ML19224A785
| ML19224A785 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 04/19/1979 |
| From: | Ditmore D, Kolar M, Thiesing J INDUSTRY ADVISORY GROUP |
| To: | |
| References | |
| OSP-790419, TASK 21, TASK-21, NUDOCS 7905300293 | |
| Download: ML19224A785 (6) | |
Text
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IAG Memo #IA-21 CRITERIA FOR ABORTING ATTEPPT TO ESTABLISHNdTURALCIRCULATION
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INDUSTRY ADVISORY GROUP
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D. C. Ditmore M. J. Kolar J. Thiesing G. L. Zigler April 19, 1979 167 274
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CR!.TERIA FOR ABORTING ATTEMPT TO ESTABLISH NATUUL CIRCULATION
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The purpose of this nieTio is to define criteria to be used by plant personnel
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for aborting an attenpt to establish natural circulation at TMI-2.
The problem is approached by (1) identifying all parameters which affect the
. reactor coolant system (RSC) and can be measured with existing equipment, (2) identitying all detecters available for measuring the parameters identified in (1), (')) selectina those parameters which can be used to show that natural circulation has ng been achieved, (4) identifying those parameters selected in (3) which can be interpreted by a plant operator utumbiguously, (5) list the possible scenario's which lead to the attempt to reach natural circulation, (6) describe the secuence of events for each scenario listed in (5), and (7) define the criteria for abortino the attempt to reach natural ciruclation.
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RCS Parameters (Measurable),
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Tempera tures f
Pressures r
vt Acoustic Signal Neutron Detector Gamma Detector
' Volume (pressurizer and/or makeup tank level)
Thermal Noise Pressure Noise Instrument Degradation Transient vs. Steady State Measurements (for each of above)
Available Detectors Temperateces
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iot (3 RTD's, 1 on B and 2 on A) wide range (ambient to 550 F) I 10 F '
U T
cold (4 RTD's,1 in each leg) - narrow rance (500 F to 650 F) I 10 F 0
0 0
T In Core T/C's - 44 working Pressurizer RTD - wide range (liquid portion) (0 - 500 F) I 10 F Secondary system temps in steam generator
' In Core Neutron detectors (SPND's can be used fore-1700 F indication) s Pressures P (3 pressure transduces, 1 on B and 2 on A) 0-1000 psig Containment pressure Acoustic Signals Upper tube sheet of A & B Gener. (2 each)
Lcwer tube sheet of A & B Gener. (1 each) y 167 276
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Acoustic Sianals (Cont.)
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fh Upper reactor vessel head (outside) (2, 90 apart on bolts) 1ower reactor vessei (2, 1 on center in core guide and 1 on outside guide, both outside vessel)
Both souhd and CRT spectrum available frcxn each of above.
Neutron detectors Source range (BF3 - themal neut) (2,180 apart) 0 Ex-Core Intermediate range (2, 180 apart) compenssted icn chambers (Power range (4, 90 apart) unccmpensated ion chambers Gama Detectors Power range (4, 90 apart) ex-core uncomp. fon chambers Volume 3
Make up flow +
pressurizer level + letdown flow ^ P + T - no automatic cale available Pressurizer level (3 DP's, I working, l questionable,1 failed)
(Heater bank power spikes as each is uncovered)
(Press. RTD will eventually give info)
Thermal Noise N incore T/C's dedicated to thennal noise Pressure Noise Loop A & Loop B - 1 each press. transd.
_ Instrument Degradation Pressurizer level Incore SPND's
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12 (on strip charts) incore T/C's That (A loop) on strip chart
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-idY N
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p' b Parameters which show Natural Circulati Core Temperatures and rate of change on Not Achieved (Key Parameters)
T T
hot.
cold, and rate of change Pressure Upper head acoustic detector (violent b tli n
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Lower head acoustic detector (debris falli ng)
Source range BF Thermal noise (boiling)3 (criticality) - rate of change cality)
Pressurizer level Key Parameters _ Interpretable Unambi oucusly g Cperator Thot Tcold, and rate of change Source Range BF 3
Pressurizer levei Other key parameters require the presen
,s to interpret.
ce of an experienced diagnostician Initiation Scenario's A.
Current status; reactor coolant pump (RCP) another pump.
trips; unable to start B. ' Planned trip of RCP Current status implies that experien Cable Spreading and Control Rooms.
ced diagnosticians are not present in able within about two hours.Experienced diagnostician may be avail No back-up analysts imediately avail bl Plant trip implies:
a e.
ing Rooms, back-up diagnosticians and aexperienced
_n, a e Spread-required diagnosticians and analysts im dinalysts available on-s e
ately available via phone.
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SE0VENCE OF EVENTS h
Scenario A
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1.
Pump 2A trips with system at ~850 PSI.
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Attempt to start 1A - call for assistance from diagnosticians.
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If 1A doesn't start, reactor operator attempts to achieve natural circulation.
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If natural circulation is not achieved, attempt to start 18.
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If 1B doesn't start, attempt to start 28.
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If 28 doesn't start, abort by going to HPIS while maintaining secondary side of 'A' steam generator at 580".
Scenario B 1.
Pump g tripped at oreselected pressure (>/ 850 PSI) 2.
Re, actor operator attempts to achieve natural circulation 3.
If natural circulation is not achieved, abort by attempting to start one of four pumps.
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If no pumps start, go into reflux boiler mode; diagnosticians and analysts interpret results. ABORT BY G0ING TO HPIS.
CRITERIA FOR ABORTING S,cc..ario A
,If one of the RCP's starts, there will probably be mechanical movement of the core; this could change the distribution of " hot" and " cold" core T/C's.
s There is no current criteria to tt 11 the operator what to do in this case.
For example, if the temperatures rise rapidly on one or more T/C's, what should the operator do?
At this writing, there is a question on whether the BF counters are showing 3
ak very near criticality.
If the core moved, a rapid increase in BF eff 3
.j count rate would indicate approach to criticality.
There is probably no 167 279
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-o-Scenario A (Cont.)
0 rechenicai response which couid ee meee before the increesed heet generation would re-distribute any loose fuel pellets. Therefore, the operator cjould be left with a completely different distribution of " hot" and " cold" T/C's.
For the above reasons, there is no logical way that the core T/C'c can be counted on to give an unambiguous signal to the operator. Therefore, the caly criteria available are Thot. Tcold, their rate of change, and the rate of change of the BF counter.
Since the rate of change of these 3
instruments is not automatically printed out, an unambiguous interpretation cannot be assured. Therefore, only Thot, Tcold are available. Conse-quently, one criteria for aborting the attempt to achieve natural circulation in this case is:
T "TcojgTsat - Margin > Abort.
hot The current 8&W margin of 100 F is adequate and (probably) conservative.
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e e
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