ML19290A226
| ML19290A226 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 09/06/1979 |
| From: | Mattson R Office of Nuclear Reactor Regulation |
| To: | Gorinson S PRESIDENT'S COMMISSION ON THE ACCIDENT AT THREE MILE |
| Shared Package | |
| ML19290A225 | List: |
| References | |
| NUDOCS 7910240121 | |
| Download: ML19290A226 (39) | |
Text
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[(p %qh UNITED STATES
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NUCLEAR REGULATORY COMMISSION
... j WASHINGTON, D. C. 20555 September 6, 1979 Mr. Stanley M. Gorinson Chief Counsel President's Commission on the Accident at Three Mile Island 2100 M Street N.W.
Washington, D.C.
20037
Dear Mr. Gorinson:
By letter dated August 30, 1979, you required that a chronology on the hydrogen bubble flammaoility concern at TMI-2 be provided to the President's Comission by Friday, September 7.
It is provided here as Enclosure 1.
An explanation of the development of the chronology should aid i_n.its interpretation. A first draft was compiled on August 20, 1979. On.
August 21, the first draft was distributed for review by the principal staff involved with the bubble and by the Comissioners of the NRC.
Some of the staff participants provided written responses (see Enclosure 2) and some attended a meeting cn August 28 to discuss the draft chronology.
As a result of the corments received, a number of additions were made.
A final draft was prepared and sent to the NRC Commissioners on August 29 and to a wider segment of the NRC staff on August 30 for review and comment.
Substantial additions were again suggested. The memoranda containing these suggested additions are provided here in Enclosure 3. is a list of the names and office affiliations of all NRC employees who were afforced an opportunity to comment upon the final draft chronology. Copies of the two draft' chronologies and my transmittal memoranda are available in the NRC files for your review, upon request.
Each entry in the chronology is annotated tc show the source of the information it contains. The types of sources include transcripts of Comission meetings, transcripts of telephone voice recordings from the NRC Incident Response Center (IRC), contemporaneous notes written by the NRC staff or Commissioners, and memoranda written since the accident. All of these source documents have been made available to the Presicent's Comission. For the sake of brevity, the contents of the transcripts, notes, and memoranda have been sumarized in constructing the chronology to highlight the hydrogen flamability concerns.
79102 4 0 / L /
2226 128
/.
Mr. Stanley M, Gorinson 2
September 6, 1979 In addition to such documented entries, the chronology contains a number of
" recollections." The only back up sources for the recollections are the minds of the individuals to whom they are attributed.
The recollections were given to me in handwritten notes or in conversations to fill in important blanks in ;he chronology.
I made only a limited personal review of the transcripts of the IRC voice recordings in constructing and editing this chronology. That review was used to corroborate some of the significant milestones.
Where differences in substance were identified between the notes, memoranda or recommendations of two contributors, I called the differences to their attention but did not intervene to require their resolution.
It is likely that remaining differences are caused by irreconcilable differences in memory or by the confusion in the IRC from March 29 through April 1 that was generated by poor ' communications and poor crisis management.
With these caveats, I believe the chronology provided in Enclosure 1 identifies the origins of the concern of the agency with the potential flammable nature of the hydrogen in the reactor coolant system ~at TMI-2, the sources and nature of the expert advice sought by the agency in dealing with this concern, and the key decisions reached on March 31 and April 1 by the Commission and its principal staff.
Sincerely, Roger J. Mattson, Director Lessons Learned Task Force
Enclosures:
1.
Chronology of TMI-2 Hydrogen Subble Concerns 2.
Memoranda commenting on first draft of chronology 3.
Memoranda cormienting on final draft of chronology 4.
List of employees given an opportunity to review and comment on final draft.
cc: NRC Public Document Room All persons listed in Enclosure 4 All persons named in Chronology Mitchell Rogovin, NRC Special Inquiry 2226 129 William J. Besaw, DOC
~
CHRONOLOGY OF TMI-2 HYDROGEN BUBBLE CONCERNS Thursday, March 29, 1979 1800-2200
- Lauben (recollection) - Mattson, Novak, Minners, Israel, Lauben at IRC.
Information from site indicates unusual " softness" of primary system when attempts were made to depressurize.
Discussed possible sources for gas bubble (zirconium - water reaction, radiolysis, steam formation).
Estimated radiolysis from TMI FSAR data.
Called Matt Taylor on same subject.
about 2030
- M. Taylor (memo) - I received a cali 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 hydrogen if TMI-2 reactor was to be reduced 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 hydrogen estimates was at Bethesda office, but that he'd try to recall work of approximately 10 years ago and get back to HQ-IRC shortly with an estimate.
about 2200
- M. Taylor (memo) - I called Bethesda HQ-IRC (Minners/Novak et al.) with a back-of-envelope estimate for radiolytic hydrogen generation considering near-atmospheric pressure levels and non-boiling bulk coolant temperatures.
These estimates made at home relied on past experience and analysis, recall of ORNL experimental work and results, ORSORT notes of 1963, MIT hand-book on Reactor Safety (T. Thompson et al.) and extrapolations to and assumptions about TMI-2 conditions.
The estimate was roughly 1.4 SCF of hydrogen per hour for these conJitions, but HQ-IRC was advised to use a 1-2 SCF of hydrogen per hour range because of considerable uncertainty about actual TMI-2 fuel conditions and fission product releases to coolant, etc.
Taylor also advised that if HQ-IRC wanted better estimates and more detail on radiolytic hydrogen behavior, they should make contact with Dr. Bud Zittel of ORNL, or possibly Prof. 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 approximately 10 years ago.
Evening
- Novak (memo) - With regard to any information I may have received from S&W regarding the presence of free oxygen in the vessel, I have no recollection of any information transmitted to me on this subject.
I do recall having several conversations with B&W personnel during the evening hours of March 29 and for the first few hours of March 30 (before leaving for TMI-2 site) regarding a variety of subjects, but primarily concerned with the state of core coolaaility and the size of the gas bubble
}
A s
. Thursday, March 29 (cont'd) inside the reactor coolant system.
My personal recollection is that the members of the staff were evaluating the pros and cons of maintaining the conditions that existed in the reactor coolant system as opposed to depressurizing the system.
Friday, March 30 Morning
- Mattson (recollection) - in IRC worki.ig on thermocouple data and how to get hydrogen out of reactor coolant system so reactor could be depressurized without interrupting core cooling.
Morning
- Tedesco (notes) - considering problem of how to get gas out without inhibiting core cooling.
Calculated approximately 3
30 ft / day of hydrogen and oxygen at 1000 psi, 275 F from radiolysis (not assuming recombination and therefore conserva-tive).
Tedesco estimated effect of releasing 1500 ft3 of
. hydrogen from RCS (conser.vative estimate of volume) was a 2%
increase in containment concentration of hydrogen.
(Based on COGAP* calculation with G = 0.44 and gamma in core water of 5%).
Morning
- Milstead (memo) - on Faiday, March 30, 1979, Jim Shapaker, Walt Butler and I were requested by Robert Tedesco to try to estimate the contents of a bubble, then reported to be about 1000 ft3 in volume, in the reactor vessel and its projected growth rate assuming radiolysis of the reactor coolant.
We performed analyses of the post-accident generation of hydrogen and oxygen due to radiation induced dissociation of water using the COGAP code.
In addition on March 30, 1979, we gathered all the data we could find on the limits of flammability and detonation of hydrogen-oxygen mixtures and the overpressure effect of hydrogen combustion.
Morning
- Hendrie (recollection) - I had a series of discussions with NRC staff at the IRC - notably Denton - on the reactor condition, the releases, etc.
During one discussion with Denton on the reactor condition, which included the estimate of a noncondensible volume in the system of about 1000 ft3 (presumably hydrogen from a large metal-water reaction), I speculated on the radiolytic decomposition rata and on whether free oxygen was being generated and going into the bubble.
My initial thought was that the net evolution rate of oxygen was probably small, due to the recombina-tion (or back-reaction).
I recalled that a hydrogen gas overpressure is used in PWR's to inhibit net oxygen evolution in normal "C0 GAP is a computer code for calculations involving hydrogen-oxygen concentrations within reactor containments.
It is used by the Division of Systems Safety in audit calculations performed in review -of power reactor license applications.
See Appendix A to Standard Review Plan Section 6.2.5.
2226 131
o t'
as 3-Friday, March 3_0 (cont'd) operation, and that the effect was probably going on in the present accident condition.
However, I wanted an estimate of the next oxygen evolution rate and asked Denton to put some people to work on it.
I later repeated this request to other staff members.
I also asked for estimates of the flammability limit and the detonation limit (the lowest oxygen concentration, in hydrogen-steam, for upward flame propagation and for an explosive mixture).
Midday
- Denton (memo) - My recollection is that Chairman Hendrie was the first to call my attention to the possibility of combustion of the hydrogen within the reactor vessel.
Conversation took place by phone on Friday, March 30, sometime after I had arrived at the site.
I am, fairly certain it occurred after I had been made aware of the pressure spike from hydrogen burning within the contaiment.
I recall that I first heard about the spike while in a car proceeding to the helicopter.
Midday
- Tedesco (notes) - calculating rate of growth of gas volume by radiolysis using conservative estimate of source terms because of incomplete information of actual THI-2 situation.
1240 Mattson telecon with Hendrie and other Commissioners (Comm. transcriots) - Mattson summarizes thermocouple data and their implications for staff's earlier conclusion of extensive core damage; reports learning earlier that morning of containment pressure spike on Wednesday afternoon and staff conclusion it was hydrogen explosion; reports method of measuring volume of bubble in vessel and present size of bubble; concludes that the bubble is mostly hydrogen; indicates that radiolytic' decomposition would be very small, therefore bubble mustchave been caused by considerable amount of metal-water reaction; reports difficulty in finding ways to get rid of bubble without uncovering the core; expressed concern that bubble could grow by radiolysis and eventually uncover the core.
about 1540 Hendrie telecon with Thornburgh (Comm. transcript, oages 126 and 127) question from the Governor's staff:
Phone voice:
What are the potentials for an explosion that would rupture the core? Rupture the vessel?
Chairman Hendrie:
There isn't any oxygen in there to combine with that hydrogen so the answer as far as I know is pretty close to zero.
2226 132
. Friday, March 30 (cont'd) 1600
- Lanning (memos) - requested by Ron Scroggins to join himself, Stan Fabic, and Pete Anderson to go to Bethesda concerning accident at TMI-2.
Briefed by R. Budnitz concerning existence of bubble in reactor vessel.
Presented data of pressure versus change in pressurizer level and change in incore temperature measurements.
Bubble size was approximately 1000 cubic feet @ 1000 psi and 280*F, and increasing.
Concerned that core would uncover due to growth.
