ML20211B027

SER Accepting Second 10-year Interval Inservice Insp Requests for Relief RR-A16,RR-A17 & RR-B9 for Plant, Unit 1

ML20211B027
Person / Time
Site:	Davis Besse
Issue date:	08/13/1999
From:	NRC (Affiliation Not Assigned)
To:
Shared Package
ML20211B021	List: ML20211B016 ML20211B027
References
NUDOCS 9908240204
Download: ML20211B027 (9)

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UNITED STATES

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NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20665-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGUj_ATION QN THE SECOND 10-YEAR INTERVAL INSERVICE INSPECTION REQUESTS FOR RELIEF RR-A16. RR-A17. AND RR-B9 DAVIS-BESSE NUCLEAR POWER STATION DOCKET NUMBER: 50-346

1.0 INTRODUCTION

I The inservice inspection of the American Society of Mechanical Engineers (ASME) Code 1

Class 1,2, and 3 components shall be performed in accordance with Section XI of the ASME Boiler and Pressure Vessel Code (Code) and applicable addenda as required by 10 CFR 50.55a(g), except where specific written relief has been granted by the U.S. Nuclear Regulatory Commission (Commission or NRC) 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 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 preservice examination requirements, set forth in the ASME Code,Section XI, " Rules for laservice 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 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 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 ASME Code,Section XI, for Davis-Besse Plant's second 10-year inservice inspection (ISI)intervalis the 1986 Edition. The components (including supports) may meet the requirements set forth in subsequent editions l-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.

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12-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 50.55a(g)(6)(i), the Commission may grant relief and may impose altemative requirements that are determined to be authonzed 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 January' 4,1999, FirstEnergy Nuclear Operating Company (FENOC), the

licensee for Davis-Besse Nuclear Power Station, submitted the following requests for relief from the requirements of the ASME Code,Section XI,1986 Edition duiing the second inservice

. inspection (ISI) interval of Davis-Besse.

Relief Request RR-A16 pertains to eliminating the system hydrostatic test for a 4-foot segment of piping in the decay heat removal system located between two isolation valves downstream of

- the reactor coolant piping.

Relief Request RR-A17 requests use of Code Case N-416-1, "Altemative Pressure Test Requirement for Welded Repairs or installation of Replacement items by Welding, Class 1,2, and 3," with limitations included in NRC Draft Regulatory Guide DG-1050.

Relief Request RR-89 requests substituting radiography of butt welded main feedwater riser welds with liquid penetrant examination of the root weld, and ultrasonic and magnetic-particle examination of the final weld.

The staff has reviewed and evaluated the licensee's request for the above reliefs and the supporting information for Davis-Besse, Unit 1.

2.0 DISCUSSION 2.1 Relief Reauest RR-A16

- 2.1.1 Component identification

. ASME Class 1 Decay Heat Removal Piping between Valves DH 11 and DH 12 2.1.2 Code Examination Requirement The ASME Code,Section XI,1986 Edition, Subsection IWB-2500, Yable IWB-2500-1, Examination Category B-P, item No. B15.51, requires a system nydrostatic test at or near the end of each inspection interval. The pressure retaining boundary during the hydrostatic test shall include all Class 1 components within the system ooundary.

2.1.3 Licensee's Request for Relief The licensee requests relief from performing the Code-required hydrostatic test for a segment of Class 1 piping approximately 4 feet in length located between isolation valves DH 11 and

' DH 12.1 Valves DH 11 and DH 12 are installed in the normal cooldown line from the reactor

. coolant system (RCS) to the decay heat removal system (DHRS).

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2.1.4 Licensee's Proposed Altemative

- The required hydrostatic test pressure for the piping between DH 11 and DH 12 is 2155 psig.

i in lieu of the hydrostatic test at the required pressure, this segment of piping will be VT-2 l

' examined,' with. the insulation removed, for leakage of boric acid residue at normal operating pressure of 45 psig during plant shutdown. The piping will have undergone a 4-hour hold at l

greater than 200 psig and several days of operation at 45 psig. Since the decay heat system contains borated water, any pressure boundary leak would be identifed by the formation of i

l boric acid crystals at the location of leakage.

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i 2.1.5 Licensee's Basis for Relief.

The licensee assessed the following three options available to perform the hydrostatic test of the segment of piping between valves DH 11 and DH 12.

