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Forwards Info in Response to NRC 921125 SER of Util 920408 Response to Rev to NUREG-0619 Re Routine Insp Criteria for Feedwater & CRD Return Line Nozzles.Util Surpassed Available Guidance Re Capability of phased-array UT Exam Technique
	ML20127N635
Person / Time
Site:	Oyster Creek
Issue date:	01/21/1993
From:	J. J. Barton; GENERAL PUBLIC UTILITIES CORP.
To:	; NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
	RTR-NUREG-0619, RTR-NUREG-619 C321-92-2357, NUDOCS 9302010011
	Download: ML20127N635 (15)
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609 971 4000 Wnters Direct Del Numbof; January 21, 1993 C321-92-2357 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555

Dear Sir:

Subject:

Oyster Creek Nuclear Generating Station (0CNGS)

Docket No. 50-219 Revision to NUREG Oo19 Routine Inspection Critoria for feedwater and Control Rod Drive Return Line Nozzles Reference 1:

NRC letter dated November 25, 1992 and Related Safety Evaluation Report Reference 2:

GPU Nuclear letter (C321-92-3018), dated. April 8,1992.

Reference I was transmitted to GPU Nuclear in response to our proposal (Reference 2) to revise the requirements of NUREG 0619, and requires GPU Nuclear to:

1.

Examine all four (4) feedwater (FW) and one (1) Control Rod Drive Return Line (CLDRL) nozzle during the current 14R refueling outage.

It' further states that if flaw indications are -interpreted te bc.

cracks, the supplementary liquid penetrant-(PT) examinations must be performed.

2.

Submit certain information to the NRC for staff review before-the end of the current 14R refueling-outage. The information requested requires us to:

A.

Demonstrate the smallest dimensions of the FW nozzle thermal fatigue crack that can be reliably detected and sized using the-Phased Array Ultrasonic Testing (UT) examination technique.

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Provide the technical basis demonstrating that the Phased Array-UT examinations are capable of detecting defects that can grow l

to an unacceptable size prior to the next inspection. This includes analyzing inspection and laboratory data, considering-the flaw sizes assumed.in our Fracture Mechanics Analysis (FMA).

C, Provide the fMA demonstrating the acceptability of the_

Phased Array UT examinations based or, the minimum detectable flaw size.

The information contained herein responds to your request _for certain-o information arior to the end of the current outage. With the exceptioe of th0 results of t w current Phased-Array UT examination of the FW and CRDRL nozzles, the information requested has previously been provided.

In response to request #1 above, GPU Huclear scheduled, prior to the issuance.

of Reference 1, the examination of the FW nozzles for the 14R refueling outage.

For the FW nozzles, this action is consistent with NUREG-0619 t

requirements, and was based on the assumption that the NRC would not authorize our proposal (Reference 2) to defer examination of the FW nozzles unti_1 the 15R refueling outage.

Altho' ugh GPU Huclear is also examining the CRDRL ' nozzles during the current refueling outage, it is not required.

The previous CRDRL nozzle examination was completed during the 13R refueling outage and would not-be required-until the 18R refueling outage.

By requiring the CRDRL examination during the current outage the NRC is, in effect, changing the NUREG-0619 requirements.

1 In response to request #2 above, GPU Nuclear has previously responded to.the information required, as follows:

A.

There is no need to demonstrate the " smallest" dimensions of the FW nozzle thermal fatigue crack that can be _ reliably detected and sized using the Phased-Array UT examination technique.

The GPU Nuclear methodology begins with an assumed thermal fatigue 1 crack size for-the FW and CRDRL nozzles, each representing the minimum statistically detectable notch depth in the-respective nozzle.:.

Next, these cracks are interacted withithe local thermo-mechanical stresses by means of= linear elastic fracture mechanics methods in-order to-assess crack growth._ The:results indicate-that the assumed cracks will notJgrow to a depth requiring-repair over a 10 year-interval. ' Crack sizes smaller than those assumed arelinherently represented by the assumed? crack sizes.

For the FW nozzle the assumed thermal < fatigue crack sizelis-Oil 72. inch in depth,:and for the-CRDRLtnozzle:it is 0.132 inch in depth. The_next step involves demonstrating the. capability of-the' Phased; Array UT-examination 32192357.LTR-m....

