ML19322C672
| ML19322C672 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 01/18/1980 |
| From: | NRC COMMISSION (OCM) |
| To: | NRC COMMISSION (OCM) |
| References | |
| TASK-TF, TASK-TMR NUDOCS 8001180321 | |
| Download: ML19322C672 (2) | |
Text
s MEM0 TO FILE s
Re; Cr all Statement that GDC 13 Criteria were not met with re 'grd to water level instrumentation After consultation with Tom Cox and Joe Scinto, it appears that this is not quite accurate. GDC 13 is written with the same standard as many GDC criterion: The instrumentation required to meet this grade-(" safety (grade") is only that as appropriate to assure adequate safety. GDC 13).
Since the water level instrumentation was not deemed necessary to bring a plant to shutdown, it was not safety graded and therefore need not meet GDC 13.
The point seems to be that the reactor could be shut down without water levei instrumentation.
ECCS etc. was all automatic.
A seond point is that even if this water level instrumentation had been deemed saftey grade, if it e xisted only in the Pressurizer it wouldn't have made any difference in the TMI-2 accident, as the Pressurizer indication read properly It was the A unanticiapted void in the reapor which caused the prhlems.
THE ISSUE all of this raises for me is the uselessness of the GDC.
If all (as it seems) are written with such loopholes (that may be too strong) of what value is it? I guess this goes to be the central point about the GDCs: they ass are not dictates of design but provide only guidance.
Joe Scinto recommended that we see the response to Creswell's memo on this subject. He also pointed out that the accident at Oyster Creek (a BWR) in no way was minimized by the proper functioning of-gu water level instrumentation, although he agreed such instrumentation is necessary to assess the consequences of an accident.
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The safety analysis I core severe cooldown transients, such as the
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loss of feed-:ater ev;;;DridiEa'tes that
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~ he water volunie could decrease t
-.tha the...s.ys t en vol. u. me exc.lu. sive of tifeTr.esisu rizer'.~ During '
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to less
'g the emp_ tying _of_-the pressurizer,would be fol' owed by
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such an e..- - -
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a pressure reduction below the saturation point and the formation of
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small voi d throughout'nuchJ ffth i piirary systen.
This would rsi I ~ ~~~
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' result in 'thfloss of core coolin;; bicause'thiloids would be dispers d
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e over a large voluse[and forced flow would prevent them lf rom coal ~escing I
suf ficicntly to prevent. core cooling.
The hi;;h pressure coolant injection pu ps are started automatically when the primary pressure decreases below 1600 psi.
Therefore, any pressure reduction which is sufficient to allow voiding will also result in water injection which,
will rapidly restore _the. primary water to norcal levels.
s For these reasons, we believe that the inability of the pressurizer 7
and normal coolant makeup system to control sore transients does not
\\ b provide a basis for requiring more capacity in these systecs, b N[,
General Design Criterion 13 of Appendix A to 10 CFR 50 recuites instrumentation to nonitor variables over their anticipated range H
a for " anticipated cperational occurrences".
Such occurrences are
'specifically defined to include loss of al'1 offsite power The f ct that T cold goes off scale at 520 F is not considered to be a devi" tion
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from this recuire.ent because this indicator is backed up by wide N
range temperature indication that extends to a low liait of 50 F.
Neither do we consider the naheup flow conitoring to deviate since the aaount of' takeup flow in excess of 160 gpc does not appaar to be a significant factor in the course of these occurrences.
The loss of pressurizer water level indication could be considered to deviate from GDC 13, because this level indication provides the principal means of determining the primary coolant inven te r'f.
However, provision
-of a. level indication.that would cover all anticipated occurrenc'es~na,v
,not b_e practical., As discussed above_,. ~th~c l.
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o s t. ot reedvater event can lead to a momentary condition wherein no teani.igful level exists,
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because the entire prinary systen contains a t
steaa water aixture.
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It should be noted that the introduction to Appendix A (last paragraph)
A recognizes that fulfillment of sece of the criteria cay not always be 3
appropriate. This introduction also states that departures f rom the f ' Criteria cust be identified and justified.
The discussion of GDC 13 "Q
p in the Davis Besse FSAR lists the water. level, instrumentation,_but y
i does not cention the nossibility of loss of water level indication i
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'duri5g transients T'h'is appa rent olission in the safety analysis
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. vill be subj ect'ed to 'further ~ review.
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P00R DR Mq, CHECK WITH TOM C0X WHETHER THIS SAME DEFICIENCY EXISTS IN TMI FSAR.
THE POINT HERE IN MY OPINION, IS THAT THE REGULATORY SYSTEM I
ALLOWED THIS D B FAILURE TO SLIP BY. HAD IT BEEN P_ROPERLY EVALUATED 1
WOULD WE HAVE SEEN THE INSTRUMENT FAILURE DURING TRANSIENT PROBLEM IN ADVANCE, ALLOWING FOR SHUTDOWN ORD.ER?
.