ML19253D045
| ML19253D045 | |
| Person / Time | |
|---|---|
| Issue date: | 11/26/1979 |
| From: | Pappas H NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Wright G ILLINOIS, STATE OF |
| References | |
| NUDOCS 7912120545 | |
| Download: ML19253D045 (1) | |
Text
'o, UNITED STATES l 'j,.,,,7/
h' Q:'[-[*/'(' 'g NUCLEAR REGULATORY COMMISSION c
REGION lil 799 ROOSEVELT ROAD o,g, ' W,[
Gl EN E LLYN, ILUNolS 60137
- ...+
NOV 2 61979 State of Illinois Department of Public Health ATTN:
Mr. Gary N. Wright, Chief Division of Nuclear Safety 535 West Jefferson Street Springfield, IL 62761 Gentlemen:
The enclosed IE Bulletin No. 79-26 titled " Boron Loss From BiR Control Blades was sent to the following licensees on November 20, 1979:
ACTION Commonwealth Edison Company Dresden 1, 2, 3 (50-10, 50-237, 50-249)
Q' sad-Cities 1, 2, (50-254, 50-265)
Consumers Power Company Big Rock Point (50-155)
Dairyland Power Cooperative LACBWR (50-409)
Iowa Electric Light and Power Company Duane Arnold (50-331)
Northern States Power Company Monticello (50-263)
INFORMATION American Electric Power Service Corporation Indiana and Michigan Power Company D. C. Cook 1, 2 (50-315, 50-316)
Cincinnati Gas & Electric Company Zimmer (50-358)
Clevelard Electric Illuminating Company Perry 1, 2 (50-440, 50-441)
Commonwealth Edison Company Braidwood 1, 2 (50-456, 50-457)
Byron 1, 2 (50-454, 50-455)
La Salle 1, 2 (50-373, 50-374)
Zion 1, 2 (50-295, 50-304) 1540 331 79121 20 54-5
NOV 2 61979 State of Illinois.
Consumers Power Company Midland 1, 2 (50-329, 50-330)
Palisades (50-255)
Detroit Edison Company Fermi 2 (50-341)
Illinois Tower Company Clinton 1, 2 (50-461, 50-462)
Northern Indiana Public Service Company Bailly (50-367)
Northern States Power Company Prairie Island 1, 2 (50-282, 50-306)
Ohio Edison Company Erie 1, 2 (50-580, 50-581)
Public Service of Indiana Marble Hill 1, 2 (50-546, 50-547)
Toledo Edison Company Davis-Besse 1 (50-346)
Union Electric Company Callaway 1, 2 (50-483, 50-486)
Wisconsin Electric Power Company Point Beach 1, 2 (50-266, 50-301)
Wisconsin Public Service Corporation Kewaunee (50-305)
Sincerely, s',
C n
e Admini rative Branch
Enclosure:
IE Bulletin No. 79-26 cc w/ enc 1:
Mr. D. W. Kane, Sargent & Lundy j}fQ2 Central Files Reproduction Unit NRC 20b Local PDR NSIC TIC
UNITED STATES SSINS: 6820 NUCLEAR REGULATORY COMMISSION Accession No.: 0FFICE OF INSPECTION AND ENFORCEMENT 7910250475 WASHINGTON, D.C. 20555 November 20, 1979 IE Bulletin No. 79-26 BORON LOSS FROM BWR CONTROL BLADES Description of Circumstances: The General Electric Company (GE) has informed us of a failure mode for control blades which can cause a loss of boron poison mat (rial. 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 boron loss have so far been confined to locations in the poison tubes with more than 50 percent Boron-10 (B10) 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 4 B C as helium and lithium concentrations grow. Once primary coolant penetrates 4 the cladding (i.e., the cracking has progressed through the cladding wall and the helium-lithium pressures are sufficient to open the crack), boron is leached out 10 of the tube at locations with more than 50 percent B local depletion (local depletion is considered to be twice the average depletion). It was further found 10 with similar cracking but with less than 50 percent local 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 10 worth of the blade is reduced by 10 percent, which corresponds to 42 percent B depletion averaged over the top quarter of the control blade. Because of the 10 leaching mechanism, GE has reduced the allowance for B depletion averaged over the top quarter of the control blade from the 42 percent value to 34 percent. The safety significance of boron loss DUPLICATE DOCUMENT scram reactivity. Although shutdown c Entire document previously entered into system under: b ANO N o. of pages: h}}