ML20073B384
| ML20073B384 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 04/04/1983 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20073B377 | List: |
| References | |
| NUDOCS 8304120308 | |
| Download: ML20073B384 (3) | |
Text
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NUCLEAR REGULATORY COMMISSION o
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION SUPPORTING AMENMiENT NO. 74 TO FACILITY OPERATING LICENSE NO. DPR-51 ARKANSAS POWER AND LIGHT C0f1PANY ARKANS'AS NUCLEAR ONE, UNIT NO.1
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DOCKET NO. 50-313_.
I Introduction By letter dated February 22, 1979, as supplemented by letters dated August 18, November 30, and De.cember 23, 1982, and February 15, 1983, Arkansas Power and Light Company (the licensee or AP&L) requested amendment to the Technical Specifications (TSs) appended to Facility Operating License No. DPR-51 for Arkansas Nuclear One, Unit No.1
( ANO-1).
The amendment would allow the Acoustic Emission (AE) method for inservice volumetric examination of the reactor coolant pump flywheels.
Discussion General Design Criterion 4, " Environmental and Missile Design Bases,"
of Appendix A,10 CFR Part 50, requires, in part, that nuclear power plant structures, systems,,and components important to safety be protected against the effects of missiles that might result from equipment failures. Because reactor coolant pump flywheels have large masses and rotate at speeds of approximately 1200 revolutions per minute during normal operation, a loss of flywheel integrity could result in high energy missiles and excessive vibration of the reactor coolant pump assembly. The safety consequences could be significant because of possible damage to the reactor coolant system, the containment, or the engineered safety features. To prevent loss o.5 structural integrity, we have recomended that all flywheels conform to the material, design and inspection requirements of Safety Guide 14 which recommends that the flywheels should have a complete ultrasonic volumetric and surface examination at approximately 10-year intervals coinciding with a plant shutdown for refueling or maintenance.
The ANO-1 flywheels are of a unique shrink-fit design with spoked
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we6 and with limited access for inspection. In order for the licensee to perfonn an ultrasonic (UT) and surface'(MT or PT) examination of a flywheel, they must remove f.he rotor assembly from the pump and disassemble the flywheel from the rotor.
8304120308 830404 PDR ADOCK 05000313 P
Since the flywheels are shrunk fit, their renoval is not recomended by the manufacturer.
In addition, the licensee estimates that UT and MT or PT.of the four ANO-1 flywheels' would' result in.120 man-rem total radiation exposure.
In lieu of the surface and volumetric examination recommended by Safety Guide 14, the licensee proposes to perform an AE examination of the upper, flywheels on each of the four reactor coolant pumps.
The extent of examination will be the full volume of the flywheel.
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In the AE method of examination, acoustic energy output from an advancing crack is utilized to locate the defect. The licensee proposes-to activate potential crack progression by heating to increase the static stress from 62.5% of yield to 90'. of yield. Due to the shrink fit, the hoop stress at the inner bore is 62.5% of yield when the flywheel is at rest. The licensee proposes to increase the static stress on the flywheel by maintaining an average temperature difference (AT) between the rotor web and the inner fiber of the flywheel of 150'F.
This AT will be accomplished by strapping resistance heaters to the rotor web. The feasibility of this heating method has been confirmed j
on a mockup of a.one-quarter section segment and a finite element
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analysis. In order to measure the AT during the AE examination, temperature sensors will be placed at critical locations which were established during tests on the mockups.
The licensee indicates that the acceptance /rejectio'n criteria would be based on the interpretation of the AE response by the inspector and that all AE response signals that indicate a crack progression would be evaluated by other nondestructive examination methods to size the defects.
Evaluation We have reviewed the licensee's proposed method of volumetric examination of the ANO-1 reactor coolant pump flywheels and the proposed TSs.
Since it is not feasible to perform surface and volumetric examination of ANO-1 flywheels to the extent recommended by Safety Guide 14 and the radiation exposure to plant personnel can be significantly reduced by perforir.ing AE instead of UT and MT or PT, we consi_ der that AE with an induced stress of approximately 90% of yield is an' acceptable alternative method for inservice surface and volumetric examination of the ANO-1 flywheel s.
In addition, based on this review, we have determined that'the i
proposed TSs meet the intent of Safety guide 14 for volumetric and i
surface examination of reactor coolant ' pump flywheels at 10-year intervals, and they are therefore acceptable.
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Environmental Consideration l
We have detemined that the amendment does not authorize a change
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j in effluent types or total amounts nor an incressa in power level i
and will not result in any significant envirorsnental* impact. Having j
made this determination, we have further concluded that the amendment
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involves an action which is insignificant from the stand environmental ' impact and, pursuant to 10' CFR 551.5(d)(4) point of
, that an j
environmental impact statement, or negative declaration and environ-i mental impact appraisal need not be prepared in connection with the issuance of this amendment.
i Conclusion i
i We have concluded, based on the considerations discussed above, that:
l (1) because the amendment does not involve a significant increase in j
the probability or consequences of an accident previously evaluated, does not create the possibility of an accident of a type different d
i from any evaluated previously, and does not involve a significant reduction ir, a margin of safety, the amendment does not involve a i
significant hazards consideration. (2) there is reasonable assurance I
that the health and safety of the public will not be endangered by i
operation in the proposed manner, and (3) such activities will be conducted in compliance with the Commission's regulations and the issuance of this amendment will not be inimical to the common i
defense and security or to the health and safety of the public.
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Dated: April 4,1983 J
j The following NRC personnel have contributed to this Safety Evaluation:
l G. Vissing, B. Elliot.
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