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technique to be capable of detecting and sizing actual thermal fatigue cracks at least as small as the assumed crack sizes indicated above, Through blind testing alone, GPU Nuclear has l

demonstrated that the Phased-Array UT examination technique can actually detect and-size thermal fatigue cracks smaller than those assumed in our FMA.

See Peference 2, and the information provided during.the September 9, 1992 audit at the Siemens facility in r

Chattanooga, Tennessee.

B.

The effort described in "A"

' we obviates the need to address NRC requirement 20, above.

This new NRC requirement requires a crack growth analysis over a 4-year period, which according to NUREG-0619-i would be the next required FW nozzles. examination. As stated in "A" above, if a crack size equivalent to or less than that assumed in our FMA will not grow to a depth requiring repair over a 10-year

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period, it will not do so in a shorter, 4 year tima period.- St<n Reference 2.

C.

As stated above, the GPU Nuclear FMA is based on assumed crack' sizes which will not grow to a depth requiring repair over a 10 year interval. The assumed crack sizes are the minimum, statistically detectable sizes upon which our proposed inspection frequency.is based.

Reference 2 provides a report, which shows the results of our FMA, justifying cur proposed 10 year inspection frequency. The Phased Array VT examination technique has demonstrated the-capability to detect cracks smaller than those assumed in our FMA.-

l The attachment identifies additional, specific NRC statements-from Reference I which we feel misrepresent our efforts to date,'and provides necessary clarification.

.GPU Nuclear'has surpassed the available guidance in demonstrating the capability of the Phased-Array UT examination technique. While so doing, the NRC has been apprised of our ef forts and progress throughout this period via-correspondence, telecons, two audits, public meetings, etc.

1

-In addition, GPU Nuclear'has ccmpleted the 14R refueling outage Phased-Array VT examination'of the 4 feedwater nozzles and 1 CRDRt. nozzle. No crack:like indications were detected in ary of the 5 nozzles examined.

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C321-92-2357

Page 4 Thus, we have clearly demonstrated that the Phased Array VT examination technique, together with our fliA, forms the basis for revising the f1VREG 0619 requirements.

As a result, we request the f1RC review our previous submittal (Reference 2) and provide GPU lluclear authorization to implement proposals 1 and 2 therein.

Upon completion of ASl4E B&PV Code Section XI, Appendix VIII qualification, GPU lluclear will seek llRC authorization to perform VT inspections once each inservice inspection interval of 10 years, in accordance with the ASl4E code.

Sincerely,

/

1

. J. B>rton esident & Director a

Oyster Creek

\\p1p Attachment cc: Administrator, Region I f1RC Reside.;t Inspector, OC Alex Dromerick, f1RC Project fianager

-32192357.LTR

ATTACHMENT d

f 1.

COVER LETTER, 2 PARE RAPH. 2"d AND 3'd SENTENCES NRC STATEMENT:

At the audit, the staff determined that some of the fatigue cracks in the GPU Nuclear mock ups could not be detected with the sensitivity (gain) used at OCNGS during the 12R and 13R outages. During future nozzle inspections, Siemens plans to modify their examination procedure to significantly increase the instruments sensitivity consistent with the mock-up results.

GPUN CLARIFICATION: During the audit, GPU Nuclear candidly informed the NRC that one implanted thermal fatigue crack in a specific region of the FW nozzle mock-up could not be detected with the instrument sensitivity previously used at OCNGS (8db).

GPU Nuclear also informed the NRC that one implanted thermal fatigue crack in the CRDRL nozzle mock up could not be detected regardless of the increased instrument sensitivity. All other implanted thermal fatigue cracks in the FW and CRDRL nozzles were detected with the same instrument sensitivity used during the 12R and 13R outages (8db).

The sensitivity increase from 8db to 12db is not considered significant (see GPU Nuclear clarification no. 6), and is only applicable to a specific area on the FW nozzle, where the undetected (at tha lower instrument sensitivity only), individual implant was located.

As a result, only the ap)licable Siemens FW nozzle examination procedure will se revised to use a 12db instrument sensitivity in one specific area of the FW nozzles.