Participated in performing heat-up and boil off calculations for core.
about 1828
- Hendrie telecon with McCormick (Comm. transcriot, page 192) -
Congressman McCormick apparently asked if the hydrogen in the vessel could react.
Hendrie replied:
Chairman Hendrie:
No, because we'.re only at a thousand pounds.
That will be one of the things that people will be looking at, Mike.
I don't know -- I don't know -- well I ought to be getting an update from the site at any moment now.
I'm not sure that -- I think the reactor situation will keep it in this state for another day or so probably while we try to think through very carefully the, you know, the route out from here.
I don't think, you know, there isn't anything in the core it can react with.
You know, ha?; No.
There's either none or very little, because the hydrogen got there from a metal-water reaction and you don't get, it isn't a radiolytic bubble.
about 1930
- Commission discussion of hydrogen in vessel (Comm. transcript.
pages 217 to 225) - Hendrie answers Bradford question on why reactor won't go cold in its present situation:
Chairman Hendrie:
The problem with this thing is that --
I'll get to Roger and his troops later tonight.
I want a calculation of the radiolytic disassociation rate.
At the moment, we've got a hydrogen bubble with some steam --
maybe some steam in it in the head of the vessel.
It's probably pretty pure hydrogen.
The reason is that the evolution is from a metal-water reaction in which you just get hydrogen, you don't get anything else in a gaseous form.
There are two other ways that you get hydrogen in these situations, however, and the one which is of concern is the radiolytic disassociation of water, just ionization; just ionizing the particles of water gives you hydrogen and oxygen.
2226 133
i Friday. March 30 (cont'd)
Now some of the oxygen will trap out as oxide on the structure but some of it will work its way back up.
So over some period of time which is probably of the order of many days or a week or weeks, you're going to begin to get enough oxygen up in there to worry about the thing.
And if there's anything I don't particularly think I need at the moment it's flammable - you know, for the bubble to be in a flammable configuration.
This generates a discussion about how long it would take to reach flammable mixture (Hendrie says "a long way out guessing its some days"), how much oxygen would be required (Hendrie says "you need to get up to 4 percent by volume oxygen to have a mixture which is minimally flammable"), and whether there is axygan in the bubble (Hendrie says "there's probably no oxygen up there now, but as time goes on, definitely why you'll keep building oxygen...").
Hendrie concludes this part of conversation by saying that he'll make sure a team is started ~
working on radiolytic decomposition calculations.
2000
- Lanning (memo) - T. Murley.(INEL notes) requested L. Ybarrondo and others at EG&G, Idaho to ascertain the detonation potential of hydrogen gas in reactor vessel (details of request unknown).
after 2000
- Lanning (memo) - W. Lanning and T. Murley initiated Semiscale Test to explore venting of bubble through pressurizer relief valve.
Obtained system volumes and pipe sizes from Ed Kane at B&W/Lynchburg.
Obtained current TMI-2 conditions from Tad Marsh at IRC.
Bubble volume in TMI-2 was 1000 ft, pressurizer 3
pressure 1100 psi and hot leg temperature 280 F.
Noted that pressure surge line had potential for water seal due to geometry layout provided by B&W.
Recollect there was a lot of uncertainty concerning size of relief valve opening.
after 2200
- Lanning (memo) - Reviewed system description and piping diagrams concerning ways to vent bubble.
Reviewed make-up and purification system in attempt to resolve blockage of letdown line.
Evening
- Butler (recollection) and John Weeks, BNL (memo) - Walter Butler of NRC asked me to estimate being possible the build up of hydrogen in the containment by radiolysis of water in a high y field.
I in turn discussed it with Dr. Harold Scnwarz of SNL Chemistry Department.
His rougn guess was that tne hydrogen may build up to several percent whicn should be approaching the ignition point.
The higher the temperature (above 100*C),
however, the greater would be the recombination rate and the less the build-up of hydrogen.
2226 134
Friday, March 30 (cont'd) after 2240
- Hendrie telecon to Eisenhut at IRC (notes and IRC voice transcript) - Hendrie concerned over condition of bubble; Hendrie making calculation that isn't coming out good; Hendrie and Eisenhut estimated volume of helium fill gas in fuel rods; Hendrie says he has asked people to worry about oxygen evolution in the vessel coming from radiolysis; asks Eisenhut to get other people to do a totally independent calculation of evolu-tion rate; Hendrie asks for estimate of detonation pressures; Eisenhut notes his having talked to (Tom) Anderson of Westinghouse to get an independent estimate of radiolysis; Eisenhut says he will also ask Levine and his people to. start working on the problem.
about 2300
- M. Taylor (memo) - took phone call at site from Chairman J. Hendrie, NRC, who asked that the following item be relayed (note on this call passed to D. Ross):
Express concern about oxygen evolution in TMI reactor vessel and possibility of hydrogen / oxygen explo-sion; he asked for these concerns to be relayed to Bethesda staff so they would get moving on an assessment.
2400
- Commission discussion (Comm. transcript, oages 227-229) - After telephone conversation with Stello at site, Hendrie discusses radiolytic decomposition, back reaction in clean and dirty water, change in 4 percent flammability limit as a function of pressure, etc.
Saturday, March 31 0015
- Eisenhut (notes) - told Stello at site that IRC concerned with hydrogen explosion - hydrogen and ox9 gen mixture in dome (of reactor) - notes contain reference to Dr. Zittel of ORNL.
early am
- Hendrie telecen to Eisenhut (notes and IRC voice transcriot) -
Hendrie asks is gas stripped out in dome (of the reactor) or is it going around in loop?
Eisenhut says that Taylor (at site) and B&W are both working the questions on radiolytic evolution of oxygen (and detonation of hydrogen).
0100 - 0200 - M. Taylor (memo) - called Bethesda HQ and relayed to Dr. S. Hanauer the concern about oxygen evolution and the possibility of explosion in the reactor vessel.
Taylor asked Dr. Hanauer to assure staff gave prompt attention to this matter.
about 0200
- Hendrie telecon to Mattson (recollection) - check oxygen addi-tion rate and potential for RCS explosion; Hendrie calculations of oxygen generation rate indicate there is a problem.
Hendrie said he talked to Eisenhut earlier about this problem, but wanted Mattson to confirm that people were working on it.
2226 135
i 4.
o Saturday, March 31 (cont'd) 0200 Minners (notes) telecon to W.
Lanning in RES - Research staff getting calculation started on hydrogen explosion.
Notes contain reference to Dr. Zittel of ORNL.
0200 Lanning (memo) - Received call from W. Minners who requested a calculation of the explosive force of a stoichiometric mixture of hydrogen and oxygen inside vessel.
Assume mixture contents for a 1000 cubic foot bubble at 1000 psi which would produce the largest force.
after 0200 Lanning (memo) - W. Lanning (memory) requested L. Ybarrondo (EG&G) to perform calculation requested by Minners.
after 0200 Lanning (memo) - monitored progress of Semiscale Test.
Trans-mitted preliminary results of first test to B&W and IRC.
B&W requested second test, doubling the size of the bubble and including HPI flow.
0530 Minners (notes) telecon with Jim Taylor of B&W - explosive force of stoichiometric mixture of hydrogen and oxygen (1000 ft3 @ 1000 psi, 280 F, instantaneous burn) is 14000 psi.
0535 Stello telecon to Eisenhut (notes) asks for best expected gas evolution rate; can we get burn in reactor vessel or piping?;
contingency plan.
D. Eisenhut and S. Hanauer tell V. Stello of B&W results for hydrogen burn in RCS (see 0530 above).
about 0700 Lanning (memo) - At request of W. Minners and in coordination with S. Levine, B. Budnitz, T. Murley (and I) supplied informa-tion to INEL, Battelle Columbus and Sandia Laboratories to calculate hydrogen burning and explosion potential.
S. Levine transmitted results (of the Semiscale test) to IRC.
Assisted in evaluating various methods for scavenging hydrogen from primary coolant system.
e&rly a.m.
Budnitz (recollection) - In conversation with Saul Levine and Tom Murley of RES, either late Friday or early Saturday, the following divisions of responsibility were arrived at.
All tasks were to be carried out by contact with contractors and consultants around the country.
I was to be in charge of working out at what level of oxygen in pure hydrogen the threshold of combustibility would be reached, and at what higher threshold the explosion possibility would set in.
I was then to be concerned with the properties of a fast combustion event and of an explosion, such as the duration of and strength of the pressure pulse inside the TMI vessel from such an event.
I was also to be concerned with finding any possible mechanisms that might set off such a combustion or explosion event inside the primary TMI vessel.
Finally I was to try to find experts 2L226 136
a Saturday, March 31 (cont'd) who could suggest and evaluate methods (using chemicals or physical means) to remove or decrease the hydrogen within the primary system.
I recall that Tom Murley undertook the work with Wayne Lanning to study the feasibility of hydrogen removal out the pres-surizer relief valve.
This last resulted in performance of a quick experiment early Saturday morning at Semiscale at Idaho National Engineering Lab, and another on Monday morning, April 2.
I recall that beginning on Saturday morning Levine and Murley undertook to contact experts on the issue of how much oxygen build-up there would be in the primary system, including the crucial factor of oxygen recombination.
after 0800
- Lanning (memo) - W. Lanning (memory) assisted R. Budnitz in.
evaluating various. methods for scavenging hy'drogen from primary coolant system.
Discussed Minners' request'with S. Levine, R.
Budnitz and T. Murley.
1030
- Hendrie telecon to Mattson (Comm. transcript and IRC voice transcript) - acknowledges that Eisenhut had passed information to Commission from B&W about hydrogen burn in reactor vessel (see 0530 above), and asked about oxygen generation rate and Westinghouse calculation; concerned about rapid approach to flammability.
Hendrie asked Mattson to put pressure on getting answer.
about 1035
- Commission discussion (Comm. transcript) - Hendrie reports to Commissioners that Denton is working on bubble problem.
1100
- Lanning (memo) and Noonan (recollection) - V. Noonan contacted B. Saffel (EG&G) requesting status of finite element reactor coolant system stress model if needed for a hydrogen detonation calculation.
after 1100
- Lanning (memo) - Transmitted preliminary results of Semiscale test to B&W (Bob Jones).
I recall S. Levine discussing results with someone at IRC.
Discussed results of test with J. Cudlin (B&W) and calculation performed by B&W.
am
- Budnitz (memo) - I worked heavily on Saturday and Sunday on the question of understanding the issue of hydrogen combustibility and kinetics in a reactor vessel such as at TMI.
On referral from Richard Garwin of IBM, I called Dr. Harry Petschek of AVC0 Everatt Research Laboratory on the morning of Saturday, March 31, finally reaching him at home in late morning.
