ML20198H235
| ML20198H235 | |
| Person / Time | |
|---|---|
| Site: | Brunswick  |
| Issue date: | 09/08/1997 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20198H233 | List: |
| References | |
| NUDOCS 9709170047 | |
| Download: ML20198H235 (6) | |
Text
_
6't0%
k UNITED STATES
}
NUCLEAR REGULATORY COMMISSION
%,..... /g WASHINGTON, D.C. 30646 4 001 SAFFTY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION ASME CODE CASE N-509 AND ALTERNATIVE TO HPCI PUMP STUD INSPECTION BRUNSWICK STEAM ELECTRIC PLANT UNIT NOS. 1 AND 2 CAROLINA POWER & LIGHT COMPANY DOCKET NOS: 50-324 AND 50-325
1.0 JNTRODUCTION
The Technical Specifications (TS) for the Brunswick Steam Electric Plant (BSEP), Unit Nos. 1 and 2, state that the inservice inspection (ISI) 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 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)(1).
l that alternatives to the re 10 CFR 50.55a(a)(3) states authorized by the NRC, if (quirements of paragraph (g) may be used, when
- 1) the proposed alternatives would arovide an acceptable level of quality and safety, or (ii) compliance wit1 the specified requirements would result in hardship or unusual difficulty 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 3reservice examination requirements, set forth in the ASME Code,Section XI, "lules for Inservice Inspection of Nuclear Power Plant Components " to the extent practical within the limitations of design, geometry, and materials of construction of the comoonents.
The regulations require that inservice examination of components and system pressure tests conducted during the first 10-year interval and subsecuent intervals compl with the requirements in the latest edition and addenca of the ASME Code, y Section XI, incor) orated by reference in 10 CFR 50.55a(b) on the date 12 months prior to tie start of the 120-month interval, subject to the limitations and modifications listed therein. The applicable ASME Code,Section XI, for Brunswick Units 1 and 2, during the second 10-year ISI interval is the 1980 Edition through the Winter 1981 Addenda.
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 and subject to Commission approval.
Pursuant to 10 CFR 50.55a(a)(3), by letter dated March 11, 1997. Carolina Power & Light Company (CP&L or the licensee), requested approval for implementing the alternative rules of ASME Section XI Code Case N-509,
" Alternative Rules for the Selection and Examination of Class 1, 2, and 3 Integrally Welded Attachments.Section XI. Division 1," to be applied to the
[ f So$k o O 0024 p
, ISI program and by letter dated April 1, 1997, the licensee further requested a) proval to use an alternative to the above Code for volumetric examination of t1e high pressure coolant injection (HPCI) system main pump studs for Brunswick Units 1 and 2.
The staff's review and evaluation of the licensee's request and supporting information is noted below.
2a, DISCUSSION:
Code Case N-509. Alternative Rules for the Selection and Examination of Class
- 1. 2. and 3 Inteora'ly Welded Attachments.Section XI. Division 1 Comoonent identification l
Integrally Welded Attachments specified in Table IWB-2500-1 (Categories B-H I
i and B-K-1): Table IWC-2500 1 (Category C-C): and Table IWD 2500-1 (Categories D A, 0-B, and D C) of ASME Code,Section XI, 1980 Edition througn Winter 1981 Addenda.
I Code Reauirement For Class 1. Examination Category B-K-1, volumetric or surface examination, as applicable, is required for all integrally welded attachments exceeding 5/B-inch design thickness during the first and second intervals when implementing Program B.
For Class 2. Examination Category C-C, surface examination is required for all integrally welded attachments exceeding 3/4-inch design thickness, For Class 3, Examination Categories D A, D-B. and D C, visual examination is required for all integrally welded attachments corresponding to those component supports selected by IWF-2510(b).
Reauest for Relief Relief is requested from the existing Code requirements for determining the extent of examination of Class 1, 2 and 3 integrally welded attachments to piping as defined in ASME Section XI, Articles IWB, IWC, and IWD of the ASME Boiler and Pressure Vessel Code, 1980 Edition through Winter 1981 Addenda.
l The licensee proposes to use the ASME Code Case N 509 which allows alternative requirements for visual and surface examination of integrally welded attachments of Code Class 1, 2, and 3 components. The alternative requirements of this Code Case implements a sampling plan similar to the one for component supports contained in Code Case N- 01, " Alternative Rules for Examination of Class 1. 2, 3 and MC Component Sup) orts of Light-Water Cooled Power PlantsSection XI, Division 1 " which has )een incorporated into NRC Regulatory Guide 1.147.
