ML20217P744

SE Accepting Licensee Request for Second 10-yr Insp Interval to Use ASME Section IX Code Case N-416-1, Alternative Pressure Test Requirement for Replacement Items by Welding, Class 1,2 & 3,Div 1 at Plant Per 10CFR50.55a(a)(3)(i)

ML20217P744
Person / Time
Site:	Calvert Cliffs
Issue date:	04/07/1998
From:	NRC (Affiliation Not Assigned)
To:
Shared Package
ML20217P732	List: ML20217P730 ML20217P744
References
NUDOCS 9804100176
Download: ML20217P744 (4)

Text

e -

i

. n,%  !

p 1 UNITED STATES

t. g j NUCLEAR REGULATORY COMMISSION WAsMINGToN, o.C. 30806 0001 l

0*****#  !

i SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION ON ASME CODE CASE N-416-1 l

EQB l CALVERT CLIFFS NUCLEAR POWER PLANT. UNIT NOS.1 AND 2 BALTIMORE GAS AND ELECTRIC COMPANY DOCKET NOS. 50-317 AND 50-318 I

1.0 INTRODUCTION

l l The Technical Specifications for Calvert Cliffs Nuclear Power Plant, Unit Nos.1 and 2 state that .

the inservice inspection and testing of the American Society of Mechanical Engineers (ASME) l Code Class 1,2, and 3 components shall be performed in accordance with Section XI of the  ;

ASME Boiler and Pressure Vessel Code (ASME Code) and applicable Addenda as required by l l 10 CFR 50.55a(g), except where specific written relief has been granted by the Commission pursuant to 10 CFR 50.55a(g)(6)(l).10 CFR 50.55a(a)(3) states that attematives to the l requirements of paragraph (g) may be used, when authorized by the NRC, if (1) the proposed altematives would provide an acceptable level of quality and safety or (ii) compliance with 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 pre-service examination requirements, set forth in the AS;'E Code,Section XI, " Rules for Inservice i Inspection of Nuclear Power Plant Components," to thw axtent practical within the limitations of design, geometry, and materials of construction of the components. The regulations require that p

inservice examnation of components and system pressure tests conducted during the first ten-year interval and subsequent intervals 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 twelve months prior to the start of the 120-month interval, sub.ilet to the limitations and }

modifications listed therein. The applicabie edition of Section XI of the ASME Code for the  ;

second ten-year inservice inspection interval for Calvert Cliffs Units 1 and 2 is the 1983 Edition, including the Summer 1983 Addenda. The components (including supports) must 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(g)(5)(iii), if the licensee determines that conformance with certain code requirements is impractical for its facility, the licenses shall submit information to support the determination. After evaluation of the determination, pursuant to 10 CFR 50.55a(g)(6)(1), the l Commission may grant relief and may impose attemative requirements that are determined to be '

9004100176 980407 PDR ADOCK0500g7 Enclosure o.

)

,c

't 2-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.

By letter dated February 25,1998, Baltimore Gas and Electric Company (licensee) requested approval for the implementation of the altemative rules of ASME Section XI Code Case N-416-1 dated February 15,1994, titled "Altemative Pressure Test Requirement for Welded Repairs or installation of Replacement items by Wolding Class 1,2, and 3,Section XI, Division 1," pursuant

- to 10 CFR 50.55a(a)(3)(i) to be applied to the inservice inspection (181) program for Calvert Cliffs Units 1 and 2. . _ _. _ _ . _ . . .

The staff has reviewed and evaluated the licensee's reausst and suppor1ing information to use Code Case N-4161 as a proposed altomative to the Code requirements for Calvert Cliffs Units 1 and 2.

2.0 DISCUSSION CODE CASE N-416-1 ALTERNATIVE PRESSURE TEST REQUIREMENT FOR WELDED REPAIRS OR INSTALLATION OF REPLACEMENT ITEMS BY WELDING CLASS 1,2, AND 3 -

SECTION XI, DIVISION 1 -

L System / Component AaaHe=M= to Use of CM C4se:

ASME Class 1, 2, sad 3 Components with welded repairs or replacements installed by welding.

Code Reauirement Affected by Use of cme C+==:

The 1983 Edition through Summer 1983 Addenda, ASME Code,Section XI, lWA-4400(a) requires that a system hydrostatic test be performed following repairs by welding. Similarly, a system hydrostatic test is to be performed following installation of replacement items by welding, as required by IWA-4600. The system hydrostatic tests are to be conducted in accordance with IWA-5000.

Licensee's Proposed Altemative to Code Reauirement:

"The attemative to hydrostatic pressure festbg provided by ASME Code Case N-416-1, subject to the condition outlined in Reference (b), will be utilized.

American Society of Mechanical Engineers Code Case N-416-1 states that,in lieu of a hydrostatic pressure test, a system leakage test may be used provided the following requirements are met.'

m) Non-destructive examination shall be performed in accordance with the methods and

. acceptance criteria of the applicable Subsection of the 1992 edition of ASME Section Ill.

b) Prior to or immediately upon retum to service, a visual examination (VT-2) shall be I performed in conjunction with a system leakage test, using the 1992 edition of 1 Section XI, in accordance with paragraph IWA-5000, at nominal operating pressure y and temperature.' '

(

i i

t ,

l 3- i

. c) Use of this case shall be documented on an NIS-2 Form.

The condition outlined in Reference (b) is that additional surface examinations should be performed on the root (pass) layer of butt and socket welds of the pressure retaining boundary of Class 3 components when the surface examination method is used in I accordance with Sechon lii."

Reference (b) in the above licensee's statement refers to

• Draft Regulatory Guide DG-1050.

