IR 05000553/1979012
| ML17249A945 | |
| Person / Time | |
|---|---|
| Site: | Phipps Bend  |
| Issue date: | 10/16/1979 |
| From: | Murphy C NRC Office of Inspection & Enforcement (IE Region II) |
| To: | Parris H Tennessee Valley Authority |
| Shared Package | |
| ML17249A946 | List: |
| References | |
| NUDOCS 7910250498 | |
| Download: ML17249A945 (6) | |
Text
ENCLOSURE 1 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.
C.
20555 SSINS No.:
6300 Accession No.:
7910250498 IE Information Notice No. 79-29 Date:
November 19, 1979 Page 1 of 2 LOSS OF NONSAFETY"RELATED REACTOR COOLANT SYSTEM INSTRUMENTATION DURING OPERATION This notice contains information regarding a loss of reactor coolant system instrumentation as a consequence of a failure of a static transfer switch to transfer to an alternate supply.
At 3: 15 p.m.
on November 10 with Unit 3 of the Oconee Station at 100 percent power, the main condensate pumps tripped, apparently as a result of a techni-cian performing maintenance on the hotwell level control system.
This led to reduced feedwater flow to the steam generators, which resulted in a high reactor coolant system (RCS) pressure reactor trip and simultaneous turbine trip at 3: 16:57 p.m.
At 3: 17: 15 p.m., the inverter power supply, nonsafety-related, feeding all power to the integrated control system (ICS) tripped and failed to automatically transfer its loads from the DC power source to the regulated AC.power source.
The inverter had tripped due to blown fuses, resulting in loss of RCS indicators and recorders in the control room, except one wide range RCS pressure recorder.
This condition existed for approximately three minutes, until an operator could reach the equipment room and switch the inverter manually to the regu-lated AC source.
As a result of the power failure to the ICS, all valves controlled by the system assumed their respective fail positions.
This resulted in a cool down of the RCS to 1635 psi and 530 degrees F.
The opera-tor, expecting this condition, started all makeup pumps and opened the asso-ciated high pressure injection valves to the RCS which limited the rate of RCS pressure reduction and associated reduction in pressurizer level.
At 3:20:42 p.m.,
power was restored to the ICS and RCS conditions were restored.
Although RCS cooldown limits were exceeded, the pressurizer and steam genera-tors did not go dry, and at least 79 degrees F subcooling was maintained during this event.
No engineered safety features actuation setpoints were reached, and, except for the components discussed above, no component malfunc-tions occurred.
The licensee has installed a redundant electromechanical transfer switch between the loads and the regulated supply.
This switch will actuate and
, power the loads from the regulated supply should the original static switch fail to transfer.
Longer term resolution of the need or desirability to separate these instru-ments onto diverse electrical supplies or to provide redundant instrumentation display channels for operator use from essential power supplies are also under
Enclosure
IE Information Notice No. 79-29 Date:
Nov'ember 19, 1979 Page 2 of 2 consideration.
It is anticipated that further NRC evaluations will result in issuance of an IE Circular, Bulletin, or NRR Generic letter in the near future which will recommend or request specific applicant or licensee actions.
This Information Notice is provided to inform licensees of a possibly signifi-cant matter.
It is expected that recipients will disseminate the information to all operational personnel working at their licensed facilities. If you have questions regarding this matter, please contact the Director of the app.opriate NRC Regional Office.
No written response to this Information Notice is require n
ENCLOSURE
IE Information Notice No. 79-29 Date:
November 19, 1979.
Page 1 of
RECENTLY ISSUED IE INFORMATION NOTICES Information Notice No.
79-20 (Revision No.
1)
79-21 79-22 79-23 79-24 79-25 79-26 79-12A 79-27 Subject Same Title as 79-20 Transportation and Com-mercial Burial of Radio-active Material gualification of Control Systems Emergency Diesel Gener ator Lube Oil Coolers Overpressurization of Con-tainment of a PWR Plant After a Main Steam Line Break Reactor Trips at Turkey Point Unit 3 and
Breach of Containment Integr ity Attempted Damage to New Fuel Assemblies Steam Generator Tube Ruptures at Two PWR Facilities Date Issued to Issued 9/7/79 Same as 79-20 9/7/79 All Power and Research Reactors with OLs 9/14/79 All Power Reactor Faci-lities with an OL or CP 9/26/79 All Power Reactor Faci-lities with an OL or CP 10/1/79 All Power Reactor Faci-lities with an OL or CP 10/1/79 All Power Reactor Faci-lities with an OL or CP 11/5/79 All Power Reactor Facil-ities with an OL or CP 11/9/79 All Fuel Facilities, Research Reactors and Power Reactors with an OL or CP 11/16/79 All Power Reactor Faci-lities with an OL or CP 79-28 Overloading of Structural 11/16/79 All Power Reactor Faci-Elements Due to Pipe Support lities with an OL or CP Loads
.