ML20206P547
| ML20206P547 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 01/04/1999 |
| From: | Jeffery Wood CENTERIOR ENERGY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 2564, NUDOCS 9901120184 | |
| Download: ML20206P547 (10) | |
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- nP Daws-Besse Nuclear Pbwer Stanon gg 5!.91 North State Houte 2 m
Oak Harbor. Ohio 43449-9700 John K. Wood 419-249-2300
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VicePresident Nuclear Fax:419-321-8337 Docket Number 50-346 License Number NPF-3 Serial Number 2564 January 4, 1999 United States Nuclear Regulatory Commission Document Co.. trol Desk Washington, DC 20555
Subject:
Request for Relief from Certain American Society of Mechanical Engineers (ASME)
Code Requirements for Inservice insp:ction for the Davis-Besse Nuclear Power Station j
Ladies and Gentlemen:
The purpose of this letter is to request relief pursuant to 10CFR50.55a(a)(3) from certain requirements of Section XI of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code for the Davis-Besse Nuclear Power Station (DBNPS). Details concerning the requested relief are provided in attached ReliefRequests RR-A16, RR-A17, and RR-B9.
ReliefRequest RR-A16 requests relieffrom Section XI of the ASME Code,1986 Edition, No Addenda, Code Item B15.51 which requires a system hydrostatic test of Class 1 piping. Relief l
from performing the system hydrostatic test of the piping between valves DH 11 and DH 12 is requested. Toledo Edison proposes to perform VT-2 visual examination of this piping while the Decry Heat Removal System is in service and also perform ultrasonic and liquid penetrant examinations cf the welds attaching DH 11 anr! DH 12 to the piping.
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ReliefRequest RR-A17 requests relief from Section XI of the ASME Code,1986 Edition, No Addenda, Subarticle IWA-4400, Pressure Tests, which requires hydrostatic testing of Class 1,2, and 3 Systems followmg welded repairs or installation of replacement items by welding. Toledo Edison proposes to utilize the alternative methods specified in Code Case N-416-1.
Relicf Regrest RR-B9 requests relief from Section XI of the ASME Code,1986 Edition, No Addenda, Subarticle IWA-4400, Pressure Tests, which requires hydrostatic testing of Class 1,2.
and 3 Systems following welded repairs or installation of replacement items by welding. During the eighth refueling outage, the main feedwater spray plates on both Steam Generators were replaced. This required the addition of new welds in each of the main feedwater riser pipes.
< SD 9901120184 990104 T PDR ADOCK 05000346 P
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Docket Number 50-346 License Numb:r NPF-3 Serial Number 2564 Page 2 Subsequent revision of Code Case N-416 (Code Case N-416-1) permits the ehmination of the previously deferred hydrostatic test. However, one of the conditions of Code Case N-416-1 is that non-destructive examination (NDE) methods meet the requirements of the 1992 Edition of ASME Section III. The 1992 Edition of ASME Section III requires a radiographic exandnation of butt welds in piping. The use of i rasonic and magnetic particle examination as an alternative -
t to radiographic examination is re.]uested.
0-Toledo Edison requests : hat these relief requests be approved by June 30,1999, to support the testing and inspections required for the twelfth refueling outage scheduled to start in Spring 2000.
Should you have any questions or require additionalinformation, please contact Mr. James L.
Freels, Manager - Regulatory Affairs, at (419) 321-8466.
Very truly yours, O
DHL/dic cc: J. L. Caldwell, Acting Regional Administrator, NRC Region III A. G. Hansen, NRC Project Manager -
K. S. Zellers, Acting DB-1 NRC Senior Resident Inspector Utility Radiological Safety Board n
Docket Number 50-346 License Number NPF-3 Serial Number 2564 I
Page1 l
RELIEF REQUEST j
RR-A16 j
Component
Description:
ASME Class 1 Decay Heat Removal Piping between Valves DH 11 and DH 12 ASME Code Class:
4 ASME Section XI, Class 1 Piping ASME Examination Requirements ASME Section XI,1986 Edition, No Addenda, Subsection IWB-2500, Table IWB-2500-1, Examination Category B-P, Item No. B15.51 requires e system hydrostatic test at or near the end of each inspection interval. The pressure retaining boundary during the hydrostatic test shallinclude all Class I components within the system boundary.
