ML20045G888
| ML20045G888 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 07/06/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20045G881 | List: |
| References | |
| NUDOCS 9307160106 | |
| Download: ML20045G888 (6) | |
Text
I f(panog jo, UNITED STATES 4
j NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555
%.'... + p j
SAFETY EVALVATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION t
RELATED TO Tijf SECOND TEN-YEAR INTERVAL INSERVICE INSPECTION PROGRAM PLAN AND RE0 VEST FOR RELIEF 92-001. REV. 1 ENTERGY OPERATIONS. INC.
ARKANSAS NUCLEAR ONE. UNIT 2 DOCKET NO. 50-368
1.0 INTRODUCTION
Technical Specification 4.0.5 for Arkansas Nuclear One, Unit 2 (ANO-2) states that inservice inspection and testing of the 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 Code and i
applicable addenda as required by 10 CFR 50.55a(g), except where 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 preservice examination requirements, set forth in the ASME i
Code,Section XI, " Rules for Inservice Inspection of Nuclear Power Plant Components," to the extent practical within the limitations of design, geometry, and materials of construction of the components.
The regulations require that inservice examination of components and system pressure tests conducted during each 10-Year Interval comply with the requirements in the latest edition and addenda of Section XI of the ASME Code incorporated by reference in 10 CFR 50.55a(b) on the date Nelve months prior to the start of i
the 120-month inspection interval, subject to the limitations and modifications listed therein.
The components (including supports) may meet the requirements set forth in subsequent editions and addenda of the ASME Code incorporated by reference in 10 CFR 50.55a(b) subject to the limitations and-modifications listed therein.
Pursuant to 10 CFR 50.55a(g)(5)(iii), 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 j
9307160106 930706 PDR ADOCK 0500 0
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10 CFR 50.55a(g)(6)(i), the Commission may grant relief and may impose alternative requirementi that are determined to be authorized by law, will not endanger life, property, or the common defense and security, and are otherwise in the public interest, giving due consideration to the burden upon the licensee that could result if the requirements were imposed.
Alternatively, pursuant to 10 CFR 50.55a(a)(3), the NRC will evaluate the licensee's determination that either (i) the proposed alternatives provide an acceptable level of quality and safety or that (ii) code compliance would result in hardship or unusual difficulty without a compensating increase in safety.
Proposed alternatives may be used when authorized by the NRC.
In an NRC Safety Evaluation (SE) dated November 22, 1991, the staff concluded that the ANO-2 Second 10-Year Interval Inservice Inspection (ISI) Program Plan, submitted on January 12, 1990, was unacceptable and not in compliance with the regulations for the reasons listed in Section 2.0 of that SE.
During a December 10, 1991 conference call, and in a letter dated January 15, 1992, the licensee committed to make the changes necessary to make the program acceptable.
The licensee submitted a revision to the Second 10-Year Interval ISI Program Plan in a letter dated July 31, 1992.
In this revision, changes were made to include volumetric examination of 7.5% of all Examination Category C-F-1 piping welds greater than 4 inch NPS (Nominal Pipe Size) regardless of the wall thickness.
In addition, the licensee provided a discussion regarding the other deficiencies cited in the November 22, 1991 SE.
1 During an on-site NRC (Region 1 NDE Van) review of the ANO-2 Second 10-Year Interval ISI Program Plan, including the July 31, 1992 submittal, it was noted i
that volumetric examinations of Examination Category C-F-1 welds had been shifted from thick walled systems (23/8 inch) to thin walled systems (<3/8 inch) without shifting the associated surface examinations.
Since it was not the staff's intent to reduce associated examinations (i.e., surface examinations or examination of component supports), it was concluded that the shifting of volumetric examinations in this way was not acceptable.
In response, the licensee committed to perform both surface and volumetric examinations of Examination Category C-F-1 piping systems less than 3/8 inch nominal wall thickness and revised their program accordingly in the submittal dated October 9, 1992.
2.0 EVALUATION The staff, with technical assistance from its contractor, the Idaho National Engineering Laboratory (INEL), has evaluated the AN0-2 Second 10-Year Interval ISI Program Plan, the revisions included in the July 31, and October 9, 1992 submittals, and Request for Relief 92-001, Revision 1.
The review is summarized in the following sections.
A.
In the NRC SE dated November 22, 1991, the ANO-2 Second 10-Year ISI Program Plan was found unacceptable for the following reasons:
(1)
Class 2 piping welds in the Containment Spray (CS) and Shutdown i
Cooling (SC) systems were completely excluded from volumetric examination based on wall thickness; (2) Augmented examinations in accordance with Branch Technical Position (BTP) MEB 3-1, " Postulated Rupture Locations in Fluid Systems Inside and Outside Containment"; US NRC Regulatory Guide 1.150, " Ultrasonic l
Testing of Reactor Vessel Welds During Preservice and Inservice Examination"; and I&E Bulletin 79-17, " Pipe Cracking in Stagnant Borated Water Systems at PWR Plants" were not addressed; and (3)
Discrepancies were noted between the " Itemized Weld List" of the January 15, 1991 submittal and the " Summary of Examinations" table submitted on January 12, 1990.
