ML20009F224
| ML20009F224 | |
| Person / Time | |
|---|---|
| Site: | Allens Creek File:Houston Lighting and Power Company icon.png |
| Issue date: | 07/27/1981 |
| From: | Read J Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20009F186 | List: |
| References | |
| NUDOCS 8107300156 | |
| Download: ML20009F224 (12) | |
Text
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07/37/81 UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION -
BEFORE THE ATOMIC SAFETY AND LICENSING BOARD In the Matter of
)
)
HOUSTON LIGHTING & POWER COMPANY )
Docket No. 50-466
)
(Allens Creek Nuclear Generating )
Station, Unit 1)
NRC STAFF SUPPLEMENTAL TESTIMONY OF JACQUES B. J. READ'ON ACCIDENTAL RELEASES OF 133 - XENON-DOHERTY 40 Q:
Will the witness please state his name, place of employment, and duties performed?
My name is Jacques B. J. Read, and I'am employed by the Accident Evaluation A:
Branch, Division of Systems Integration, Office of Nuclear Reactor Regulation, hbfl308shgggp r
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U.S. NLclear Regulatory Commission.
I am a nuclear chemist. A copy of my professional qualifications is attached to this Supplemental Testimony.
Q:
What is the purpose of your testimony?
A:
The purpose of my testimony is to respond to the following contention:
Doherty Contention 40 alleges that, "the doses from credible accidents at ACNGS will exceed 10 CFR Part 100 lim.its because the Regulatory Guide criteria for calculating such doses significantly underestimates the release of Xenon 133, as demonstrated by the releases that occurred during the accident at TMI."
Q:
What is the calculated release of 133-xenon from Three Mile Island using the relevant Regulatory Guide, and what is the estimated release which actually occurred?
A:
This contention is based upon statements contained in " Board Notification -
TMI Releases (BN-79-23)," dated June 27, 1979.
In this notification, it is stated that the 133-xenon release as computed using the instructions in Regulatory Guide 1.4, "Assumpt.ans Using In Evaluating the Potential Radiolog-ical Consequences of a Loss of Coolant Accident for Pressurized Water Reacto s,"
as applied to Three Mile Island, Un~; 2, was 600,000 curies.
The notification also quotes a preliminary estimate of the actual release, made it.srtly af ter the accident and dated April 12, 1979, as being 13 million curies of 133 xenon.
In the months following the accident, all data from all organizations monitor-ing releases were extensively reviewed by both the NRC and others in order to 2
a
estimate more accurately the releases to the environment.
The estimate of
)
J. G. Kemeny et al, " Report of the President's Commission on the Accident at Three Mile Island - The Need for Change:
The Legacy of TMI," dv ed October, 1979, is not expressed as total curies released, but gives dose estimates cc..asponding to about 2 million curies of 133-xenon.
F Rogovin, et al, "Three Mile Island - A Report to the Commissioners and the Public,"
NUREG/CR-1250, dated January,1980, estimated that 2.5 million curries of 133-xenon were released.
Q:
Were any other radioactive gases released from TM1 in amounts exceading those calculated using the instructions set forth in Regulatory Guide 1.41 A:
No.
As stated in Soard Notification BN-79-23, the accidental releases from TMI were virtually all 133-xenon, an isotope which, in the Regulatory Guide 1.4 computations, contributes only a very small fraction of the resultant potential doses.
As also stated in the notification, this 033 composition is that which would be released from fission products which had " aged,"
i.e., in which the precursors of ot ar noble gas isotopes had decayed to comparatively small concentrations.
Q:
Is there a generally accepted explanation for the composition of the gas released from TMI?
A:
Yes.
Such predominance of 133-xenon is wholely consistent with the sequence of events described by Kemeny et al, referenced earlier.
3
l The TMI accident began at 4:00 AM on Wednesday, March 28, 1979.
As reported by Kemeny et al, significant cladding damage had occurred by 6:00 AM, and by 7:20 AM at least a large fraction of the gaseous radio-isotopes originally contained in the reactor fuel had been released 1
l through the pressurizer into the containment building.
