NRC Generic Letter 1980-43
| ML031350399 | |
| Person / Time | |
|---|---|
| Issue date: | 05/12/1980 |
| From: | Engelken R NRC Region 4 |
| To: | |
| References | |
| BL-80-013 GL-80-043, NUDOCS 8007140587 | |
| Download: ML031350399 (5) | |
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.1° UNITED STATES
' <tNUCLEAR REGULATORY COMMISSION
REGION V
ffJJJi~/ t1990 N. CALIFORNIA BOULEVARD
SUITE 202, WALNUT CREEK PLAZA
- *WALNUT CREEK, CALIFORNIA 94596 May 12, 1980
Docket No. 50-397 Washington Public Power Supply System P. 0. Box 968
3000 George Washington Way Richland, Washington 99352 Attention: Mr. N. 0. Strand Managing Director Gentlemen:
The enclosed IE Bulletin No. 80-13 is forwarded to you for information. No written response is required. If you desire additional information regarding this matter, please contact this office.
Sincerely, R. E. Engelken Director Enclosures:
1. IE Bulletin No. 80-13
2. List of Recently Issued IE Bulletins cc w/enclosures:
M. E. Witherspoon, WPPSS
W. C. Bibb, WPPSS
J. P. Thomas, WPPSS
W. J. Talbott, WPPSS
G. C. Sorensen, WPPSS
8007140
s77
SSINS No.: 6820
Accession No.:
UNITED STATES 8002280661 NUCLEAR REGULATORY COMMISSION
OFFICE OF INSPECTION AND ENFORCEMENT
WASHINGTON, D.C. 20555 May 12, 1980
IE Bulletin No. 80-13 CRACKING IN CORE SPRAY SPARGERS
Description of Circumstances
Instances of cracking in core spray spargers have occurred at two BWR facilities.
This trend indicates a need for more intensive inspection of these components during subsequent refueling outages.
Oyster Creek Nuclear Generating Station Jersey Central Power and Light Company notified the NRC on October 18, 1978, that a crack had been found in Core Spray Sparger System II during remote visual inservice inspection at their Oyster Creek Nuclear Generating Station.
The crack was located at 208 azimuth and extended at least 180 circumferen- tially around the sparger. An evaluation of the event by the licensee postu- lated that deformation of the sparger had occurred during fabrication and installation which led to cracking by Intergranular Stress Corrosion Cracking (IGSCC) during service in the BWR environment. A temporary repair was effected by installing a clamp assembly over the crack. The licensee's analysis indicated that the crack had relieved the stresses present and therefore precluded further cracking. The NRC safety evaluation permitted operation until the next refueling outage and required inspection of the sparger at that time.
The NRC was informed by the Jersey Central Power and Light Company on January 16, 1980 that further cracking was discovered in the core spray spargers during an inservice inspection conducted in conjunction with the refueling outage. A total of twenty-eight cracks 0.001 to 0.002 inches in width and of varying lengths were identified in both core spray spargers. The licensee stated that they believed the majority of additional cracks were present earlier and not discovered during the 1978 inspection due to inspection equipment limitations. Near term repair consisted of the application of nine additional clamp assemblies in areas of the spargers where cracks were visually observed on the accessible portion of the sparger and UT indications were present in the inaccessible portion of the sparger and in the junction box region. The licensee analyzed the flow characteristics of the spargers and determined that adequate flow distribution would be maintained if thru wall cracking .005 inches wide and 180 in length were present. The licensee stated that the installation of the clamps would assure the sparger would maintain its physical integrity and remain in place.
IE Bulltin No. 80-13 May 12, 1980 The repair measures proposed were determined by the NRC to be adequate until the following refueling outage. The NRC evaluation stated that actions should be taken to develop and install an improved replacement system at the following refueling outage.
Pilgrim Nuclear Power Station On January 31, 1980 the Boston Edison Company (BECo) informed the NRC that five indications in the upper core spray sparger and two indications on the lower core spray sparger at the Pilgrim Nuclear Power Station were identified during remote visual inservice inspections. The indications were confirmed as cracks after hydrolasing and brush cleaning. The licensees evaluation indicated that the sparger will retain structural integrity throughout the next cycle, although core spray flow distribution may be affected due to through-wall cracks. However, core spray flow delivery to the shroud interior would not be expected to decrease. A loose parts analysis was presented which addressed
(1) corrosion, (2) flow blockage, and (3) control rod interference.
To support power operation in Cycle 5 with the core spray sparger in its present condition, BECo has reanalyzed ECCS taking credit only for core spray reflood, taking no credit for core spray heat transfer. The submission by BECo is currently under review by the staff. The analysis is expected to cover a full spectrum of core spray failures. It is expected that the limiting condition will be the failure of recirculation suction line. A MAPLHGR limit red't.tion will likely be imposed during Cycle 5 to compensate for the assump- tion of no core spray heat transfer.
