ML20236L752
| ML20236L752 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 07/06/1998 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20236L708 | List: |
| References | |
| NUDOCS 9807130157 | |
| Download: ML20236L752 (4) | |
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4 UNITED STATES 3
j NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 200eH001
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION l
ON TEMPORARY RELIEF FROM ASME CODE SECTION XI REQUIREMENT IWA-5250 FOR BALTIMORE GAS AND ELECTRIC COMPANY CALVERT CLIFFS NUCLEAR POWER PLANT. UNIT NO. 2 -
DOCKET NO. 50-318
1.0 INTRODUCTION
i The Technical Specifications for Calvert Cliffs Nuclear Power Plant, Unit No. 2 states that the I
inservice inspection and testing of the American Society of Mechanical Engineers Boiler and I
Pressure Vessel Code (ASME Code) Class 1,2, and 3 components shall be performed in
- accordance with Section XI of the ASME and applicable Addenda as required by
.' pursuant to 10 CFR 50.55a(g)(6)(i). '10 CFR 50.55a(a)(3) states that altemativ I
requirements of paragraph (g) may be used, when authorized by the NRC, if (i) the proposed altematives would provide an acceptable level of quality and safety or (ii) compliance with the l
.specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.
l Pursuant to 10 CFR 50.55a(g)(4), ASME Code Class 1,2, and 3 components (including l
. supports) shall meet the requirements that become effective subsequent to editions specified in 10 CFR 50.55a(g)(2) and (g)(3), 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 I
inservice examination of components and system pressure tests conducted during the first ten-year interval and subsequent intervals comply with the requirements in the latest edition and addenda of Section XI of the ASME Code incorporated by reference in 10 CFR 50.55a(b) on the date twelve months prior to the start of the 120-month interval, subject to the limitations and modifications listed therein. The applicable edition of Section XI of the ASME Code for the second ten-year inservice inspection interval for Calvert Cliffs Units 1 and 2 is the 1983 Edition, including the_ Summer 1983 Addenda.' 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)(iii), if the licensee determines that conformance with an examination requirement of Section XI of the ACME Code is impractical for its facility information, it should be submitted to the Commission in support of that determination. After evaluation of the determination, pursuant to 10 CFR 50.55a(g)(6)(i), the Commission may grant relief and may impose altemative 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, 9907130157 990706 PDR ADOCK 05000318 p
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. giving due consideration to the burden upon the licensee that could result if the requirements were imposed.
By letter dated May 27,1998, Baltimore Gas and Electric Company (licensee) requested a
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temporary relief from the requirement of section IWA-5250 of the applicable ASME Code,Section XI to delay the repair of a leak in the saltwater inlet pipe to Unit 2 Component Cooling Heat Exchanger No. 21 to no later than August 15,1998, and to allow a temporary non-code repair of the leak until that time.
The NRC staff, has reviewed and evaluated the licensee's proposed attemative to the Code requirements, pursuant to 10 CFR 50.55a(g)(6)(i) for Calvert Cliffs Unit 2.
2.0 DISCUSSION
Component Apolicable for Temporary Code Relief:
Portion of saltwater piping containing a half-coupling located at the inlet of No. 21 Component Cooling Heat Exchanger. A smallleak was discovered at the edge of the fillet weld connecting the half-coupling to the main 24-inch diameter piping. This is designated as ASME Code x
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Class 3.
H Code Requirements Affected by the Proposed Relief Reouest:
The 1983 Edition through Summer 1983 Addenda, ASME Code,Section XI, subsection IWA-5250, states: "(a) The source of leakages detected during th3 conduct of a system pressure test shall be located and evaluated by the Owner for corrective meawres as 'silows:"
"(2) repairs or replacements of components shall be performed in accordance with IWA-4000 or IWA-7000, respectively."
r Licensee's Proposed Attemative:
To perform a Code repair of the leaking weld between the half-coupling and the main 24-inch saltwater pipe which requires either replacement of the half coupling or replacement of the spool piece containing the leak, the unit must be shutdown since there is insufficient time in the Technical Specification Action Statement to perform the necessary replacement. Therefore, the licensee has proposed the following attemative:
o Install a rubber-lined pipe clamp to stop the leakage from the saltwater pipe, o An initial operability assessment for the Component Cooling Heat Exchanger No. 21 by evaluating the leakage from the saltwater system, should the half-coupling completely fail.