The licensee responded to these deficiencies in a conference call held on December 10, 1991, and in submittals dated January 15, July 31, and October 9, 1992.
Class 2 Pinina Welds:
The licensee modified the program to apply a 7.5%
l examination sample to all non-exempt Examination Category C-F-1 welds regardless of wall thickness. This was accomplished by shifting examinations from welds 3/8 inch or greater to the welds less than 3/8 inch.
This distribution is reflected in the July 31, and October 9,1992 submittals.
The revised sampling plan prorates the examinations for all C-F-1 systems such that 7.5% of each system is examined and no systems are excluded from examination.
Since the surface examinations were shifted along with the volumetric examinations, and since it appears that no ISI examinations of component supports have been eliminated by the shifting of welds, the plan now reflects compliance with the regulations for Examination Category C-F-1 piping systems.
Auamented Examinations: Augmented examinations in accordance with BTP MEB 3-1, IE Bulletin 79-17, and Regulatory Guide 1.150 were not included or addressed in the licensee's original submittal. These deficiencies are addressed in the licensee's July 31, 1992 submittal as follows:
Regarding BTP MEB 3-1, the licensee states that ANO-2 currently meets all of the requirements of MEB 3-1, Revision 0, and has reviewed the requirements of MEB 3-1, Revision 2, for applicability to ANO-2. The current Code-required examination sampling has been supplemented with an augmented program to volumetrically examine all main run circum-ferential and longitudinal piping welds on both main steam headers from the containment penetrations to the first restraint just beyond the main steam' block valves.
The piping weld examinations that comprise this augmented program have been equally distributed over the Second 10-Year Inspection Interval.
Since break points are postulated outside containment on each of the main feedwater system 4
piping lines at the containment penetrations where the line is anchored by the flued head (a terminal end), volumetric examination for these piping lines is not required by MEB 3-1, Rev 2.
k f
.- 1 Regarding IE Bulletin 79-17, the licensee believes that the intent of the bulletin has been met by revising the program to include volumetric examinations of 7.5% of all Examination Category C-F-1 piping welds greater than 4 inches NPS regardless of wall thickness.
The. intent of IE Bulletin 79-17 was to address inside diameter-(ID) surface degradation by imposing volumetric examinations of austenitic stainless steel piping systems containing stagnant borated water.
These examinations were meant to augment the Code requirements and ensure that no system would be overlooked during ISI.
Inclusion of i
l the shutdown cooling and containment spray systems in the examination sample meets the intent of IE Bulletin 79-17.
Regarding US NRC Regulatory Guide 1.150, the licensee states that performance of the reactor vessel examinations will comply with this i
document.
l Based on the above responses, the staff concludes that the licensee has met the intent of the three documents in question and, therefore, is performing adequate examinations during the Second 10-Year ISI Interval.
)
l Document Discrenancies: The licensee stated, during a. conference call held on December 10, 1991 and in a letter dated January 15, 1992, that.the January 15, 1991 submittal superseded the January 12, 1990 submittal, and I
that any errors would be fixed in the next (July 31,1992) submittal.. It l
appears that the licensee has corrected the errors in the-previous submittal s.
l B.
Reauest for Relief No.92-001. Revision 1. Examination Cateaory C-F-1.
Item C5.10. Circumferential and Lonoitudinal Pipina Welds Code Reauirement:
Table IWC-2500-1, Examination Category C-F-1, Item C5.10 requires surface and volumetric examinations, as defined by IWC-2500-7, for piping welds 3/8 inch or greater nominal wall thickness (NWT) in piping greater than NPS 4.
Footnote (2) of Table IWC-2500-1, i
Examination Category C-F-1 states the following:
(2)
"The welds selected for examination shall include 7.5%, but not less than 28 welds, of all austenitic stainless steel or high alloy welds not exempted by IWC-1220.
(Some welds not exempted by IWC-1220 are not required to be nondestructively examined per Examination Category.
l C-F-1.
These welds, however, shall be included'in the total weld l
count to which the 7.5% sampling rate is applied.) The examinations shall be distributed as follows:
(a) the examinations shall _ be distributed among'the Class 2 systems prorated, to the ' degree practicable, on the number of nonexempt austenitic stainless steel or high alloy welds in each' system (i.e., if a system contains 30% of the nonexempt welds, then 30% of the nondestructive examinations required by Examination-Category C-F-1 should be performed on that system);
i
f,
- l (b) within a system, the examination shall be distributed among terminal ends and structural discontinuities prorated, to the degree practicable, on the number of nonexempt terminal ends and structural discontinuities in that system; and (c) within each system, examinations shall be distributed between line sizes prorated to the degree practicable."
