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0128V |

X7GJ17-H790 i;;

June 16, 1989 |

|

U.S. Nuclear Regulatory Commission !ATTN: Document Control Desk

.

Washington, D.C. 20555 ]

PLANT HATCH - UNITS 1, 2 INRC DOCKETS 50-321, 50-366

;

OPERATING LICENSES DPR-57, NPF-5 |PROPOSED RHCU WELD EXAMINATIONS |

PER GENERIC LETTER 88-01 i

Gentlemen: i

- On June 30, 1988, Georgia Power Company (GPC) responded to GenericLetter' (GL) 88-01, "NRC Position on IGSCC in BHR Austenitic Stainless i

Steel Piping." Included in our response was a request to exclude from ;examinations, the non-safety-related reactor water clean-up (RWCU) piping :

located downstream (outside containment) of the double isolation valves. !

By letter- dated October 24, 1988, - the NRC denied this exclusion due to |lack of justification. On April 5,1989, GPC met with the NRC to . discuss |

the hardship involved with inspecting all these additional welds. Based H

on the discussion . agreement was reached to perform a sample inspection ;

plan, with - the understanding that we predetermine our flaw evaluation ;criteria for scope expansion prior to the outage, and provide the -

criteria to the NRC for their review. ~The enclosure presents our :

proposed examination plan and the flaw evaluation criteria for the j,,

subject piping. ;,

You may contact this office at any time if you have questions. II2Si.1cerely.'1

/@.d __ _ o C.1W- !

W. G. Hairston, III

GKM/ebJ

Enclosure: Proposed RHCU Held ExaminationsPer Generic Letter 88-01 )

c: (See next page.) , , j

890620034o 890616PDR ADOCK 05000321p_ PDC

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iU.S. | Nuclear: Regulatory Comission'

June:16,-1989-- Page Two

p1.

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; c: ;Georcia Power Comitnyn.. Mr. H.. C. Nix, Geinral Manager - Nuclear Plant

Mr. - L. . T.. Gucwa, Fanager Engineering and Licensing - Hatch-GO-NORMS

1' U.S. Nuclear Reaulatory Commission. Washinoton. D.C.

Mr. L. P. Crocker, Licensing Project Manager - Hatch

U.S. Nuclear Reaulatory Commission. Reaion II,

Mr.~ S. D. Ebneter, Regional AdministratorMr. J. E. Menning, Senior. Resident Inspector - Hatch'

.

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0128V

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1. : ENCLOSURE

PLANT HATCH UNITS 1, 2NRC DOCKETS 50-321, 50-366

OPERATIAG LICENSES DPR-57, NPF-5PROPOSED RHCU HELD EXAMINATIONS

PER GENERIC LETTER 83-01

I

_Our June 30, 1988 letter requested excluding approximately 130 reactorwater clean-up (RNCU) welds (combined number of welds for both units)from the ultrasonic testing (UT) requirements of Generic Letter (GL)

'88-01 and NUREG-0313, Revision 2. The subject piping welds are located.

outside primary containment and are not considered part of the reactor |

coolant primary pressure boundary.

. Our relief request was based on three considerations: (1) The piping isisolable. Two, upstream, automatically-actuated isolation valves close |upon a variety of initiation signals indicative of a leak or break; (2) |ALARA considerations. The estimated personnel exposure for inspection iand related activities would range from 0.4 to 6 rem per weld, dependingon location; and (3) The piping is not safety-related and has never been 1

part of our ASME Section XI Program. The NRC initially denied our reliefrequest by letter dated October 24, 1988.

This relief request does not pertain to the Class I portions of the RHCUpiping, which have been replaced.

These . welds would be considered Category G welds per GL 88-01(non-resistant, not inspected material) because they have not beenultrasonically examined previously. Therefore, in accordance with the

. generic letter, all of the subject Unit 2 RNCU welds would have to beinspected during the 1989 maintenance / refueling (H/R) outage and all the jUnit I welds exaained during the 1990 outage. Inspection of all these ;

welds would approximately double the number of UT examinations forintergranular stress corrosion cracking (IGSCC)-susceptible weldsotherwise required by GL 88-01.

.

i

On April 5, 1989, GPC personnel met with the NRC staff to discuss the |

burden associated with inspection of the subject welds and verbally i

agreed to a sample examination plan. The following paragraphs detail ouraugmented inspection plan for the RHCU piping welds outside the outboardisolation valve. Specifically, the number and location of the selected. welds in the subject piping, and flaw evaluation criteria for scopeexpansion are discussed.