The bulk of the radioactive noble gas that was released from TMI into the environment, however, did not leak from the containment building, but from the waste gas system in the auxiliary building.
The gas in this latter system had evolved from reactor coolant water which had been brought into the auxiliary building during the course of the accident.
The xenon in this system was radiogenic, i.e., it had been formed by the radioactive decay of iodine isotopes which were dissolved in the reactor coolent, and it escaped through the auxiliary building vent predominantly during Thursday and Friday, March 29 and 30, 1979.
, the time of the largest releases, most of the noble gas fission product which had been in the damaged fuel rods at 4:00 AM on Wednesday was in the containment building atmosphere, where it remained.
Summarizing this sequence of events, during and following the periods of core damage, noble gases (krypton and xenon) which were released from the fuel. entered the gas phase present within the reactor pressure vessel.
This gas phase, consisting of hydrogen, water vapor, and fuel plenum gas (noble gases fission products and helium), was periodically vented to the contain-Iodine, similarly released from the core, dissolved in the liquid ment.
reactor coolant also present in the reactor pressure vessel.
In effect, the accident acted to separate the iodine from the noble gases due to the vastly different water solubility and ease of chemical reaction they 4
po s a.en. s.
Subst ant.la l.imounts of re.u i nr a on lant. e uni.a in inq ili.su lveel iodine, were bruual t by la llno. into lanks located in the auxill.iry busliling, h
where the iodine transmuted by decay into xenon.
A failure in t he syst em designed to collect this xenon permitted it to escape.
Q:
Are any other radioisotopes of the noble gases susceptible to release by radiogenesis?
A:
Not to the extent possible with 133-xenon.
Al' fission product radioisotopes of iodine transmute into xenon isotopes upon decay.
Except for the decay of 133-iodine into 133-xenon, however, these decays either have half-lives which are too short, or.the decay produces stable (naturally. occurring) xenon isotopes or isomers of stable isotopes.
Similarly, the half-lives of the tromine isotopes producing radioactive krypton isotopes are very short, ranging from 15 reconds to 2.4 minutes.
o Q:
Do the loss-of-coolant accidents described in the Regulatory Guider have computed releases foe all isotopes which are greater than all other postulated accidents evaluated by the staff?
A:
Not necessarily.
For many particularly dangerous radioisotopes, such as 131-iodine and 88-krypton, the assumed releases are greater than for any other accident; however, for other specific radioisotopes, the defined loss-of-coolant accident may not be the postulated accident having the greatest releases.
There are several instances of postulated accidents which have less potential hazard to the public than the loss-of-coolant accident, but which are computed to release greater amounts of some isotopes.
5
Q:
Would the Allere. Creek fission product. releases f rom a loss-of-coolant accident be estimated by using the instructions in Regulatory Guide 1.4?
A:
No.
Assumptions to be used in evaluating loss-of-coolant accidents are described in Regulatory Guide 1.3 for boiling water reactors such as Allens Creek, and in Regulatory Guide 1.4 for pressurized water reactors such as Three Mile Island, f:
Briefly, what are the main similarities and differences between these two Regulatory Guides?
A:
The discussions of atmospheric dispersion, source term, and chemical composition in these guides are identical.
The assumptions concerning containment leak rates are different, in that a pressurized water reactor containment is assumed to leak at a reduced rate after the first day following the accident, while a boiling water reactor containment is assuneu to leak at the same rate throughout the entire accident.
Q:
Did the accident at Three Mile Island produce doses in excess of the dose i
guidelines in 10 CFR Part 100?
l l
j A:
NO.
The 10 CFR Part 100 dose guidelines are 300 Rem thyroid dose and I
25 Rem whole bndy dose, computed at either the exclusion area boundary during the first two hours of the accident or at the low population zone boundary over the entire course of the accident.
At Three Mile Island there was no abnormal release during the first two hours of the accident, and no unambiguous evidence of radioiodine, the source of thyroid dose, 6
off-site.
Kemeny et al estimated the maximum potential off-site dose as 0.07 Rem whole body dose over the entire course of the accident, with average doses of less than 10% of annual natural background to people within several milec of the reactor.
