ML17053C669
| ML17053C669 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 06/02/1981 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17053C668 | List: |
| References | |
| NUDOCS 8106120399 | |
| Download: ML17053C669 (4) | |
Text
SAFETY EVALUATION REPORT Introduction In accordance with the requirements of IE Bulletin 80-13, the Nine Nile Point Unit No.
1 has examined the accessible portions of the core spray spargers and the associated internal piping by a remote underwater TY.
4 Oblique,;lighting of various angles and intensities was used coupled.
with the resolution of 0.001 in. diameter wires to enhance the view of sparger surface.
'Descri tion and Evaluation VL
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About 45 hours5.208333e-4 days <br />0.0125 hours <br />7.440476e-5 weeks <br />1.71225e-5 months <br /> of videotape of the core spray spargers and internal piping wer'e generated and two cracks were discovered.
One crack segment discovered is'lj'2" long by 0.02" wide, the other one is 1/4" long by 0.001" to 0.003"
" wide.
Intergranular stress corrosion cracking is considered as the most probable cause of crack initiation.
Since all service 1oadings except for m 1 P
the infrequent and low injection loading are insignNicant, the crack propagation initially was caused by residual stresses left in the spargers after its installation.
The nature of residual stresses is self-relieving; therefore the propagation shall be limited.
Concl us ion
"'The core spray spargers-do not have a structural function; i.e.,
they are not required to withhold or support any elements other than its own weight.
The infrequent and low loading caused by injections will not impair the sparger integrity as the crack opening due to the injection transient is bounded.
The cracks thus will have no appreciable effects on structural
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'1
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integrity or hydraulic performance.
However, it will be desirable to monitor the growth of these cracks in the future.
If the results show the necessity, a replacement program similar to the one in Oyster Creek 4
should be adopted.
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