U-601217, Responds to Generic Ltr 88-01, NRC Position on IGSCC in BWR Austenitic Stainless Steel Piping. Revised Inservice Exam Program Plan Encl

Responds to Generic Ltr 88-01, NRC Position on IGSCC in BWR Austenitic Stainless Steel Piping. Revised Inservice Exam Program Plan Encl

ML20151M747
Person / Time
Site:	Clinton
Issue date:	07/29/1988
From:	Hall D ILLINOIS POWER CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
Shared Package
ML20151M751	List: ML20151M761 U-601217, Responds to Generic Ltr 88-01, NRC Position on IGSCC in BWR Austenitic Stainless Steel Piping. Revised Inservice Exam Program Plan Encl
References
DPH-0686-88, DPH-686-88, GL-88-01, GL-88-1, U-601217, NUDOCS 8808050333
Download: ML20151M747 (6)

Text

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U-601217 L30-88 ( 07-29 )-LP_

lA.120

'ILLINDIS POWER COMPANY CLINTON A%ER STATION. P.O. BOX 678. CtlNTON ILLINOIS 61727 DPH-0686-88 July 29 1988 10CFR50.,54(f)

Docket No. 50-461 U.S. Nuclear. Regulatory Commission Document Control Desk Washington, D.C. 20555

Subject:

Clinton Power Station Generic Lettet- 88-01

Dear Sir:

This letter is in response to Generic Letter 88-01, "NRC Position on IGSCC [Intergranular Stress Corrosion Cracking] in BWR Austenitic Stainless Steel Piping".

Attachment 1 contains responses to the specific items listed in the Generic Letter. Attachment 2 is the revised Inservice Examination Program Plan. This Program Plan includes revisions due to Generic Letter 88-01 requirements and other revisions due to program changes initiated by Illinois Power Company. Attachment 3 is a summary of the changes'made to the Inservice Examination Program Plan which are not related to this' Generic Letter, and Attachment 4 includes revised relief requests associated with these c.hanges and a current relief request index.

Clinton Power Station's next refueling outage is scheduled to start in January 1989. It is requested that the changes to the Inservice Examination Program Plan due to Generic Letter 88-01 be approved by October 1, 1988, to allow sufficient time to plan the refueling outage activities related to the Inservice Examination Program.

I hereby affirm that the information in this letter is correct to the best of my knowledge.

ly ours, Ji

?yyBo0333ggo,g, -

p DOCK 05000461 PNU . Hall Vice President DPH/kar Attachments }0 i0I 1,

cc: NRC Clinton Licensing Project Manager ( (

NRC Resident 2.1spector Regional Administrator, Region III, USNRC '

Illinois Department of Nuclear Safety

g Attachment 1

1. Item "Your current plans regarding piae replacement and/or other measures taken or to be ta'<en to mitigate IGSCC and provide assurance of continued long-term piping integrity and reliability."

Response

a) Piping components: Generic Letter'88-01 applies to the Reactor Recirculation System piping, portions of the Reactor Water Cleanup System piping and to portions of the Residual Heat Removal System piping made of austenitic stainless steel that is four inches or larger in nominal diameter and contains reactor coolant at a temperature above 200*F during power operation.

Illinois Power (IP) has no plans for pipe replacement. During construction, material selection and processing, steps were taken to mitigate Intergranular Stress Corrosion Cracking (IGSCC) as follows:

With the exception of the Reactor Recirculation System piping, all stainless steel piping in contact with the reactor coolant is 316L stainless steel and, therefore, has less than 0.03% carbon content. The P.cactor Recirculation System piping is fabricated primarily of 304 stainless steel.

Certain portions of the piping have been changed to "nuclear grade" type 316 stainless steel which contains less than 0.03% carbon. The remainder has had "Corrosion Resistant Cladding" (CRC) applied in the vicinity of field welds so that no heat-cffected type 304 stainless steel will be in contact with the reactor coolant. The piping assemblies were solution annealed after all shop i welding and application of the CRC.

b) Reactor Pressure Vessel (RPV) attachments and appurtenaaces: The RPV head spray and vent plaing is made of carbon eteel classified as P-1 by tae American Society of Mechanical Engineers (ASME)

Boiler and Pressure Vessel Code and is therefore not susceptible to IGSCC. None of the RPV internal components require volumetric examinations in accordance with Section XI ef the ASME Code. Twenty-four (24) Clinton Power Station (CPS) RPV nozzle assemblies have Inconel 182 l _.

buttering at their safe-end connections. Of the twenty-four (24), twenty-three (23) require ultrasonic testing (UT). The control rod drive nozzle safe-end connection does not require UT because it is less than four inches in diameter.

c) Hydrogen Water Chemistry: IP plans to use a Hydrogen Water Chemistry (HWC) system at CPS. A plant modification has been prepared to perform the HWC pre-implementation test. This test is scheduled for August to September 1988. Based on the results of the HWC test, the final design and installation of a HWC system are expected to be initiated in 1989 and completed in 1990.

d) Stress Improvement (SI): Twenty-four (24) RPV nozzle assemblies have Inconel 182 buttering at their safe-end connections and are potential candidates for stress improvement. Industry experience with SI is relatively recent. As mentioned before, IP plans to use a HWC system at CPS, and its installation may mitigate IGSCC on these nozzle assemblies.