Ultrasonically examine the entire area in the vicinity of the leak to measure pipe wall o
thickness.
Perform structuralintegrity evaluation of the pipe containing the half-coupling to o
ensure that the structuralintegrity of the flawed piping remains acceptable until the code repair of the leak is completed.
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Perform an evaluation that in the event of a complete failure of the half-coupling, the
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saltwater system would still be able to fulfill its design function.
Perform an evaluation of the' impact of flooding in the Component Cooling Water o
i Pump Room and the effect of spray on nearby safety-related equipment.
o Perform an evaluation of potentialloss of temperature indication of saltwater inlot
' temperature to the heat exchanger as a result of failure of the temperature indicator installed on the half-coupling.
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. o Perform augmented Inspection of the temporary repair by performing a visual check of the Component Cooling Heat Exchanger Room during each shift and an ultrasonic axaminatica of the area around the half-coupling once every 3 months.
Commitment to repair or replace the flawed piping when preparation is complete, but o
no later than August 15,1998.
3.0' EVALUATION AND CONCLUSION:
The staff noted that the licencee detected a leak in the saltwaterinlet pipe into No. 21 Component Cooling Heat Exchanger at the weld joining a half-coupling to the 24-inch j
. diameter saltwater piping. A Code repair of the leak was considered impractical without i
having the unit shut down since the time required to perform the repair exceeded the time allowed under the Technical Specification Action Statement. Following detection of
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the leak, the licensee performed an ultrasonic examination of the piping adjacent to the area of the leak and established that the required minimum wall thickness was available.
' The staff believes that due to the geometry of the weld, it would be impractical to characterize the flaw by ultrasonics. The licensee, however, stopped the leakage by installing a rubber-lined pipe clamp.
The staff has reviewed the licensee's evaluation of structuralintegrity of the 24-inch pipe i
due to a through-wall flaw in the weld joining the half-coupiing. The staff confirmed from x licensee's evaluation that there was adequate reinforcement built-in at the half-coupling which wou',d ensure structuralintegrity of the main pipe in an unlikely event of a complete severance of the half-coupling. This evaluation was performed to be valid f ar 3 months since the date of the evaluation. The staff further determined from licensee's evaluation that a loss of flow in No. 21 heat exchanger resulting from a complete severance of the half-coupling can be compensated from surplus flow through both headers of component i
cooling heat exchangers in order to sustain heat loads during accident condition by
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maintaining component cooling water temperature within acceptable limit. The licensee also evaluated potential impact of flooding and spraydown on equipment in the No. 21 Component Cooling Heat Exchanger room resulting from a worst-case leakage and d
determined the consequences to be minimal. The staff has, therefore, accepted the licensee's temporary non-code repair of the leakage due to a flaw in the weld joining a j
l; half-coupling to the saltwater piping on the basis of foregoing evaluations. ' The licensee has further instituted an augmented inspection program consisting of a visual check of i
. the No. 21 Component Cooling Heat Exchanger room during each shift to monitor
't leakage from the temporary repair and an ultrasonic examination of the area around the half-coupling once every 3 months. The staff further noted that the licensee has
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. committed to perform a permanent repair in accordance with the Code no later than I
. August 15,1998.
The staff concludes that the altematives proposed by the licensee provide a reasonable
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assurance of operational readiness and based on the impracticality of performing a Code repair without having the unit shutdown, the proposed temporary relief from the applicable ASME Code,Section XI, paragraph IWA-5250, is authorized pursuant to the provisions of 10 CFR 50.55a(g)(6)(i), for Calvert Cliffs Unit No. 2. The relief granted is authorized by law and will not endanger life or property or the common defense and security and is otherwise in the public interest given due consideration to the burden upon the licensee that could result if the requirements were imposed on the facility.
' Principal contributor: P. Patnick Date: July 6, 1998
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