2.

SER. PAGE_1. SECTI')N 1.1. LAST PARAGRAPH 2"d SENTEN((

(See also Cover 1r tter, 3rd paragraph, 2nd sentence)

NRC SER ltems 3 and 4 will be evaluated as the licensee and industry progress in the implementation of ASME Section XI, Appendix Vill, for performance demonstrations.

GPUN CLARIFICATION: The above NRC statement refers to proposals made by GPU Nuclear to (1) eliminate routine liquid penetrant (PT) examinations of feedwater and control rod-drive return line nozzles,-and (2) following successful-Appendix Vill UT qualification,- demonstration of adequate sensitivity for Oyster Creek specific assumed flaw sizes and successful 15R examinations -

(which are currently being performed since the NRC-did not authorize deferral) showing no cracks.

perform UT inspections once each inservice inspection (ISI) interval (every 10 years) in accordance with the ASME code.

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Attachment-

' Page 2-HUREG-0619 encourages the continued development of UT-techniques for the fW nozzle examinations.

The NVREG further states that, "Should future developments and the results of inservice UT examinations demonstrate that UT techniques can detect small nozzle thermal fatigue cracks with the acceptable reliability and consistency, these techniques could then form the basis for modification of the inspection criteria..." GPU Nuclear feels that our efforts to-date have accomplished this. Upon completion of.ASME B&PV Code Appendix Vill qualification,- GPU Nuclear will seek NRC authorization to perform UT inspections-once each inservice inspection interval.of 10-years in accordance with the ASME code.. To consider our.

proposals generically until the." industry". catches-up, penalizes our efforts toward demonstrating that-the capability of the Phased Array technique forms the basis for revising the NUREG-0619 requirements for GPU Nuclear.

3.

SER. SECTION 2.0 PAGE 2. 2* SENTENCE a

NRC STATEMENT:

For the OCNGS configuration a scheduled liquid.

penetrant test was required of one nozzle after the.

sixth refueling outage or ninety startup/ shutdown.

cycles, i.e., the 13R outage.

GPUN CLARIFICATION: GPU Nuclear discussed deferral of the'13R liquid penetrant examination via our. letters, 5000-90-1857, dated January 18,.1990 and-5000-90-1954-l (C320-90-697),-dated July 12,1990. !The:NRC letter dated December 13, 1990 and. attached SER authorized the deferral of the routine liquid penetrant from the-13R outage. -This NRC authorization..in effect,;

voided the previous commitment.

-s

=4.

SER. SECTION 3.0. PAGE 2.1" PARAGRAPH. 4th SE'NT M l'RC STATEMENT:

The conclusion of the NRC staff's December 13,.1990..

SE-was that the licensee could: consider the 13R the9 beginning-of a new inttrval..for performing:the NUREG--

0619 Table 2 inspections provided the licensee-satisfled the followingcconditions::

1.

Performed a UT of all-FW andlthe-CRDRL nozzles during-the.13R outage with_the phased-array UT--

system,-

2.

Used the NUREG-0619 acceptance' criteria: for;> flaw

-indications interpreted to be cracks, i.e.,; remove'the sparger..and perform a:

supplemental PT, and

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Attachment Page 3 3.

Introduced thermal fatigue cracks into the GPU Nuclear noz:10 mock-ups and defined the capabilities of the UT system.

CPUN CLARIFICATION:

The SER referred to above actually-states the following, on pages 3 and 4:

"1herefore, based on the licensee's experience during the past 73 startup/ shutdown cycles and five refueling outages, modifications, results of various FW and CRDRL nozzles HUREG-0619.

requirement reviews by the licensee and NRC, and the effectiveness of the proposed Phased Array

~f system's qualification method, the staff has found the licensee's pro)osed FW and CRDRL nozzle UT inspection to se acceptable for.the 13R outage provided:

1.

Any surface indication detected by the i

phased array system and not proven to be t

geometric in r,ature will require that-a liquid penetrant examination be performed-i that meets the requirerents.of Section XI.

2.

