ML20099K278
| ML20099K278 | |
| Person / Time | |
|---|---|
| Site: | Fort Saint Vrain  |
| Issue date: | 03/01/1985 |
| From: | Lee O PUBLIC SERVICE CO. OF COLORADO |
| To: | Johnson E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| References | |
| P-85061, NUDOCS 8503200225 | |
| Download: ML20099K278 (3) | |
Text
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PUBLIC SERVICE COMPANY OF COLORADO P.
O. BOX e4O OENVER.
COLORADO 80206 oscia n. tzz March 1, 1985 Fort St. Vrain vic ' " * * *'
Unit No.1 P-85061 3' i[$ @ @ O U k M
Regional Administrator Region IV 7
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U.S. Nuclear Regulatory Commission 3
611 Ryan Plaza Drive, Suite 1000 Arlington, Texas 76011 y
Attn: Mr. E. H. Johnson
SUBJECT:
Additional Documentation Requested by NRC
REFERENCE:
PSC Letter Dated 01/30/85, Lee to Johnson, P-85032
Dear Mr. Johnson:
This letter is to inform you of a recent decision by PSC to use the existing material on one component part associated with the Control Rod Cable material replacement program. As stated in the referenced letter, this part was scheduled to be replaced during the current outage with a part made from Inconel as a preventative measure against stress corrosion.
However, due to material delivery problems, some of the existing material will be used, as justified below. This subject was discussed with members of your staff and personnel from Los Alamos National Laboratory in a telephone conversation on 2/13/85.
The part involved is the " clevis bolt" used to connect the Control Rod onto the lower end of the new Inconel CRD cable.
This bolt is discussed in GA Report No. 907822 and PSC Safety Analysis Report No.
EE-12-0009, Issue A attached to the referenced letter. The existing material is a high strength steel AMS 5735 or AMS 5737 (A286). The installed bolt has no significant torque and therefore no resulting tensile stress.
Calculations of the actual loading stress due to bending moment and shear load result in a very insignificant stress 8503200225 850301 hd6 f
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P-85061 Page 2 level. To identify if residual stresses are high enough to present a chloride stress corrosion concern, a magnesium chloride test was run on one of the A286 clevis bolts, followed by examination for evidence of stress corrosion. A review of the test results concluded that the A286 material was acceptable for use.
It is important to consider that new clevis bolts made of the A286 material are being installed instead of reusing the existing. bolts. When Inconel bolts are received, PSC will install them on the remaining assemblies.
A286 clevis bolts installed at this time will be replaced during subsequent control rod replacements. The consequences of failure of these bolts have been evaluated and determined to have no adverse effect on the health and safety of the public. Attachment A to this letter shows a _ revision to.GA Report No. 907822 which. corrects an error in the referenced drawing /part number.
A safety analysis review has been performed on the proposed revision of an engineering change notice'(CN-1933B) which temporarily retains the existing A-286 corrosion resisting steel material for the clevis bolt. This review showed that this is not an unreviewed safety 7
question because the material of the bolt is not subject to high enoug; tensile stresses to promote stress corrosion cracking in the bolt, even if the bolt is exposed to a moist chloride environment in the PtRV.
Further, should the bolt fail for any reason, its connecting control rod will fall into the fully inserted position, its safe shutdown position.
During the telephone conversation on 2/13/85, PSC informed your staff of another possible delivery problem on the cap screws which hold the manual rewind gear to the CRD hub. The delivery problem has been resolved for that part and the new material identified in the referenced letter will be installed on all CRD assemblies.
PSC will proceed with our current outage work as outlined above.
If you have any questions, please contact Mr. M. H. Holmes at (303) 571-8409.
Very truly yours, h
- 0. 1. Lee, Vice President Electric Production ORL/FWT:pa cc: Jim Miller Los Alamos National Laboratory
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I
907822 N/
7Ataft 7 TABLE 2-1 (continued)
ORIGINAL MATERIAL REPLACEMENT MATERIAL REPLACE-ORIGINAL MENT COMPO-MINIMUM (PSI)
MINIMUM (PSI)
MATERIAL GE0METI PART NO.
PART NO.
NENT SPEC.
YIELD ULTIMATE SPEC YIELD ULTIMATE CHANGE CHANGl D1201-251 D1201-251 Cable AISI
115,000 -
ASME SB-446 140,000 170,000 Yes No Item 1 Item 2 140,000 ASTM B-446 (347 S.S)
(Alloy Inconel 625)
D1201-252 D1201-252 Anchor AISI 30,000 70,000 AISI 85,000 110.000 Yes No (304 S.S)
(416 S.S)
Item I same j
D1201-253 D1201-253 Bushing AISI 4130 130,000 140,000 AISI 4130 130,000 140,000 No No (Steel)
(Steel) l Item I same i
D1201-254 D1201-254 Guide ASTM A519 35,000 55,000 ASTM A519 35,000 55,000 No No Item 1 Item 1 GR HT 1015 GR HT 1015 (Steel)
(Steel) i D 12." 255 D1201-255
- Nut, AISI-C-30,000 70,000 AISI-C-30,000 70,000 No Yee Item 1 Item 2 Bushing 1018/C-1018/C-1020
.1020 1201-263 D1201-263 Rod End AISI 30,000 70,000 ASTM B-446 60,000 120,000 Yes No (304 S.S)
(Inconel 625)
Item 2 same lockwell No No Rockwell AMS 5630 D1201-263 D1201-263 Ball AMS 5630 Item 3 (440 C)
C 60 (440 C)
C 60 h
No D1201-263 D1201-263 Race AMS 5643 115,000 140,000 AMS 5643 115,000 140,000 No 4
Item 4 (17-4 PH) 17-4 PH g
160,000 AMS 5670 105,000 165,000 Yes Yes D1201-100 03993ff Bolt AMS 5735 4
Item 18 027387 or AMS (Inconel 5737 (A286:
X-750)
D1201-103 027938 Retaining AMS 5643 115,000 140,000 AMS 5643 115,000 140,000 No No Item 18 Item 2 Ring (17-4 PH)
(17-4 PH)
D -- -
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