry Experience
- IMI nozzles are exposed to lower temperatures (558oF) than Control Rod Drive Mechanism (CRDM) nozzles (605oF)
- Alloy 600 material is generally less susceptible to stress corrosion cracking at lower temperatures
- Visual inspections of the IMI nozzles have not been routinely conducted in United States plants
- Inspections of IMI nozzles at thirteen French plants have not discovered cracking or leaking
Davis-Besse Davis-Besse Nuclear Power Station Nuclear Power Station April 4, 2003 9
EDF vs. B&W Nozzle Configuration B&W Current Nozzle Configuration EDF Nozzle Configuration Original Configuration
Davis-Besse Davis-Besse Nuclear Power Station Nuclear Power Station April 4, 2003 10
- Boron and rust deposit trails were observed on the sides and bottom of the reactor vessel
- No build-up of boric acid deposits or corrosion products on top of insulation
- No evidence of wastage on bottom of reactor vessel IMI Nozzles at Bottom of Reactor Vessel (Post-cleaning)
Inspection Results Summer 2002
Davis-Besse Davis-Besse Nuclear Power Station Nuclear Power Station April 4, 2003 11 Deposit Characterization Summary
- Boron and Lithium were higher at several IMI nozzle locations than in flow trails and more comparable with previously analyzed upper head deposit samples
- Minor species (Uranium, Barium, Thorium, Strontium, & Zirconium) were higher at several IMI nozzle locations than in the flow trails.
However, the lack of activity associated with these species did not support reactor coolant as the source
- Inconsistent concentration gradients along possible flow trail paths
Davis-Besse Davis-Besse Nuclear Power Station Nuclear Power Station April 4, 2003 12 Deposit Characterization Conclusion
- From the results of the analysis, it was inconclusive whether the flow trails at the bottom of the reactor head and IMI nozzle deposits had a common source
- Framatome ANP was tasked to conduct simulation testing to determine the ability to visually detect the presence of very small leaks that would be associated with a cracked weld or IMI nozzle
Davis-Besse Davis-Besse Nuclear Power Station Nuclear Power Station April 4, 2003 13 Simulation of IMI Nozzle Leakage Craig Hengge Engineer - Plant Engineering
Davis-Besse Davis-Besse Nuclear Power Station Nuclear Power Station April 4, 2003 14 Leakage Simulation Test Program Objectives
- Confirm that very small leak rates would result in visible boric acid crystals at the exit of the annulus between the nozzle and reactor vessel
- Characterize the residue deposit chemistry that exits the annulus
Davis-Besse Davis-Besse Nuclear Power Station Nuclear Power Station April 4, 2003 15 Leakage Simulation Test Facility
- Facility designed/built to achieve the primary and secondary side temperature and pressure conditions for Babcock and Wilcox pressurized water reactor systems
- Project performed in accordance with Framatome ANP Quality Assurance Program
- Mockup design and fabrication controlled
- Material traceability maintained during fabrication
- Test procedures written and approved
- Calibrated instruments used for all measurements (leak rates measured on best-effort basis)
Davis-Besse Davis-Besse Nuclear Power Station Nuclear Power Station April 4, 2003 16 Leakage Simulation Test Basic Description of Test
- Demineralized water containing Boric Acid and Lithium in the primary system holding tank was pumped through a series of electric heaters to achieve desired test temperature
- Water entered nozzle mockup assembly, heated up the mockup to primary side temperature and was free to leak through capillary tubing into annulus
- Pressure was monitored by transducers and temperatures by thermocouples (data recorded)
Davis-Besse Davis-Besse Nuclear Power Station Nuclear Power Station April 4, 2003 17 Leakage Simulation Test Mockup
- Test Assemblies consisted of an Alloy 600 nozzle (3.990 inch outer diameter) inserted into an AISI 8620 carbon steel head with a 0.010-inch annulus
- Various lengths of 0.005-inch and 0.010-inch inner diameter stainless steel capillary tubes were tested to simulate a range of potential leak rates
Davis-Besse Davis-Besse Nuclear Power Station Nuclear Power Station April 4, 2003 18 Leakage Simulation Test Collection of Deposits
- Test leakage was condensed, collected as liquid, and weighed at discrete time intervals
- Mockup was disassembled and inspected to determine the distribution and quantity of residue deposits, and for evidence of flow assisted corrosion (FAC)
- Nozzle was removed and visually examined
- Photographs of observed deposits were taken prior to collecting the deposit samples Test #1 (leak rate: 0.015 gpm)
Nozzle OD showing leak path Test Simulation Photo Test #5 (leak rate: 0.0006 gpm)
Crusty yellow deposit buildup on nozzle wall at annulus discharge Test Simulation Photo
Davis-Besse Davis-Besse Nuclear Power Station Nuclear Power Station April 4, 2003 19 Leakage Simulation Test Parameters
- Five tests conducted at varying leak rates