The phased-array system should demonstrate the capability to detect thermal fatigue-cracks that are'O.172 inch in depth. The-demonstration need not be a blind e

demonstration, as an example; if data is-available from other test (such as PISC 11

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orpastinserviceinspectionexami_ nations) could be used to illustrate-crack detection capability."

Furthermore, during'a-telephone 1 conversation on January 17,1991,.the NRC was informed that the-FW-nozzles were not in the inspection plan;for

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the 13R refueling outage,-since they were-inspected during the' previous 12R refueling r

outage. GPU Nuclear also informed the NRC that we were taking credit fornthe 12R inspection of!

the FW nozzles in-lieu of a 1_iquid. penetrant examination in 13R.- The NRC was:also informed that we did not plan to perform a liquid; s

penetrant examination for just any surface _-

indication.. If. indications were found,-GPU,.

Nuclear planned to evaluate them for continued:

service in accordance with-ASME Section XI, e

1 32192357.LTR' 4

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Attechment

' Page 4 5.

& SECTION 3.0. PAGE 2. 5" PARAGRAPH.1" AND 2* SENTENCES -

NRC STATEMENT:

The licensee and the staff had a public meeting on July 23, 1992, to discuss the implementation of NUREG-0619 at DCNGS. The licensee informed the staff that an ultrasonic test of the four feedwater nozzles was not conducted during the 13R outage.

GPUN CLARlflCATION: As stated in the GPU Nuclear clarification No.'4 above, GPU Nuclear informed the NRC during the January 17, 1991 tele) hone conversation that the FW nozzles were not in tie inspection plan for the 13R refueling outage.

Furthermore, in GPU Nuclear' letter C321-91-2094(500091-2038), dated April-18, 1991, the NRC was informed that the FW nozzles were previously inspected in 12R. We also reported on-the 13R CRDRL nozzle inspection results.

Thus the NRC was informed before July 23, 1992, that 1

the FW nozzles were not going to be inspected during.

the 13R refueling outage.

6.

SER. PAGE 3. SECTION 4.1.1. 2* AND 3d SENTENCES NRC STATEMENT:

Some of the fatigue cracks in the mock-ups could not.

be detected.

During future inspections, Siemens.

plans _to modify-their examination' procedure to-significantly increase the instrument sensitivity (gain) above the levels used at 0CNGS during'the 12R-

- and 13R outages.

GPUN CLARIFICATION: _ In a " blind" test demonstration during' August,.1992, implanted thermal fatigue cracks smaller than 0.172 inch in depth in the FW nozzle mock-up and smaller -

than 0.132 inch'in depth ~in the_CRDRL mock-up were-detected at-the same instrument sensitivity (8db),

previously used at OCNGS during the 12R and~13R outages.

This clearly demonstrates that thermal-fatigue cracks can'be detected at an instrument sensitivity of 8 db in-FW and CRDRL nozzles.--

The only Siemens procedure (s) which will. be revised is (are) the applicable FW Nozzle examination procedure (s).

The' procedure (s) will;bel revised to require the use of a 12db instrument sensitivity-(instead of 8db) in one region 'of: the FW nozzles-only. This regicn-corresponds-to the single region where one isolated implanted thermal fatigue crack was not-detected at 8db.-

No procedural changes are-planned for the CRDRL instrument sensitivity.-

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Page 5-The increase in sensitivity from 8db to 12 db is not considered significant.

The increase of 4db from a perfect corner reflector, such as a notch, would increase that response by approximately 30% of full Screen Height (FSH) (e.g., an increase of 4db on a 50% FSH notch reflection would increase the signal to approximately 80% FSH).. This methodology-is-not as.

clear cut when considering reflections from an actual crack.

The nature of cracks is such that they are not always perfect corner reflectors. Some cracks are un oriented, meaning they are not perpendicular to the angle of incidence of the; sound beam.

In such<

1 cases, some or possibly all the sound energy is reflected away from the transducer. This probably is the case of the implanted ~ thermal fatigue cracks-which are also very tight and isolated.

