ML16341D676
| ML16341D676 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon, Rancho Seco, 05000000 |
| Issue date: | 04/02/1986 |
| From: | Stello V NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| To: | Zschau E HOUSE OF REP. |
| Shared Package | |
| ML16341D677 | List: |
| References | |
| NUDOCS 8604100177 | |
| Download: ML16341D676 (8) | |
Text
The Honorable Ed Zschau United States House of Representatives Washington, DC 20515 Dear Congressman Zschau:
This is in response to your letter dated February 27, 1986, to Chairman Palladino, in which you addressed concerns expressed by one of your constituents, Mr. Autry Nassar.
Mr. Nassar expressed concern over the safety of the Rancho Seco and Diablo Canyon nuclear power plants.
Additionally, you specifically requested information related to an event which occurred at Rancho Seco on December 26, 1985.
The single reactor at Rancho Seco and the two reactors at Diablo Canyon were licensed for power operation on August 16,
- 1974, November 2, 1984 and August 26, 1985, respectively.
The operating licenses were issued by the NRC following an extensive design review by the NRC technical staff and authorization by the Commission.
The designs of the Rancho Seco and Diablo Canyon power stations have incorporated design improvements that reflect lessons learned from the Three Mile Island accident and the potential for a serious
- accident, such as a core meltdown, is considered to be very small.
We consider the present designs of the Rancho Seco and Diablo Canyon nuclear plants to be safe and the plants can operate without endangering the health and safety of the general public. Nonetheless, a recent event at Rancho Seco discussed below revealed some deficiencies that will need corrective actions prior to the restart of the plant.
On December 26, 1985, automatic safety systems shutdown the Rancho Seco nuclear plant after electrical power was lost to a control system, specifically, the Integrated Control System (ICS), which controls the operation of various valves, pumps, control rods, and the turbine generator.
The automatic safety systems following the ICS power failure functioned as designed.
However, the ICS controlled pumps and valves, which reverted to a preset position following the ICS power failure, caused steam and water flows to continue unmodulated after the shutdown.
Following the automatic
- shutdown, the lack of ICS control over the steam and water flows resulted in overcooling of the reactor system.
Although the overcooling exceeded the normal operating limits, the transient was well within the design limits of the plant.
The NRC initiated an Incident Investigation Team
( IIT) to investigate the transient.
The IIT presented its findings to the Commission on February 25, 1986.
A copy of the IIT report is enclosed for your information.
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'Althou'gh the December 26, 1985, event did not endanger the health and safety of the general public, the ICS control failure revealed deficiencies in plant mechanical, electrical and control systems, plant maintenance, operator training, plant operating and emergency procedures, and plant human engineering considerations.
The NRC staff is developing a plan for corrective action and Rancho Seco will not be permitted to resume operations until the identified issues are resolved and authorization is granted by the Commission.
I trust that this information resolves the concerns raised in your letter.
Sincerely, ~igfnai signa/ gy piet or Stop],1.
Victor Stel'lo, Jr.
Acting Executive Director for Operations
Enclosure:
Incident Investigation Team Report Distribution:
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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 FRON REP.
ED ZSCHAI.I EDO PRINCIPAL CORRESPONDENCE CONTROL ilv/<<
DUE: ~~721M6'DO CONTROL: 00i495 DGC DT: 02/27/86 FINAL RFPLY:
TG-CHAIRMAN PALLADINO FGR
- IGNATURE OF:
EXECUTIVE DIRECTOR DESI SFCY NO: 86-203 ROUTING:
DATE: 03/07/86 ASSIGNED TCI:
NRR CONTACT:
BENTON CONSTITUENT, AUTREY NASSAR EXPRESSES CONCERNS RE SAFETY AT RANCHO SECO 8, DIABLO CANYON JMARTIN GCUNN IN GHA I'I TAYLOR HEI. TEI'1ES SPECIAL INSTRUCTIONS OR RENARKS:
NRR RECEIVED:
D3/OT/86 ACTION:
~DPLB=--'QIRABLIB~ j, NRR ROUTING:
DENTON/EISENHUT PPAS NOSSBURG/TONS
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OFFICE OF THE SECRETARY CORRESPONDENCE CONTROL TICKET PAPER NUMBER'CTION OFFICE:
AUTHOR:
AFFILIATION:
LETTER DATE:
SUBJECT:
ACTION:
DISTRIBUTION:
CRC-86-0203 EDO LOGGING DATE: Mar 5 86 E. Zschau-Const Ref U.S.
HOUSE OF REPRESENTATIVES Feb 27 86 FILE CODE: ID6R-5 Rancho Seco Expresses concerns with past nuclear safety recordss at Rancho Seco and Diablo Direct Reply OCA to Ack SPECIAL HANDLING: None NOTES:
DATE DUE:
SIGNATURE:
AFFILIATION:
Mar 5 86 DATE SIGNED:
ED0 "-- 001095
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