ML20138A691
| ML20138A691 | |
| Person / Time | |
|---|---|
| Site: | Bellefonte  |
| Issue date: | 11/25/1985 |
| From: | Hufham J TENNESSEE VALLEY AUTHORITY |
| To: | Grace J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| NUDOCS 8512120085 | |
| Download: ML20138A691 (2) | |
Text
n TENNESSEE VALLEY AUTHORITY CHATTANOOGA. TENNESSEE 37401 SN 1578 Lookout Place o
er 25,1 8 BLRD-50-438/82-72 BLRD-50-439/82-66 U.S. Nuclear Regulatory Commission Region II Attn: Dr. J. Nelson Grace, Regional Administrator 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323
Dear Dr. Grace:
BELLEFONTE NUCLEAR PLANT UNITS 1 AND 2 - ROUTING OF MAKEUP TANK OUTLET LINES - BLRD-50-438/82-72, BLRD-50-439/82 FINAL REPORT The subject deficiency was initially reported to NRC-01E Inspector C. H. Hehl on October 15, 1982 in accordance with 10 CFR 50.55(e) as NCR BLN BLP 8228.
This was followed by our interim reports dated November 12, 1982, March 22 and December 12, 1983, and January 25, 1985.
Enclosed is our final report.
If you have any questions concerning this matter, please get in touch with R. H. Shell at FTS 858-2688.
Very truly yours, TENNESSEE. VALLEY AUTHORITY J. W. Hu an Manager i ensing ar Risk Protection i
Enclosure cc: Mr. James M. Taylor, Director (Enclosure)
-Office of Inspection'and Enforcement U.S. Nuclear Regulatory Commission Washington, D.C.
20555 Records Center (Enclosure)
Institute of Nuclear Power Operations 1100 Circle 75 Parkway, Suite 1500.
Atlanta, Georgia 30339 l
hbk Ob 8
I 1 1 An Equal opportunity Employer
N a.
O ENCLOSURE BELLEFONTE NUCLEAR PLANT UNITS 1 AND 2 ROUTING 0F MAKEUP TANK OUTLET LINES NCR BLN BLP 8228 BLRD-50-438/82-72 AND BLRD-50-439/82-66
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10 CFR 50.55(e)-
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FINAL REPORT Description of Deficiercy TVA. identified a deficiency in whicn the routing of the makeup tank discharge line to the train A makeup pumps could have allowed dissolved gases (mainly hydrogen) to come out of solution due to a pressure drop in the line and collect at a high point of the piping.
The gas buildup could result in reduced net positive suction head being available to the pumps and codid result in pump damage.
The train A pumps were the only pumps affected by this condition.
The makeup tank discharge line was routed such that a high point existed above the water level in the tank.
The Hydraulic Institute Standards warn that if a 4
high point-in suction piping becomes filled with air it can prevent proper operation of the pump.
In most systems, the high point can be vented when the i
pump is being started and the air will be eliminated. With pressurized hydrogen as a cover gas, the high point will be at a lower pressure than'the tank, thus allowing the dissolved hydrogen to steadily come out of solution at the high point.
Therefore, the root cause is the failure to realize when the pipe was being routed that the pressurized hydrogen cover gas was a unique problem which should have been considered in the design of this system.
Safety Implications The makeup pumps are required during emergency operations to provide high-pressure injection (HPI) to the reactor coolant system.
If the train A makeup pumps were to become inoperable because of damage due to insufficient net positive suction head, they would not be available to perform their intended safety functions.
Therefore, if this condition had remained uncorrected, the safe operation of the plant could be adversely affected.
Corrective Action TVA has completed the redesign and has issued the necessary drawings for rerouting the 4-inch makeup tank discharge piping to an elevation below the makeup tank water level. An associated 1-inch vent line has also been rereouted.
The analysis of the revised piping design has been completed and affected piping supports have been redesigned.
TVA has also completed the necessary redesign of electrical cable routing due to the reloration of motor-operated valves IFCV-452-A and VHAB-161.
This design work was done under engineering change notice (ECN) 1587.
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