The. actual thermal fatigue cracks that have been seen in:the- _

field are much larger / wider, and if these were used-as the implants, it is likely that there would not-have been the need for adding the 4db. This increase

- i has been shown by experimentation on the'feedwater nozzle mockup to be an improvement to the technique; therefore, 4db was added to the Siemens procedure for scanning the specific zone corresponding to the. zone-in the FW mock up where:the single crack was not detected at 8db. As in any examination performed, when improvements are made which are verified byL experimentation, those improvements will be incorporated. Any ultrasonic calibration which is performed using notches cannot guarantee the-detection of a flaw not oriented perpendicular to the sound (e.g., examinations for intergranular stress corrosion cracking in. boiling water reactor-stainless steel ?iping). Cracks which may have the samo:

througi wall dimension as calibration notd.es will not have the same amplitude ~ response if oriented di f ferently.

th 7.

SER. PAGE-3. SECTION 4.1.1. 4 SENTENCE i

NRC STATEMENT:

GPU Nuclear did not provide a: technical basis explaining the impact;of the-mock-up demonstration-on the actual number or size of the cracksLthat coulds

-escape detection during previous examinations.1 2

GPUN CLARIFICATION: GPU Nuclear specifically-addressed this issue during.

the September 9, 1032 auditlin Chattanooga, Tennessee u

l:

and provided a one page document. titled " Process L

Differences - Impact" during the above meeting..

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3 l Attachn+nt Page 6 During the audit the NRC wac. informed that no_ impact is expected since the worst stresses occur _on the i

blend radius.

This form of cracking'does not occur.

as single, isolated flaws in the nozzle bore,: and the cracking experienced in the field is substantially larger (i.e., longer, deeper and wider) than the impianted cracks.

Thus, the blind _ mock up demonstration does provide evidence that the Phased-Array UT examination technique removes concerns about nozzle integrity with respect to cracks that could have escapad detection during previous examinations.

- 8.

$1R. PAGE 3. SECTION 4 1.2 1

NRC STATEMENT:

Siemens changed the phased array UT; system computer j

programs after conducting the 12R examination at OCNGS.

Therefore, the licensee may not be able to.

compare the 12R data with future inspection results.-

GPUN CLARif! CATION: Technological advancements prompted Siemens' to improve the Phased Array UT-system computer after conducting the 12P examination at OCNGS. _However,

'_1 the NRC was informed during the September 9, 1992 audit in Chattanooga, Tennessee that only minor.

4 hardware changes were all _that was necessary -in order' to replay previous data.

Also, there is no requirement to. compare old data with new data. - The licensee may elect'to do this, depending on what new data may reveal. Florver, comparison of old and new data ic_.not mandatory.

9.

SER. PAGE 3. SECTION 4'.l.3 NRC STATLMENT:

Only a partial UT of the CRDRL nozzle was performed' during the 12R outage.

GPUN CLARIFICATION:-The NRC statement does not indictite that the portion of the CRDRL nozzle which was not-inspected during the 12R. outage was inspected during the 13R~ outage, thus completing the inspection of the CRDRL nozzle.-

a,-

10.

SER. PAGE 3. SECTION 4.1.4 NRC STATEMENT!

. The feedwater nozzle-to-vessel weld 'is required to be; examined per ASME Section'XI and was: examined'at the same time as the FW nozzle examinations. The mock-up.

results indicating that the-12R_ instrument gain was_-

t not'high_enough.may_ impact the examination-results-from the feedwater nozzle to-vessel weld.

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Attachment a

Page 7_-

i GPUN CLARIFICATION: The above statement is speculative and unrelated to the requirements of NUREG 0619.

The feedwater nozzle to-vessel welds were examined in accordance 1

with ASME Code Section XI, 1974 W/S '75 Addendum using scanning angles and calibration biccks meeting the requirements of the code.

11.

SER. PAGE 3. SECTION 4.1.5. 2* AND 3 SENTENCES d

NRC STATEMENT:

At the September 9, 1992 audit, the combination of~

the maniaulator and data acquisition system used during t1e mock-up activities was not available.

Therefore, the staff was not able to observe the;-

acquisition of data with the-phased-array: system or to evaluate the methodology described in the examination procedure.

GPUN CLARIFICATION: During the September 9,1992 audit, the diLt3 acouisition system used during the mock-up activities was present, but not set up.

it was thought that.

setting up for the data analysis demonstration was-more-im)crtant.