1. The valve DH 12, the first isolation valve off of the RCS, could be opened while the plant is l

in hot standby (Mode 3) at full pressure and temperature to pressurize the piping between DH 11 and DH 12 to 2155 psig. Howisver, Technical Specification (TS) 3.5.2 prohibits opening of either isolation valve when the RCS pressure is greater than 328 psig.

Therefore, DH 12 may not be opened to pressurize the piping during the normal RCS hydrostatic test.

2. The segment of piping including valves DH 11 and DH 12 is installed inside a watertight enclosure (Decay Heat Pit) which protects the valves from flooding following a Loss of i

Coolant Accident (LOCA). This pit could be opened in Mode 3 to perform hydrostatic testing by pressurizing the piping between the valves with a hydrostatic pump. However, TS 3.5.2 requires that the Decay Heat Pit be closed and sealed in Modes 1,2, and 3, and opening the Decay Heat Pit would make both Low Pressure injection pumps in'>perable and result in entry into TS 3.0.3.

3. The reactor vessel could be defueled and the RCS drained down to disassemble DH 12 and perform a temporary modification to the valve disk of DH 12 to establish test conditions (DH 11 and DH 12 were modified to prevent pressure locking by drilling a vent hole in the upstream disc of valve's wedge).

The licensee considers each of the above options to be a hardship or an unusual difficulty l

without a compensating increase in the level of quality and safety.

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2.1.6 Evaluation Based on the requirements of the Technical Specifications, the hydrostatic test of the segment of piping between valves DH 11 end DH 12 would require the licensee to defuel the reactor vessel and drain the RCS below the level of the valve DH 12 to perform necessary modification to the disk, prior to pressurizing.

The piping between DH 11 and DH 12 is a 4-foot section of seamless stainless steel pipe connected to the stainless steel valves DH 11 and DH 12 by field welds. Both pressure boundary welds between the valves and the section of the pipe are usually subjected to a volumetric and a surface examination in accordance with the ASME Code,Section XI, during each inservice inspection interval. The absence of any detectable flaw provides assurance of I

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structural integrity of the welds. The staff believes that the purpose of a hydrostatic test is to ensure leak-tight integrity of the pressure boundary as opposed to the structural integrity. The application of a test pressure above the operating pressure during a hydrostatic test, however, results in enhancing any existing leakage.

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In regard to the operation of the decay heat system, the valves DH 11 and DH 12 are normally opened before the RCS pressure reaches 260 psig during an RCS cooldown, in order to meet

. TS 3.4.2 requirements for Low Temperature Overpressure Protection. Two reactor coolant

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pumps normally continue to run in one loop with the decay heat system in operation while the

system cools to an RCS temperature corresponding to 200 psig. The time required for the RCS to cool down to this temperature from when DH 11 and DH 12 are opened is normally in excess 3

? of 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.~ This is followed by long-term cooling at a pressure of approximately 45 psig using the decay heat system. The licensee has committed to mair.taining pressure above 200 psig with DH 11 and DH 12 open for 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> in preparation for the VT-2. -

' Since the decay heat system contains borated water of the RCS, the licensee proposes to take credit for the normal system walkdown during the outage to detect any boric acid leakage in the subject piping, if leakage were occurring in this section of piping during normal operating conditions, it would be evident from boric acid residue observed during the routine walkdown.

The staff has determined that the inservice examination of the welds and the routine walkdown l

for detection of boric acid leakage provides adequate assurance of structural integrity and the leak-tightness of the subject pressure boundary.-

1 2.1.7 Conclusion.

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The staff concludes that due to restrictions imposed by the Technical Specification, the hydrostatic test ~of the segment of pipe (4 feet in length) containing two welds between valves.

DH 11 and DH 12,'would require defueling of the reactor vessel and a temporary modification of

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the valve DH 12 to establish test conditions. Therefore, compliance with the Code requirement

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would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety. However, the inservice examination of the welds and the system walkdown for detection of boric acid leakage provides assurance of structural integrity and the leak-

. tightness of the subject pressure boundary welds. Therefore, relief is authorized pursuant to 10 CFR 50.55a(a)(3)(ii) for Davis-Besse for the second 10-year inspection interval.

2.2-Relief Reauest RR-A17 The licensee requests approval to use Code Case N-416-1 " Alternative Pressure Test Requirement for Welded Repairs or Installation of Replacement items by Welding, Class 1,2, and 3," with limitations included in NRC Dratt Regulatory Guide DG-1050.

2.2.1 Code Examination Requirement ASME Code,Section XI,1986 Edition, Subsection IWA-4400, Pressure Tests, requires that after repairs by welding on the pressure retaining boundary, a system hydrostatic test shall be performed in accordance with IWA-5000.

