ML20245H346
| ML20245H346 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 06/19/1989 |
| From: | Shelton D TOLEDO EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 1664, NUDOCS 8906290463 | |
| Download: ML20245H346 (3) | |
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a TOLEDO EDISON
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A Centenor Energy Company
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-DONAU)C.SHBJON Vce Premient-Nudear
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i Docket Number 50-346 j
i License Number NPF-3 1
1 Serial Number 1664 June 19, 1989 l
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United States Nuclear Regulatory Commission l
Document Control Desk j
Vashington, D. C.
20555 Subj ect:
High Pressure Injection /Hakeup Nozzle and Thermal Sleeve Gentlemen On July 2, 1988, during a combined ASME Section XI and pre-fueling visual
.I inspection several ' loose parts' vere discovered in the Davis-Besse Nuclear Power Station (DBNPS) Unit I reactor vessel. Among these loose parts were two metallic pieces resembling half cylinders, which were later determined to be a portion of the makeup /high pressure injection (HPI) nozzle thermal sleeve.
Approximately three inches of the thermal' sleeve had broken off from the end of the sleeve, which protrudes into the reactor coolant system (RCS) cold leg.
This condition permitted cold water impingement directly on the RCS cold leg cladding. Inspection of the makeup /HPI nozzle revealed linear indications throughout the area where the thermal sleeve had failed. A conservative analysis was performed, which indicated that with the thermal sleeve intact the potential crack growth is acceptable for the 40-year lifetime of the unit.
Toledo Edison submitted by letter (Serial Number 1580 dated September 15, 1988) the cause and analysis of the failure of the HPI/ makeup thermal sleeve and related effects on the nozzle to the Nuclear Regulatory Commission (NRC).
In that submittal, Toledo Edison committed to provide the NRC with an update regarding the progress of evaluation of the failure and the progress of the preparation for action on this item during the sixth refueling outage. This submittal provides the NRC with the preparations and evaluations being
_ performed for the sixth refueling outage.
l 8906290463 890619 f'
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PDR ADOCK 05000346 PNV i
g THE 7OLEDO EDISON COMPANY EMSON PLAZA 300 MADISON AVENUE TOLEDO, OHIO 43652
, Dockat Nu bar 50-346 Lic:nse Nunb:r NPF-3 Serial Number 1664 Page 2 Toledo Edison is currently proceeding with a comprehensive program which calls i
for visual inspection of the thermal sleeve, ultrasonic (UT) examination of the nozzle from the outside diameter (0.D.) to verify no adverse changes have occurred in the as-left condition of the nozzle and thermal sleeve, and piping modifications to utilize an alternate HPI nozzle for normal makeup flow.
The visual inspection of the thermal sleeve vill involve inspecting the inside diameter using fiberoptics similar to the fiberoptic inspection which was performed when the failure was initially discovered and described in Serial Number 1580. The results of this inspection vill be utilized to verify continued acceptability of the thermal sleeve.
If no indications are observed, the sleeve vill be considered acceptable for further operation.
If any indications are observed, a dye-penetrant (PT) examination vill be performed. The thermal sleeve vill be replaced if indications are discovered.
An enhanced UT examination vill be performed on the nozzle from the nozzle outside diameter.
This technique, vnich is currently under development, is considered to be a significant improvement over that previously utilized.
If the inspection reveals additional defects, propagation of the as-left condition, or indications outside the existing analysis, contingency actions have been established and implementing details are being developed depending on the characteristics of the observed indications. External veld reinforcement of the nozzle and/or further fracture mechanics analysis vill be performed as necessary. Veld reinforcement would provide additional component thickness that would justify continued operation.
Based on field experience at a facility similar to Davis-Besse, there would be no significant velding or personnel radiation exposure concerns.
If the inspection and examinations reveal no additional defect, no propagation of the as-lef t condition, or indications within the e.tisting analysis, the results of the previous analysis vill be considered to remain valid. This vill ensure acceptability of continued operation for an additional cycle. A similar inspection vill be performed at the seventh refueling outage to assess the existence of any potentiel. degradation.
A plant modification package is under development which vill install new piping to re-route makeup flow through an alterrate HPI nozzle. This modification vill eliminate the possibility of thermal cycling on the present makeup /HPI nozzle caused by the cold makeup flow.
The enhanced UT examination vill also be performed on the alternate nozzle to obtain baseline information for use in any necessary future evaluations.
The modification and examination will be completed during the sixth refueling outage.
Considering the lifetime of the original thermal sleeve, Toledo Edison expects that no cracks have initiated in the replacement unit.
With an effective thermal sleeve in place, it is believed that no growth has occurred in the crack-like indications in the nozzle.
Toledo Edison vill inspect the i
makeup /HPI nozzle and thermal sleeve as outlined in this letter to confirm or l
negate these predictions.
A summary of the results of these examinations, corrective actions taken during the outage, and action planned for the seventh l
refueling outage vill be submitted to the NRC before the end of the sixth I
refueling outage. Toledo Edison considers that the above modification and 1
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1 Dociszt; Nu:bir 50- 346--
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. inspection plan satisfactorily addresses-the failure concerns related to the-
@p HPI thermal sleeve and nozzle.'. Toledo Edison is currently-scheduling-activities for the sixthirefueling outage. Any changes to the; process
' described:above.could'significantly impact the scheduling of the outage; Therefore,' Toledo Edison requests that any' questions or. concerns lbe identified _
-priorLto: July,7, 1989.
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(_f If you have any questionsLconcerning this matter, please contact EMr. R.-V.'Schrauder, Nuclear Licensing Manager,-at (419) 249-2366.
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'Very trul yours,
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R ccs P. M. Byron,,DB-1 NRC-Senior. Resident. Inspector _
l A. B. Davis, Regional Administrator, NRC Region III
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T. V. Wambach, DB-1LNRC Senior Project' Manager s
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