To set up for data acquisition _would

-- have'tacen a couple of hours.- The NRC was made aware of this and did not request-any changes.

12. E R. PAGE 3. SECTION 4.2.,1 NRC STATEMENT:

The licensee has not demonstrated that the exa_minations previously performed provide adequate-assurance that the five nozzles in the region dcfined by NUREG 0619 are free of cracks.

GPUN CLARIFICATION: The Phased Array UT examination technique'has=

demonst' rated the_ capability to detect the kinds:of flaws that can develop in nozzles. Assurance that:

the nozzles are free.of cracks in the region defined by NUREG-0619 is based,on the _results of _" blind"-

tests conducted on the FW and CRDRL nozzio mock-ups, it'has been documented that the Phased Array UT' technique detected, during " blind"_-testing ~

demonstrations of a FW nozzle mock-up--33-out of=33 notches (see NRC-SER dated December 13, 1990,-Page 3, 2* paragraph) varying in size from 0.030 to 0.468 inch in depth (see the attachment to GPU Nuclear letter C320 90 697_ [5000-90-1954), dated July 12, 1990).

Attachment:

Page-10 16.

SER. PAGE 4. SECTION 5.1.1" SENTENCE HRC STATEMENT:

The licensee has not demonstrated the smallest dimensions of the feedwater nozzle thermal fatigue crack that can be reliably detected and sized using the phased array UT system.

GPUN CLARIFICATION: 1here is no need to demonstrate the " smallest" dimensions of the FW nozzle thermal fatigue crack that can be reliably detected r'l sized using the Phased Array system. GPU Nucleat has demonstrated that the Phased-Array UT examination technique can detect and size thermal fatigue cracks smaller than the size assumed in our fracture mechanics analysis for the FW and CRDRL nozzles.

17. SLR. PAGE 4. SECTION 5.1. 3d. 4*h AND 5 SMTENCES th (See also Cover letter, 3rd PARAGRAPH, 4th and 5th SENTENCES)

NRC SER STATEMENT:

Therefore, the licensee must analyze their inspection and laboratory data, considering the_ flaw sizes assumed in their fracture mechanics analysis, and provide for staff review of the technical bases demonstrating that the phased-array UT examinations are capable of detecting defects that could grow to.

an unacceptable size prior to the next inspection.

The fracture mechanics analysis. demonstrating the acceptability of the phased array UT examinations based on the minimum detectable flaw sizo should be included.

This information should be submitted'for-staff review before the end of the 14R outage.

GPUN CLARIFICATION: The data gathered from the current Phased Array UT examination of the FW~and CRDRL nozzles has to be analyzed to determine if there are any flaws.'which would compromise. nozzle integrity,sprior to restart since these may require further inspection. The NRC is imposing a new requirement when it mandates that' GPU Nuclear perform a crack growth analysis to demonstrate detection of cracks that could grow to an unacceptable size prior to the next inspecti_on.: This inspection -period is two ref aeling outages. This' requirement is not-. imposed on' licensees by NUREG-0619.

GPU Nuclear has..previously provided the-technical basis (see GPU Nuclear letter C321-92;2055:

[5000-92-3018] dated April 18, 1992) to demonstrate-that the Phased-Array UT examination technique is:

capable of detecting defects that will not grow tolan '

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, Attachment Page 11 unacceptable size over a-10 year period.

Requiring a-crack growth analysis for the aeriod covered by the requirements of NUREG 0619. Ta)1e 2 prior to tina next inspection (over a 4 year seriod) is unprecedented,.

and besides, is enveloped >y the analysis discussed in the above referenced technical: basis.

The NUREG does not require a license to demonstrate, 'over. the-inspection interval cited therein, that a defect.will not grow to an unacceptable size. The Phased Array-UT. technique has already demonstrated lt can' detect and size flaws smaller than that' assumed in.our fracture mechanics analysis.

For GPU Huclear, the sizes assumed in our fracture' mechanics analysis'are the minimum sizes upon which we are basing our proposed 10 year inspection interval. Thus, we have demonstrated that we can detect flaws smaller than these.

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ML20127N635

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