Licensee's Code Relief Reauest:
Relief is requested to perform a 7.5%
l sampling of all welds in Category C-F-1 piping systems greater than 4-inch NPS regardless of wall thickness.
Licensee's Basis for Reauestino Relief:
The Code requires that a 7.5%
sampling rate be applied to all Category C-F-1 welds not exempted by IWC-1220.
The total weld count to which the sampling rate is applied includes welds required to be examined (i.e., 23/8 inch NWT) and welds not required to be examined (i.e., <3/8 inch NWT).
The total number of welds required to be examined are then distributed, in a prorated manner, among those systems requiring examination.
Those piping welds less than 3/8 inch NWT, while not required to be examined, have an impact on the number of examinations required in system piping greater than or equal to 3/8 inch NWT.
For ANO-2, the piping in the containment spray (CS) and residual heat l
removal (RHR) systems and the majority of the safety injection (SI) system has a NWT bi less than 3/8 inch.
The NRC, in its SE of the ANO-2, Second Interval ISI Program Plan, requested that ANO-2 select a 7.5% sampling of welds in these systems for examination. These examinations must include both volumetric and surface methods. As discussed in a December 10, 1991, conference call, ANO-2 would effectively be doubling its efforts, since these welds have already been factored into, and have significantly increased, the number of welds to be examined in those systems whose NWT l
is greater than or equal to 3/8 inch. Therefore, AND-2 has applied the 7.5% sampling rate across the board for Category C-F-1 piping regardless of NWT.
This has ensured that a prorated and equal share of the examinations are distributed among system piping equal to or greater than 3/8 inch NWT and system piping less than 3/8 inch NWT. To accomplish this, ANO-2 has removed some of the previous weld examination selections in those systems greater than or equal to 3/8 inch NWT. A flat 7.5%
sampling of the welds in these systems is now selected, instead of an adjusted higher percentage due to the influence of the piping welds less than 3/8 inch.
Licensee's Proposed Alternative Examination: A flat 7.5% sampling of all C-F-1 welds (regardless of wall thickness) will be performed in lieu of the distribution required by the Code.
Staff Evaluation: The Code requires examination of 7.5% of all Examination Category C-F-1 welds not exempted by IWC-1220.
Welds less than 3/8 inch NWT in piping greater than NPS 4 are not required to be i
I i
1 l
l l examined by the Code, but must be included in the weld population.
This stipulation increases the examination sample size for the heavier walled piping systems.
10 CFR 50.55a(b)(2)(iv)(A) states that " Appropriate Code Class 2 pipe welds in the residual heat removal systems, emergency core cooling systems and containment heat removal systems shall be examined." The staff has previously determined that it is appropriate'and prudant to perform volumetric examinations on the thin walled welds in these systems that have been totally excluded from examination by the Code. This is particularly important in plants with a significant percentage of thin-walled piping (<3/8 inch). At ANO-2, the systems excluded from examination in the original program plan represent over 40% of the C-F-1 weld population. The staff considered complete exclusion of the CS and SC systems to be significant and concluded that 7.5% of the welds in these systems should be examined in order to make the program plan acceptable.
The licensee's proposed alternative is to perform volumetric and surface examinations on a flat 7.5% sampling of all non-exempt Examination Category C-F-1 welds regardless of wall thickness.
Distributing the examinations in this way does not reduce the total number of C-F-1 welds examined, but does distribute examinations among all non-exempt welds.
Considering the large percentage of thin-walled welds at AN0-2, this distribution of examinations is prudent ar.d provides an acceptable level of quality and safety.
Therefore, pursuant to 10 CFR 50.55a(a)(3)(1), the i
staff concludes that the licensee's proposed alternative is authorized.
3.0 CONCLUSION
Pursuant to 10 CFR 50.55a(g)(5)(iii), the licensee determined that conformance with certain Code requirements is impractical for its facility and submitted the supporting information to justify the use of a proposed alternative.
The staff has reviewed Request for Relief 92-001, Revision 1, and pursuant to 10 CFR 50.55a(a)(3)(i) has concluded that the licensee's proposed alternative provides an acceptable level of quality and safety and, therefore, is authorized.
Regarding the program plan, the staff concludes the' ae licensee has adequately addressed the deficiencies cited in the
/ ember 22, 1991, SE and that the Arkansas Nuclear One, Unit 2 Second 10-Yeai Interval ISI Program Plan, with the revisions submitted on July 31, and October 9, 1992, constitutes the basis for compliance with 10 CFP, 50.55a(g) and Technical Specification 4.0.5 and is therefore acceptable.
Principal Contributors:
T. McLellan M. Khanna Date: July 6, 1993