Held Selection

A review was performed to determine the RHCU weld population which may bemost susceptible to IGSCC. Seven Unit 2 RHCU welds (approximately 10% of |

tthe applicable weld population) have been selected for ultrasonic testing(UT) inspections. The selection of the seven welds was determined based

0128VHL-517 E-1

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ENCLOSURE (Continued)

PROPOSED RHCU WELD EXAMINATIONSPER GENERIC LETTER 88-01

on accessibility, ALARA considerations, and IGSCC susceptibility. Figure1 shows a schematic of the Unit 2 RHCU piping. GPC plans to inspect two6-inch diameter welds and three 4-inch diameter welds between theoutboard isolation valve (F004) and the entry to the regenerative heatexchanger. The regenerative heat exchanger is a counter flow heatexchanger which allows heat from the hot reactor fluid inlet flow to betransferred to the fluid being returned to the reactor after filtering.After leaving the regenerative heat exchangers the operating temperatureof the fluid has dropped considerably on the inlet side of the system.Two 4-inch welds will be examined on the fluid return side after exitingthe regenerative heat exchanger. To summarize, five welds will beexamined on the hot leg inlet side of the regenerative heat exchanger,and two welds will be examined on the hot leg outlet side. Studies haveshown that IGSCC is more likely in piping which operates at highertemperature.

Expansion of scope to include another seven welds will depend on theresults of the initial inspection relative to the flaw evaluationcriteria discussed below.

Flaw Evaluation Criteria

Held inspection and disposition of crack-like indications (e.g., overlaydesign) will be in accordance with Generic Letter 88-01/NUREG-0313,Revision 2 guidance. Scope expansion criteria will not be in accordancewith the GL.

Reportable indications for the purpose of scope expansion will be basedon the ' leak-before-break criteria described below, in lieu of those ofNUREG 0313, Revision 2. The subject piping is not consideredsafety-related and can be isolated. The welds in this piping were notradiographer and have not been included in our ASME Section XI Program.This means that reliable baseline data on the welds is not availsble.

Our intent is to use these criteria to determine unacceptable crackingfor the purpose of scope expansion. Structural Integrity Associates(SIA) was retained by GPC to assist in the development of the scopeexpansion criteria. The conclusion of this effort is that any axialflaws, or single circumferential flaw with length less than approximately30% of the circumference would tend to leak before breaking, and thuswould not be a cause for concern if they were present in uninspectedwelds in this non-safety system. The allowable flaw length depends onthe magnitude of the applied stress. A review of the stress report forthe subject piping (including the seven welds selected for inspection),indicates that the applied stresses are bounded by the range of stress

0128VHL-517 E-2

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ENCLOSURE (Continued)

PROPOSED RNCU HELD EXAMINATIONSPER GENERIC LETTER 88-01

level reported in Table 1. Table 1 shows the allowable flaw length as afunction of applied stress and pipe diameter, generated using aconservative set of material properties.

The proposed criteria of Table 1 is independent of flaw depth, since flawgrowth through-wall in small diameter piping is predicted to be rapid.The tendency observed in numerous cracking incidents in small BWR lines(112 inch diameter) is for local through-wall growth (due to asymmetriesin the stress pattern) rather than for uniform growth around thecircumference. Thus, industry experience supports these leak beforebreak arguments.

In summary, when the identified flaws in the inspection sample are axial,or when a circumferential flaw in the weld is shorter than the lengthsidentified in Table 1, expansion of the inspection sample is notrequired. (It should be noted that any detected flaw indication [ormultiple circumferential indications] near the length in Table 1 would beevaluated on a case-by-case basis, to determine if sample expansion isrequired )

If our initial examinations identify one or more welds with flaws largerthan the above criteria, GPC will either examine an additional sevenwelds as indicated by the above criteria, or discuss our findings withthe NRC. The additional welds will be selected considering the magnitudeof applied stresses in those welds related to Taule 1, as well as thesusceptibility criteria used to select the original sample, plus any newinformation gained from the initial examinations.

If one or more welds in the subsequent examinations have flaws longerthan that identified in Table 1, the inspection scope would not beautomatically expanded. At that point, GPC would discuss, with the NRC,our resolution plan relative to the subject piping. If the subsequentwelds do not have flaw indications as large or larger than Table 1, GPCwill plan to inspect an additional 7 welds during the nextmaintenance / refueling outage and follow similar guidelines regarding flawevaluation and scope expansion.

Plant Hatch Unit 2 has a maintenance / refueling outage scheduled tocommence around September 1, 1989. Similar RHCU IGSCC inspections onUnit I would occur during the Spring of 1990 refueling outage.

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j-IENCLOSURE'(Continued)

TABLE'1,

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Permissible Flaw Lenaths vs.-Stress~For Non-Safety Grade RHCU Pinina Held Inspections

, . .6" Pipe 4" Pipe

Applied Stress Critical Length Critical Length.(KSI)- (% of Circumference) . % of Circumference)(

.14.1 18.4%- 21.0%

9.4 29.6% 32.4%

4.7 47.3% 49.0%

Notes:

1. Criteria is independent of flaw depth.

'2. A detected flaw indication (or multiple small indications) near thesize indicated by this table will be evaluated on a case by casebasis..

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