He responded 2226 137
Saturday, March 31 (cont'd) immediately by indicating that he and some colleagues could assist in understanding the issue of hydrogen combustibility and combustion kinetics in a reactor vessel such as at TMI.
Later that day and through Sunday, April 1, I spoke, two or three times, to Dr. Petschek and one or two of his colleagues.
I was their sole NRC contact as far as I know.
They worked on the question of what concentration of oxygen in pure hydrogen would be the threshold for combustion, particularly at the temperatures and pressures thought to be present at TMI (about 1000 psi at many hundreds of degrees F), and reported back sometime Sunday on those.
Dr. Petsenek also referred me to Dr. Bernard Lewis in Pittsburgh, who turned out to be a highly-regarded expert in just these same issues.
I finally reached Dr. Lewis on Sunday morning, April 1 (see below).
Twice during this period (Saturday, March 31) I talked with Dick Garwin about hydrogen combustion.
He gave me insights into how important the back reaction is in a proper calculation of the pressure pulse during a fast burn or detonation of hydrogen in a vessel like the TMI reactor vessel.
am
- Budnitz (memo) - All day Saturday I worked, off and on, on the idea that a snake-like device might be obtained which might be inserted into the primary system to remove the " gas bubble" Dr. Richard A. Garwin of IBM first suggested this idea to me.
I telephoned Dr. Heinz Heinemann of Lawrence Berkeley Laboratory on this subject, and on his referral to Mr. Joseph Penick of Mobile Oil.
Later that day, Saul Levine contacted Edward Mason of Amoco on the same subject.
Although much effort was spent on the part of many people in those companies, and there were many telephone calls back and forth between NRC (me) and various people, neither contact ultimately resulted in anything of use to us.
I contacted Mr. Penick on Saturday morning, March 31.
He said that he thought Mobil could assist NRC with advice on the availability of snake-like devices to extract gas from a TMI-like pressure vessel.
He called back later during the weekend (I recall his return contact as occurring on Sunday, April 1) and indicated that devices such as we sought were not readily available in the Mobil Corporation, and unlikely to be available elsewhere in the petroleum industry.
The problem was that the path into the reactor vessel from the outside to the upper dome was too tortuous for the use of the devices that did exist, and the fabrication of a special device would be quite difficult.
I believe that I was Mobil's sole NRC contact on this subject.
Our (negative) results were communicated from time to time to the IRC people, mainly to R. Mattson and O. Eisenhut in my recollection.
2226 138
t
. 4 Saturday, March 31 (cont'd)
- Budnitz (memo) - As a subsidiary activity on Saturday and part am of Sunday, I attempted to find experts around the country who might suggest various chemical means to remove hydrogen from the primary pressure vessel.
I first called Dr. Heinz Heinemann of Lawrence Berkeley Laboratory, in the morning of Saturday.
Dr. Heinemann is a chemical engineer at my former laboratory in Berkeley and is a colleague and friend there, who spent most of his life working for Mobil Oil Corporation.
Dr. Heinemann discussed with me the question of addition of catalytic chemical agents to decrease the hydrogen in water solution.
Dr. Heinemann gave me the names of several catalysis chemists who might have expertise in this matter, and also enlisted the advice of two Berkeley colleagues.
We talked several times over the weekend of March 31-April 1, but I learned sometime on Sunday, April 1, that this problem was being. attacked by engineers at the GPU Service Corporation, and I turned'over to Bob Cutler at GPUSC the names of experts I had turned up.
am
- Budnitz (memo) - Dr. Laura Cherubini called me on her own from
'her home in Billerica, Massachusetts, on Saturday, March 31, with a suggestion of biological / chemical means to reduce or eliminate hydrogen dissolved in the reactor coolant water.
I do not know how Dr. Cherubini received a reference to me.
The method was to use algae that trap hydrogen from solution by presence of free electron acceptors.
Since I was not expert in this matter, I turned it over to others at NRC for follow-up.
However, by the time anything more could be done with this suggestion, the perception of the importance of a " hydrogen bubble" had diminished, and I think that no further follow-up occurred.
1050
- Mattson (notes) telecon with Tedesco - Discussed results of B&W explosion calculation (see 0530, above).
Mattson listed questions for Tedesco to ask of Westinghouse (and KAPL).
They were (1) evolution rate, (2) how soon flammable, (3) is oxygen stripping out and going into dome, (4) is oxygen staying dissolved, (5) what does it mean as we go to flammability limit, and (6) how does flammability limit change at high pressure.
Westinghouse (Bill Brown) estimated that at 3 days the total gas generation by radiolysis will be 7700 scf.
- Mattson (notes) - told Tedesco to go to Brodsky to get Naval am Reactors nelp on hydrogen and oxygen problem after 12 noon.
Case had suggested to Mattson that Brodsky should be asked to help on this problem.
Levine (memo) - I spoke with Robert Ritzmann of Science Applica-am tions concerning hydrogen and oxygen generation rates in TMI-2 vessel in the period March 31 - April 1 (starting Saturday a.m.).
2226 139
. Saturday, March 31 (cont'd)
He informed me that although one could calculate an increase of 1% oxygen per day v'thout considerations of a reformation rate of hydrogen and oxygea due to bubble back pressure, that the 1%
rate was probably too high.
He also said that he felt the rate was probably no higher than 0.1 percent per day and could be zero, but that he did not have the data to calculate an explicit rate.
I spoke with Dr. Kouts of BNL several timas on Saturday and Sunday concerning the possibility of a hydrogen explosion in the reactor vessel.
His view was that this would not be likely.
He referred me to Harold Schwarz (on Sunday - see 1500 hours0.0174 days <br />0.417 hours <br />0.00248 weeks <br />5.7075e-4 months <br />) as a source for precise information.
am
- Noonan (memo and recollection) - The Engineeri g Branch of 00R contributed in the review and eva.ation of two main issues regarding the TMI-2 event:
- 1) Potential overpressure within the reactor coolant system due to a postulated detonation of the hydrogen bubble, and 2) the determination and specification ou reactor vessel pressure-temperature limits for various postulated cooldown transients. We did not keep a log of our activities, however, senior members of our staff worked a number of evenings and several weekends as well as regular hours in late March and'early April on these issues.
While we were of the opinion (Saturday afternoon) that the hydrogen could not explode due to the 3arcity or absence of oxygen (see excerpt of memo by W. Hazelton, below), we were directed (by Darrell Eisenhut) to assume specified hydrogen /
oxygen ratios and determine detonation pressures.
The actual calculations were performed for us by Dr. Norman Slagg and his staff at USA ARRADCOM, Oover, N.J. who also hat the results confirmed by Lawrence Berkeley Lab., University of California (see Attachment 2).
The results of these analyses are in our files. We also had several phone discussions with B&W regarding this matter.
EB personnel evaluated the dynamic response of the reactor vessel to the postulated hydrogen detonations.
Noonan does not recall to whom he passed his and Hazelton's concern that Ritzman was in error about the possibility of oxygen being generated.
He remembers talking to Research people, with whom he was in close proximity in the Maryland National Bank Building Of fices of NRC, and he recalls talking to NRR people by telephone who were located in IE offices just outside the IRC, but he doesn't remember who, specifically, he gave the message to on Saturday afternoon that he believed Ritzman was wrong.
Although Noonan felt that there would be no net oxygen generation in the TM!-2 vessel, he knew that others were doing more sophisticated calculations.
Therefore, when 2226 140
. Saturdsy, March 31 (cont'd) asked to do the explosion and stress calculations for the reactor coolant system, he and his people proceeded with Dr. Slagg (see below, Saturday evening) to answer what they thought was a conservative question of "what if a flammable or detonable mixture is reached?".
- Hazelton (memo) - Because I heard that there was a hydrogen am bubble in the reactor vessel, I wanted to evaluate the possibility of hydrogen damage to the reactor vessel material.
After coming to the office (about 9:00 a.m.) and checking information in my files, I concluded that there would be no problem in the near term, but this was based on information about 15 years old.
Therefore, I decided it would be prudent to check with experts in this field.
I called Dr. John Weeks of Brookhaven and Richard T. Begley of Westinghouse, explained the situation and described the conditions.
They both called back after several hours and-confirmed that my analysis was correct.
Mr. Begley reminded me that Dr. Shewman is also particularly knowledgeable in this area, and suggested that I check with him, which I did.
Dr. Shewman called back after about tnree hours and again confirmed my assessment that the specific alloy used in the reactor vessel - (Manganese Moly)
-is resistant to hydrogen damage, and that no bad effects would be expected unless the pressure and temperature were significantly increased for long periods of time.
In parallel with this activity, I was helping other members of the Engineering Branch in the assessment of effects of a possible explosion in the reactor vessel.
Input.to us included the percentage of hydrogen, oxygen, and steam in the bubble.
I expressed concern that the oxygen level assumed was far too high, and in fact, I believed that it would be negligible, and no explosion should be postulated.
I asked Mr. Noonan to find out why high oxygen levels were being assumed.
He found out (from Tom Murley) that a man named Ritzmann was doing the calculations, and obtained his phone number.
I called him (about noon), we discussed the approach he was using, and I expressed my concern that no credit was being taken for recombination in the dissociation calculations.
He referred to some old work done by Fletcher and Gallagher that I was not familiar with.
I then decided to check with the man they had reported to, Paul Cohen (ex-Westinghouse and Bettis, retired),
and John Weeks of Brookhaven.
They both confirmed that the high hydrogen overpressure would drastically inhibit the dissociation production of oxygen, and in fact, one way to remove the hydrogen might be to add oxygen to the water to
" getter" the hydrogen.
2226 141
. Saturdsv, March 31 (cont'd)
I relayed this information, including recommendations to check with P. Cohen through Mr. Noonan to the group responsible, but apparently I did not succeed in changing anyone's mind, because for several days I kept hearing on television that the reactor vessel was in imminent danger of blowing up because the oxygen level was increasing to the danger point.
I was not pleased, am
- John Weeks, BNL (memo) - Warren Hazelton asked me what information I had on tne thermocynamics and kinetics of the reaction of hydrogen at a high temperature and pressure inside the reactor vessel on the possible decarburization of and methane formation in the vessel mater # 11.
I discussed this subject wth David Gurinsky and J. Chow of 8NL, M. Gensamer, Professor Emeritus at Columbia and A. Ciuffreda of Exxon Research.
The stainless steel cladding on the inner surface of the vessel would be a partial barrier to hydrogen provided it were intact.
There is enough of a chance of a flaw in this cladding, however, that no credit should be taken for it in estimating the performance of the reactor vessel material.
The reactor vessel is made of a pressure vessel steel (ASTM A-533-B) which contains 1% Mn, 0.5% Ni and approximately 0.5% Mo.
The oil industry is con-tinuously concerned about hydrogen induced decarburization of steels in their refinery equipment.