- Primary water leaked at controlled rates (0.0004 to 0.015 gpm) into an annulus
- Capillary tubing was used to achieve low leak rates
- Tests were conducted at both Mode 1 and 3 plant operating temperatures and pressures
- Leakage was collected for analysis
- Test mockup was inspected after each test Test #2 (leak rate: 0.0017 gpm)
Inside of nozzle showing capillary tube arrangement Test Simulation Photo
Davis-Besse Davis-Besse Nuclear Power Station Nuclear Power Station April 4, 2003 20 Leakage Simulation Test Test Matrix TEST # DURATION BORON LEAK RATE 1
6.3 Hours 2680 ppm 0.015 gpm 2
8 Hours 2680 ppm 0.0017 gpm 3
8 Hours 2680 ppm 0.0004 gpm 4
8 Hours 1134 ppm 0.0012 gpm 5
55 Hours 2680 ppm 0.0006 gpm (0 gpm after 47 hr)
- All tests resulted in visible residue on nozzle and vessel surface
- Significant Lithium deposits left at nozzle/vessel surface
Davis-Besse Davis-Besse Nuclear Power Station Nuclear Power Station April 4, 2003 21 Leakage Simulation Test Test #1 (leak rate: 0.015 gpm)
Inside of vessel head after removal of nozzle, showing eroded leak path Before cleaning Test Simulation Photo Test #1 (leak rate: 0.015 gpm)
Post test view of nozzle/vessel head assembly Annulus Test Simulation Photo Annulus
Davis-Besse Davis-Besse Nuclear Power Station Nuclear Power Station April 4, 2003 22 Leakage Simulation Test Test #2 (leak rate: 0.0017 gpm)
Nozzle OD showing buildup of white deposits Test Simulation Photo Test Simulation Photo Test #2 (leak rate: 0.0017 gpm)
Close-up view of head-to-nozzle annulus showing buildup of white deposits at exit of annulus Annulus
Davis-Besse Davis-Besse Nuclear Power Station Nuclear Power Station April 4, 2003 23 Leakage Simulation Test Test #3 (leak rate: 0.0004 gpm)
Post test view of nozzle/head assembly & thrust plate Test Simulation Photo Test #3 (leak rate: 0.0004 gpm)
Nozzle surface deposits Test Simulation Photo
Davis-Besse Davis-Besse Nuclear Power Station Nuclear Power Station April 4, 2003 24 Leakage Simulation Test Test #4 (leak rate: 0.0012 gpm)
Nozzle outer diameter showing buildup of white deposits at discharge of annulus Test Simulation Photo Test #4 (leak rate: 0.0012 gpm)
Close-up of head-to-nozzle annulus showing buildup of white deposit at exit of annulus Test Simulation Photo
Davis-Besse Davis-Besse Nuclear Power Station Nuclear Power Station April 4, 2003 25 Leakage Simulation Test Results
- Small leak rates (equivalent to 0.0004 gpm in mockup) were detected by the presence of a small amount of material at the annulus exit
- Large leak rates (equivalent to 0.015 gpm in the mockup) were easily detected by presence of a considerable amount of rust-colored material extending down the nozzle outer diameter
- All leak rates were detected by both Boron and Lithium concentrations in the deposits Test #5 (leak rate: 0.0006 gpm)
Crusty yellow deposit buildup on nozzle wall at annulus discharge Test Simulation Photo
Davis-Besse Davis-Besse Nuclear Power Station Nuclear Power Station April 4, 2003 26
- Visible evidence of small leakage would be present on the IMI nozzle even for very small leaks
- Deposits may appear crusty with light yellow coloration
- Significant levels of Lithium (concentrations could reach levels of 15,000 ppm or higher) would be present in the deposit in addition to high Boron levels Leakage Simulation Test Conclusions Test #3 (leak rate: 0.0004 gpm)
Nozzle surface deposits Test Simulation Photo
Davis-Besse Davis-Besse Nuclear Power Station Nuclear Power Station April 4, 2003 27 Leakage Simulation Test Conclusion
- Based on the results of test, there is confidence that leakage would be visually discernable at an IMI nozzle
Davis-Besse Davis-Besse Nuclear Power Station Nuclear Power Station April 4, 2003 28 Reactor Vessel IMI Nozzles Inspection Plan
- Planned visual inspections prior to startup:
- Obtain wipe samples from selected IMI nozzles to establish baseline chemistry
- Perform video inspection of IMI nozzles
- Perform visual inspection of IMI nozzles with Reactor Coolant System (RCS) pressure at 250 psig
- Raise RCS to Mode 3 operating pressure and hold
- Lower the RCS pressure
- Re-perform video inspection of IMI nozzles
- If required, obtain additional wipe samples for chemical analysis
Davis-Besse Davis-Besse Nuclear Power Station Nuclear Power Station April 4, 2003 29
- Davis-Besse is installing a FLÜS Online Leak Monitoring System to detect/locate under vessel leakage
- 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 FLÜS Online Leak Monitoring Sensor Element Non-Sensitive Tubing
Davis-Besse Davis-Besse Nuclear Power Station Nuclear Power Station April 4, 2003 30 FLÜS Installation
- Install sensor tube between the reactor vessel insulation and reactor vessel
- Expected sensitivity of approximately 0.004 to 0.02 gpm (sensitivity test during Mode 3)
- System sensitivity is dependent on the air tightness of reactor vessel insulation
Davis-Besse Davis-Besse Nuclear Power Station Nuclear Power Station April 4, 2003 31 Closing Comments Gary Leidich Executive Vice President - FENOC