ML19210C122
| ML19210C122 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 11/07/1979 |
| From: | Groce R YANKEE ATOMIC ELECTRIC CO. |
| To: | Ziemann D Office of Nuclear Reactor Regulation |
| References | |
| TASK-05-13, TASK-5-13, TASK-RR WYR-79-131, NUDOCS 7911130302 | |
| Download: ML19210C122 (5) | |
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Mr Telephone 6l7 366-90ll TWI 7IO-390-0739 YANKEE ATOMIC ELECTRIC COMPANY a321 WYR 79-131 20 Turnpoko Road Westborough, Massachusetts 01581 Yauxse
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November 7, 1979 United States Nuclear Regulatory Commission Washington, D.C.
20555 Attention: Office of Nuclear Reactor Regulation Mr. D. L. Ziemann Operating Reactors Branch #2
References:
(a)
License No. DPR-3 (Docket No. 50-29)
(b) NRC Letter to Yankee Rowe dated September 12, 1979 (c) YAEC Letter to NRC dated July 18, 1975
Dear Sir:
The enclosed information is in response to your letter, Reference (b),
regarding steam generator water hammer.
We trust this information adequately addresses your concerns; however, if yeu should desire additional information, please contact us.
o Very truly yours, YANKEE ATOMIC ELECTRIC COMPANY Robert H. Groce Senior Engineer - Licensing RA/kaf Enclosures 1320 151 302 7911130 4
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Enclosure Page 1 8
QUEETION 1 Provide information that demonstrates that the feedwater system and steam generator water level at your facility have been subjected to those trans-ient conditions that are conducive to water hammer, i.e.,
the addition of cold feedwater or auxiliary feedwater to steam-filled feedwater piping and feedring.
(See NUREG 0291, Page 4 that was forwarded to you on September 2, 1977.) Include the following:
1.
Describe the expected behavior of steam generator water level as a result of reactor trip from power levels greater than 30% of full power.
Include actual plant me surements of steam generator level and other available related data such as feedwater flow and auxiliary feed-water flow.
2.
Provide the number and causes of loss of feedwater events during'the operational history of the plant.
You may re-fer to material submitted previously.
3.
Provide the number and causes of_ loss of off-site power events during the operations history of the plant.
RESPONSE 1 1.
On all reactor trips from a reactor power level greater than 30% of full power the Yankee Rowe boiler feed pumps are automatically tripped.
Therefore, following a trip from greater than 30% of reactor power it is expected that the steam generator feed flow will decrease to zero and the level will decrease below the feed ring.
The auxiliary leed flow is a manually initiated system and is not required to be ini-tiated on a routine trip from power.
1 i
2.
D'uring the operational history of Yankee Rowe there have been five I
loss of feedwater flow events which were initiated by a malfunction of plant equipment which led to a reactor scram due to a loss of feed-water.
Based on the operating design of the feedwater system as stated in 1. above, Yankee Rowe considers these events as loss of feed-water flow versus loss of feedwater events.
These events were as followr a)
On May 18, 1964 a manual scram from 137 MWe was initiated because of feedwater system problems.
The problem was initiated while valving in an idle condensate pump which caused a dip in the condensate pump discharge header which then caused the boiler feed pump:. to trip on low suction pressure.
This was not a malfunction of plant equipment.
b)
On August 25, 1966 an automatic reactor scram from 160 MWe was initiated due to low steam generator water levels.
The low steam generator levels were caused by the short circuiting of feedwater through a boiler feed pump when the pump was secured and its discharge check valve stuck open.
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7 Enclosure Page 2
~~~c)
On August 25, 1966 while the plant was operating at a power level of 15 ffWe the No. 3 steam generator wide range level began to drop.
A noticeable feed-water Ifne hammer was associated with this event.
The cause of this event was due to the feedwater con-trol valve locking in the near closed position. The locking of the feedwater control valve in position is a feature that occurs on loss of control air supply.
NOTE:
This event was report as A0 66-6 9
d)
On November 13, 1967 an automatic scram from full load was initiated due to low steam generator levels. The low steam generator levels were caused by the automatic tripping of the boiler feed pumps on low suction press-ure.