They have prepared a graph stating the safe temperature and pressure for steels (Nelson Diagram) in the American Petroleum Institute report API-941, which was most recently modified in 1977.
A steel of the composition used in the Three Mile Island vessel should be safe from decarburization by 1000 psi of hydrogen at temperatures up to 7000 F for indefinite use.
Exceeding this temperatere or pressure for short periods would not cause serious damage as there is a definite incubation time, of a matter of several days, before problems begin to develop.
Mo appears to be even more effective than Cr in retarding this decarburization although the reasons are not clear.
The same steel without the Mo would only be safe up to 500*F at 1000 psi of hydrogen.
I think the upper part of the reactor vessel should be carefully checked for any possible damage from decarburization prior to its return to service.
A copy of the curve showing this relation-ship as revised in 1977 is appended to this memorandum.
Hazleton also asked whether radiolysic of the water within the vessel could add oxygen to the hydrogen gas bubble.
In my opinion, it should not.
Radiolysis of water proceeds by a complex chain reaction and can be prevented even by a small overpressure of hydrogen in an operating PWR.
The high hydrogen pressures over the coolant at Three Mile Island should totally prevent oxygen formation.
In fact, Harold Schwarz stated it may be feasible to remove the hydrogen by simply adding oxygen slowly to the coolant; this could, admittedly, be risky.
I
- 2226, 142
. Saturday, March 31 (cont'd) think we should be very careful not to use chemicals such as sulfate or sulfur bearing compounds to react with the hydrogen since these could be reduced by the excass hydrogen to sulfides which are very harmful to a number of the materials in the system, especially the Inconel steam generator tubes.
It might complicate the return of the unit to service.
I recommended that a nitrate (such as potassium nitrate) be used if one wished to go by this route.
However, I think the best means of aydrogen resoval would be through venting it from the primary
'colant into the containment where it can be recombined with xygen.
1130
- Gilinsky (Comm. transcript) - major hydrogen problem in the pressure vessel.
1145
- Gilinsky (Comm. transcriot) people in IRC talking about 10%
145
- Commissioners (Comm. transcriot) - discussion of vessel rupture by hydrogen explosions in RCS generating missiles or containment rupture.
1145
- Hendrie (Comm. transcriot) - 1000 cubic feet of hydrogen in vessel, if released to containment, takes you well into the flammability range.
Wants an opinion from the flammability crowd - I've got it out working in the vendor shops and else-where, Bettis and so on.
late am
- Murley (memo) - On Saturday, March 31, we received a question from the staff at the IRC whether there could be sufficient oxygen gas in the primary system to form an explosive mixture and thereby constitute a threat to the reactor pressure vessel.
The answer to this question proved to be elusive.
I discussed this question with staff members from INEL (Sid Cohen, Ron Ayers and Jack Liebenthal).
Concurrently, Saul Levine called Bob Ritzmann of Scierce Applications, Inc., and we understood that Bob Tedesco of NRR was contacting staff at KAPL.
The information I received from INEL was based on reported data from the Cooper plant (a BWR) and wa; scaled down to the power level of 25 MWt.
Their conclusions, which they stressed were extremely conservative, were that the hydrogen btbble contained about 2.2% oxygen and that it would take at least 4 to 5 more days to reach 5% oxygen concentration.
I was la er given some data from the Advanced Test Reactor (ATR) that was purported to support the data from the Cooper plant /
2L226 143
. Saturday, March 31 (cont'd)
I found it very difficult to piece together all of the informa-tion into a consistent story.
The Cooper BWR data were not directly applicable to TMI (a PWR) although there was some boiling in the TMI core.
Similarly, the ATR is a low pressure (150 psi) reactor and was also not directly applicable to TMI.
Late on Saturday evening I received a call from Rob Ritzmann who reported that he was not having much luck in calculating the oxygen concentration, although he believed it was below the flammability limit.
about 1200
- Tedesco (notes) called Brodsky got name and number for Venurs at KAPL.
1200
- Denton telecen briefing of Commission and IRC staff (Comm.
transcript and IRC voice tace) general briefing on status at site by Denton.
Hendrie tells Denton that he talked to Mat (Taylor) and Vic Stel,lo-last night about a concern that he (Hendrie) had about evolving oxygen from radiolytic decomposition into the bubble.
At some of the rates that have been quoted we're either at or getting close to flammability if the 4%
limit is correct at 1000 psi.
We've got people frcm Bettis and Westinghouse working on it.
Hendrie says this must be considered in the sense of what sort of risk it presents and what does it mean about our judgment on advising the Governor either for some further evacuation - limited evacuation measures or a general recommendation.
We didn't cover this scenario with the Governor.
Hendrie says either he or Denton should call the Governor and make him aware of it.
Denton says he calls the Governor every two hours and will follow up with it the next time he calls.
Two concerns are expressed:
- 1) are we already close enough to a situation (hydrogen + oxygen explcsion in the reactor vessel) where we ought to consider some further evacuation and 2) if we get the bubble out to containment, belief is expressed that we'll be flammable.
1310
- Levine telecon to Mattson (notes) - Levine reports that Ritzmann of SAI (formerly at Battelle Columbus Laboratory and a physical chemist used by the Reactor Safety Study for his hydrogen expertise) says 2% oxygen present now, could be 3 depending on g-factor (the rate of production from gammas could be 10 times higher, but Ritzman doesn't believe it).
Ritzman also tells Levine that mixture ignition could occur at 8 to 9% oxygen, with detonation higher by factor of 2 or 3.
Levine also reports that Sid Cohen (INEL) says 5% oxygen in 4-5 days; 900*C required for spontaneous detonation in wet environment; burns first.
- 2226, 144
.. Saturday, March 31 (cont'd) 1400
- Milstead (memo) - On Saturday, March 31, 1979, we contacted GE personnel at KAPL regarding the THI-2 problem.
At about 2:00 p.m.
on March 31, we first talked to the GE personnel. We asked them for information regarding the flammability and detonation limits for oxygen / hydrogen mixtures and pressure effects and Navy data on experimental determination of radiolysis rates.
We csked that KAPL also use their resources to try to estimate the contents of the bubble and its possible growth rate.
The possibility of gumma induced recombination of hydrogen and oxygen was discussed and it was KAPL's initial reaction that recombination in the bubble was not a strong possibility.
1400
- Tedesco telecon to Mattson (notes) - Tedesco reported that Westinghouse (Brown) working and Navy (E. Venurs of KAPL) working on hydrogen evolution rate calculation.
Depressuriza-tion will not get rid of all gas because of high point collec-tion,-describes best conditions for depressurizing.
1406
- Tedesco (notes) - Westinghouse believes oxygen may stay in solution; at low temperatures, the recombination of hydrogen and oxygen is not likely.
KAPL can't preclude free oxygen at this time oxygen and hydrogen generated by radiolysis not likely to recombine if there is " boil off."
Release of all hydrogen in RCS to containment yields 2 volume percent hydrogen increase in contaiment.
about 1415
- Mattson (recollection) briefs Hendrie at IRC preparing Hendrie for press conference.
Described current state of knowledge of IRC staff.
Relied on input from Levine (1310 above) and Tedesco (1400 above).
I do not recall telling Chairman Hendrie of either a plus or minus uncertainty in the preliminary estimates of Mr. Ritzmann that had earlier been provided to me by Mr. Levine.
I do recall telling the Chairman of both the Ritzmann and the INEL estimates relayed to me by Mr. Levine.
1445 Hendrie and Case cress conference (transcriot) present situation is not one to hold for a long time; principle problem at the moment is to work out means of working with gas bubble in the vessel; may be prudent to evacuate as precautionary measure when changing status of reactor to deal with bubble; consider evacuation to distances between 10 and 20 miles; considering ootions for removing gas bubble; concern over potential for explosion of hydrogen in the vessel; working on that problem very intensively; no ignition sources at hand; preliminary indication is that we are some time from any possibility of a flammable condition.
Case recalls elaboration on the risks of the 'rarious options for continued core cooling - depressurizing or not depressurizing.
- 2226, 145
. Saturday, March 31 (cont'd) 1500
- Denton telecon to Mattson (notes) - reports that Stello stopped degassing by Met Ed because of concern with hydrogen addition to containment; Denton concerned with hydrogen in vessel; Novak says GPU wrong, bubble size not decreasing.
1527
- Full Commission meeting (transcript, o. 28) - in IE directors office with Case and Mattson; concentrated on potential for hydrogen explosion in Reactor Coolant System.
Mattson, relying on Ritzman input to Levine, advises that it will require several days to reach flammability limit and he is confident that estimate is not an underestimate of the explosion potential at that time.
Uncertainties in the estimates were discussed.
1600
- Milstead (memo) - At about 4:00 p.m. on March 31, 1979, we again contacted KAPL.
KAPL provided us with the results of experiments run for the Navy to determine the flammability and detonation 1imits for hydrogen / oxygen mixtures in a range of pressures and temperatures applicable to the TMI problem.
Based on their information and our estimates of hydrogen and oxygen concentrations in the bubble, we estimated that we were near the lower flammable limit in the bubble.
KAPL informed us that combustion at the lower flammability limit would result in a very small pressure increase (about a factor of 1.2).
Based on bubble and oxygen growth rates which we had calculated we estimated that it would take about 10 days to 2 weeks to reach the lower detonable limit in the bubble.
KAPL indicated that because of the low temperature in the bubble, they would not predict recombination of hydrogen and oxygen in the bubble.
KAPL indicated that gamma induced recombination would be morr!
likely in the reactor coolant liquid and indicated that they were looking into this.
1605
- Tedesco (notes) telecon with KApL - flammability limit curve supplied by KAPL - in 10 days @ 3.5% steam and 10.9% oxygen, can burn - KAPL agrees with Tedesco radiolysis source term of 28-39 cubic feet per day at 1000 psi.
Appears now nearing burn threshold but at present 4.7% steam and 4.8% oxygen, the mixture cannot burn.
Not close to detonation range for 2 weeks or more - hydrogen and oxygen are not recombining (in the bubble) because of low temperatures - in a nonboiling liquid regime, gamma flux could cause recombination, effective about i month after shutdown if oxygen and hydrogen dissolve in liquid.
Autoignition is a strong function of amount of water vapor.
1605
- Tedesco telecon to Mattson (notes) - answering six questions posed by Mattson at 1050 hours0.0122 days <br />0.292 hours <br />0.00174 weeks <br />3.99525e-4 months <br /> - results of talking to Ernie Vernus of KAPL and Irv Pinkel of NASA - KAPL agrees with con-servative estimate of 28-39 cubic feet per day of hydrogen and 2226 146
. Saturday, March 31 (cont'd) oxygen at 1000 psi by radiolysis (about 13 cubic feet per day of oxygen).