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2.2.2 Licensee's Proposed Altemative g.

/ The licensee requests approval to use Code Case N-416-1 " Alternative Pressure Test

Requirement for Welded Repairs or installation of Replacement items by Welding, Class 1, 2,

~and 3," with limitations included in NRC Draft Regulatory Guide DG-1050.

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Code Case N-416-1 allows a system leakage test in lieu of a hydrostatic test for welded repairs or installation of replacement items by welding in Class 1,2, and 3 systems provided the following requirements are met.

(a). and acceptance criteria of the applicable Subsection of the _1992 Edition of th Nondestructive examination (NDE) shall be performed in accordance with the methods Code, Section Ill.

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

(c)

Use of this Case shall be documented on an NIS-2 Form.

In addition to those requirements of Code Case N-416-1, DG-1050 states that additional surface examinations will be performed on the root layer of butt and socket welds of the

' pressure retaining boundary of Class 3 components when the surface examination method is used in accordance with ASME Code, Section Ill.

2.2.3 Licensee's Basis for Relief

- Alth6 ugh only the repaired / replaced portion of the system requires testing, it is often necessary to extend test boundaries well outside the repaired / replaced portion of the system to establish isolation and fill and vent the system for the hydrostatic test. Additional pumps are often required to obtain test pressures. Since the test pressure is above the normal operating pressure, any pressure relief valve must be removed or gagged. A typical hydrostatic test requires approximately 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> to perform with a test crew of 3 and each test on an average results in a personnel exposure of approximately 150 mrems, For the reasons described above compliance with the Code requirement to perform a

- hydrostatic test of the repaired pressure boundary would result in hardship or unusual difficulty without a compensating increase in the level of qualRy and safety.

2.2.4 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 Code,Section XI, in accordance with paragraph IWA-5000, at nominal operating pressure and

temperature. This Code Case also specifies that the non-destructive examination (NDE) of welds be performed in accordance with the applicsbie subsection of the 1992 Edition of ASME Code, Section Ill.

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The latest edition of ASME Code,Section XI and Section Ill, 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 tests 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 which has been accepted by the staff in previous safety evaluations. Nevertheless, the NDE requirements of post-weld repair remain the same in both versions of the Code. Therefore, the staff finds that

~ the NDE requirements of the 1992 ASME Code,Section XI, as referenced in Code Case N-416-1, are equivalent to those of the 1989 ASME Code,Section XI.

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Hardships are generally encountered with the performance of hydrostatic testing performed in accordance with the Code.' For example, sinca hydrostatic test pressure would be higher than the nominal operating pressure, hydrostatic pressure testing frequently requires significant effort to set up and perform. The need to use special equipment, such as temporary attachment of test pumps and gages, and the need for individual valve lineups can cause the testing to be on critical path.

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

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

pressure testing is primarily regarded as a means to enhance leakage detection during the

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

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 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 interval, 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.

Following completion of welding, the Code requires volumetric examination of repairs or i

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 con l unction with the 10-year hydrostatic tests and the periodic pressure tests.

Considering the NDE performed on Code Class 1 and 2 systerm and considering that the hydrostatic pressure tests rarely result 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 performing hydrostatic testing. However, considering the nature of NDE requirements for Code Class 3 components, the staff does not n*'

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7' believe that elimination of the hydrostatic pressure testing while only performing system y

pressure testing is an acceptable attemative to hydrostatic testing, unless additional surface j

examinations are performed on the root pass layer of butt and socket welds on the pressure' u

roteining boundary of Class 3 components when the surface examination method is used in accordance with Section Ill.-

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. 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

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~ 111, 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 welds need i

be performed only when those pressure retaining welds are required to have a surface E examination performed in accordance with the 1992 Edition of Section lil, For those Class 3 l welds receiving radiography in lieu of a surface examination in accordancs with Section lil, no j

additional surface examination of the root layer needs to be performed.

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Conclusion:

The staff concludes that compliance with the Code hydrostatic testing requirements for welded.

l repairs or replacements of Code Class 1,2, and 3 components would result in hardships without a compensating increase in the level of quality and safety. Accordingly, the licensee's -

proposed altemative to use Code Case N-416-1 is authorized for Davis-Besse, pursuant to 10 CFR 50.55a(a)(3)(ii) considsring that the licensee will perform additional surface examinations on the root pass layer of butt and socket welds on the pressure retaining boundary t'f Class 3 components when the surface examination method is used in accordance -

with Sec'.cn Ill.

