ML18153D243
| ML18153D243 | |
| Person / Time | |
|---|---|
| Site: | Surry, Sequoyah  |
| Issue date: | 02/16/1993 |
| From: | Strosnider J Office of Nuclear Reactor Regulation |
| To: | Hebdon F Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML18153B357 | List: |
| References | |
| NUDOCS 9303010018 | |
| Download: ML18153D243 (3) | |
Text
MEMOIWOII FOR:
FROM:
SUBJECT:
e e
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON. O.C. 20lil5 0001 FEB 16 1993 Frederick J. Hebdon, Director Project Directorate 11-4 Division of Reactor Projects I/II Jack Strosnider, Chief Materials and Chemical Engineering Branch Division of Engineering STRUCTURAL INTEGRITY REPORTING REQUIREMENTS FOR ASME CODE CLASS 3 COMPONENTS The Materials and Cheaical Engineering Branch has reviewed your questions regarding leakage in Code Class 3 components.
Due to insufficient detail regarding the Sequoyah leak event, we are unable to address it more specifically than in the general discussion of existing documents and staff positions as follows.
When a leak occurs in a Code Class 3 pipe, one of the first actions necessary is deten11ining whether it is pressure boundary or non-pressure boundary leakage. Non-pressure boundary leakage is most typically experienced as
- flange gasket and valve packing leaks. Gasketing and packing in a mecha.nical joint (such as a pipe flange, valve bonnet, or packing gland) is not considered part of the pressure boundary under Code rules. The bolting itself is considered the pressure boundary.
The Mechanical Engineering Branch, NRR, has issued soae guidance on the use of sealants, such as Funnanite, for stopping leaks in mechanical connections. This method may be (and is frequently) used as a teaporary corrective measure for this class of leaks without any requirement for relief from NRR.
Application of this method ii
!lll1 acceptable for pressure boundary leaks.
Pressure boundary leaks are those where the structural integrity of the pipe or component has been violated. Exilll)les are wall thinning due to erosion/corrosion and through wall leaks due to pitting or cracks. Regardless of the Code Class of the pipe or c0111ponent, the ASME Code and 10 CFR 50.55a(g)(4) require pressure boundary integrity be maintained in accordance with approP-r11te Code des.ign criteria.
By evidence of pressure boundary leakage, tlie_.-Cocl* r1qutrllilents are not satisfied. Therefore, the regulation is not.. t~;alllld the coaponent 11Ust be considered inoperable and the appropriatf..systlll LCO aust be entered. This guidance 1s contained in Generic Letter 91-Ja Off degraded-conditions and operability. Should a licensee decide that sOIII,.,..., repair, other than a Code qualified repair, is desirable to
/
avoid an unplanned unit outage, the licensee must first request relief from the provisions of the ASME Code under the provisions of 10CFR S0.55a(a)(3) or
{a)(6){g)(i).
Technical contacts: R. Her111ann 504-2768, G. Hornseth 504-2756
F. An exception to the structural integrity rules involves the plugging of heat exchanger tubes.
Flaw removal and structural integrity are not considered in the Code rules for tube plugging.
For heat exchangers, leakage rates are usually the limiting condition. Note, however, that steam generator tube inspection and plugging are governed by different rules and receive close scrutiny by NRR.
Recognizing that the regulations and Code requirements may impose an undue number of start-up and shutdown cycles on unit facilities if a Code repair was required for every instance of leakage on certain classes of Code Class 3 pipe, the staff provided the guidance contained in Generic Letter 90-05.
Although the title of the GL is *GUIDANCE FOR PERFORMING TEMPORARY NON-CODE REPAIR OF ASME CODE CLASS 1, 2, AND 3 PIPING*, the crux of the letter is concerned with IIIOderate energy Code Class 3 pipe only. Moderate energy Code Class 3 is defined as less than 200°F and 215* ps1g. Class l, 2 and high energy class 3 pipe require relief on a c~se-by-case basis, if it is to be considered by the staff at all.
~~
Another requirement of the GL, for moderate energy class 3 pipe, is that the:
leak must be unisolable, and that a Code repair would require a unit shutdown.
If the leak can*b** isolated, and a repair completed within the LCO ti111e period for the affected system, then a Code repair is required.
Ano'ther important aspect of GL 90-05 is that it only applies to piping. This restriction is often overlooked by licensees during its *application*.
- Pumps, valves, strainers, and other non-piping components are not considered under the guidance of GL 90-05: Requests for relief froa the Code repair requirements are still considered on a case by case basis for these components. Usually, these components can be isolated*, thus, a Code repair should be the first option.
-~
With respect to the timing and execution of the GL 90-05 relief request process for moderate energy class 3 pipes, the staff has adopted the foll owing:
- 1.
Proapt flaw and structural evaluation (within the *ti111 allowed by the systa LCO).
- 2.
If the provtstons of the Glare 111et, a reversible leak mitigating measure 1111 be applied.
- 3.
Augaentld tnspectton coapleted within 15 days of discovery o*f1\\he initial leaf". Addtttonal details are provided in GL 90-05.
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A re11*f request 11Ust then be sent to NRR within 30 days.
For cases where the licensee deviates froa the provisions of GL 90-05, the licensee should promptly contact NRR through the PM.
The licensee 11Ust provide a thorough safety evaluation and structural analysis of the proposed te111Porary actions. Subllittal of the relief request must be proapt, usually by fax the next working day after discussion with the~staff. Thes~ actions are
e F. regarded by the staff as interim relief until the written SER is issued.
Should the staff, upon review of the submitted material, decide to deny the request, the facility returns to the LCO.
In su11111ary, non-pressure boundary leaks do not require relief. Pressure boundary leaks on safety related systems always require relief when a Code repair is not perfonned.
Each incident requires consideration, either on a case by case basis, or under the guidance of GL 90-05 for moderate energy class 3 pipe. Attached for reference are 2 letters providing detailed discussion of relief request issues and staff positions.
Attachments:
As stated cc:
A11 Project Directors Distribution Central F11 e EMCB RF GHornseth RAHermann f\\W.w """.,,. fw:
Jack Strosni~er, Chief Materials and Chemical Engineering Branch Division of Engineering DE:EMCB GHornseth:gh:tc
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