ML19323B600
| ML19323B600 | |
| Person / Time | |
|---|---|
| Site: | Crystal River, Rancho Seco, 05000303  |
| Issue date: | 04/04/1980 |
| From: | Michelson C NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD) |
| To: | Tedesco R Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8005130738 | |
| Download: ML19323B600 (2) | |
Text
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.so r 932 APR 4 1980 U
- 'EMORA:'0UM FOR:
Robert L. Todesco, Cliaf rnan B&W Reactor Transient Response Task Force FP,0!!:
Carl ;11chelson, Director Office for Analysis and Evaluation of Operational Data
SUBJECT:
ADDITIC!!AL OPERATIO:!AL DATA FOR C0!!SIDERATICl1 BY THE TASK FORCE During our review of the recent Crystal.tiver event, we came across Abnor~al Report Co. 74-3 (Enclosure 1) filed by ;he Sacramento ;iunicipal Utility District on Septe:f.cr 20, 1974. Me believe this report contains inforr.aticn which should-be of intere:t to your task force.
He note that in Secticn 4.2 of your draft reportl you identify that:
The tables of events in Appendix B represent the best information available at tha time this report was prepared, and that:
The relatively severe transients have been identified, but the total population of transients reasins unknc.sn.
e believe that the Rancho Seco event night add some additional insight because of the following:
1.
The event apparently incluced a high pressura transient (greater than 2400 p:i' and the safety valve,s) on the prinary ucro challenged.
2.
The failure of the "X" pcuer supply apparently affected several valve controllers producing condition: allouin; the overpressurization. Additionally, as the IE
'IC: TAB analysis (Enclosure 2; notes, the controllers de not fall open or closed.
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raft PJREG-CCG7, Transient 2enp"onne of Babccc!: & Wilccx-Designed Reactors, C
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l dated April 0, 10C9.
E THIS DOCUMENT CONTAINS POOR QUALITY PAGES e
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Robert L. Tedesco If you have any questions regarding this catter, please contact Jin Creswell on extension 29560.
I carl Michelson, Director Office for Analysis and Evaluation of Operational Data
Enclosures:
1.
Abnorraal Repcrt No. 74-3 2.
IE RO:TA3 Analysis cc w/ enclosures:
C. Serlinger F.. Scrncro D. Eisenhut
- a. Hartfield E. Jordan C. Johnson Distribution:
M entral File AE00 Reading File J
AE00 Chron. File JCreswell, AE00 H0rnstein, AE00 CMichelson, AE00 l...
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CACRAF.' ENTO !.'UNICIPAL UiltliY D:STBICT O C201 3 Street. Scx 15133. Sa:tamento. Ca if:rnia 95810: [sts) 41L: -
September 20, 1974 Director Directorate of Licensing U. S. Atomic Energy Comission k'ashington, D. C.
20545 AEC Oocket t'o. 50-312 Rancho Seco fluclecr Generating Station, Unit ;o. 1 Abnor..a1 Occurrence t'o 74-3
Dear Sir:
Enclosed is a copy of Abneraal Report No. 74-3 relctive to inverter S1D.
Sincerely yours,
. LG I
/ J./J. Mattitoo Assistant General Manager and Chief Engineer Enclesure ec:
R. H. Engelken, Region V '
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DOCKET l'O. 50-312-74-3 Recortino Date:
September 18, 1974 Occurrence Date:
September 10, 1974 Time:
0558 Facility:
Rancho Seco fiuclear Generating Station Unit tio. 1 Clay Station, California Jdentification of Occurrenc~e:
Reactor Coolant System overpressure during heatup Condition Prior to Occurrence:
The plant was at refueling shutdcwn ccepleting final testing prior to initial criticality.
Descriotion of Occurrence:
On the morning of Septerber 10, 1974, the reacter coolant system m
temperature was being increased within the limits of the heatup curve established in the Technical Specifications.
The system was stabilized at 355'F and 1700 psia to insert cecked rods and remove all the shutdown bypass" keys fro. the 'rcactor protection instrucentation as recuired by the operating procedure. After remving this shutdexn bypass inhibits, the reactor system was in the process of increasing pressure by er.ergizing the pressurizer heaters.
