ML20134L285
| ML20134L285 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 11/14/1996 |
| From: | Hill W NORTHERN STATES POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9611200225 | |
| Download: ML20134L285 (4) | |
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Northem States Power Company Monticetto Nuclear Generating Plant 2807 West Hwy 75 Monticello. Minnesota 55362 9637 November 14,1996 10 CFR Part 50 Section 50.55a US Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 MONTICELLO NUCLEAR GENERATING PLANT Docket No. 50-263 License No. DPR-22 Reouest for Relief No. 9 for the 3rd 10-Year interval Inservice Inspection Prooram On August 5,1994 we submitted for review the latest revision of Monticello's third 10-year Inservice Inspection (ISI) Examination Plan. The purpose of this letter is to submit for review and approval ISI Relief Request No. 9 to the third 10-year plan.
Monticello*s Relief Request No. 9, entitled "Use of High Alloy /High Nickel Calibration Block for Dissimilar Metal Welds", fulfills the following commitment made in our September 19,1996 letter which responded to the Notice of Deviation in your August 20,1996 letter.
"NSP will submit a relief request in lieu of invoking IWA-2240 for procedure NSP-UT-
- 16. The relief request will be submitted by November 15,1996."
This letter contains no new Nuclear Regulatory Commission commitments.
Please contact Sam Shirey, Sr. Licensing Engineer, at (612) 295-1449 if you require further information.
M//let.
A William J Hill Plant Manager Monticello Nuclear Generating Plant c:
Regional Administrator-lil, NRC Mel Holmberg, NRC Region ll1 NRR Project Manager, NRC l/] I g Sr Resident inspector, NRC
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State of Minnesota Attn: Kris Sanda J Silberg : ISI Relief Request No. 9 9yyM8,85.m - m m Smc 9611200225 961114 PDR ADOCK 05000263 G
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Anachment No.1 Monticello ISI Relief Request No. 9 (Rev. 0)
Use of High Alloy /High Nickel Calibration Block for Dissimilar Metal Welds SYSTEM: Various Class: 1 & 2
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l Category: See Table 1 Item: See Table 1 4
Examination Reauirements; l
lll-3411 (b) of ASME Section XI 1986 edition, Appendix 111 states:
" Calibration blocks for dissimilar metal welds shall be fabricated from the material specified for the side of the weld from which the examination will be conducted, if the examination will be conducted from both sides, calibration reflectors shall be provided in both materials."
Proposed Alternative:
For examination of dissimilar metal welds conducted from both sides, the proposed calibration is to be based on a single block fabricated from the material specified for the high alloy /high nickel side of the weld. If indications other than geometry are noted on the carbon steel side, the scans will be repeated utilizing a calibration block of the same or of similar material (material of similar chemical analysis, tensile properties, and metallurgical structure).
i Basis for Relief:
10 CFR 50, Section 50.55a(a)(3) states (in part):
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" Proposed alternatives to the requirements of paragraphs... may be used when...
(i) The proposed alternatives would provide an acceptable level of quality and safety,..."
Prior to the Winter 1985 revision of the code, paragraph 111-3411 stated the following; (a) The calibration blocks shallbe fabricated from one of the materials specified for the piping being joined by the weld.
(b) Where the examination is to be performed from only one side of the joint, the calibration block material shall be of the same specification as the material on that side of thejoint.
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i (c) If material of the sart.: specification is not available, material of similar chemical analysis, tensile properties, and metallurgical structure may be used.
Since the third interval requires a change from the 77 Edition S78 Addenda to the 1986 edition of the Section XI code, a new requirement is i;aposed upon the plant.
Compliance with this new requirement would require the plant to procure new calibration blocks for the carbon steel side of the dissimilar metal welds shown on Table 1.
Our existing calibration blocks have been procured for dissimilar metal examinations based on previous code requirements and opting for the conservatlv? 3pproach of using a block based on the high alloy /high nickel side of the weldment ratner than the carbon side (see below).
The Monticelb piant has determined that our existing calibration blocks along with a procedurc: requirement to scan at high sensitivity levels (if the material noise level in the component is not a minimum of 10% full scale height (FSH), the instrument gain is increased accordingly) and record all suspected flaw type indications regardless of amplitude, is a conservative and acceptable alternative method.