Based on results from other sparger inspections and previous pipe cracking experience, cold work and sensitization during fabrication and installation stresses are considered to be the major factors in causing the observed cracks at the Pilgrim Station. The cracks are hypothesized to be initiated and propagated by intergranular stress corrosion (IGSCC).
A meeting was held with representatives from GE in Bethesda, Maryland on March 13, 1980 to discuss core spray sparger cracking at BWRs. At the meeting GE provided the following information:
1. In February 1979, GE issued to BWR licensees Service Information Letter (SIL) No. 289 that recommended inspection of the core spray spargers for visual indications of cracking. To date, 19 of 21 plants inspected have no observed cracking. Cracks have been found at 2 facilities (Pilgrim and Oyster Creek).
2. The key contributors to IGSCC vary from plant-to-plant, although stresses from cold work and sensitization during fabrication and installation are considered prime factors leading to IGSCC at Pilgrim and Oyster Creek.
Because the cause of cracking is not yet confirmed by metallurgical analysis, GE is developing tooling to extract sparger samples to verify the postulated cracking mechanism.
IE Bulletin No. 80-13 May 12, 1980 3. GE is evaluating methods of improving the sparger inspection techniques, and is considering a modification to the SIL, if warranted.
The staff agreed that improved inspection techniques should be developed and metallurgical examinations should be performed to determine the mode of failure.
The staff asked GE to keep them informed of progress in these areas.
Actions to be Taken by Licensees:
For all boiling water power reactor facilities with an operating license:
1. At the next scheduled and each following refueling outage until further notice, perform a visual inspection of the Core Spray Spargers and the segment of piping between the inlet nozzle and the vessel shroud. Remote underwater TV examinations are acceptable if adequate resolution can be demonstrated. The viewing in situ of 0.001 in. diameter fine wires is considered as an acceptable means of demonstrating suitable resolution of the TV examinations. Such techniques as the use of oblique lighting, and the ability to light from each side independently are considered useful in enhancing the image of cracks to facilitate detection.
2. In the event cracks are identified during examination of the core spray sparger system, the location and extent of the indications shall be recorded and reported to the NRC. Supplementary examinations using volumetric methods may be performed to aid in characterizing the extent of cracking in nonvisible locations. An evaluation shall be submitted to NRR for review and approval prior to return to operation.
.3. Any cracking identified in the core spray cooling system shall be reported to the Director of the appropriate NRC Regional Office within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of identification.
4. A written report of the results of the examinations including any corrective measures taken shall be submitted within 30 days of the comple- tion of the examination to the Director of the NRC Regional Office with a copy to the NRC Office of Inspection and Enforcement, Division of Reactor Operations Inspection, Washington, D. C. 20555.
Approved by GAO, B180225 (R0072); clearance expires 7-31-80. Approval was given under a blanket clearance specifically for identified generic problems.
, It~ e IE Bulletin No. 80-13 Enclosure May 12, 1980
RECENTLY ISSUED
IE BULLETINS
Bulletin Subject Date Issued Issued To No.
80-12 Decay Heat Removal System 5/9/80 Each PWR with an OL
Operability
80-11 Masonry Wall Design 5/8/80 All power reactor facilities with an OL, except Trojan
80-10 Contamination of 5/6/80 All power reactor Nonradioactive System and facilities with an Resulting Potential for OL or CP
Unmonitored, Uncontrolled Release to Environment
80-09 Hydramotor Actuator 4/17/80 All power reactor Deficiencies operating facilities and holders of power reactor construction permits
80-08 Examination of Containment 4/7/80 All power reactors with Liner Penetration Welds a CP and/or OL no later than April 7, 1980
80-07 BWR Jet Pump Assembly 4/4/80 All GE BWR-3 and Failure BWR-4 facilities with an OL
80-06 Engineered Safety Feature 3/13/80 All power reactor (ESF) Reset Controls facilities with an OL
80-05 Vacuum Condition Resulting 3/10/80 All PWR power reactor In Damage To Chemical Volume facilities holding Control System (CVCS) Holdup OLs and to those with Tanks a CP
79-O1B Environmental Qualification 2/29/80 All power reactor of Class IE Equipment facilities with an OL
80-04 Analysis of a PWR Main 2/8/80 All PWR reactor facilities Steam Line Break With holding OLs and to those Continued Feedwater nearing licensing Addition
80-03 Loss of Charcoal From 2/6/80 All holders of Power Standard Type II, 2 Inch, Reactor OLs and CPs Tray Adsorber Cells