The pressure was increased to 1950 psig which is above the icw pressure trip of 1900 psio and all the reactor protection channels were reset.
Cencurrent with this heatup, a routine inspection of plant ecuipment was being conducted.
As an cperator was walking thrcugh the "D" inverter rcon, he heard a " snapping" sound comino frem the interncis of the SiD inverter cabinet.
The operator informed the Shift Supervisor of tha situa:fon and he also inspected the inverter.
The olant was not being effected by the inverter problem and sf ace an electrical technician was expected to report to work within an hour, the Supervisor decided to have the technician work on the system.
L'han the technicicn arrived at 0500, he c;cned tha cabinet and observed an inductor heat sink ground screw f ug loose and it uns sparking to the grounding bar.
To prevent electrical trans'ients and further degrada-tion of the inductor lug, he advised that the SlD inverter be de-energized and he would start repair of the unit incediately.
At 0537 witn the electrical i
technician ready, 510 was secured.
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f The reactor operated smoothly until 05a9 when the high reactor coolant pressure alarm sounded.
This indicates at least 2255 psig reactor coolant pressure and the operator inspected his indicators.
The wide range pressure recorder indicator was reading 1950 psig; the narrow range pressure recorder indicator ("B" loop pressure) was at 1950 psig, and the narred range pressure indicator ("A" loop pressure) was at 2400 psig and rising sharply.
The operator decided that the latter reading was correct and he stopped the high pressure makeup pump.
The pressure quickly decreased and at 2100 psig the operator energized the pressurizer heaters to assure that the "A" loop pressure was responding correctly and that there was still a steam bubble in the pressurizer.
Shortly after the heaters were energized, the pressure started to increase and he was confident that the "A" loop pressure indicator was respcnding to true reactor coolant conditions and that a steam bubble was still in the pressurizer.
The reactor coolant pressure was decreased to 1900 psig by natural decay and then reduced to 1600 psig by request of the plant Superintendent to centralize the loci point within the limits of the heatup curve until a complete analysis of
.the situation cculd be made.
4 Corrective Action Taken or Whidi Should be Taken:
An analysis of the pressure transient by the on-site liechanical Engineer detert ined that the reactor ccolant system did not sustain any adverse effect because:
1.
The reactor coolant system terperature was above 100*F.
2.
The pressurization occurred under isothermal conditions.
3 The system design pressure of 2500 psic was not exceeded.
~
4 These pressure / temperature conditions are permitted by the Technical Specifications for leak testing per Section 3.1.2.2(a).
In addition to the internal analysis, an external review of the Pressure-Time transient was conducted at Babcock & Wilcox Comoany in Lynchburg, Virginia.
They concluded that the pressure spike had no harmful consequences on the reactor coolant sys tem.
Desicnation of Accarent Cause:
Design Analysis of Occurrence:
One of the syster.s that the S1D inverter supplies is _the reactor non-nuclear instrumentation "X" power.
This bus feeds numerous signal ccnverters, transnitters, indicaters, controllers, recorders and selectcr stations.
The specific modules on this bus which relate directly to the l
pressurization of the reacter coolant systec are:
l 1.
Seal Injection Flcw Transmitter. and Valve Controller, l
When the SID inverter was secured the seal injection l
valve went to 505 cpen which is the neutral (zero signal) control position..
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s 2.
Makeup Flow Controller.
When the 51D inverter was secured, the makeup flow control valve tent to 50%
open which is the neutral (zero signal) control position.
3 Letdown Flow Transmitter.
When the 510 inverter was secured, the letdown flow valve went to 50% open which is the neutral (zero signal) control position.
4 naactor Coolant Pressure !!arrcw Range P.ecorder B l.oop.
When the SlD inverter was secured the recorder drive stopped and the indicator stcpped at the pressure indicated.
5.
Reactor Coolant Pressure Wide Range Recorder B Loop..