Approaching flammability now (5% mole fraction of oxygen @ 4.7% mole fraction of steam).
Detonation limit 10 days to 2 weeks in future.
Oxygen probably won't recombine, will stay free, might be some recombination due to gamma flux.
20% overpressure if burned at flammability limit.
KAPL had no evidence of spontaneous ignition under present conditions.
about 1625
- Hendrie telecon to Thornburgh (Comm. transcript) - discussion of evacuation and NRC press conference earlier that afternoon.
Hendrie mentions hydrogen flammability problem and notes that it is not near term; "not something that we have to deal with here immediately."
pm Hazelton (recollection) and John Weeks, BNL (memo) - I estimate that as much as 3200 lbs. of Zr may have reacted with water to produce the hydrogen bubble, as'suming it occupied 750 <:u. ft.
at SC9*C and 1000 psi, as stated by Hazelton.
This suggests that over 10% of the Zircaloy cladding in the core was converted to oxide by reaction with the water.
Whether or not the remaining Zircaloy could act to remove hydrogen from the water by hydride formation is not clear.
However, the hydrogen overpressure during normal PWR operation does not cause significant hydriding of the fuel cladding so that hydrogen removal from the bubble by this mechanism seems unlikely.
This hydrogen (10-50cc STP/kg H O) amounts to a maximum of 3.24 lb.
2 in the primary coolant (329,200 kg) so clearly, the majority of the hydrogen bubble came from some other source such as Zr-H O 2
reactions, if the bubble was as large as described by Hazelton on March 31, 1979.
about 1800
- Milstead (memo) - We contacted KAPL again on March 31, sometime after 6:00 p.m.
KAPL recommended that we not try to bleed the bubble from the RCS to the containment but that we continue to degas while maintaining RCS pressure.
They felt there was sufficient likelihood of oxygen recombination in the reactor coolant to continue degassing the coolant through the makeup system rather than release the bubble to the containment.
1800
- Tedesco (notes) - update hydrogen / oxygen calculations with new measurement of 880 cubic foot bubble at 875 psi.
Result is 5.8% mole fraction oxygen and 4.3% r.:ak fraction steam at this time.
(According to flammability limit curve drawn by Tedesco
@ 1600 hrs (notes), this is right on the burn threshhold.)
KAPL prefers to try gamma induced recombination in the core and vessel rather than bleeding hydrogen into containment where oxygen concentration is high.
2226 147
, Saturday, March 31 (cont'd) 1800
- Berlinger (recollection) - Lauben and Berlinger (at site) were asked by Stello to provide Stello and Matt Taylor with general information on hydrogen / air flammability and detonation limits.
Information was transmitted to Taylor and Stello including 4%
flammability limit and 8% detonation limit (most probably 16%
at TMI conditions).
These figures were off the top of the head best estimates based on our previous experience in combustion processes.
Stello was advised to contact Dr. Bernard Lewis (Pittsburgh, Pa.) as a known authority in this area.
1845
- Noonan telecon to Mattson (notes) - vessel explosion calculation by consulta' t Merriman says stoichiometric burn of hydrogen and oxygen (wor,t case) yields 20,000 psi overpressure.
B&W puts in effect of water vapor and calculates 7850 psi total pressure and accounting for enriched hydrogen reduces to 3000-4000 psi.
Estimate 11,000 psi to fail bolts, 12,000 psi to fail head (all static pressures, dynamic could be better or worse).
2023 Associated Press editor's advisory (Columbia Journalism Review) -
Urgent (with nuclear) the NRC now says the gas buoble atop the nuclear reactor at Three Mile Island shows signs of becoming potentially explosive.
A story upcoming.... (Later press accounts say the mixture is now two to three percent oxygen and could be potentially explosive in about two days when it reaches five percent.) AP apparently relied upon three sources in the NRC Staff - Frank Ingrahm, Ed Case and an anonymous source.
Later on, Denton advised the press at 2130 and again at about 2200 in the Governor's press conference in Harrisburg that the bubble was two percent oxygen, could become flammable at 8 percent, explosive at 16 percent, and there were 12 days before an explosion was possible.
evening
- Denton (memo) - I was subsequently (throughout Saturday) briefed often by Chairman Hendrie and by individuals in the IRC on oxygen evolution estimates and the flammability and detonation limits for hydrogen-oxygen mixtures.
The estimates and limits varied with time throughout Saturday.
In my meeting with the Governor and in press conferences on Saturday night, I relied upon the most recent estimates obtained by phone from Chairman Hendrie prior to leaving the site for Harrisburg.
My concerns were considerably heightened by the AP story and I returned to the site to determine if our perception of the situation had in fact changed and asked that plans be developed for the possibility that the bubble could not be removed in the next few days.
2226 148
. Saturday, March 31 (cont'd) early evening
- Stello (memo) - Sometime Saturday, I had a call from someone in the White House inquiring about the AP story that had been released.
I indicated that I did not know the facts regarding that issue and since there was a reference to statements made by Frank Ingram, I suggested the story was most likely released from Bethesda and referred the caller to the Operations Center in Bethesda.
I cannot fix the time, but believe it was probably late afternoon or early evening, Saturday.
Shortly after the telephone call referred to above, I recall speaking to Mr. Case in Bethesda, trying to find out the basis for the concern over the hydrogen bubble.
This phone conversation provided me with the first insights to the concerns held by personnel in Bethesda.
I believe I indicated that I did not share the same concern at that time.
early evening
- Novak (memo) - With regard to any discussions I had concerning the potential for a hydrogen explosion inside the reactor vessel, the only conversation I had occurred the evening of March 31.
The discussion took place between V. Stello and myself at the NRC trailer complex at TMI.
At the time Stello informed me of a concern staff personnel in Bethesda had regarding the potential for a hydrogen explosion inside the reactor vessel.
I recall Stello mentioning he did not believe the concern was real but was unable to convince Bethesda staff personnel to change their view.
evening
- Stello (memo) - During the evening of Saturday, March 31, and morning hours of April 1, I asked Mat Taylor to look into the hydrogen problem from the point of view assuring the need to start the containment atmosphere hydrogen recombiner and the possibiility of adding oxygen to the hydrogen bubble believed to be inside the reactor vessel, such that a burn or explosion of a hydrogen-oxygen (mixture) might result.
evening
- Mattson (recollection and IRC voice transcriots) - told by Noonan that Dr. Norman Slagg could co authoritative vessel explosion calculations.
Asked Noonan to get the work started that night.
about 2000
- M. Taylor (memo) - received verbal request from V. Stello to give thougnt and analysis to following matters and to advise him on these before shift end:
1.
Possible "what if" system scenarios and possible consequence outcomes plus best action courses that might be followed, 2226 149
. Saturday, March 31 (cont'd) 2.
Try to make hydrogen balance calculations to estimate zirconium water reaction magnitudes and where hydrogen sources might be, 3.
Give best judgment on whether or not hydrogen explosion in vessel should be of worrying concern.
Here it should be noted that Taylor recalls discussing with Stello the Taylor estimate of 1.4 SCF of hydrogen per hour (see 2200 hours0.0255 days <br />0.611 hours <br />0.00364 weeks <br />8.371e-4 months <br /> on March 29).
The specific time on March 31 when this information was discussed with Stello is not recalled.
It is believed to have been during the latter part of the prior shift, sometime in the am, e.g., 0400-0800.
2200
- Anonymous (perhaps Don Davis) notes in IRC of conversation with Jim Taylor on miscellaneous toolcs - B&W feels that t'ydrogen recombination is. taking place under gamma flux.
2200
- Novak (memo) - In reviewing the notes that were available in the IRC, there was indication that B&W had discussed free oxygen after 10:00 p.m. on March 31, 1979.
I discussed these not;es with Don Davis, formerly of the staff, and he does recall discussions between staff personnel with regard to the amount of oxygen that might be present in the gas bubble.
He stated that it was possible he had discussions with 8&W (Nitti) regarding this concern.
Don Davis also thought that Steve Hanauer was the staff member with whom he had these discussions.
I talked to Steve Hanauer on this subject and he noted that he first arrived at the incicent center at 2:00 a.m. on March 31 and recalls discussions with Davis regarding hydrogen solubility but none with regard to oxygen.
(Ed. note - The conversations described here by Novak were held by him recently, not at the time of the accident.)
2200
- Berlinger (recollecticnl - Lauben and Berlinger (at dinner) discussed the possibility for a hydrogen explosion in the reactor vessel.
We concluded, based on available information, that the probability of a hydrogen explosion in the reactor vessel was very remote since oxygen levels in the reactor vessel would have been c'epleted during cladding oxidation.
The effects of radiolysis were unknown at that time.
2230
- Levine telecon to Mattson (notes) - INEL says now about 2%
oxygen in RCS, oxygen beirg evolved at about 1% per day.
Using Cooper data scaled to,,TMI-2 decay power level,12 days required from 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> after start cf accident until mixture reaches 6%
oxygen level, probably no detonation source in the RCS.
Ritzmann still thinking and working with AVC0 experts.
4 2226 150
22 -
Saturday, March 31 (cont'd) 2200-2400
- M. Taylor (memo) - in THI-2 control room participated with V. Benaroya et al., on procedures review and progress toward hook-up of the containment hydrogen recombiners.
Sunday, April 1 about 0100
- Murley (memo) - Some time after midnight on Sunday morning, I went to the Incident Response Center where Roger Mattson asked what we were finding.
I told him that the picture on oxygen concentration was confused, but that a conservative estimate seemed to be that the oxygen concentration in the hydrogen bubble was increasing at the rate of 1% per day after reactor scram.
about 0130
- Eisenhut (notes) telecon Ross (corresponding notes from Ross at site appear to indicate Mattson on phone also) - using makeup adds oxygen, maybe replace air with nitrogen or carbon dioxide.
Eisenhut notes say Ross told explosive potential of hydrogen /
oxygen bubble was:
2-3% oxygen now in bubble 1% oxygen added per day.
6-8% oxygen flammability limit 12% oxygen detonation limit.
Have never seen spontaneous detonation.
0200
- Tedesco (recollection) telecon with Taylor at site - discussed hydrogen calculations; Tedesco indicated results obtained in Bethesda and given to site were conservative and there was no.
immediate concern with detonation.
about 0200
- M. Taylor (memo) - contacted R. Tedesco (Bethesda) to find out what were latest assessments from Bethesda regarding reactor vessel hydrogen and oxygen concentrations and explosion potentials.
Tedesco advised that most recent Bethesda calcula-tions indicated the following concentrations in the reactor vessel. (from netes):
3 16.5 ft, oxygen (radiolysis) 3 s103 ft, hydrogen (radiolysis) 3 s615 ft, hydrogen (Zr-water reaction) s765 fta (approximate bubble size estimate)
Tedesco also relayed some KAPL info on flammable / detonable concentrations, and he pointed out present estimates indicated that there would be approximately 10 days before explosive concentrations would.e reacned in the reactor vessel.
