ML20198P069
| ML20198P069 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 12/28/1998 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20198P055 | List: |
| References | |
| NUDOCS 9901060290 | |
| Download: ML20198P069 (5) | |
Text
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UNITED STATES s
j NUCLEAR REGULATORY COMMISSION
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WASHINGTON, D.C. Saama -t 9
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION OF THE THIRD 10-YEAR INTERVAL INSERVICE INSPECTION PROGRAM PLAN REQUEST FOR RELIEF NUMBER 9 NQBTHERN STATES POWER COMPANY MONTICELLO NUCLEAR GENERATING PLANT DOCKET NUMBER 50-263
1.0 INTRODUCTION
The Technical Specifications (TS) for the Monticello Nuclear Generating Plant state that the inservice inspection (ISI) cf American Society of Mechanical Engineers (ASME) Code Class 1,2, and 3 components shall be performed in accordance with Section XI of the ASME Boiler and Pressure Vessel (B&PV) Code and applicable addenda as required by 10 CFR 50.55a(g),
except wherc specific written relief has been granted by the Commission pursuant to 10 CFR 50.55a(g)(6)(i).10 CFR 50.55a(a)(3) states that alternatives to the requirements of paragraph (g) may be used, when authorized by the NRC, if (i) the proposed alternatives would provide an acceptable level of quality and safety or (ii) compliance with the specified requirements would result in hardship or unusual difficulties without a compensating increase in the level of quality and safety.
Pursuant to 10 CFR 50.55a(g)(4), ASME Code Class 1,2, and 3 components (including supports) shall meet the requirements, except the design and access provisions and the pre-s,ervice examination requirements, set forth in the ASME Code,Section XI, " Rules for Inservice Inspection of Nuclear Power Plant Components," to the extent practical within the limitations of des;;'. geometry, and materials of construction of the components. The regulations require that inservice examination of components and system pressure tests conducted during the first 10-year interval and subsequent intervals comply with the requirements in the latest edition and addenda of Section XI of the ASME Code incorporated by j
reference in 10 CFR 50.55a(b) 12 months prior to the start of the 120-month interval, subject to the limitations and modifications listed therein. The applicable edition of Section XI of the
- ASME Code for the Monticello Plant third 10-ye'ar ISI interval is the 1986 Edition. Pursuant to 10 CFR 50.55a(g)(5), if the licensee determines that conformance with an examination requirement of Section XI of the ASME Code is not practical for its facility, information shall be submitted to the Commission in support of that determination and a request made for relief from the ASME Code requirement. After evaluation of the determination, pursuant to 10 CFR i
9901060290 981228 i
PDR ADOCK 05000263 P
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L 50.55a(g)(6)(i), the Commission may grant relief and may impose attemative requirements that I
are determined to be authorized by la.v, will not endanger life, property, or the common defense and security, and are otherwise in the public interest, giving due consideration to the burden l
upon the licensee that could result if the requirements were imposed.
l In a letter dated November 14,1996, Northern States Power Company (the licensee),
submitted its Third 10-Year Interval Inservice Inspection Program Plan Request for Relief Number 9 (RR-9) for the Monticello Plant. The licensee proposed using an alternative to certain ASME Code requirements, specifically the use of calibration blocks in ultrasonic test
. (UT) procedure ISI-UT-16, Revision 11.
2.0 EVALUATION The licensee submitted the subject request for the third 10-year interval. The Code of record for the third intervalis the 1986 Edition of Section XI of the ASME Code. The information l
provided by the licensee in support of the request has been evaluated and the bases for its disposition are documented below.
2.1 Code Reauirement:
I Section XI, Appendix lil, paragraph lll-3411 (b) states, " Calibration blocks for dissimilar metal welds shall be fabricated from the material specified for the side of the weld from which the evaluation will be conducted. If the examination will be conducted from both sides, calibration reflectors shall be provided in both materials."
2.2 Licensee's Code Relief Request
- Pursuant to 10 CFR 50.55a(a)(3)(i), the licensee requested relief from the paragraph 111-3411 (b) requirement for using calibration biccks of both materials in the calibration of UT equipment fo,' dissimilar metal welds. The relief request is for 23 dissimilar metal welds listed in the attached Table 1.
2.3 Licensee's Basis for Reauestina Relief: (as stated in the submittal) 10 CFR 50, Section 50.55a(a)(3) states (in part): Proposed alternatives to the requirements of paragraphs... may be used when... (i) The proposed attematives
. would provide an acceptaole level of quality and safety,..
Prior to the Winter 1985 revision of the code, paragraph 111-3411 stated the following:
(a) The calibration blocks shall be 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 the same specification as the material on that i
side of the joint.
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(c) if material of the same 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 l
the 1986 edition of the Section XI code, a new requirement is imposed upon the l
plant. Compiiance with this new requirement would require the plant to procure new calibratir.,n 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 conservative approach of using a block based on the high alloy /high nickel side of the weldment rather than the carbon side (see below).
The Monticello plant has determined that our existing calibration blocks along with a procedural 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 ali suspected flaw type indications regardless of amplitude, is a conservative and acceptable attemative method.
