ML17158C053
| ML17158C053 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 04/04/1997 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML17158C050 | List: |
| References | |
| NUDOCS 9704090229 | |
| Download: ML17158C053 (6) | |
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~8 RE00 (4
0 Cy Cl UNITED STATES NUCLEAR REGULATORY COMMISSION OF THE SECOND 10-R INSERVICE INSP CTION PRESSURE TEST PROGRAM ELIEF RE UEST NO.
RRPT-6 PENNSYLVANIA POWER AND LIGHT COMPANY SUS UEHANNA STEAM ELECTRIC STATION UNITS 1
AND 2 DOCKET NOS.
50-387 AND 50-388 O
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R WASHINGTON, D.C. 205Ii&4001 Cy SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION
- 1. 0 INTRODUCTION The Technical Specifications for Susquehanna Steam Electric Station, Units 1
and 2, state that the inservice inspection (ISI) and testing of the American Society of Mechanical Engineers (ASME) Code Class 1,
2 and 3 components shall be performed in accordance with Section XI of the ASME Boiler and Pressure Vessel Code and appli,cable Addenda as required by 10 CFR 50.55a(g),
except where specific written relief has been granted by the Commission pursuant to 10 CFR 50.55a(g)(6)(i).
It is stated in 10 CFR 50.55a(a)(3) 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 of this section 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 Inservice 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 refer'ence in 10 CFR 50.55a(b) on the date 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 Susquehanna Steam Electric Station, Units 1 and 2, during the second 10-year inservice inspection (ISI) interval, is the 1989 Edition.
The components (including supports) may meet the requirements set forth in subsequent editions 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.
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
(
9704090229
'770404 I
PDR ADOCK 05000387 P
lb
Code requirement.
After evaluation of the determination, pursuant to 10 CFR 50.55a(g)(6)(i),
the Commission may grant relief and may impose alternative requirements that are determined to be authorized 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'6,
- 1997, PP8L, the licensee for Susquehanna Steam Electric Station, requested approval to use the alternative to the 1989
~ Edition of the ASME Boiler and Pressure Vessel
- Code,Section XI, in regard to the requirement that source of leakages detected during the conduct of a system pressure test shall be located and evaluated by the Owner for corrective measures.
If leakage occurs at a bolted connection, the bolting shall be removed, VT-3 visually examined for corrosion and evaluated in accordance with IWA-3100.
The licensee,
- however, proposes to apply the requirements of the 1990 Addenda to the above Code which requires that if leakage occurs at a bolted connection, one of the bolts shall be removed, VT-3 examined, and evaluated in accordance with IQA-3100.
2.0 DISCUSSION Re uest to use Alternative to 1989 Edition of ASME Boiler and Pressure Vessel Code Section XI Relief Re uest No.
RRPT-6 1989 ASME Code Section XI Re uirement Subsection IWA-5250(a)(2) requires that the source of leakages detected during the conduct of a system pressure test shall be located and evaluated by the Owner for corrective measures.
If leakage occurs at a bolted connection, the bolting shall be removed, VT-3 visually examined for corrosion and evaluated in accordance with IWA-3100.
Licensee's Code Relief Re uest:
"If leakage occurs at any bolted connection on other than a gaseous
- system, one of the bolts shall be removed, VT-3 examined, and evaluated in accordance with IWA-3100.
The bolt selected shall be the one closest to the source of leakage.
When the removed bolt has evidence of degradation, all remaining bolting in the connection shall be removed, VT-3 examined, and evaluated in accordance with IWA-3100.
This is as provided by the 1990 Addenda of ASME Code Section XI paragraph IWA-5250(a)(2).
All VT-3 visual examinations shall be completed prior to return to service of the component."
Licensee's Basis for Re uest:
"While leakage from a bolted connection might eventually cause degradation of the bolting, VT-3 visual examination of a sample of the bolting provides assurance that any degradation of the bolting is identified at an early stage.