Basis for Relief The basis for relief provided by the licensee follows:
Code Case N-509 improves the examination of Class 3 integrally welded attachments by changing the Code-required VT-3 examination to a more applicable VT-1 examination. The VT-1 examination is more stringent and more likely to identify the
3-kinds of degradation that are most detrimental to a welded attachment.
Code Case N 509 no longer exempts integral attachments based on base material design thickness as currently allowed by ASME Section XI for Class 1 and Class 2 components.
in addition, unlike Section XI of the ASME Code, this Code Case requires an examination whenever component support member deformation (e.g., broken, bent, or pulled out parts) is identified on Class 1. 2. and 3 components.
This Code Case implements a sampling plan similar to the one for component supports contained in Code Case N 491 which has been incorporated into Regulatory Guide 1.147.
Code Case N 509 requires selection of component supports for examination in j
accordance with IWF of the 1990 Addenda of the ASME Code.
The Brunswick Plant will implement Code Case L 509 using the selection guidelines for component supports contained in Code Case N-491.
Code Case N 491 contains the same requirements for i
i selection of component sup) orts for examination as the 1990 Addenda. Code Case N-491 aas been approved b and incorporated into Regulatory Guide 1.147.y the NRC staff The Brunswick Plant will examine a minimum of 10 percent of the total number of non exempt integral attachments on Class 1. 2. and 3 systems.
Since a random sampling of componer.t supports for examination in accordance with Code Case N 491 provides an acceptable level of quality and safety, then selecting a similar sampling of component support integral attachments for examination in accordance with Code Case N 509 also provides an acceptable level of quality and safety.
The extent of examinations required by Code Case N 509 still includes essentially 100 percent of the length of the attachment weld by using methods approved by the ASME Code.
Section XI.
The smaller sample size receives an equsi or more detailed examination which still provides for plant qu:lity and safety but reduces engineering and examination costs as well as personnel radiation exposures overall.
in addition, this Code Case still requires additional and successive examinations for attachments whose examinations reveal flaws or relevant conditions that exceed the acceptance standards of the ASME Code.Section XI.
3a.
EVALUATION:
The licensee has proposed. as an alternative to the Code requirements, to apply the requirements of Code Case N-509 for the examination of integrally welded attachments on Class 1, 2. and 3 piping and com3onents.
CodeCase N-509 provides alternative sampling requirements for tie examination of Class
- 1. 2. and 3 integral attachments.
The licensee proposed to examine 10 percent of the integral attachments in each of the nnn exempt Code Class 1. 2. and 3 systems in accordance with Code Case N-509 requirements.
Based on industry
4 experience in the United States that no significant loading conditions or known material degradation mechanisms relating to integral attachment welas in nuclear power plant piping have become evident, the licensee concludes that continued examination to the extent required by the 1980 Edition of the ASME Section XI with Addenda through the Winter 1981, is not warranted, i
The staff finds that a sampling process, if extended to welded attachments, would provide assurance that service related degradation is not occurring and a minimum sample of 10 percent of all integrally welded attachments in Code Class 1, 2, and 3 systems, it sufficient to assure that degradation, if occurring, will be detected.
Further, should a service induced defect be aetected in these welds, the ASME Code Case N 509 specifies examination expansion criteria to ensure degradation in other attachment welds would be detected.
Therefore, the staff concludes that the use of the alternative contained in Code Case N 509, with a minimum 10 percent selection of all integrally welded attachments in each Code class, will provide an acceptable level of quality and safety, 4a. CONCLUSION:
Based on the above discussions, the staff concludes that the licensee's proposed use of Code Case N 509 cs an alternative to the Code requirements is acceptable with the condition that a minimum 10 percent sample of all non-exempt integrally welded attachments to piping, pu m, and valves, in Class 1, 2, and 3 systems, is examined.