(Revision 12 to Regulatory Guide 1.147) Inservice inspection Code Case Acceptability ASME  !

. Section.XI, Division 1, February 1997." _ _ . .

l 3.0 ' EVALUATION In lieu of hydrostatic pressure testing for welded repairs or installation of replacement items by  ;

welding, Code Case N-416-1 allows a system leakage test using the 1992 Edition of ASME l Code,Section XI, in accordance with paragraph IWA-5000, at nominal operating presture and  !

temperature. This Code Case also specifies that the non-destructive examination (NDE) of l welds be performed in accordance with the applicable Subsection of the 1992 Edition of ASME '

Code, Section lil, The latest edition of ASME Code,Section XI and Section lil, referenced in 10 CFR 50.55a, is the 1989 Edition.' The staff has compared the system pressure test requirements of the 1992 Edition of Section XI to those of the 1989 Edition and determined that the 1992 Edition of the Code imposes a more uniform set of system pressure test requirements for Code Class 1,2, and 3 systems. The terminology associated with the system pressure test requirements for all three

]

code classes have been clarified and streamlined. The test frequency and test pressure associated with these tet,ts, have not been changed. The hold time for the test has either remained unchanged or increased. The corrective action with respect to removal of bolts from a leaking bolted connection, however, has been relaxed in the 1992 Edition and has been accepted by the staff in prulous safety evaluations. The NDE requirements of post-weld repair, remain the same in both versions of the Code. Therefore, the staff finds that the requirements of the 1992 ASME Code,Section XI, as referenced in Code Case N-416-1 are similar to those of l the 1989 ASME Code,Section XI. j l

Piping components are designed for a number of loadings that would be postulated to occur l under the various modes of plant operation. Hydrostatic testing only subjects the piping j components to a small increase in pressure over the design pressure and, therefore, does not {

present a significant challenge to pressure boundary integrity. Accordingly, hydrostatic pressure l

testing is primarily regarded as a means to enhance leakage detection during the examination of  ;

components under pressure, rather than solely as a measure to determine the structuralintegrity j of the components.

i The industry experience has demonstrated that leaks are not being discovered as a result of  ;

hydrostatic test pressures propagating a pre-existing flaw through walls. The experience, however, indicates that leaks in most cases are being found when the system is at normal j operating pressure. This is largely due to the fact that hydrostatic pressure testing is required only upon installation and then once every 10-year inspection intorval, while system leakage tests at nominal operating pressures are conducted a minimum of once each refueling outage for ,

Class 1 systems and each 40-month inspection period for Class 2 and 3 systems, in addition,  !

. leaks may be identified by plant operators during system walkdowns which may be conducted as often as once a shift. ,

l

1

, , . . . - , j

4 i}

• y 4

1 Follomng completion of welding, the Code requires volumetric examinaten of repairs or replacements in Code Class 1 and 2, but requires only a surface examination of the final {

weld pass in Code Class 3 components. There are no other NDE requirements for Code Class 3 components except for VT-2 visual examination for leaks in corjunction with the 10 year hydrostatic tests and the periodic pressure tests. i Considering the NDE performed on Code Class 1 and 2 systems and considering that the

~ hydrostatic pressure tests rarely resuWt in pressure boundary leaks that would not occur during system leakage tests, the staff believes that increased assurance of the integrity of Class 1 and 2

' welds is not commensurate with the burden of pefformity; hydrostatic testing. Considering the . ,

nature of NDE requirements for Code Class 3 components, the staff does not believe that 1

elimination of the hydrostatic pressure testing while only performing system pressure testing is an  :

acceptable attemative to hydrostatic testing unless additional surface examinations are performed on the root pass layer of butt and socket welds on the pressure retaining boundary of

)

I Class 3 components when the surface examination method is used in accordance with Section Ill. The Licensee, however, has proposed to examine the root (pass) layer of butt and socket welds. This proposal addresses the staffs concems and is acceptable.

For clarification, it should be noted that, consistent with the Code Case requiring performance of NDE in accordance with the methods and acceptance criteria of the 1992 Edition of Section lit, the scope of examination should also be in accordance with the 1992 Edition of Section Ill. The additional surface examination of the root layer of Class 3 pressure retaining weids should be performed only when those pressure retaining welds are required to have a surface examination performed in accordance with the 1992 Edition of Section lil. For those Class 3 welds receiving radiography in lieu of a surface examination in accordance with Section Ill, no additional surface examination of the root layer needs to be performed.

4.0 CONCLUSION

The staff concludes that use of Code Case N-416-1 with additional surface examination on the l root pass of butt and socket welds of Class 3 pressure retaining boundary would provide  !

equivalent protection as that provided by the applicable Code. Therefore, the licensee's l proposed attemative would provide an acceptable level of quality and safety. Accordingly, the '

licensee's proposed altemative to use Code Case N-4161 is authorized for Calvert Cliffs Units 1 and 2, pursuant to 10 CFR 50.55a(s)(3)(i) provided that the additional surface examinations are performed on the root pass layer of butt and socket wolds on the pressure retaining boundary of Class 3 components when the surface examination method is used in accordance with Section Ill. Use of Code Case N-416-1, with the additional surface examination as noted above, is authorized for the duration of the second ten-year ISI interval at Calvert Cliffs Units 1 and 2, until such time as the Code %se is approved by reference in Regulatory Guide (RG) 1.147. At that time, if the licensee intends to continue to implement this Code Case, the licensee must follow all provisions in Code Case N-4161 with limitations issued in RG 1.147, if any.

k Principal Contributor: P. Patnisk I i

Date: April 7,1998 i

_