Basis for Relief:
Valves DH I1 and DH 12 are installed in the normal cooldown iine from the Reactor Coolant System to the Decay Heat Removal System (see figure below). DH 12 is the first isolation valve off of the Reactor Coolant System while DH 11 is the second isolation valve. The ASME Class I boundary extends through DH 12 to DH 11. The piping between DH 11 and DH 12 is a four foot section of 12-inch seamless schedule 140 piping with a 1 inch drain line and a % inch by-pass line around DH 12. Two 12-inch pipe welds which connect the piping to the valves are the only large bore pipe welds within the l
boundary. This piping is installed within a watertight enclosure (Decay Heat Pit) which l
protects DH 11 and DH 12 from flooding following a Loss ofCoolant Accident (LOCA).
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Request RR A16
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Docket Number 50-346 License Number NPF-3 Serial Number 2564 Attachaient 1 Page 2 Valves DH 11 and DH 12 are motor operated gate valves with flexible wedges. NRC Information Notice 92-26, " Pressure Locking of Motor Operated Flexible Wedge Gate Valves," provides information regarding flexible wedge gate valves which may be subject to pressure locking under certain operating conditions. Toledo Edison's evaluation of this Information Notice identified that DH I1 and DH 12 were susceptible to pressure locking.
Subsequently, DH 11 and DH 12 were modified by drilling a small vent hole in the upstream disc of each valve's wedge to eliminate the pressure locking concern.
The required hydrostatic testing pressure of the piping between DH 11 and DH 12 is 2155 psig. During the eleventh refueling outage, the piping between DH 11 and DH 12 was pressurized during Mode 5 to determine if hydrostatic test pressures could be achieved.
At 800 psig, the pressure lockmg vent hole allowed leakage past the DH 12 upstream disc.
This confirmed that in order to perform the hydrostatic test of the piping between DH 11 and DH 12, the Reactor Coolant System must be pressurized to prevent flexing of the DH 12 wedge. Compliance with the pressure / temperature limits of Davis-Besse Nuclear Power Station (DBNPS) Technical Specification 3.4.9.1 requires the plant enter Mode 3 prior to attaining the Reactor Coolant System pressure of 2155 psig required to perform the hydrostatic testing.
Three options are available to hydrostatic tot the piping between valves DH 11 and DH 12:
Option one is to open valve DH 12 while in Mode 3 at full temperature and pressure to pressurize the piping between DH 11 and DH 12 to 2155 psig. The piping could then be examined remotely through the Decay Heat Pit Inspection Port. Opening DH 12 while in Mode 3 is not considered viable as Technical Specification 3.5.2 prohibits DH 11 or DH 12 from being open when the Reactor Coolant System pressure is greater than 328 psig.
Therefore, DH 12 may not be opened to pressurize the piping during the normal Reactor Coolant System hydrostatic test.
The second option requires entry into the Decay Heat Pit while in Mode 3 with the Reactor Coolant System at full temperature and pressure, and pressurize the piping between DH 11 and DH 12 with a hydrostatic pump. Entering the Decay Heat Pit while in Mode 3 requires removal of the Decay Heat Pit cover to provide access to the Decay Heat Pit with the Reactor Coolant System at full temperature (532"F) and pressure (2155 psig). The hydrostatic test would be performed by pressurizing the piping between DH 11 and DH 12 with a hydrostatic pump to obtain the required test pressure. Technical Specification 3.5.2 requires the Decay Heat Pit be sealed and closed in Modes 1,2, and 3.
Opening this pit in Mode 3 requires an intentional entry in Technical Specification 3.0.3 as it would make both Low Pressurc Injection pumps inoperable. As Technical Specification 3.0.3 is not intended to be used as an operational convenience which permits redundant safety systems to be out of service, this is not an acceptable option.
r Docket Number 50-346 License Number NPF Serial Number 2564 Page 3
. Toledo Edison considers these options a hardship and a detriment to the quality and safety of the Reactor Coolant System.
i The third option requires the reactor vessel to be defueled and the RCS drained down to disassemble DH12 and perform a temporary modification to the disk to establish test conditions. Toledo Edison considers this option to be a hardship and unusually difficult y
without a compensatory increase in the level of quality of safety.
Reliefis requested in accordance with 10CFR50.55a(a)(3)(ii). Compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level ofr; ality and safety.
Alternative Examination:
In lieu of the hydrostatic test, the piping between DH 11 and DH 12 will be VT-2 examined prior to closing the Decay Heat Pit while the Decay Heat Removal System is inservice. The piping between DH 11 and DH 12 is in the normal Decay Heat Removal flowpath during outages. The normal operating pressure in this condition is 45 psig which is maintained for several days while the Decay Heat Removal System is in service. As the l
Decay Heat System is borated, any pressure boundary leakage would be identified by the formation ofboric acid crystals.