- 2226, 151
.. Sunday, Aoril 1 (cont'd)
Taylor recalls Tedesco mentioned some bounding kinds of calcula-tions on the effect of an explosion in the reactor vessel 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.
0300
- Anonymous notes in IRC call from Olshinski at site - relays bubble measurement procedure.being used by Met Ed.
0430 Eisenhut (notes) telecon with Dr. Marty Haas @ Univ. of Buffalo KAPL document as source of hydrogen solubility, detonation limits and peak overpressures.
Eisenhut " passed info to buable group of staff."
about 0800
- M. Taylor (memo) - advised V. Stello as to the following:
1.
Hydrogen balance estimates were very rough, but these suggested a Zr-water reaction magnitude in the range of 25-32%.
[ Note these estimates depended on assumptions about reactor vessel bubble si;:e and on the nature (local vs. free-field) of the hydrogen deflagration observed at roughly 9-10 hours into the accident.
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 expl'osion in the reacto,r 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 approximately 10 years ago.
This work covered various post-accident coolant chemistries, temperature conditions and system configurations--flowing and static.
Impc,ctantly,
those experiments where basic ph chemistries were involved led to highest hydrogen yields approaching 7-8 atmospheres (recall) before recombination terminated the net yield of hydrogen and oxygen by radiolysis (i.e., back and forward reactions were equal).
This suggested no net evolution of oxygen should be anticipated at the actual TMI-2 reactor vessel conditions of 900 to 1000 psi.
Further, the ORNL work with these basic coolant chemistries were assumed to approximate the TMI conditions where NaOH had actually been introduced early ir. the accident.
This ORNL work of approximately 10 years ago also indicated an interesting oxygen scavenging behavior, i.e., oxygen evolution was not 2226 152
. Sunday, April 1 (cont'd) stoichiometric with hydrogen.
This behavior fu-ther suggested that any free oxygen (if it possibly *xisted in the bubble space inasmuch as this might be attributable to the use of non-degassed water from the barated water storage tank) could be subject to the same scavenging behavior.
These above factors when taken with the realization that the hydrogen reducing environment at TMI probably exceeded, by far, the routine reducing environment
.usually used in PWRs, plus the need for an ignition source, led to a judgment that a hydrogen explosion in the reactor vessel was of an extremely remote possibility.]
3.
Tedesco's estimates were describad.
4.
Some possible "what if" scenarios a.1d thoughts were avail-able for discussion when Stello had further time and need to consider these.
early am
- Stello (me^o} - This issue (hydrogen combustion in reactor vessel) was discussed on and off during that period (late March 30 and early April 1) and my best recollection is that it was concluded that no net oxygen would evolve as a result of radiolysis since the back reaction due to the hydrogen over-pressure would force all of the oxygen produced to be recombinec with the hydrogen to form water.
Neglecting the hydrogen overpressure, results of analysis by Mat Taylor suggested an oxygen evolution rate of about 30 standard cubic. feet per day could occur.
With this evolution rate, it would take many weeks to reach a flammable mixture.
Mat Taylor's advice to me was that I should not have any con-cerns for the potential of a hydrogen burn or explosion within the reactor vessel.
I believe I also requested others to seek information from representatives of various companies that were located at the site.
I believe John Collins returned with some information that suggested GPU (and possibly B&W) also did not consider the hydrogen in the vessel to present a hazard from a burn or explosive nature.
0840
- Eisenhut (notes) telecon Vollmer at site - no firm info (at site) on gas in reactor vessel; Taylor thinks not flammable.
about 0840
- Eisenhut (notes) conversation with Mattson - Ritzmann using ORNL and AVC0 and Tedesco using KAPL and Westinghouse estimate:
2L226 153
. Sunday, Aoril 1 (cont'd) oxygen production rate 1% per day by radiolysis, 5% oxygen in pure hydrogen is flammability, 12% oxygen in oure hydrogen is detonation, impurities raise these values, but Budnitz says not much.
Budnitz says that microscopically, at almost any temperature, the mixture might possibly ignite on sharp surfaces so unclear whether KAPL and cthers are right abcut no spontaneous ignition at flammability limit.
Tom Murley quotes Picatiny Arsenal (Slagg) as source on hydrogen flammability.
0900 Berlinger (recollection) - Berlinger at site was asked by Stello/Vollmer to calculate the change in containment hydrogen concentration which would occur if the RCS bubble, assumed to be all hydrogen at 1000 to 1500 ft, 875 psia and 300*F, was 3
vented to containment.
The analysis results were transmitted to Stello/Vollmer and left in 'the NRR trailer files.
The results indicated a change in containment hydrogen concentra-tion from $1.9% to N3.5%.
Since the hydrogen concentration in containment was stabilizing at s2% the possibility of a contain-ment hydrogen explosion appeared remote, unless conditions changed dramatically due to radiolysis.
am
- Murley (memo) - On Sunday morning someone suggested that I collect information on what pressures could be generated if there were a hydrogen explosion in the pressure vessel.
I found that Vinct Noonan of NRR was the focus in NRC for these analyses and I therefore was involved cnly peripherally.
I received information that Dr. Norman Slagg of Picatinny Arsenal had made calculations showing a sharp peak pressure of 12,600 psi for the case of a detonation of a 1000 cu. ft.
bubble containing a mixture of 83% hydrogen, 12% oxygen and 5%
steam.
This pressure appeared to be consistent with information received by Bob Budnitz from Dr. Bernard Lewis of Pittsburgh that pressures could reach 5 times initial pressure for deflagra-tion and 13-14 times initial pressure for detonation (where Po = 1000 psi is the pressure of the bubble and the system initially).
This information was passed on to Vince Noonan and I had little further involvement after Sunday afternoon.
0900 Ma'tson (notes) telecon Dr. Normal Slacq of Picatiny Arsenal -
12% oxygen, 5% steam, 83% hydrogen yields 12,600 psi " striking the wall."
IRC voice transcripts indicate Mattson and Noonan agreed to have Slagg begin these calculations the previous evening.
222'6 154 4
. Sunday, April 1 (cont'd) 0915
- Mattson (notes) conversation with Murley, Levine, Budnitz -
preparing for departure to TMI with Hendrie; nite shift briefing Mattson who has just returned ta the IRC.
Group reached decision on hydrogen explosion potential for transmittal by Mattson to Denton and Stello at site.
Levine or Murley advised Mattson that Ritzmann had talked to B&W, that the INEL use of Cooper data was uncertain, and that the INEL estimate was to be believed more than theoretical approach of Ritzmann.
Group decided upon following:
5% oxygen realistic flammability limit 11% oxygen realistic detonation limit 900 F spontaneous combustion threshold 1% per day oxygen production rate 5% oxygen content @ Sunday am 0915
- Levine'(recollection) - recalls'that the group agreed that these values for'the rate of oxygen production and the present oxygen content were upper bound estimates.
0915
- Murley (memo) - Later that morning (around 9:00 a.m.)
Roger Mattson met with Saul Levine, Bob Budnitz and me at the IRC prior to leaving for the TMI site.
Chairman Hendrie, Commissioner Gilinsky and Commissioner Kennedy came and went throughout this short meeting as I recall.
Mattson summarized the following information as the distillation of all of the input he had received:
Flammability limit 1 5% oxygen in pure hydrogen Detonation limit 1 12% oxygen in pure hydrogen Combustion limit 1 18% oxygen in pure steam Oxygen production rate : 1% oxygen per day in hydrogen /
oxygen bubble Current exygan concentration 5% oxygen in hydrogen bubble 0915
- Budnitz (notes) - Meeting with Mattson, Levine, Murley, and me.
Mattson was about to depart for the TMI-2 site by car with Chairman Hendrie, and he asked for an up-to-date, agreed-upon set of numbers about the " bubble." We all agreed on the following set of numbers, which were written down by me and are in my notes:
1.
Best estimate for flammability limit, pure oxygen in pure hydrogen at 1000 psi = 5% oxygen.
2.
Best estimate for detonation limit, pure oxygen in pure hydrogen at 1000 psi = 12% oxygen.
2226 155
.. Sunday, Aoril 1 (cont'd)
We also agreed that the best estimate for total production of oxygen from radiolysis in tha TMI vessel would be about 5%
oxygen (as fraction of bubble) as of the present time if there were no recombination.
We also discussed the fact that other people among our NRC contractors were actively calculating the true oxygen which would be smaller than the radiolysis production rate because of chemical recombination.
We discussed together that the 5% oxygen / hydrogen ratio was a pessimistic estimate, in the sense that the actual value was surely not larger and might be smaller.
I remember us discussing how probable it was that the number would ultfuately turn out to be much smaller.
I remember that we were not yet sure that a smaller number would result from the accurate calculations underway at that time.
Some difference of opinion existed as to how "sure" we were of what estimates by which experts, and Mr. Levine was more confident than the others that the oxygen would not be a problem.-
I remember that Commissioner Bradford came into our brief meeting just as it was breaking up, and we acquainted him with our discussion.
- a. m.
- Lanning (memo) - Bob Jones (B&W) requested second test'in' Semiscale.
Suggested doubling size of bubble and include HPI flow based on B&W's contingency plan for depressurization.
Remainder of day spent primarily on coordinating Semiscale test results and second test.
Provided answers to various Labs and individuals who were working on hydrogen explosion, degassing, radiolysis and recombination of hydrogen and oxygen (nu notes available).
a.m.
- Tedesco (recollection) telecon to K. Woodward of Pickard and Lowe - called on request of Murley.
Discussed results of radiolysis calculations in containment.
Recall that Woodward's estimates were high compared to those of NRC staff.
- a. m.
- Butler telecon to Tedesco (recollection) - Butler gave results of staff discussion with I. Pinkel aDout hydrogen in containment.
about 1200
- Mattson (recollection) meeting with Hendrie, Stello and Denton at Middletown airport - relayed information agreed to at IRC with Murley, Budnitz and Levine before departure to site.
Stello strongly believed IRC was wrong and that oxygen was being recombined because of high hydrogen concentration.
Mattson and Stello had not talked earlier because of the press of other assignments and different working schedules and agreed that the two different points of view needed rapid resolution.
2226 156
. Sunday, April 1 (cont'd)
President Carter was briefed by Denton and Stello about the hydrogen explosion problem and was told about the uncertainty of staff conclusions at that time.
pm
- Levine (memo) - I spoke with James Proctor of the Naval Surface Weapons Center about the effects of a hydrogen explosion on vessel integrity.
He said the cylindrical portion of the vessel would be subjected to about 6% strain, which should not break it, and that it would also be subjected to a lifting force of about 1.5 x 10s lbs.