The requirements described above create a hardship for this plant and potentially compromise radiation safety.
Removal of all bolting from a bolted connection is not always required to assure absence of significant corrosion and other forms of significant deterioration.
- Further, removal of all bolting is not always advisable, as some connections become more difficult to seal after disassembly, in contrast to retightening a connection already assembled.
The complete disassembly of a connection in a radiation area would frequently result in significant personnel radiation exposure.
The ASME has recognized the potential for such conditions and has subsequently modified this
. requirement to allow the removal and evaluation of one bolt closest to the leak in a bolted connection reported as leaking.
In the 1990 Addenda and later editions of ASME Code Section XI, paragraph IWA-5250(a)(2) has been improved to state, "If leakage occurs at a bolted connection, one of the bolts shall be removed, VT-3 examined, and evaluated in accordance with IWA-3100.
The bolt selected shall be the one closest to the source of leakage.
When the removed bolt has evidence of degradation, all remaining bolting in the connection shall be removed, VT-3 examined, and evaluated in accordance with IWA-3100."
Although not yet endorsed by the
- NRC, this updated requirement indicates the future direction of the industry.
ASME Code Intent Interpretation XI-I-92-51 states that it is not the intent of IWA-5250(a)(2) that, if leakage is detected at a bolted connection during the pressure test of a gaseous
- system, the bolting be removed for a VT-3 examination.
This is reasonable because a leak from a gaseous system is not likely to induce any corrosion of the bolting at a bolted connection."
Licensee's Alternate Provision:
"The source of leakages detected during the conduct of a system pressure test shall be located and evaluated by the Owner for corrective measures as follows:,
If leakage occurs at any bolted conn'ection on other than a gaseous
- system, one of the bolts shall be removed, VT-3 examined, and evaluated in accordance with IWA-3100.
The bolt selected shall be the one closest to the source of leakage.
When the removed bolt has evidence of degradation, all remaining bolting in the connection shall be removed, VT-3 examined, and evaluated in accordance with IWA-3100.
This is as provided by the 1990 Addenda of ASME Code Section XI paragraph IWA-5250(a)(2).
All VT-3 visual examinations shall be completed prior to return to service of the component.
3.0 VALUATION CONCLUSION In accordance with the 1989 Edition of the ASME Code,Section XI, when leakage
'occurs at bolted connections, all bolting is required to be removed for VT-3 visual examination.
Removal of all bolting from a bolted connection,
- however, is not always required to ensure absence of significant corrosion or other forms of degradation.
In lieu of the Code-required removal of all bolting to perform a VT-3 visual examination, the licensee has proposed to perform a VT-3
visual examination of the one bolt closest to the leak.
The removal and examination of one bolt by a VT-3 inspector, is consistent with the requirements of 1990 Addenda to the ASME Code,Section XI.
The subject addenda to the.Code, considers the evaluation of the bolt closest to the leak to be a sound engineering practice to detect evidence of degradation and assess the potential for failure.
When the removed bolt has evidence of degradation, all remaining bolting in the connection shall be removed, VT-3
- examined, and evaluated in accordance with IWA-3100.
This concept provides an acceptable level of quality and safety since the area exposed to leakage is
- evaluated.
- Hence, the licensee proposes to incorporate the provisions of IWA-5250(a)(2) of the 1990 Addenda to the ASME Code,Section XI, to the inservice pressure test program for Susquehanna Units 1 and 2, to determine the condition of bolting and/or the root cause of the leak.
The staff's review concludes that the proposed alternative to implement the provisions of IWA-5250(a)(2) of the 1990 Addenda in lieu of that required by the 1989 ASME Code,Section XI, would provide an acceptable level of quality and safety and therefore, is authorized pursuant to 10 CFR 50.55a(a)(3)(i).
Principal Contributor:
P.
Patnai k
'ate:
Apri l 4, 1997
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