ML19290A236
| ML19290A236 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 08/27/1979 |
| From: | Taylor M NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| To: | Mattson R Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML19290A225 | List: |
| References | |
| NUDOCS 7910240180 | |
| Download: ML19290A236 (5) | |
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UNITED STATES
[ *, e g[%j NUCLEAR REGULATORY COMMISSION
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WASHINGTON, D. C. 20555 A
%.s-p August 27, 1979 MEMORANDUM FOR: Roger J. Mattson, Director Lessons Learned Task Force THRU:
Frank H. Rowsome, Acting Director Probabilistic Analysis Staff, RES FROM:
M. A. Taylor, Sr. Reactor Safety Engineer Probabilistic Analysis Staff, RES
SUBJECT:
CHRONOLOGY OF EVENTS: TMI-2 HYDROGEN reflects a chronology on the TMI-2 H2 matters that I recall having any personal knowledge of or direct involvement with.
I hope this contributes to rounding out that chronology of events circulated by your August 21, 1979, memo.
I trust that Enclosure 1 will be discussed with those I have mentioned so that we will be advised as to the completeness and accuracy of my recollections.
Note that the specific times of day cited herein should be regarded as being very approximate.
I found the chronology in your August 21 memo to be quite enlightening about Bethesda efforts concerning the H2 explosion potential.
Because I was largely outside of these Bethesda events and at the TMI-2 front lines, I have no constructive comments or corrections to make.
~ ///,.f f-M. A. Taylor Sr. Reactor Safety Engineer Probabilistic Analysis Staff Office of Nuclear Regulatory Research
Enclosure:
As Stated cc:
S. Levine R. Budnitz J. Murphy 2226 176 7910240 /fO
THI-Ho Concerns Chronolooy of Events (re'211ed by M. Taylor from his involvement in H2 matters)
Thursday, March 29, 1979 s2030 M. Taylor received a call at home from T. Novak and W. Minners who were at the Bethesda HQ-IRC.
Question asked was what would be the radiolytic generation rate of H if TMI-2 reactor was to be reduced 2
to low pressure levels to permit operation of the low pressure decay heat removal system.
Taylor advised that most of his info for making such H2 estimates was at Bethesda office, but that he'd try to recall work of s10 years ago and get back to HQ-IRC shortly with an estimate.
s2200 Taylor called Bethesga HQ-IRC (Minners/Novak et.al.) with a back-of-envelope estimate for radiolytic H2 generation considering near-atmospheric pressure levels and non-boiling bulk coolant temperatures.
The estimate was roughly '. 4 SCF H /hr for these conditions, but HQ-IRC 2
was advised to use a 1 ". SCF H2/hr range because of considerable uncertainty about actual TMI-2 fuel conditions and fission product relearas to coolant, etc. Taylor also advised that if HQ-IRC wanted bette: estimates and more detail on radiolytic H2 behavior, they s hot. ' make contact with Dr. Bud Zittel of ORNL, or possibly pror. Reed Johnson, U.Va. (currently technical member on ASLB).
Dr. Zittel, in particular, had considerable experimental experience with post-accident radiolysis at our (i.e., AEC) request s10 years ago.
Friday, March 30, 1979 s2300 At TMI Site M. Taylor took phone call from Chairman J. Hendrie, NRC, who asked that the following items be relayed (note on this call passed to D. Ross):
1.
Convey thanks/ congratulations to H. Denton en the good job' being done and on his press briefing, 2.
Convey to V. Stello that before things were over, the TMI duties could be of benefit to his waistline, IThese estimates made at home relied on past experience and. analysis, recall of ORNL experimental work and results, ORSORT notes of 1963, MIT handbook on Reactor Safety (T. Thompson et.al.) and extrapolations to and assumptions about TMI-2 conditions.
2226 177
3.
Express concern about 02 evolution in TMI reactor vessel and possibility of H -0, explosion; he asked for these concerns to p
be relayed to Bethetda staff so they would get moving on an assessment.
Saturday, March 31, 1979 s0100-At TMI Site 0200 M. Taylor called Bethesda HQ and relayed to Dr. S. Hanauer the concern about 02 evolution and the possibility of explosion in the R.V.
Taylor asked Dr. Hanauer to assure staff gave prompt attention to this matter.
s2000 M. Taylor received verbal request from V. Ste71o to give thought and analysis to following matters and te advise him on these before shift end:
1.
