ML19322C342
| ML19322C342 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco, Crane |
| Issue date: | 07/13/1978 |
| From: | Zwitzig G Office of Nuclear Reactor Regulation |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| TASK-TF, TASK-TMR NUDOCS 8001160880 | |
| Download: ML19322C342 (5) | |
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UNITED STATES N ATECtj e I1 4
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'4 NUCLEAR REGULATORY COMMISSION l
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WASHINGTON, D. C. 20656 a
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July 13, 1978 f
Docket No. 50-312 LICENSEE: SACRAMENTO MUNICIPAL UTILITY DISTRICT FACI'ITY:
RANCHO SECO NUCLEAR GENERATING STATION L
SulfARY OF MEETING HELD ON JUNE 20, 1978, TO DISCUSS C00LDOWN TRANSIENT OF MARCH 20, 1978 A list of attendees is given in Attachment 1.
The agenda followed during the meeting is given in Attachment 2.
Introduction Following the occurrence of the subject transient okMarch.20.1978, the licensee submitted the prompt and followup reports recuired by the facility operating license. The followup report of March 31, 1978-provided a comprehensive preliminary description of the transient, an assessment of the cause of the transient and a description of the correc-tive action..Further discussion of the transient was contained in the s' Inspection Report by. the Comission's Office of Inspection and Enforcement dated April.21,1978, from J. L. Crews to J. J. Mattimoe.
The purpose of this meeting was to obtain further information concerning the event in order toidetermine:
1.
Whether additional corrective action, including changes in system design, was needed.
2.
Whether the automatic initiation of the emergency feedwater pumps i
by an Engineered Safety Features Actuation Signal (ESFAS) should be retained as a design feature, and
- 3. iWhethe there.wereotherifailuresorlinit'iatingeventszthatcouldl
.cause a similar transient.
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. The meeting was held at the reactor site to facilitate [ access'to design drawings and permit. inspection of the Control Room and, the cLinstrumentation available to the operators.
Summary Highlights of the meeting were as follows:
1.
The loss of the 24 volt power supplies not only caused a loss of input signals to the Integrated Control System (ICS), but also caused a. loss of many signals displayed in the Control Room. This Joss of display, however, did not affect the operability of the Reactor Protection System.
- 2...The.licenseeindicatedthatiRanihoSecowas.theonlyBabcock.L
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~and Wilcox'(B&W) designed. facility where emergency.feedwater.
,,(EFW) flow was initiated by an' ESFAS.
They stated that this
_came.about because: their. evaluation : indicated that EFW flow!
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had been assumed in the B&W. analyses of_ the LOCA and Core Flood Tank line break. Subsequent evaluation, however, has indicated that theTpresence or absence.of EFW flow has. little effect on the consequences of these postulated accidents.
The licensee indicated that, depending on the results of a current rg-evaluation of the postulated steam line break accident, he may propose '
eliminate ESFAS initiation of EFW flow.
3.
The licensee discussed the results of the revien of this matter
. by_ a specially appointed technical committee.* Some of the (consnittee's recommendations were as follows:
a.
The use of non-conducting caps or plugs or the transporting of the bulb fixture to a remote location during the changing of bulbs on the back-lighted pushbutton assemblies.
b.
The testing of breakers, fuses, transfer switches, power supply monitors, etc. to assure proper coordinacion.
3 c.
To consider performing studies of several matters including use of lower rated fuses in conjunction with current-limited j
power supplies, and improvements in the Non-Nuclear Instru-mentation (NNI) D.C. power supply configuration.
- In his letter of March 31, 1978, the licensee connitted to provide the findings of the Committee to the NRC Regional Office.
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3-d.
To,tudy the practicability of providing instrument indications or computer readouts in the Control Room necessary for cuntrolled plant cooldown which would not be affected by loss of the NNI power supplies.
- 4. IDuring the'" brainstorming"Lsession~ none of the attendees postulatedi
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manother mechanism orLfailure which would. initiate a'similar transient.
(Note: Because of the limited discussion of this subject at the meeting, the staff does not consider this a closed item.)
Conclusion The licensee was advised that we would review the information provided and inform him of any additional corrective actions we concluded were appropriate.
- 3. B.
wetz g, Project Manager Operating Reactors Branch #4 Division of Operating Reactors Attachments:
1.
List of Attendees 2.
Agenda b
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,f ATTACHMENT 1 LIST OF ATTENDEES MEETING ON RANCHO SECO COOLDOWN TRANSIENT SMUD Ron Colombo S. I. Anderson Lloyd Stephenson John D. Dunn Nonn Brock Bob Dieterich Ron Rodriguez Donald C. Blachly John V. McColligan Pierre Oubre NRC Phil Johnson-IE:V M. Chiramal
,. John Anderson-Oak Ridge Nat'l. Lab iRichard Lobe 1L Dom Tondi Gerald B. Zwetzig Bob Dodds B&W Joel T. Janis i
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ATTACHMENT 2 AGENDA March 1978 Reactor Transient
(,1)
A brief description of the Integrated Control System as installed at Rancho Seco, presented by Norm Brock, Senior Instrument & Control Engineer.
(2)
General descriptica of sequence of events prior to, during and fc11oving cooldove and a sue: mary of the valid and nonvalid instrument indications available to Operators during the transient, presented by Don Blachly, Associate Mechanical Engineer.
(3)
Review of electrical drawings pertinent to event, presented by John Dunn, Supervising Electrical Engineer.
(4)
Corrective action (implemented and planned) including a discussion of adequacy, presented by John Dunn, Supervising Elcetrical Engineer.
'(5)
Reasons for providing SFAS automatic start of auxiliary feedpumps and consequences if SFAS automatic start is deleted, presented by Stan Anderson, Associate Nuclear Engineer.
(6)
'" Brainstorm"' session' on other initiating events 'which'could* cause i iignificant.cooldowni ransients. ~~~ ^ " "
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