Justification for Grantino Relief:
It is believed that the use of a single calibration standard for initial examination as noted above meets the requirements of 10 CFR Part 50, Section 50.55 (a) (3) to provide an acceptable level of quality or safety, or that compliance with the specified requirements would result in hardship or unusual difficulties without a compensating increase in the level of quality and safety.
The use of the high alloy /high nickel block for an examination performed from both sides of a dissimilar metal weld is considered appropriate for the following reasons; a) The sensitivity established on a high alloy /high nickel block is generally equal to or greater than that which would be obtained on a carbon steel block. This provides a conservative reference sensitivity for examinations from the carbon steel side of the weldment.
b) The examination procedure requires the following;
" Scanning shall be performed at the following gain levels, as applicab le:
For angle beam examinations; a minimum of +6dB above Primary Reference (DAC) level, in addition,if the material noise level (Baseline Roll)in the component being examined is not a minimum of 10% FSH, the instrument gain shall be increased accordingly.
For straight beam examination, +6dB above reismnce level."
"Any reflector suspected to be a flaw (i.e. crack) shail be evaluated and recorded, regardless of amplitude or size."
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'c) The velocity difference between high alloy /high nickel steels and carbon steels is minor and does not result in a significant angle variation.
d) The procedure requires reexamination using a calibration block of similar materialif indications are noted that are not attributable to geometry. This ensures proper evaluation data is recorded.
e) Use of two separate calibrations for examination of a single component may result 4
i in greater radiation exposure to personnel due to increased time at the examination l
site, required to perform separate setups and exams.
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Jime Period Relief is Reauested For:
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i Relief is requested for the Third Ten Year Interval Acoroval:
Not yet approved, NRC SER is pending.
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r Table 1 - Dissimilar Welds
$]/.N Jiq ltem fdH!f Mati 1 Mail 2 Confia 995 13142-42-A W-3 89.11 A106 GR B A182 TP347 Pipe to Pipe 996 13142-42-A W-4 89.11 A182 TP347 A106 GR B Pipe to Pipe 1367 73880-A W-2 89.10 A240 304 A234 WPB Pipe to El 423 13142-20-C W-22 89.11 A182 F304 A508 CL 11 Flange to Noz 2388 FIG 1 W-9 B9.11 A508 CL ll A182 F304 Noz to Flange 2731 1S1-19 W-1 B5.20 B166 A336 CL F8 Noz to SE 2048 97005-B W-18 B5.10 A182 F316 A508 CL 11 SE to Noz 2034 97005-B W-4 B5.10 A182 F316L A508 CL il SE to Noz 2062 97005-B W-32 B5.10 A182 F316L A508 CL ll SE to Noz 1964 97004-A W-25 B9.10 A333 GR 6 A358 316L Pipe to Pipe 1884 97003-A W 25 89.10 A333 GR 6 A358 316L Pipe to Pipe 1906 97003-B W-4 B9.10 A358 316L A333 GR 6 Pipe to Pipe 2041 97005-B VI.11 B5.10 A182 F316L A508 CL ll SE to Noz 2055 97005-B W-25 B5.10 A182 F316L A508 CL ll SE to Noz 2171 97006-B W-32 B5.10 A182 F316L A508 CL 11 SE to Noz 2164 97006-B W-25 B5.10 A182 F316L A508 CL 11 SE to Noz 2143 97006-8 W-4 B5.10 A182 F316L A508 CL ll SE to Noz 2150 97006-8 W-11 B5.10 A182 F316L A508 CL ll SE to Noz 2157 97006-B W-18 B5.10 A182 F316L A508 CL ll SE to Noz 1995 97005-A W-1 B5.10 A508 CL 11 A403 316W Noz to SE 2102 97006 A W-1 B5.10 A508 CL 11 A403 316W Noz to SE 2729 ISI-16 W-1 85.10 A336 CL F8 A508 CL 11 SE to Noz 2730 ISI-16 W-2 B5.10 A336 CL F8 A508 CL 11 SE to Noz 4
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