The licensee's proposed alternative to use Code Case N 509 provides an acceptable level of quality and safety and is, therefore, authorized pursuant to 10 CFR 50.55a(a)(3)(1).
The licensee is authorized to use Code Case N-509 until such time as the Code case is included in a future revision 01 Regulatory Guide 1.147.
At that time the licensee should follow all provisions and any limitations that may be described in Regulatory Guide 1.147 concerning the use of Code Case N-509.
2b.
DISCUSSION:
6$fE Code.Section XI Relief Reauest on Hiah Pressure Coolant Iniection (HPCI)
Pumo Stud InsDettion Code Reauirement The ASME Code,Section XI, 1980 Edition with Addenda through the Winter 1981.
Table IWC-2500-1 requires a volumetric examination of the studs for the HPCI main pump during each 10 year interval.
Licensee's Relief Recuest There are 17 HPCI main pump studs that connect the upper aump casing to the lower pump casing and have cap nuts which are torqued to 3000 foot-pounds each.
A volumetric examination of the studs by ultrasonics requires removal of the cap nuts since the studs are completely restricted from the top by the cap nuts.
During the 1995 refueling outage of BSEF. Unit 1 the licensee was unable to remove the cap nuts using proper equipment and the proper procedure.
The licensee has determined that the best option for removal of the cap nuts
5-without damaging the studs is to destructively remove (i.e.
cut) the cap nuts. Hweve". 9 out of the 17 studs can be volumetrically examined from the bottom of the stud with tne pump casing configuration.
For the current inspection interval, the licensee requests relief from conducting volumetric examination of the remaining studs that require destructive removal of cap nuts for volumetric examination.
if the HPCI main ) ump requires disassemoly for maintenance or repair during the remainder of tle current 10 year inspection interval, the licensee will perform volumetric examination of the remaining pump ctuds, finis for Relief The basis for relief provided by the licensee follows:
The sampling selection (more than 50 percent of the HPCI main pump studs) provides reasonable assurance that degradation of the HPCI main pump pressure retaining components-(casing and studs) will be identified.
The alternative visual examination is performed each outage, and the VT 2 examination is performed once ser period. Thus, these visual examinations are performed muc1 more frequently than the ASME Code volumetric examination, which is 3erforme.d only once during each 10 year inspection interval.
)uring this 10-year inspection interval, the lPCI main Sump has been visually examined after each outage for leacage and VT 2 examined at reactor pressure for two periods with no degradation noted to the HPCI main pump pressure retaining components.
This provides a significant check of degradation on an ongoing basis rather than once every ten years.
The accessible HPCI main pump studs (i.e.
9 of the 17 studs) have already been volumetrically examined with no indications or degradation noted.
This sampling provides reasonable assurance that the remaining studs have not experienced significant degradation.
3b.
EVALUATION:
The staff has evaluated the licensee's submittal of the request for rel'ief' from the ASME Code.Section XI, 1980 Edition including the Winter 1981 Addenda, on the volumetric examination of the HPCI main pump studs.
During the second inspection interval, the licensee performed two VT 2 visual examinations of the pum) pressure retaining boundary and, following each refueling outage, the H)CI system including the pump was walked down to inspect for leakage at system operating There was no leakage observed at the pump pressure boundary. pressure,Furthermore. volumetric examination of 9 out of 17 studs did not show any defect or degradation.
Hence, it is reasonable to assume that there has been no degradation mechanism affecting the pump studs.
The staff, therefore, has determined that the licensee's volumetric examination of the accessible studs, along with visual examinations of the pump pressure retaining boundary during the current interval, provide s
=
l 6-an acceptable level of quality and safety.
1 4b. CONCLUSlQS:
Based on the staff's review of the licensee's request for relief from the requirements of the ASME Code.Section XI. 1980 Edition including the *. inter 1981 Addenda. Table IWC 2500 1 main pump studs that are access. a volunetric examination of 9 out of :
u'Cl ible and a VT 2 visual examination dur ' ig system pressure test of the pump pre,ssure boundary. would provide an acceptable level of quality and safety for the remainder of the second 10-year inspection interval.
Therefore, the proposed alternative is authorized pursuant to 10 CFR 50.55a(a)(3)(1).
i t
e o