ML19210E684
| ML19210E684 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 11/23/1979 |
| From: | TENNESSEE VALLEY AUTHORITY |
| To: | |
| Shared Package | |
| ML19210E680 | List: |
| References | |
| NCR-16P, NUDOCS 7912050530 | |
| Download: ML19210E684 (1) | |
Text
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1 ENCLOSURE SEQUOYAH NUCLEAR PLANT UNITS 1 AND 2 DAMAGED TUBES IN CONTAINMENT SPRAY HEAT EXCHANGERS NCR 16P 10 CFR 50.55(e)
FIRST INTM REPORT Description of Condition While draining containment spray heat exchanger 1B, it was discovered that a significant amount of leakage was occurring across the heat exchanger.
When t's heat exchangers were disassembled, tube fragments were found in the lower 1.
The tubes of both unit I heat exchangers were then examined using,
addy current probe. This examination revealed that several tubes in containment spray heat exchangers lA and 1B were damaged.
The apparent cause of the damage was flow induced vibration, which is a result of improper design of the tube bundle supports by the vendor.
The manufacturer of the heat exchangers is Industrial Process Engineers Inc., a company which has now gone cut of business.
Safety Implications Had this condition gone uncorrected, an intolerable number of tubes could have failed.
This would inhibit the containment spray system from perform-ing its intended safety function.
During a LOCA, this condition could have led to excessive leakage across the heat exchanger and thus the possibility of releasing radioactive water through the Essential Raw Cooling Water (ERCW) System.
Corrective System Approximately 5.6 percent of the tubes in the 1B heat exchanger and 0.9 percent of the tubes in the LA heat exchanger will need to be plugged.
This includes all of the tubes with defects having 50 percent or more wall loss.
To prevent further tube wear, the tubes will be staked.
The plugging and staking of the unit 1 heat exchangers will be completed before initial criticality.
It has been determined that the reduced heat transfer area
_cause o# Lhe plugged tubes will not adversely affect the functioning o f tl.e system.
The unit 2 heat exchangers, which have not been operated, will be staked in order to prevent vibration induced tube wear.
The unit 2 heat exchangers will be staked before fuel loading of unit 2.
A further review has determined that the Component Cooling System (CCS) teat exchangers were also manufactured by Industrial Process Engineers Inc.
TCee wear was also found in the CCS beat exchangers.
There are 1950 tubes in ea h of the three CCS heat exchangers. Of these, all tubes having defects with wall losses of greater than 30 percent will be plugged.
The actual number of tubes that will be plugged is 36, 7, and 3 in the A, B, and C heat
- exchangers, respectively.
A full flow vibration test is scheduled to be performed on the CCS heat exchangers to determine if excessive vibration is occurring.
This test, the plugging, and any additional corrective action will be completed before initial criticality.
1502 268 7912050 53o