ML19332A703
| ML19332A703 | |
| Person / Time | |
|---|---|
| Site: | Humboldt Bay |
| Issue date: | 08/29/1980 |
| From: | Engelken R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| To: | Crane P PACIFIC GAS & ELECTRIC CO. |
| References | |
| NUDOCS 8009180130 | |
| Download: ML19332A703 (1) | |
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UNITED STATES
.8 NUCLEAR REGULATORY COMMISSION E
REGION V e[-
o 1990 N. CALIFORNIA BOULEVARD SUITE 202, WALNUT CREEK PLAZA 4,,,a WALNUT CREE K, CALIFORNIA 94596 August 29, 1980 Docket tio. 50-133 Pacific Gas and Electric Company 77 Beale Street San Francisco, California 94106 Attention: Mr. Philip A. Crane, Jr.
Assistant General Counsel Gentlemen:
The enclosed IE Bulletin No. 79-26, Rev.1, is forwarded to you for action.
The original IE Bulletin No. 79-26 has been revised to adjust the required completion date for reporting the results of examination of an exposed control blade and to correct a typographical error. The revision is identified by use of "R1" in the right margin.
In order to assist the NRC in evaluating the value/ impact of each Bulletin on licensees, it would be helpful if you would provide an estimate of the manpcwer expended in conduct of the review and preparation of the report (s) required by the bulletin.
Please estimate separately the manpower associated with corrective actions necessary following identification of problems through the bulletin.
A written response is' required.
If you desire additional information regarding this matter, please contact this office.
Sincerely, qcN-R. H. Engelken Director
Enclosures:
1.
IE Bulletin No. 79-26, Rev.1 2.
List of IE Bulletins Recently. Issued cc w/ enclosures:
J. D. Shiffer.PG&E-E. Weeks, PG&E-(Humboldt Bay W. A. Raymond, PG&E i
8009180/50 Q.
l SSINS flo.: 6820 Accession flo. -
l UtlITED STATES 8006190042 flVCLEAR REGULATORY COMMISSION OFFICE OF IflSPECTION Af!D E!!FORCEMENT NASHI"GTON, D.C.
20555 August 29, 1930 IE Bulletin No. 79-26 Rev.1 BORON LOSS FROM BWR CONTROL BLADES Description of Circumstances:
i The General Electric Company (GE) has informed us of a failure mode for control blades which can cause a loss of boron poison material.
Hot cell examinations of both foreign and domestic blades have revealed cracks near the upper end of stainless steel tubing and loss of boron from the tubes.
The cracks and baron loss have so far been c 50 percent Baron-10 (B*gnfined to locations in the poison tubes with more than
) local depletion. Observed crack sizes range from a quarter to a half inch in length and from one to two mils in width.
GE has postulated that the cracking is due to stress corrosion induced by solidification of boron carbide (B C) particles and swelling of the compacted i
g B C as helium and lithium concentrations grow.
Once primary coolant penetrates thecladding(i.e.,thecrackinghasprogressedthroughthecladdingwalland the helium-lithium pressures are sufficient to open the crack), ggron is leached out of the tube at locations with more than 50 percent B local i
depletion (local depletion is considered to be twice the average depletion).
It was further found with similar cracking but with less than 50 percent local 1
depletion of B
, that leaching did not occur even though primary coolant had penetrated the cladding.
The cracking and boron loss shorten the design life of the control blade.
According to the GE criteria the end of design life is reached when the reactivity wgth of the blade is reduced by 10 percent, which corresponds to 42 percent B depletion averaged over the top quarter of the control glade.
y Because of the leaching mechanism, GE has reduced the allowance for B deple-tion averaged over the top quarter of the control blade from the 42 percent
],
value to 34 percent.
i DUPLICATE DOCUMENT Entire document previously entered into system under:
h ANO No. of pages:
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IE Bulletin flo. 79-26 Rev.1 Enclosure August 29, 1980 RECErlTLY ISSUED IE BULLETIflS Bulletin Subject
, Date Issued Issued To flo.
80-20 Failures of Westinghouse 7/31/80 To each nuclear Type W-2 Spring Return power facility in to l'eutral Control Switches your region having an OL or a CP 80-19 Failures of Mercury-7/31/80 All nuclear power Uetted Matrix Relays in facilities having Reactor Protective Systems either an OL or a CP of Operating fluclear Power Plants Desianed by Combus-tion Engineering 80-18 Maintenance of Adequate 7/24/80 All PWR power reactor Minimum Flow Thru Centrifugal facilities holding OLs Charging Pumps Following and to those PWRs Secondary Side High Energy nearing licensing Line Rupture Supplement 2 Failures Revealed by 7/22/30 All BWR power reactor to 80-17 Testing Subsequent to facilities holding OLs Failure of Control Rods to Insert During a Scram at a BWR Supplement 1 Failure of Control Rods 7/18/80 All BWR power reactor to 80-17 to Insert During a Scram facilities holding OLs at a BWR 80-17 Failure of Control Rods 7/3/80 All BWR power reactor to Insert During a Scram facilities holding OLs at a BWR 80-16 Potential flisapplication of 6/27/80 All Power Reactor Rosemount Inc., Models 1151 Facilities with an and 1152 Pressure Transmitters OL or a CP with Either "A" or "D" Output Codes 80-15 Possible Loss Of I!otline 6/18/80 All nuclear facilities With Loss Of Off-Site Power holding OLs 80-14 Degradation of Scram 6/12/30 All BWR's with an Discharge Volume Capability OL