He could not calculate whether the main loop piping could hold the vessel down when subjected to this force, since he did not have detailed information on plant layout.
Midday
- Budnitz (memol - On Sunday morning, on referral from Harry Petschek of AVC0 Everett, I reached Dr. Bernard Lewis of Combustion and Explosives Research, Inc., of Pittsburgh.
He acknowledged that he had much expertise on the combustibility of hydrogen and oxygen; indeed, he is the coauthor of a definitive text book on this subject.
He and an assistant, reached at home on Sunday morning, worked through that day and part of Monday, April 2, and gave important advice on the issues that governed the physical behavior of hydrogen and oxygen burning in conditions such as were thought to exist within the primary vessel at TMI.
I was Lewis' sole NRC contact during this period.
He gave information about the mixture of oxygen in pure hydrogen that would be a combustion threshold, talked at length to me about the physical difference between combustion and explosion, and what would be the impact of gaseous impuri-ties including steam.
He reported back his prelim'inary conclu-sions sometime after midday on Sunday, April 1, and his final conclusions in midmorning of Monday, April 2.
He calculated pressure ratios (pressure within a fast burning situation vs.
starting pressure), denotation thresholds, heat release, flame temperatures, and other parameters.
His insight was valuable in providing a perspective on which parameters were, and which were not, important in modifying the result of what was easily calculated using approximations.
Thus the approximate calcula-tions were refined, and the refinements were better understood by me.
Dr. Lewis' best astimate about midday Sunday was that the
" pressure pulse" would be about 5500 psi for a fast combustion event (requires above about 5% oxygen) and about 13,000 psi for an explosion (requires above about 12% oxygen).
On Monday, Dr. Lewis revised the 5500 estimate cownward to about 3200 psi.
2226 157
S
. Sunday, Aoril 1 (cont'd)
Midday
- Lanniao (memo) - Requested and provided information to INEL to perform second test in Semiscale.
Obtained plan from B&W on proposed HPI flows versus time.
Coordinated information to Labs concerning hydrogen explosion, degassing, radiolysis and recombination of hydrogen and oxygen.
Midday
- Budnitz (recollection) - By about midday on Sunday, there emerged a reasonably reliable consensus among our outside expert contacts about two questions:
now large the short pressure pulse might be if a fast combustion event were to occur inside the TMI primary vessel, and at what pressure the vessel would approach its " yield point" and its " ultimate" point, thereby compromising the integrity of tha primary system.
I was responsible for coordinating the forme concern and Tom Murley brought together the information on tne latter.
Our general conclusion at that time was that, for about 1000 cubic feet of pure hydrogen with oxygen just above the threshold value of about 5% at 1000 psi, the " pressure pulse" would be about 5500 psi.
This came mainly from Dr. Lewis of Pittsburgh (on Monday, Dr. Lewis revised his best estimate downward to about 3200 psi).
The " yield point" of the vessel, according to Tom Murley' seemed to be coming out at about 6000 psi.
Both of these numbers had rather large uncertainties, of which I and Murley were acutely aware.
I discussed these rough results with Saul Levine, who suggested that I tell Chairman Hendrie, who was at the TMI site.
I spoke by phone with Hendrie and relayed this to him, expressing the uncertainties to him as well as the numerical best estimates.
This call occurred just prior to my meeting with the other Commissioners, which began at 1350.
I was requested to give, and did give a briefing on the same subject to the other four NRC Commissioners, all gathered together in the NRC Incident Response Center.
This 15-minute briefing was attended also by Len Bickwit (NRC General Counse?),
and about 15 other NRC people.
This briefing can be found verbatim in the Commission transcripts.
about 1345
- Commission Meetino at IRC with Budnitz (Comm. transcript, po.94-116) - Commissioners Gilinsky, Kennedy, Bradfora and Ahearne discuss evacuation scenarios for hydrogen combustion in reactor vessel (pp. 94-99).
Thompson relays info from IRC staff that mixture is then 5% oxygen and flammable.
Budnitz gives briefing on current assessment by IRC staff of bubble situation (pp. 100-116).
He concludes that if a fast hydrogen burn were to be initiated, vessal integrity would be compromised.
Didn't know of any initiation mechanisms.
Budnitz says that 2226 158 Sunday, April 1 (cont'd) during burn, pressure will increase by a factor of 5.5.
Burn will last 10-20 msec.
If 1000 psi before burn, pressure during burn will be very close to yield strength of the pressure vessel.
A little over 10% oxygen is needed to sustain detonation.
In detonation, pressure is increased by a factor of 13.5 - the pressure vessel would be lost.
Budnitz also points out that if the temperature rises to 680*F, the.nixture will go off spontaneously - no ignition source would be needed.
early pm Milstead (memo) - On Sunday afternoon (April 1, 1979), KAPL reported to the NRC staff in Bethesda the results of analysis performed with Naval Reactor water chemistry code.
Using the code and assuming 10% of the core in boiling KAPL predicted a bubble growth rate of 0.4 fts/ day.
If it were assumed the entire core was in boiling the growth rate could be 8 ft / day.
3 The reason for this low bubble growth was that total recomb-ina-tion of the oxygen formed by radiolysis in the reactor coolant was predicted due to the large amount of hydrogen in solution.
KAPL's analysis indicated the buoble contents to be almost entirely hydrogen (from metal water reaction) and indicated a net radiolysis of zero in the reactor coolant for most of the transient.
On this basis, it was concluded that the bubble had not reached a flammable oxygen content and would not be expected to.
KAPL indicated that effective oxygen recombination in the reactor coolant would be predicted for hydrogen concentrations in the coolant greater than 0.1 scc /kg.
They suggested the degassing process be continued and a minimum concentration of 1.0 scc /kg be maintained in the reactor coolant to prevent net radiolysis in the reactor vessel.
On Sunday afternoon (April 1, 1979), we performed a series of COGAP analyses assuming radiolysis in the containment sump only and no recombination of oxygen.
Our analysis indicated 5-day hydrogen production rates from about 600 scf/ day (0.03%/ day by volume in the containment) to about 3600 scf/ day (.21%/ day in containment).
The 3600 scf/ day rate was calculated using the conservative assumptions of Regulatory Guide 1.7 (i.e., G Value of 0.5 molecules /100 EV and a TID release in containment).
Our best estimate calculations resulted in 5 day hydrogen growth rates of 600 to 1000 scf/ day (0.03%/ day to 0.05%/ day ii containment).
These analyses used estimates of fissio9 products in solution which closer matched the RCS sample obtained on March 30, 1979, and a best estimate G Value of 0.33 molecules /100 EV.
Our best estimate calculations compared favorably with estimates of potential hydrogen growth rate calculated by the d
Office of Research.
2226 159
. Sunday, April 1 (cont'd) pm
- Levine telecon to Tedesco (recollection) - Discussed calculations of radiolysis in containment using TIO source term.
Levine advised that estimates appeared high because of use of radiation source term larger than THI-2 sample analysis.
Tedesco directed staff to revise calculation to approximate TMI-2.
pm
- Stello (memo) - I recall outlining for the Chairman (at the site) the basis upon which I did not believe the hydrogen bubble in the reactor vessel could reach an explosive potential.
Basically, I reiterated the results of the reasoning we (at the site) had gone through that morning and previous night.
I requested the Chairman that before any further action be taken on this issue, that I be given some time to contact some other experts to see if I could get additional technical information.
pm
- Mattson (recollection) - worked at site command post following briefing of President to resolve differences in IRC and' site positions on oxygen generation by radiolysis.
about 1430
- Benaroya (recollection) - After working the graveyard shift, woke-up in the motel room thinking about the hydrogen-oxygen problem in the gas bubble.
He tried to call the NRC command center in the trailer, but all phones were busy.
He finally decided to call the TMI-2 control room and got in touch with Norm Lauben at around 1500.
Benaraya explained that normally a hydrogen concentration of 20-40 cc/kg of water is kept in the primary system to eliminate free oxygen.
At the pressure and temperature that exist <3d in the primary system, in the radiation field, 20 cc of hydrogen per kilogram of water is enough to push the reaction towards recombination.
Since we had a large excess of hydrogen, it was very unlikely~ that any free oxygen would be present in the gas bubble.
Benaroya asked that this information be relayed to the NRC trailer.
N.
Lauben called back V. Benaraya at the motel saying that he had relayed the information to Mattson, and Mattson told him that this was being calculated in Bethesda.
pm
- Rosztoczy (memo and recollection) - On April 1 and April 2 of 1979 Brian Sheron, Garry Holahan and myself performed gas bubble size calculations for TMI-2.
The work was done on Don Davis' request, who worked in the Bethesda Emergency Center at the time.
Frank Almeter (EB) was called in to help.
We also had telephone conversations with Ledyard Marsh (00R) and Paul Cohen (retired from Westinghouse) who is a well-known expert on water chemistry for nuclear plants.
Mr. Cohen was very helpful.
2226 160
t Sunday, April 1 (cont'd)
We were asked on April 1 p.m. to review the method used by B&W for determining bubble rize.
Our con:lusion was that the method had two errors:
.nar major error in the solubility term by omitting the correction factor to account for elevated pressure and temperature and a small error in the multiplier in front of the equation.
Both of these are documented in the attached memo prepared by B. Sheron dated April 5, 1979.
During the course of our work we also recognized that the anomalous behavior of the letdown line during the bubble measurements introduced large uncertainties in the bubble size.
We recommended, therefore, to close the letdown line during measurements.
All of this information was communicated to Davis on the evening of April 1 and early a.m. April 2.
My understanding is that the recommendation to close the letdown line during measurements was followed.
All measurements taken late on April l and early on April 2 had the line closed and showed a significantly smaller bubble size than previous measurements.
1500
- Stello (notes) - On April 1, 1970, 3:00 p.m., I requested Bettis Laboratory to evaluate the potential for radiolysis contributing oxygen to the bubble over the reactor core.
The following people participated in the evaluation:
Don Connors, Lou Bogar, Jim Wright, Ken Vogel, and Bill Walker (KAPL).
The following information was provided and was represented as the Bettis Laboratory position.
A report would be prepared if requested.
I indicated that I would let them know if there was a need.
(a) The first question I asked them to consider was if we assumed that the bubble over the reactor core is 800 cubic feet, 1,000 psi and 300*F is it possible for oxygen to be added to the bubble by a radiolysis process?
Answer:
Their best estimate analysis would indicate that no oxygen would be added to the bubble.
The analysis is derived from considering Henry's law; they would expect that under the conditions there would be 900 cc per kilogram STP of hydrogen going into the water.
Based on experi-mentally derived information with a concentration of 2 cc's per kilogram at STP in water, radiolysis would be prevented.
The experimental information was derived from data collected in the 57G prototype program and a reference is cited to data dating back to 1943.