2.3 Rehof Roauest RR-B9 2.3.1 Component identification Three (3) inch Schedule 80 ' Butt Welded Main Feedwater Riser Welds.

- 2.3.2 Code Examination Requirement Subarticle IWA-4400 of the ASME Code;Section XI,1986 Edition requires that after repairs by welding on the pressure retaining boundary, a system hydrostatic test shall be performed in accordance with IWA-5000, System Pressure Tests.

Code Case N-416-1 states that in lieu of performing the hydrostatic pressure test required by

'lWA-4000 for welded repairs or installation of replacement items by welaing, a system leakage test may be used provided the following requirements ato met:

(a) NDE shall be performed in accordance with the methods and acceptance criteria of the applicable Subsection of the 1992 Edition of Section Ill.

_ (b) ' Prior to or immediately upon retum to service, a visual examination (VT-2) shall be

- parformed in conjunction with a system leakage test, using the 1S92 Edition of Section XI,

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- in accordance with paragraph IWA-5000, at nominal operating pressure and temperature.

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(c)

Use of this Case shall be documented on an NIS-2 Form.

If the previous version of this case were used to defer a Class 2 hydrostatic test, the deferred test may be eliminated when the requirements of this revision are met.

Paragraph NC-5222 of the 1992 Edition of ASME Section 111 requires that butt welded piping Joints be radiographed.

2.3.3 Licensee's Proposed Alternative Examination in lieu of radiographic examination required by Paragraph NC-5222 of the 1992 Edition of ASME Section XI, ultrasonic examination and magnetic-particle examination of the main feedwater riser welds were performed.

2.3.4 Licensee's Basis for Relief During the eighth refueling outage in 1993, the main feedwater spray plates on steam generators 1-1 and 1-2 were replaced. The original construction code for the main feedwater header and risers was the 1967 Edition of ANSI B31.1 with the 1969 Addendum. The replacement required each of the 64 three-inch main feedwater risers be cut and removed to replace the spray plate and then reassembled with a new weld. It was estimated that radiography of the welds on the 64 main feedwater risers would have required approximatel) 2 days to complete, resulting in radiation levels above 25 mrem /hr and, thus, limiting access to the containment to perform other critical path work in the area. Each new riser weld was, therefore, examined by ultrasonic examination performed and accepted to the requirements of the 1986 Edition of ASME Section XI and ANSI B31.1. In addition, the final weld also received a surface examination using a magnetic-particle method. During the fabrication process, the root pass was also examined using a liquid penetrant examination. Each of these examinations were performed to the requirements of the 1986 Edition of ASME Section XI ar d accepted per the original construction code requirements. Following completion of the replacement, the welds were VT-2 examined at system operating temperature and pressure with no leakage found.

The examination of the new main feedwater riser welds met the requirements of Code Case N-416-1 with the exception that an ultrasonic uamination and a magnetic-particle examination were performed in lieu of a radiographic examinaten for each of the subject weld.

2.3.5 Evaluation The staff has evaluated the effectiveness of flaw detection in the main feedwater riser welds as a result of substitution of the radiographic examination with an ultrasonic and a magnetic-particle examination. The ultrasonic examination as a volumetric examination is considered to i

be more sensitive than radiographic examination in detection of flaws in the main feedwater riser welds, but has an irherent drawback of missing detection of flaws that are located in the region of the ultrasonic beam adjacent to the transducer. This is known as the near-field or Fresnel zone where detection of surface flaws are hindered due to complex beam profile. To overcome this drawback of ultrasonic examinanon, a surface examination such as the i

magnetic-particle or the liquid penetrant examination is recommended which then provides a j

satisfactory examination of the weld volume and is considered to be superior to performing only radiographic examination for the purpose of flaw detection.

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Therefore, the staff has determined that the substitution of radiographic examination with ultrasonic and magnetic-particle examinations for the main feedwater riser welds would provide L

an acceptable level of quality and safety.

2.3.6 Conclusion The staff concludes that the licensee's proposed attemative of an ultrasonic examination of the weld volume in conjunction with a magnetic-particle surface examination in lieu of the radiographic examination as required under Code Case N-416-1 for each of the main feedwater riser welds provides an acceptable level of quality and safety. Therefore, relief is authorized pursuant to 10 CFR 50.55a(a)(3)(i) for Davis-Besse during the second 10-year inspection interval.

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Principal Contributor: P. Patnaik i

Date: August 13, 1999 l