2. Item "An Inservice Inspection (ISI) Program to be implemented at the next refueling outage for austenitic stainless eteel piping covered under the scope of this letter tLat conforms to the staff positions on inspection schedules, methods and ersonnel, and sample expansion included in this letter.p'

Response

a) Inspection Schedules: The piping welds are IGSCC Category A as described in Generic Letter 88-01, Table 1. The extent and frequency of examination of the piping welds will be in accordance with the requirements in ASME Section XI, 1980 Edition through Winter 1981 Addenda. The specific welds to be examined will be selected based on the following criteria: considerations of stress level, piping and support configurations, and weld detail.

The RPV nozzle assemblies which have Inconel 182 buttering at their safe-end connections are IGSCC Category D as described in Generic Letter 88-01, Table 1. The extent and frequency of examination of items in this category will be in accordance with Generic Letter 88-01. It should be noted that surface examinations of these nozzle assemblies will be performed at the frequency specified by the ASME Code.

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l b) Inspection Methods and Personnel: The detailed procedures, the equipment, and the examination personnel (Level II or III) used in examining austenitic stainless steel component welds and austenitic stainless steel component welds with overlays, will be those qualified by a formal .

program in accordance with the Nondestructive Examination (NDE) Coordination Plan agreed upon by the Nuclear Regulatory Commission (NRC), the Electric Power Research Institute (EPRI), and the Boiling Water Reactor (BWR) Owners Group for IGSCC research, as implemented at the EPRI NDE center in Charlotte, North Carolina. It should be noted that none of the welds at CPS are currently overlaid.

On austenitic stainless steel vamponent welds with CRC, the above mentioned EPRI qualified procedures, equipment and examination personnel will be utilized to demonstrate the capabilities to detect IGSCC on CRC welds.

Level I examiners who may become qualified by demonstrating field performance capability will not be utilized in the examination of piping susceptible to IGSCC.

c) Sample Expansion: If one or more cracked welds in the IGSCC Category A welds are found by a sample inspection during the ten-year inspection interval, IP will inspect an additional sample of welds. The additional sample of welds will be approximately equal in number to those examined in the original sample. This additional sample will be similar in distribution to the original sample, unless it is determined that there is a technical reason to select a different distribution. If any cracked welds are found in this additional sample, IP will inspect all the welds in IGSCC Category A.

3. Item "A change to the Technical Specifications to include a statement in the section on ISI that the Inservice Inspection Program for piping covered by the scope of this letter will be in conformance with the staff positions on schedule, methads and personnel, and sample expansion included in this letter (see enclosed model BWR Standard Technical Specification). It is recognized that the Inservice Inspection and Testing sections may be removed from the Technical Specifications in the future in line with the Technical In this case, Saecifications Improvement programs.

this requirement shall remain with the ISI section when it is included in an alternative document."

i

Response

A change to the Technical Specification Section 4.0.5 will be submitted separately to incorporate the above NRC staff position.

4. Item "Confirmation of your plans to ensure that the Technical Specification related to leakage detection will be in conformance with the staff position on leak detection included in this letter."

Response

IP plans to implement a change to the Technical Specifications related to leakage detection which will incorporate all of the actions and requirements specified in the staff's position on leak detection.

As part of the change, IP will propose an ACTION statement based on the Standard T,echnical Specifications and also based on leakage having exceeded a 2 gpm increase within a 24-hour period as specified in Generic Letter 88-01. The action would require a plant shutdown if the noted leakage limit is exceeded unless it can be determined within four hours that the leakage increase is not associated with service-sensitive Type 304 or 316 stainless steel.

This ACTION and the other changes proposed for the CPS Technical Spacifications concerning leakage detection were d..scussed with the NRC project manager and representatives from the Technical Specification and Materials branches. It was concluded that the proposed changes are consistent with the staff position on leak detection, and are therefore acceptable in response to the Generic Letter.

5. Item "In accordance with 10CFR50.55a(o), your plans to notify the NRC of any flaws identified that do not meet IWB-3500 criteria of Section XI of the Code for continued operation without evaluation, or a change found in the condition of the welds previously known to be cracked, and your evaluation of the flaws for continued operation and/or your repair plans."

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l R'esponse Flaws detected during the examination of components covered by Generic Letter 88-01 will be categorized with regard to location, size, and orientation. These flaws will be evaluated for acceptance in accordance with the ASME Section XI, 1980 Edition through Winter '

1981 Addenda. Any flaws which exceed the acceptance criteria which is listed in the ASME Section XI, 1980 -

Edition with Addenda through-Winter 1981, will be evaluated for continued service in accordance with IWB-3600 of the ASME Section XI, 1986 Edition. Flaws which exceed the acceptance criteria which is listed in the ASME Section XI, 1980 Edition with Addenda through Winter 1981, changes found in the condition of. welds previously known to be cracked, evaluations of flaws for continued operation, and repair plans for cracked weldments will be submitted for NRC approval prior to resumption of operation.

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