As noted above, the piping between DH 11 and DH 12 is a four foot section of seamless piping connected to DH 11 and DH 12 by field welds. In addition to the VT-2 examination, each of these 2 field welds will be subjected to a surface examination and a volumetric examination during each Inservice Inspection Interval. The volumetric
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examination is a limited examination as the valve taper prevents ultrasonic scanning from l-the valve side. Even so, the weld is examined from three of the four required examination
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directions which should detect any flaw propagating through the weld. This provides additional assurance of the pressure boundary integrity of this piping.
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Docket Number 50-346 License Number NPF-3 Serial Number 2564 Page1 RELIEF REQUEST RR-A17 Component
Description:
Hydrostatic Testing of Class 1,2 and 3 Systems for Welded Repairs or Installation of Replacement Items by Welding - Request for Approval to use Code Case N-416-1 ASME Code Class:
ASME Section XI, Class 1,2, and 3 ASME Examination Requirements:
ASME Section XI,1986 Edition, No Addenda, IWA-4400 Pressure Tests, requires that after repairs by welding on the pressure retaining boundary, a system hydrostatic test shall be performed in accordance with IWA-5000; Basis for Relief:
Code Case N-416-1 provides alternative pressure test requirements for welded repairs or installation of replacement items by welding in Class 1,2, and 3 Systems.
l Hydrostatic testing is performed to verify the pressure boundary integrity of the repair / replacement. The hydrostatic tests are performed prior to returning the affected system to service. Although only the repaired / replaced portion of the system requires testing, it is often necessary to extend test boundaries well outside the repaired / replaced portion of the system to establish isolation, and fill and vent the system for the hydrostatic test. Additional pumps are often required to obtain the necessary test pressures. As the hydrostatic test pressure is above the normal operating pressures, relief valves normally installed to protect the system from overpressurization must be remov d or gagged. The hydrostatic test also stresses non-pressure l
retaining components such as gaskets, pump seals, and valve packing which increases the likelihood that these non-pressure retaining components could leak during or following the l
hydrostatic test.
1 A typical hydrostatic test takes approximately 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> to perform with a crew of 2 to 3 people.
Typical radiation levels in test areas are approximately 5 mrem. This results in a total personnel dose of approximately 150 mrem per test.
Code Case N-416-1 recognizes that system leakage tests provide an acceptable alternative to hydrostatic tests. System leakage tests are performed at normal operating pressures and temperatures, which are not significantly lower than hydrostatic test pressures. Performing these tests on systems which are in their normal lineups reduces test preparation and performance time as well as personnel exposures, while increasing system availability. Although testing is
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t Docket Number 50-346 License Number hTF-3 Serial Number 2564 Pag'e 2 performed at a lower test pressure, any pressure boundary leakage will be readily apparent, thereby ensuring the level of quality and safety of the system is maintained.
Code Case N-416-1 has been accepted by NRC in Dran Regulatory Guide DG-1050 (Revision 12 to Regulatory Guide 1.147) with limitations.
Reliefis requested in accordance with 10CFR50.55a(a)(3)(ii). For the reasons described above, compliance with the specified requirements would result in hardship or unusual difficulty without a' compensating increase in the level of quality and safety.
Alternative Examination:
Code Case N-416-1, including the limitations included in Dran Regulatory Guide DG-1050 will be used as an alternative test requirement for welded repairs or installation of replacement items by welding in ASME Class 1,2, and 3 systems.
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' Docket Number 50-346 i
License Number NPF-3 Serial Number 2564
' Attachment,3 Pag 61 RELIEF REQUEST RR-B9 Component
Description:
Three (3) inch Schedule 80 Butt Welded Main Feedwater Riser Welds ASME Code Class:
ASME Section XI Class 2
' ASME Examination Requirements:
Subarticle IWA-4400 of the 1986 Edition, No Addenda, of ASME Section XI requires that after repairs by welding on the pressure retaining boundary, a system hydrostatic test shall be performed in accordance with IWA-5000, System Pressure Tests Code Case N-416-1 states that in lieu of perwrming the hydrostatic pressure test required by IWA-4000 for welded repairs or installation of replacement items by welding, a system leakage test may be used provided the following requirements are met:
a) NDE shall be performed in accordance with the methods and acceptance criteria of the applicable Subsection of the 1992 Edition of Section III.
b) Prior to or immediately upon return to service, a visual examination (VT-2) shall be performed in conjunction with a system leakage test, using the 1992 Edition of Section XI in accordance with IWA-5000, at nominal operating pressure and l
tempemture.
c) Use of this Case shall be documented on an NIS-2 Form If the previous version of this case were used to defer a Class 2 hydrostatic test, the deferred test may be eliminated when the requirements of this revision are met.
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Paragraph NC-5222 of the 1992 Edition of ASME Section 111 requires that butt welded piping i
joints be radiographed.