2.4 Licensee's Prooosed Alternative Examination (as stated in the submittal):
For examination of dissimilar metal welds conducted from both sides, the proposea 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 othat 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).
3.0 Evaluation
Tha Monticello Code of record for the second interval was the 1977 Edition S78 Addenda of 5 < ion XI of the ASME Code. With ine third interval, Monticello's Code of record for ISI changed to the 1986 Edition with no addenda. Paragraph lll-3411 (b) in the 1986 Edition calls for calibrating UT equipment with calibration blocks fabricated from the materiai specified for the side of the weld from which the examination will be conducted, if the examination wil! be conducted from both sides, calibration reflectors shall be provided in both materials. Because paragraph Ill-4420 in the 1986 Edition of Section XI of the ASME Code requires inspection from two sides of the weld, the 1986 Edition of the Code would require two calibration blocks for the inspection of dissimilar metal welds. The changes in paragraph 111-3411 requirements from the 1977 Edition, S78 Addenda to the 1986 Edition of the Code require the licensee to secure additional calibration blocks for inspecting dissimilar metal welds.
The licensee is proposing a change to an existing UT technique from the requirements of the
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1986 Edition of the Code. The change would be to continue using one calibration block for calibrating UT equipment used for inspecting dissimilar metal welds. The licensee believes a
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single calibration block made from the more difficult to examine material in the weldment would provide an acceptable level of quality and safety (10 CFR 50.55a(a)(3)(i)). For a dissimilar l
metal wold made of carbon steel welded to high alloy /high nickel stainless steel, the licensee proposes the calibration be performed using the high alloy /high nickel stainless steel material.
The licensee describes this material as being more difficult to examine than carbon steel.
In order to fulfill the requirements of 10 CFR 50.55a(a)(3)(i), the licensee must perform a demonstration of the UT procedure. The staff believes the above stainless steel material used for calibrating UT equipment for the examination of the dissimilar metal welds listed in Table 1 is
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acceptable for the following reasons:
j a)
The examination volume for a dissimilar metal weld required by the ASME Code consists l
of the total volume of the weld plus %-inch on each side of the weld (Fig. lWB-2500-8).
1 For stainless to carbon steel welds, the weld volume consists of stainless steel weld material which has the same ultrasonic examination properties as the stainless steel calibration block that was used to calibrate the procedure.
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b)
The sensitivity established for the procedure using the stainless steel calibration block is equivalent or better than the sensitivity that would have been obtained from using a l
carbon steel block. For thicker welds, a weld buttering using inconel ^.00 # eld filler material is usually used to provide for transition of thermal expansion between the stainless and carbon steel weld material. This transition volume is more effectively j
examined with procedures that are qualified using stainless steel calibration blocks.
c)
The procedure also provides for reexamination using calibration blocks of similar i
materialifindications are noted and cannot be explained by geometry. This ensures that i
i proper evaluation data is recorded.
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d)
The procedure stipulates that any reflector suspected as being a flaw shall be evaluated and recorded regardless of amplitude or size.
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3.0 CONCLUSION
The staff concludes that the proposed alternative to paragraph Ill-3411 of Appendix lil to the 1986 Edition of Section XI of the ASME Code provides an acceptable level of quality and safety.
Pursuant to 10 CFR 50.55a(a)(3)(i), the attemative is authorized.
Principal Contributor: D. Naujock Date: December 28, 1998
Attachment:
Table 1 - Dissimilar Welds 4
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l TABLE 1 - DISSIMILAR WELDS SIN lag llam fada Matti Ma112 Config l
995 13142-42-A W-3 B9.11 A106 GR B A182 TP347 Pipe to Pipe l
996 13142-42-A W-4 B9.11 A182 TP347 A106 GR B Pipe to Pipe 1367 73880-A W-2 B9.10 A240 304 A234 WPB Pipe to El 423 13142-20-C W-22 B9.11 A182 F304 A508 CL ll Flance to Noz l.
2388 FIG 1 W-9 B9.11 A508 CL ll A182 F304 Noz to Flange l-2731 ISI-19 W-1 B5.20 B166 A336 CL F8 Noz to SE l
2048 97005-B W-18 B5.10 A182 F316 A508 CL ll SE to Noz l
2034 97005-B W-4 B5.10 A182 F316L A508 CL ll 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 l
1884 97003-A W-25 89.10 A333 GR 6 A358 316L Pipe to Pipe
- 1906 97003-B W-4 89.10 A358 316L A333 GR 6 Pipe to Pipe j
i 2041 97005-B W-11 B5.10 A182 F316L A508 CL ll SE to Noz 1
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 ll SE to Noz 2143 97006-B W-4 B5.10 A182 F316L A508 CL ll SE to Noz l
2150 97006-B W-11 B5.10 A182 F316L A508 CL 11 SE to Noz L
2157 97006-B W-18 B5.10 A182 F316L A508 CL ll SE to Noz 1995 97005-A W-1 B5.10 A508 CL ll 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 B5.10 A336 CL F8 A508 CL ll SE to Noz 2730 ISI-16 W-2 B5.10 A336 CL F8 A508 CL ll SE to Noz t
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