- 2226, 161
., Sunday, April 1 (cont'd)
(b)
I requested Bettis to provide me with an estimate of the radiolysis rate assuming there was no hydrogen over pressure in the bubble.
Answer:
Assuming no recombination was permitted, they calculate that approximately 8.4 cu. ft. per day of oxygen at STP would be generated.
This corresponds to a total radiolysis rate of 29.2 cu ft per day at STP.
The recom-bination rate was based on a g-factor that was experimentally determined from S7G and boiling water reactor data.
These data were stated to be conservative relative to PWR conditions.
The g-factor used was 0.7 molecules of oxygen per 100 EV of gamma absorbed, at 1.5 x 108 MEV of gammas per square centimete'r per second.
They assumed that 1/10 of the gamma's generated in t.he core are absorbed in the core and that 1/.15 of the gammas-absorbed in the core are absorbed by. water.
They have had informal discussions with people like KAPL who independently determined a radiolysis rate in the same ballpark (estimated to be approximately 65 cu. ft per day at STP).
Dr. Connors is going to ask KAPL for their view to see if their evaluation of the problem is the same.
about 1500
- Stello (notes) - On April 1 at about 3:00 p.m., I requested the same information of the General Electric Company (commercial) as I did from Bettis Laboratories.
The GE response was that it is theoretically possible that oxygen could be added to a hydrogen bubble over the reactor core.
However, they did not consider this would be likely and concluded that they believe that an equilibrium condition may now be present. 'They calculated a bounding number for the amount of radiolysis that could take place assuming no hydrogen overpressure.
They estimated that the bounding number is 10 cubic feet per hour at STP but believe this was too conservative since it was based on BWR data (NEDE-13148 Title KR8 Radiolysis Test, Nov. 1970) and that no credit was given for the effects of a back reaction and that the real number is much lower.
They speculated that perhaps there is no net oxygen added.
The following people participated in the evaluation:
Cliff Kent, Jerry Jacobsen, Pat Marriott, Manny Ziegler, and Don Rockwell.
about 1500
- Stello (memo) - (After) I obtained that information (from Bettis and GE)... (I presented it) to the Chairman.
I believe he was persuaded that we need not have a concern for either a burn or explosion of the hydrogen in the reactor vesscl.
Following our discussion, he placed some telephone calls to Washington to discuss this information with fellow Commissioner (s).
Q()
} ()2
Sunday, April 1 (cont'd) p.m.
- Levine (memo) - I also spoke with Harold Schwarz of BNL, I believe on Sunday afternoon, April 1.
He said that he believed that not only would oxygen not be accumulating in the hydrogen bubble, but that whatever hydrogen and oxygen were in the bubble would be depleted at fairly rapid rates.
He said that he would calculate the rates and call me later on Sunday.
On Sunday evening he told us that he had completed his calculations which confirmed that oxygen could not accumulate in the bubble and that it would in fact be depleted.
about 1500
- Budnitz (memo) - On referral from Dr. H. J. Kouts of Brookhaven, Saul Levine and I contacted Dr. Harold A. Schwarz of Brookhaven.
I am not sure when he was first reached by Levine, but both Levine and I talked to Dr. Schwarz at various times during the weekend.
Dr. Schwarz worked April 1 (beginning about 3:00 p.m. ) on calculating the production and recombination rates of oxygen in the TMI primary coolant water.
He did these calculations at home mostly, I think; telephone contacts with him during the weekend were at his home.
He reported on the considerations that were involved in his calculations, and ultimate.ly showed definitively that oxygen generation from radiolysis would not result in much oxygen in the gas phase, because of the recombi-nation reaction with the assumed large hydrogen gas overpressure and the associated dissolved hydrogen.
We were apprised of the preliminary results of Dr. Schwarz' work on Sunday afternoon, April 1, in my memory, but it was not firmed up until sometime in the evening that day.
Dr. Schwarz filed a description of his calculation with NRC on April 24.
The April 24 note to me describes well that the calculation is tricky and involves tracking down a number of chemical parameters and calculating several reaction rates.
Impurities within the TMI cooling water were important enough that information taken from con-ditions of normal reactor operations could not be relied upon.
1552
- Commission meeting at IRC (Comm. transcript, oo. 131-144) -
Commissioners Kennedy, Bradford and Ahearne discuss evacuation scenarios for hydrogen combustion in reactor vessel.
Apparently reaching a consensus to recommend evacuation that afterncon because of combustion potential.
They expressed concern over obvious differences in data coming from the staff.
They decided to advise Hendrie at site that they were concerned there may be need to consider evacuation.
Kennedy ar i Ahearne leave at 1617 hours0.0187 days <br />0.449 hours <br />0.00267 weeks <br />6.152685e-4 months <br /> to talk to Hendrie on the telephone.
- 2226, 163
- i..
Sunday, Aoril 1 (cont'd) about 1620
- Kennedy telecon with Hendrie (Ahearne recollection and notes) -
Kennedy relays to Chairman the advice of the three Commissioners at Bethesda (Kennedy, Bradford, Ahearne) that, based on Budnitz reports, they recommend that, unless people on site have better technical information, NRC recommend Governor Thornburgh advise a precautionary evacuation within two (2) miles of the plant.
This would be precautionary, just as the Friday evacuation advisory.
Hendrie informs Kennedy that oxygen not a problem -
the hydrogen in the water would capture the oxygen.
about 1700
- Mattson (notes) telecon to IRC - B&W tells IRC there is no oxygen in bubble.
Salvatore of Westinghouse remembers Bettis data which says that excess hydrogel inhibits oxygen formation by radiolysis.
Ritzmann tells IRC t.'.at one to two percent per day oxygen generation rate i-s with no accounting of inhibit'on, and hydrogen inhibits.
Levine says to use 0.1% per 3ay instead of earlier 1%. -L.evine also advises previous INEL estimate in error by factor of 10 too high.
1800
- Mattson (notes) telecon with IRC - Budnitz reports to Mattson that answers from experts range from 0 to 1% oxygen per day.
Budnitz reports that Herb Kouts of BNL thinks oxygen generation rate is small; ph is an important parameter; revised INEL calculation says 1% oxygen is now present; current estimate of IRC is less than 1% oxygen; but still working to finalize position.
about 1900
- Mattson (recollection) - Mattson and Hendrie met with Industry Advisory Group in Middletown National Guard Armory.
Ed Zebrowski of EPRI' expressed strong dismay with NRC for having incorrectly judged the hydrogen explosion potentiaT by not quickly under-standing that oxygen could not be evolved by radiolysis in a hydrogen rich environment.
Monday. Aoril 2 am
- Thadani (memo) - If my memory is correct, on Monday, April 2, I developed criteria (at the site) for the rate of degassing and the process limits that were to be maintained.
Otherwise, degsssing was to be discontinued.
about 1000
- Lauben (recollection) - Radiophone from control room to Mattson (recollection) - Lauoen has been following GPU bubble size measurement and analysis.
Expressed confidence that bubble size was decreasing dramatically.
222.b '} b
Monday, Acril 2 (cont'd) 1100
- Mattson (notes) for Denton Press Briefino - For the past several days we have been studying the potential hazard of the gas bubble in the reactor.
There has been concern that the bubble could reach a flammable condition if oxygen were being added to the hydrogen.
Our earlier statement on the effects of bubble flammability on the safety of the plant were primarily based on preliminary theoretical analysis by the technical experts.
There is also some experimental data for these conditions.
After several days of intensive consideration of the problem by these experts, we now believe that the hazard of hydrogen burning in the reactor is not nearly as severe as earlier indicated.
We have much higher confidence today that there is no near term hazard from hydrogen burning.
There is one piece of new information from the plant that contributes to our present state of cautious optimism in this area.
Measurements of the size of the bubble over the last 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> indicate that it is not as large as originally estimated, and it may be continuing to diminish.
We are studying this new information closely to determine the effectiveness of the degassification process that has now been underway for several days and the confidence that can be placed in the bubble measure-ments.
Bubble Size Encouraging signs that it is smaller than earlier measurements indicated.
measurements are better degasifyin~g thru-recembination letdown seal leakage in pump Bubble Content Our present understanding of the gas evolution and decay process says the rate of addition of oxygen is not what we originally estimated.
There may be an equilibirum condition in which there is little or no net generation of free oxygen in the reactor or even recombination of any excess oxygen (i.e.,
either slightly positive, zero or negative).
2226 165 Combustion Limits Our earlier estimates were conservative, but there is some uncertainty in the available data, so staying with the 5% and 11% limits.
s Monday, April 2 (cont'd) 1115
- Denton and Mattson oress conference in Middletown (transcriot) -
Measurements show dramatic decrease in bubble size; don't want to be stampeded into concurring bubble actually this small; certainly reason for optimism; oxygen generation rate described yesterday by Denton was too conservative; oxygen evolution rate is much less than one percent per day; we think it is safer than we did yesterday; hydrogen backpressure inhibited formation of oxygen by radiolysis.
1200
- NRC Preliminary Notification PNO-79-67H, Paragraph Two on Plant Status at 12 noon 4/2/79 states - Further analyses and consultations with experts have led to the development of a strong consensus that the net oxygen generation rate inside the noncondensible bubble in the reactor is much less than originally conservatively estimated.
Also, measurements at the plant appear to indicate that the volume of gases within the bubble is being significantly reduced.
Further developments are being '
closely followed to confirm these favorable indications.
Midday
- Lanning (memo) - Coordinated results of second Semiscale test to B&W and IRC.
B&W indicated that they were going to revise H.PI flow rates in contingency emergency plan to vent the bubble as the result of tests.
Discussed analytical predictions of time period to vent bubble in compariton to Semiscale results.
Relocated from MNBB to East-West Towers.
Performed calculations of time period to degas using pressurizer spray.
A lot of uncertainty existed concerning flow rates in pressurizer surge and spray lines and makeup and purification system (coordinated with K. Parzewski).
1220 Commission meeting (Comm. transcriot) - Hendrie tells other Commissioners of the status of the oubble concern at site as described by Denton and Mattson at 1100 press conference.
Concern is very considerably mitigated and on its way to not being of concern much longer.
There has not been any substantial evolution of oxygen at anytime in the system.
2052
- Nitti of B&W written coinion on H,/0, bubble (memo Roy to Mattson) -
includes statement that "A review of the postulated sequence of events on March 28 lead us to conclude that there is no significant amount of oxygen in the bubble that was present in the reactor coolant system of the Three Mile Island Nuclear Plant....
(the) amount of dissolved hydrogen is approximately 50 times the amount required to suppress a net radiolytic generation of oxygen."
gg
ENCLOSURE 2 MEMORANDA COMMENTIriG ON FIRST ORAFT OF CHR0r10 LOGY 2226 167