E Basis for Relief:
During the eighth refueling outage in 1993, the main feedwater spray plates on both Steam Generator 1-1 and Steam Generator 1-2 were replaced. The original construction code for tne main feedwater header and risers was the 1967 Edition of ANSI B31.1 with the 1969 Errata. The replacement required each of the 64 three-inch main feedwater risers b: cut and removed to replace the spray plate and then reassembled with a new weld (see figure below). These welds were examined using ultrasonic and magnetic particle methods, and the system hydrostatic test was deferred in accordance with Code Case N-416.
Docket Number 50-346 License Number NPF-3 Serial Number 2564 Pag'e 2 h
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a jd Main Feed Water Riser In 1993, NRC Regulatory Guide 1.147 listed Code Case N-416 as an acceptable Code Case. This Code Case permitted the hydrostatic test for the repair / replacement be deferred until the next scheduled system hydrostatic test provided the following conditions were met:
a) Prior to or immediarely upon return to service, a visual examination (VT-2) for leakage shall be conducted during a system functional test or during a system inservice test in the repaired or replaced portion of the piping system.
b) The repair or replacement welds shall be examined in accordance with IWA-4000 and IWA-7000 Replacements using volumetric examination methods (IWA-2230 Volumetric Examination) for full penetration welds or surface examination methods (IWA-2220 Surface Examination) for partial penetration welds.
Subarticle IWA-2230 recognizes radiographic examination (IWA-2231 Radiographic Examination) and ultrasonic examination (IWA-2232 Ultrasonic Examination) as volumetric examination methods. Each new riser weld was examined by ultrasonic examination performed and accepted to the requirements of the 1986 Edition of ASME Section XI and ANSI B31.1. In l
addition, the final weld also received a magnetic particle surface examination. During the i
fabrication process, the root pass was also examined using a liquid penetrant c : amination. Each of these examinations were performed to the requirements of the 1986 Edition of ASME Section XI and accepted per the original constmetion code requirements. Following completion of the replacement, the welds were VT-2 examined at system operating temperature and pressure with no leakage noted.
If a previous revision of Code Case N-416-1 was used (i.e. N-416), Code Case N-416-1 permits the deferred hydrostatic test to be eliminated when the requirements of Code Case N-416-1 are met. The examination of the new main feedwater riser welds meets Code Case N-416-1 requirements with the exception that an ultrasonic examination was performed, as permitted by
Docket Number 50-346 License Number NPF-3 Serial Number 2564 Attachmen,t 3 Pag'e 3 Code Case N-416, instead of the radiographic examination required by NC-5222 of the 1992 Edition of ASME Section Ill.
Paragraph NC-5279 of the 1992 Edition of ASME Section III permits ultrasonic examination plus i
liquid penetrant or magnetic particle examination to be substituted for radiographic examination of special welds when thejoint detail does not permit radiographic examination. Although the new riser weld is not a special weld, NC-5279 does recognize ultrasonic examination plus liquid penetrant or magnetic particle examination as an adequate substitute for a radiographic examination. Ultrasonic examination is a recognized alternative volumetric examination method, as described in Code Case N-416. The ultrasonic examinatica plus the liquid penetrant 4
examination of the root weld and the magnetic particle examination of the fmal weld provides reasonable assurance that no unallowable flaws exist in the riser welds. The main feedwater risers have been VT-2 examined twice since 1993 during the system inservice tests with no leakage noted.
If the ultrasonic examination plus the final magnetic particle examination is not an acceptable alternative to radiographic examination, it will be necessary to either radiograph the riser welds or perform a Secondary System Hydrostatic Test.
It is estimated that radiography of the welds on the 64 main feedwater risers will require approximately 2 days to accomplish in an area with an approximate radiation level of 25 mrem /hr.
During this time access to the containment would be restricted, prohibiting the performance of critical path work in the area.
Performance of Seconday System Hydrostatic Test of both trains of the main steam system requires approximately 5 days ofcritical path time as the test must be performed after feedwater cleanup with the feedwater temperature greater than 110 F to meet the pressure and temperature requirements of Technical Specification 3.7.2.1. In addition, significant man-hours are required to remove and blank the 18 Main Steam Safety Valves and to build and remove scaffolding necessary to install mechanical stops in 16 spring hangers.
Reliefis requested in accordance with 10CFR50.55a(a)(3)(ii). For the reasons described, compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
Alternative Examination:
The ultrasonic examination plus the final magnetic particle examination of the main feedwater riser welds is an acceptable alternative to the radiographic examination required by Paragraph NC-5222 of the 1992 Edition of ASME Section XI.
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