The low boiler feed pump suction pressure was caused by the tripping of the heater drain pumps which was initiated by a less of control air which automati-cally dumped the heater draia receiver to the condenser.
e)
On May 16, 1975 an automatic scram from full power was initiated due to low steam generator water levels.
The low steam generator water levels were caused by the auto-matic tripping of the boiler feed pumps. The initial investigation of all feedwater, condensate and heater drain system controls noted no abnormalities.
Further investigation suggested that the automatic con-densate recirculation solenoid trip valve could have been partially unlatched and due to vibration it could have fully unlatched, causing the recirculation valve to'open and thus trip the boiler feed pumps on low suc-tion pressure.
3.
During the nineteen years of operational history for Yankee Pawe there has been one total loss of off-site power event.
The plant was shut-down at the time of this event. The cause of the total loss of power was due to the total loss of AC experience by most of the Northeastern United States in November, 1965.
QUESTION 2 If administrative controls have been adopted to limit the flow of auxiliary feedwater for the purpose of reducing the probability of water hammer, show when they were adopted and give the answers to Items 1.1, 1.2 and 1.3 for before and after such controls were established.
RESPONSE 2 Yankee Rowe has not adopted any administrative controls to limit the flow of auxiliary feedwater for the purpose of reducing the probability of water hammer.
The auxiliary feedwater system with a maximum flow rate of approximately 90 gpm, is manually initiated by a qualified operator.
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4 Enclosure Page 3.
Based on operating experience, Yankee Rowe considers the present design and operational procedures to be adequate to preclude a water hammer.
QUESTION 3 If administrative controls have been adopted to limit the flow of auxiliary feedwater for the purp' e of reducing the probability of water hammer, show that an adequate water inventory and flow will be maintained to accomodate all transient and accident conditions.
RESPONSE 3 Yankee Rowe has not adopted'any administrative controls to limit the flow of auxiliary feedwater for the purpose of reducing the probability of water hammer.
QUESTION 4 If auxiliary feedwater flow in your facility is not at present initiated automatically for normal and accident events, present your evaluation of whether automating the actuation of auxiliary feedwater might increase the probability of inducing steam generator water hammer.
One of the signals that would automatically initiate the. flow of auxiliary feedwater would be the steam generator low water level.
This set point should be above the top of the main feedwater sparger to reduce the probability of steam generatar water hammer.
RESPONSE 4 The auxiliary feedwater flow at Yankee Rowe is not initiated automatically for normal and accident ever ts.
An evaluation on whether automating the acutation of' auxiliary feedwater versus an increase in the probability of inducing steam generator water hammer is required by NUREG-0578.
Yankee Rowe will address the above Question 4 when we submit to the NRC the de-tailed design for automating the auxiliary feedwater system as required by NUREG-0578.
QUESTION 5 Describe the means that will be used to monitor for the occurrence of steam generator water hammer and possible damage from such an event.
In-clude all instrmnentation that will be employed.
Describe the inspections that will be performed and give the frequ<.acy of such inspections.
RESPONSE 5 Based on the plant's past experience since the feedwater piping modifications performed in 1966 (described in Reference (c)), there have been relatively few and weak feedwater hammer occurrences. These occur almost exclusively (but not consistently) during a start-uj from cold shutdown.
For occurrences of water hammer which would cause a significant deviation from normal or expected performance.of plant equipment, the present Plant Information Pe-port format wculd be utilized to identify and describe the occurrence. The present Plant Information Report format requires the description of the occurrences, conditions prior to occurrence, analysis of occurrence and corrective action takea.
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Enclosure
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Page 4 QUESTION 6 Describe the reporting procedures that will be used to document and report water hammer and damage to piping and piping support systems.
Such reports were requested in our letter to you dated September 2, 1977.
RESPONSE 6 Significant operating abnormalities or deviations from normal or expected performance of plant equipment, as determined by the Plant Superintendent, are reported to higher management as Plant Information Reports (PIR).
PIR's are available at the plant and are routinely reviewed by NRC I & E person-nel.
Therefore, Yankee Rowe sees no need to provide any additional reporting procedures that will be used to document and report water hammer and damage.
to piping and piping support systems.
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