When the 51D inverter was secured the recorder drive stepped and the indicator stopped at the pressure indicated.
6 Pressure Level Recorder.
When the 510 inverter was secured, the recorder drive stopped at the level indication then current.
The response of Items 1 and 2 above amounted.to a greater cuantity of water injection into the reactor coolant system than was being reroved by Item 3.
The increased inventory accu:ulated in :ne pressurizer with a result. ant reacter coolant increase.
The pressure indicator / recorders (Iter.s 4 and 5) > ere indicatine a hon-transient conditica during the pressu m increase.
The pressurizer ~
level recorder (Item 5) was also indicating a non-transient condition during the level and pressure increase.
Only the. alan-function and the indicator /racorder on "A" loop were operational and indicating the transient condition.
Tha cperator had had difficulty in making the loop "A" recorder properly ink its recorder trace prior to the occurrence.
Although the mcorder did properly indicate pressure throughout the event, the short period over which the pressure transient occurred ude the visual display less apparent.particularly when the two other pressure recorders were indicating an apparent stable condition.
The operator stopped the pressure increase at 2403 psig which is 350 psig above the allowable pressure at 355'F during heatup. The pressurization occurred over a period of apprcxicately 22 minutes and the de;:ressuriaation to 1900 psig was over a ceriod of one J
hour and 3G tinuta.
The temperature during transient did not change frcra the ini tial 355*F.
As described under "Ccrrective Action Taken," a thorouch analysis of the transient revealed no adverse effects to the reactor ccolcr.t system.
Ecuiceent I.D.:
The.S1D inverter is manufactured by Static Products of Garland, Texas,
"adel '!o. SP-DCl20-511-250-50.
The inductcr uhich had a loose screw cn th.?
!. cat sink grcund was in tray 2 5, Section A-9, which is part of the 39 se: itching ~
bridge and is Part No. 044-013 A012-1.
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s Action Reoutred to prevent a Recccurrence:
1.
Operating personnel have been issued a more detailed explanation of what indication will be lost upon de-energizing "X" power.
2 A design change has b5ea initiated to provide dual power supplies to "X" power by means of rapid automatic switching.
3.. Until material and installation of Item 2 above can be accomplished, a manual switch has been installed to provide for manual switching of "X" AC power to an alternate power supply (lighting) when required.
The "X" DC power has been split into two separate auctioneered power supplies eithc.* of which can carry the entire "X" load.
Failure Data:
None 4
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a 95313;(91t,52 3213 n C,21. n r J "'.ACMviMo puncFAt. utsurY DISTRICT Q' 17t3 t.9m S!,eet, som t rJ23. SwmMP.Cahfod, g ,e 2 .l ',.i " l RJR74-326h(6hJ"J'/(f/ 8 ' Sep t'emb e'r 10, 1974 i sq Mr. E..L. Engelken Director of Regulatory Operations Region V AEC Regulatory Operations Office' \\ S f 1990 No. California Boulevard
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k*ainut Creek Plaza, Suite 202 p hlN Tlalnut Creek, California 94595-SEP 111974 % * '. 6 (d T.) ~ 'n:'s s. 10 N'r.,0 r;to' -Re: AEC Docket No. 50-312 P.cacho Seco Nuc1 car Gcncrating g,g Station, Unit No. 1 Abnormal Occurrence No. 74-3 'e p 's
Dear Mr. Ent;elken:
This is to report Abnornst Occurrence No. 74-3. During a partisi loss of instrucentation with the Reactor Coolant Systcc app.roxt=stely 335*, syste pressure reached 2400 pounds before action was taken to reduce it. ~Paia pressure tecpere:ure relaticnship exceeded the allevable pressure tenperature relation 'oy cpproxLutely 500 pounds. Pressure was subsequently reduced to an allowable value of 1900 psir.. Sincerely v :urs,. ] 'C k s R. 1. Q riguez /{ Plant Sup er in ce.nd3nt Rancho Seco Unit 1 Clay-Station, California 95638 PJR: sal 9 O e. ,....0.** b I.. I U O
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