Possible "wh.t if" system scenarios and possible consequence outcomes plus best action courses that might be followed, 2.
Try to make H-balance calculations to estimate Zr-H O reaction 2
magnitudesan$whereH2 sources might be, 3.
Give best judgement on whether or not H2 explosion in vessel should be of worrying concern.
v-Here it should be noted that Taylor recalls discussing the prior 1.4 SCF H /hr estimates with V. Stello.
(The specific time on March 31,21979, when this information was discussed with V. St llo is not recalled.
It is believed to have been during the latt-cart of the prior shift, sometime in the am, e.g., 0400-0800.)
s2200-M. Taylor in TMI-2 control room participated with V. Benaroya 2400 (DSS) et.al. on procedures review and prcgress toward hook-up of the containment H2 recombiners.
Sunday, Aoril 1,1979 s0200 At TMI Site M. Taylor contacted R. Tedesco (Bethesda) to find out what were latest assessments from Bethesda regarding reactor vessel H, 0,3 concentrations 2
and explosion potentials.
Tedesco advised that most recent Bethesda calculations indicated the following concentrations in the R.V.
(from notes):
s 46.5 ft, 0 (radiolysis) 2 y g jJg 3
$103 ft, H (radiolysis) 3 s615 ft, H (Zr-H O reaction) 2 3
s765 ft (apprcximate bubble si:e estimate)
Tedesco also relayed some KAPL info on flammable / detonable concentrations, and he pointed out present (stimates indicated that there would be s10 days before explosive concentrations would be reached in the R.V.
Taylor recalls Tedesco mentioned some bounding kinds of calculations on the effect of an explosion in the R.V. where explosive pressures on the order of 14,000 psi might be experienced.
Taylor recalls suggesting again that HQ-IRC make contact with Dr. Zittel of ORNL for added insights on radiolysis behavior, s0800 M. Taylor advised V. Stello as to the following:
1.
H balance estimates were very rough, but these suggested a 2Zr-H O reaction magnitude in the rary of 25-32%.
[ Note these 2
estimates depended on assumptiont W ut R.V. bubble size and on the nature (local vs. free-field, of the H2 deflagration observed at roughly 9-10 hours into the ac:;ident.
Review of pressure recorder spikes suggested local as opposed to a free-field deflagration in containment.]
2.
Personal judgment was that he (V. Stello) should not worry about the explosion in the reactor vessel since this was considered to be an exceedingly remote possibility.
[ Note that due to the press of shift change activities, the reasoning underlying this personal judgment by M. Taylor was not fully explained to V. Stello.
Reasoning relied importantly on recall of the ORNL radiolytic work done for AEC s10 years ago. This work covered various post-accident coolant chemistries, temperature conditions and system configurations--flowing and static. Importantly, those experiments where basic ph chemistries were involved led to highest H yields approaching 7-8 atmospheres (recall) before recombinakion terminated the net yield of H.,/0 by radiolysis (i.e., back and forward reactions were equaT).2This suggested no net evolution of 0, should be anticipated at the actual TMI-2 R.V. conditions of 900 to 1000 psi.
Further, the ORNL work with these basic coolant chemistries which were assumed to approximate the TMI conditions where Na0H had actually been introduced early in the accident.
This ORNL work of s10 years ago also indicated an interesting 02 scavenging behavior, i.e., 02 evoluftionwasnotstoiciametricwithH.
This behavior further 2
suggested that any free 0 (if it possibi bubble space inasmuch as $his might be atg existed in the eributable to the use of non-degassed water from the SWST) could be subject to the same scavenging behavior. These above Gctors when taken with the realization that the H reducing environment at TMI probably 7
exceeded, by far, the routine reducing environment usually used in PWRs, plus the need for an ignition source, led to a judgment that an H2 explosion in the R.V. was of an extremely remote possibility.]
3.
Tedesco's estimates were described..
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DRg7 4.
Some possible "what if" scenarios and thoughts were available for discussion when Stello had further time and need to consider these.
s0900 Made phone contact with wife to arrange for more clothing, etc., for extended TMI stay.
First learned that the media accounts in Washington had caused wide-spread public alarm / concern about H2 explosion.
Advised wife not to worry; all was stable and going OK at TMI and that media accounts were probably irresponsibly sensationalized.
2226 180
4 s
e ENCLOSURE 3 MEMORANDA COMMENTING ON FINAL DRAFT OF CHRONOLOGY 2226 181