ML20086H480
| ML20086H480 | |
| Person / Time | |
|---|---|
| Site: | Vermont Yankee File:NorthStar Vermont Yankee icon.png |
| Issue date: | 11/30/1971 |
| From: | Vandenburgh D VERMONT YANKEE NUCLEAR POWER CORP. |
| To: | Morris P US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| NUDOCS 8401170182 | |
| Download: ML20086H480 (2) | |
Text
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VERMONT YANKEE NUCLEAR POWER CORPORATION s
SEVENTY SCVEN OROVE STREET RUTI.AND, Veiotour osvoi REPLY 70; November 30, 1971 ENGINEERING OFFICE TURNPIKE ROAD WESTDORO. M ASS ACHUSETTS o1581 TELEPHONE 617.366 9011 Dr. Peter A. Morris, Director Division of Reactor Licensing h
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U. S. Atortic Energy Comnission ta tuger Washington, D. C.
20$h5 eM
Dear Dr. Morris:
g This letter is intended to provide clarifying details on the addition of a vacuum breaker in each of the turbine exhaust lines from the High Pressure Coolant Injection (HPCI) and Reactor Core Isolation Cooling (RCIC) systems.
During the performance of a preoperational test of the HPCI turbine, a vacuum was created in the exhaust line, causing unter from the suppression pool to be drawn into the exhaust line.
The water traveled at a high velocity, re-
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m he and sulting in an exceedingly fac'. c1ccurc of th ~"'
'4-caused a water hammer effect.
To prevent recurrence of this condition, Vernont Yankee has taken the fol-lowing actions on both the HPCI and RCIC systems:
1)
The swing check valves in the t trbine exhaust lines on both systems k.l have been relocated from vertica'l to horizontal runs of pipe.
- 2) Vacuum breakers have been installed on both the HPCI and RCIC exhaust lines. The vacuum breakers are, in effect, 22" check valves.
They are located inside the suppression chamber between the exhaust line penetrations and the suppressica chamber high water level.
Vermont Yankee has retested the HPCI system and conpleted the preoperation-al testing of the RCIC system since these changes were made.
These tests have resulted in satisfactory operation of both turbine systems.
Vermont Yankee has also evaluated the consequences of operating either the HPCI or RCIC system with the vacuum breaker stuck in the q:cn position, for J_ N. i 9,
'both accident and test conditions.
The HPCI turbine exhaust pressure in the
,p Ij, line at the location of the check valve is a few psi greater than the suppres-sion pool pressure for the accident conditions.
Turbine exhaust flow from an
% >J1f/ V open 25" check valve would be small, i.e., less than 10 percent of the normal
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flow in the exhaust line and much less than the steam flow present in the con-I,k ~ N, Ol tainment from an accident condition. The resultant slight increase in back
[@D pressure due to the check valve flow would have no consequence upon HPCI opera-y.,
tion and there would be no significant effect upon containment temperature or V II,37 4 prescure.
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- Dr. P. A. Morris, Director November 30, 1971 Operation of the HPCI turbine in the test mode with an open check valve would again result in a flow rate from the valve of less than 10 percent of the normal exhaust flow rate.
The exhaust vapor terrperature in this mode of opera-tion is approximately 2180F and the resulting increase in torus air space temperature would be indicated and eventually alarmed in the control room.
Assuming no corrective operator action, the exhaust vapors could eventually increase the torus to drywell differential pressure to 0.5 psi causing the vacuum breakers to relieve pressure from the torus to the drywell. However, although an introduction of steam into the dryuell would be undesirable from an operational standpoint, there would be no adverse effect upon the health and safety of the public.
Operation of the RCIC system with the 2h" check valve in the turbine exhaust line stuck open would result in flow rates of a lower magnitude and results in a similar but lesser consequence than the HPCI case.
Respectfully submitted, VERMONT YANKEE NUCLEAR POWER CORPORATION kb Donald E. Vandenburgh Vice President DEV/ah h
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