ML19319E072
| ML19319E072 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 08/01/1974 |
| From: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| To: | |
| Shared Package | |
| ML19319E068 | List: |
| References | |
| NUDOCS 8003310583 | |
| Download: ML19319E072 (2) | |
Text
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SACRAMENTO MUNICIPAL UTILITY DISTRICT C 6201 S Street, Box 15830. Sacramento. California 95813: (916) 452-3211 August 1, 1974 Dr. Donald F. Knuth, Director Directorate of Regulatory Operations U. S. Atomic Energy Commission Washington, D. C.
20545 Rancho Seco Nuclear Generating Station No. 1 High Pressure Injection System AEC Docket No. 50-312
Dear Dr. Knuth:
During testing of the safety features actuation system it was 4
determined that the makeup tank water level reached an unacceptably low level.
If this condition had gone undetected, it could have caused the loss of pump suction in one of tha two redundant high pressure injection loops.
In accordance with the District's quality assurance procedures,
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this condition was reviewed and determined to be a reportable "signifi-(,'
cant deficiency" as defined by 10CFR50.55(e) and was reported to Region V of Regulatory Operations on July 25, 1974.
Description of Deficiency - The Rancho Seco Unit No. 1 high pressure injection system consists of two independent systems capable of injecting borated water into the reactor vessel under certain loss of coolant accident conditions. The system is equipped with three high head pumps. One pump is lined up to take suction from only the borated water storage tank and is isolated by valves from the makeup tank and the other two pumps.
Its total function is related to safety. The'other two pumps are connected to a common suction header which is normally lined up to the makeup tank. During normal reactor operation, one of these pumps is in operation to provide reactor coolant pump seal water and reactor cool-ant system volume control. The other pump is in standby service in addi-tion to being part of the safety features system. The high pressure injection suction header from the borated water storage tank which serves these two pump. is also connected to the makeup tank. Borated water from the borated water storage tank is isolated from this portion of the suction header by a safety features valve that opens on safety features actuation i
signal.
During the safety features actuation test, the makeup tank level reached an unacceptably low level and the affected high pressure injection pump was manually shut down. The other high pressure injection pump, taking suction from only the borated water storage tank, continued to
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operate satisfactorily.
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V Dr. Donald F. Knuth August 1, 1974 The borated water storage tank and the makeup tanks are located at grade elevation. The high pressure injection pumps are located at the
-20' elevation. During safety features tecting, the makeup tank was pressurized with nitorgen to simulate its normal operating pressure. On safety features actuation, water from the borated water storage tank is automatically valved to both of the high pressure injection pump suction headers. At this time the borated water storage tank and the makeup tank are both valved to the suction header of one of the high pressure injection pumps. The system was desirted to depressurize the makeup tank through a safety features valve on the makeup tank. When this occurs, the head from the borated water was designed to overcome the head from the makeup tank and the suction to this high pressure injection pump should have been from the borated water storage tank. During safety features testing, it was determined that depressurization of the makup tank did not occur fast enough to prevent it from being drained before flow was established from the borated water storage tank.
Corrective Action - The corrective action is to install a motor operated valve between the makeup tank and the high pressure inj 'ction pump suction header. This valve will be actuated by a safety features signal to close on a safety feature actuation. This action will isolate the make-up tank from the high pressure injection pump suction header, and will j
prevent loss of suction to the subject high pressure injection pump.
d This work is scheduled for completion prior to fuel loar'.ing.
Should additional information on this problem be needad, or l'f we can be of further assistance, do not hesitate to call.
Sincerely yours, 0.
hYA J. Mattimoe Assistant General Manager and Chief Engineer cc:
R. H. Engelken Region V y
.