View source for L-MT-14-018, Response to NRC Request for Additional Information Regarding Relief Request RR-21, Relief from Impractical Examination Coverage Requirements Pursuant to 10 CFR 50.55a(g)(5)(iii) for the Fourth Ten-Year Lnservice Interval

{{Adams
| number = ML14052A147
| issue date = 02/20/2014
| title = Response to NRC Request for Additional Information Regarding Relief Request RR-21, Relief from Impractical Examination Coverage Requirements Pursuant to 10 CFR 50.55a(g)(5)(iii) for the Fourth Ten-Year Lnservice Interval
| author name = Fili K
| author affiliation = Northern States Power Co, Xcel Energy
| addressee name = 
| addressee affiliation = NRC/Document Control Desk, NRC/NRR
| docket = 05000263
| license number = DPR-022
| contact person = 
| case reference number = L-MT-14-018, TAC MF2654
| document type = Letter type:L
| page count = 4
| project = TAC:MF2654
| stage = Response to RAI
}}

=Text=
{{#Wiki_filter:Monticello Nuclear Generating Plant Xcel Energy@                                   2807 W County Road 75 Monticello, MN 55362 February 20, 2014                                                                  L-MT-14-018 10 CFR 50.55a(g)
ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 Monticello Nuclear Generating Plant Docket 50-263 Renewed Facility Operating License No. DPR-22

==Subject:==
Response to NRC Request for Additional Information Regarding Relief Request RR-21, Relief from Impractical Examination Coverage Requirements Pursuant to 10 CFR 50.55a(g)(5)(iii) for the Fourth Ten-Year lnservice Interval (TAG No. MF2654)

==References:==
: 1) Letter from Northern States Power Company, a Minnesota corporation (NSPM) d/b/a Xcel Energy to Document Control Desk, "1 0 CFR 50.55a Request No. 21: Relief from Impractical Examination Coverage Requirements Pursuant to 10 CFR 50.55a(g)(5)(iii) for the Fourth Ten-Year lnservice Inspection Interval", dated August 28, 2013.
: 2) Draft Request for Additional Information from NRC "Regarding Relief Request (RR)-21, Relief from Impractical Examination Coverage Requirements Pursuant to 10 CFR 50.55a(g)(5)(iii) for the Fourth Ten-Year lnservice Interval, Monticello Nuclear Generating Plant, Docket No. 50-263, (TAG No. MF2654), dated January 9, 2014.
By letter dated August 28, 2013, Northern States Power Company, a Minnesota corporation (NSPM), d/b/a Xcel Energy requested relief from examination coverage requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code, Section XI, "Rules for lnservice Inspection of Nuclear Power Plant Components," for the Monticello Nuclear Generating Plant (Reference 1, ADAMS Accession Number ML13241A236). Subsequently, by email dated January 9, 2014, (Reference 2, ADAMS Accession Number ML14010A023) the NRC provided a draft Request for Additional Information (RAI) for additional information required to complete its review. In a conference call between the NRC and NSPM on January 23, 2014, the draft RAI was accepted and the content of the RAI was discussed to the participants' satisfaction. The formal response is provided in the enclosure "Monticello Nuclear Generating Plant, Response to NRC Request for Additional Information, 10 CFR 50.55a Request No. 21, Dated August 28, 2013".
If you have any questions or require additional information, please contact Mr. Randy Rippy at 612-330-6911.

Document Control Desk Page 2 Summary of Commitments This letter makes no new commitments and no revisions to existing commitments.
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Karen D. Fili Site Vice President, Monticello Nuclear Generating Plant Northern States Power Company- Minnesota Enclosure cc:    Administrator, Region Ill, USNRC Project Manager, Monticello, USNRC Resident Inspector, Monticello, USNRC Minnesota Department of Commerce

ENCLOSURE MONTICELLO NUCLEAR GENERATING PLANT RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION 10 CFR 50.55a REQUEST NO. 21 DATED AUGUST 28,2013 NRC Question RA/-1:
In the August 28, 2013, submittal, Enclosure 2, Table A, states that component weld W-8 (head-to-flange weld) received 79% examination coverage in 2011 during the 4th interval examination, and that coverage was limited due to flange configuration. However, Enclosure 4, Table B, states that weld W-8 received 93% examination coverage in 2001 during the 3rd interval examination.
Please discuss the basis for the differences in examination methodologies between the 3rd and 4th 10-year IS/ interval examination coverage for weld W-8.
Monticello Response:
The differences noted for examination coverage between the 3rd and 4th 10-year Interval for W-8 (93% versus 79%) is due to the changes in Ultrasonic Testing (UT) methodology and related equipment implemented for the examination.
The performance-based technique for the 2011 exam, as described in the 10 CFR 50.55a Request No. 21 submittal, utilized the refracted longitudinal (RL) wave mode for all scans. The 60-degree RL probe (transducer) required for the exam has a two element, transmit-receive configuration with a dimension of 24mm x 42mm for each element. The elements are mounted in a housing whose overall length and width dimensions are 60mm x 60mm.
In comparison, the technique for the 2001 exam was performed to a procedure that complied with Sections XI and V of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, and utilized 3 separate transducers, each with a nominal element size of 1 inch (in.): One 0-degree longitudinal wave (1 in. diameter); one 45-degree shear wave (1 in. x 1 in.), and one 60-degree shear wave (1 in. x 1 in.).
The surface profile of W-8, as shown in the submittal's Enclosure 3, pages 6 of 7 and 7 of 7, depicts the thickness transition and flange curvature on the component's exterior surface. As mentioned in the submittal, these changes in the surface profile result in the transducer losing contact with the component's surface, preventing adequate coupling necessary to transmit and receive the ultrasonic sound energy for a portion of the scanning area.
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The smaller footprint of the transducers used for the 2001 examination enables them to maintain coupling for a larger percentage of the total scanning area, thereby obtaining higher examination coverage, 93% as noted in Table B of  of the submittal.
The technique and related equipment to perform the respective examinations account for the difference between the 93% coverage shown in Table B of the submittal's Enclosure 4 for the 2001 exam versus the 79% coverage obtained in the 2011 exam described in the submittal and as shown in Table A of the submittal's Enclosure 2.
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