IR 05000289/1979022
| ML19257C972 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 12/11/1979 |
| From: | Jernigan E, Lester Tripp NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | |
| Shared Package | |
| ML19257C960 | List: |
| References | |
| 50-289-79-22, NUDOCS 8001310151 | |
| Download: ML19257C972 (3) | |
Text
U. S. NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT
.
REGION I
Report No.
50-289/79-22 Docket No.
50-289 License No.
DPR-50 Priority Category C
--
Licensee:
Metropolitan Edison Company 100 Interpace Parkway Parsippany, New Jersey 07054 Facility Name:
Three Mile Island Nuclear Power Station Unit No. 1 Inspection At:
Middletown, Pennsylvania Inspection Con cted:
October 30-31, 1979 Inspectors- #, h.
/
///7Y
. P. Jernfg'an, Reactor Inspector
' date
)
date date Approved by:
, h,
/k///79 4.. E. Tripp{ Chief, Engineering Support date Section No. 1, RC&ES Branch Inspection Summary:
Inspection on October 30-31, 1979 (Report No. 50-289/79-22)
Area Inspected:
Routine unannounced inspection by a regional based inspector of the licensee's activities associated with repairing the Borated Water Storage Tank (BWST) roof.
The inspection involved 14 inspector-hours on site by one regional based NRC inspector.
Results:
No items of noncompliance or deviations from regulatory requirements were identified during this inspection.
1844 175 Region 1 Form 167 (August 1979)
8001310 /6[
DETAILS 1.
Persons Contacted Metropolitan Edison Company W. Potts, Superintendent, Technical Support J. Pearce, Mechanical Engineer 2.
BoratedWaterStorageTank(BWST}
The BWST is designed and fabricated in accordance with the American Water Works Association (AWWA) Tank Code D-100.
The tank is approximately 36-feet in diameter and 55-feet high.
It is of welded construction and fabricated of stainless steel plate.
The tank is a seismic category 1 vessel used for the storage of borated water.
The hemispherical roof is fabricated of 1/4-inch thick stainless steel plate and is of welded con-struction.
Further, the tank is outfitted with a vacuum breaker and an overflow line both attached to the roof.
The seismic calculations for the tank excluded the roof in that its primary function is for environmental protection.
a.
BWST Roof Damage A routine equipment inspection performed during the 1979 refueling outage disclosed apparent BWST roof damage.
To determine the cause of damage the licensee tested the vacuum breaker and reviewed operat-ing and maintenance of associated equipment.
Based on this review the licensee concluded the probable cause of failure to be equipment malfunction resulting in an inadvertent vacuum being drawn within the tank.
It is believed that condensation inside the vacuum breaker froze preventing it from opening.
Also, the sump pump associated with the overflow was undergoing routine maintenance.
This allowed the water level in the sump to cover the open end of the overflow line thus preventing the tank from venting.
The resultant vacuum drew approximately 60% of the roof inward up to a depth of about 4-feet.
The welds in the damaged area and portions of tank wall welds were examined using the liquid penetrant method.
Examination reports indicate that several cracks were disclosed.
These cracks were trans-verse to the longitudinal axis of the welds and were generally confined to the weld.
However, some appear to extend into the adjacent base metal.
1844 176
b.
BWST Restoration Procedure The licensee developed a procedure to restore the BWST roof to essen-tially the original contour.
This involved welding clips to the roof at predetermined locations in the concaved area.
A portable crane utilizing load equalizing equipment was used to restore the indented roof to its original contour.
c.
BWST Restoration Activities The inspector observed the implementation of the restoration proce-dure.
Approximately twenty clips were utilized to restore the tank roof to the procedural requirements.
Upon completion of the mechanical straightening operations the roof welds and adjacent base metal will be surface examined.
This examination is to determine the amount of sustained damage.
A repair procedure will be promulated to restore and assure leak tightness of the BWST roof.
The inspector had no further questions y!garding the restoration activities at this time.
3.
Exit Meeting At the conclusion of the inspection on Octd.r 31, 1979 the inspector dis-cussed his observations and summarized the ; cope of the inspection with Mr. W. Potts.
1844 177