Q:
How much 133-iodine and 133-xenon would be contained by Allens Creek Nuclear Generating Station, Unit I?
A:
If the Allens Creek reactor were to be operated at its design power of 3758 megawatts thermal for a sufficiently long time (about one month) to achieve secular equilibrium in tha 133-isobaric fission products, it would i
contain 211 million curies each of 133-iodine and 133-xenon.
This would be the largest amount of these isotopes that could exist within the reactor at any given time.
Q:
Under the assumptions in Regulatory Guide 1.3, what would occur to these isotopes in the event of a loss of-coolant accident?
A:
By the assumptions in Regula-y Guide 1.3, all 21] nillion curies of the 133-xenon would be released to the containment building atmosphere, along l
with 25%, or 53 million curies, of the 133-iodine, and equal respective fractions of all other iodine and noble gas isotopes.
Leakage of this source term from the containment, combined with other assumptions contained in Regulatory Guide 1.3, would be used to calculate off-site doses for comparison against the guidelines in 10 CFR Part 100.
1 7
Q:
Does either Regulatory Guide 1.3 or 1.4 contain instructions fnr computing doses from radiogenic 133 xenon?
A:
Not explicitly, although such computations would be implied by Regulatory Position C.1.c, which appears in both guides.
Note, however, that the total computed doses are never reported to more than two ar, at most, three significant figures.
Sources of released that are too small to affect the least significant figure reported, such as radiogenic 133-xenon, a e not listed separately.
Staff practice is outlined in Standard Review Plan 15.6.5, Appendix B, " Radiological Consequences of a Design Basis Loss-of-Coolant Accident:
Leakage from Engineered Safety Features Components Outside Containment."
Q:
Is a boiling water reactor, such as Allens Creek, capable of experiencing a release of radiogenic 133-xenon analogous to that at Three Mile Island?
?
A:
Yes, but not to the same degree.
At Three Mile Island it was necessary l
to transfer reactor coolant into a drain tank in the auxiliary building in order to make room inside the pressure vessel for the addition of concen-trated borate solution.
A boiling water reactor pressure vessel, on the other hand, has much greater ullage to accommodate liquid additions, and excess liquid volume wduld be expected to pass to the suppression pool, l
without leaving the containment building.
As a result, there would be no i
potential need or motive at Allens Creek for remo,ving reactor coolant from the containment building, although piping does exist in the design which could accomplish such removal. The most likely source of radiogenic xenon within the auxilisry building of a boiling water reactor following a l
8 f
1 i
Y, core-damaging accident would be from leakage of recirculated suppression pool water, which would be a f ar more diltite soltition of radiciodines than reactor coolant.
Q:
Assuming that a release of radiogenic 133-xenon were to occur at Allens Creek, could the dose consequences exceed the guidelines of 10 CFR Part 100?
A:
No.
We might suppose that the entire 211 million curie inventory of 133-iodine is somehow removed to the auxiliary building such that all radiogenic 133-xenon evolved from its decay is released to the environment as soon as it is created.
This hypothetical event is of course, not credible, but will certainly yield computed radiogenic 133-xenon doses that could not conceivably be exceeded by any other postulated accident.
Taking all other necessary assumptions from Regulatory Guide 1.3, the computed dose in the first two hours at the exclusion area boundary is 7.3 Rem.
The computed dose for the entire course of the accident (i.e.,
integrated to infinity in time) at the outer edge of the low population zone is 5.2 Rem.
The 10 CFR Part 100 dose guidelines for these whole body doses is 25 Rem.
It is physically impossible to exceed the dose guidelines of 10 CFR Part 100 using only radiogenic 133-xenon.
9
I STATEMENT OF PROFESSIONL QUALIFICATIONS JACQUES B. J. READ Accident Evaluation Branch Division of Systems Integration U. S. Nuclear Regulatory Commission As a member of the Accident Evaluat. ion Branch my duties include the performance of technical reviews, analyses, and evaluation of fission product behavior and of chemical phenomena involved in the safety of nuclear reactors.
Prior to the creation of the Accident Evaluation Branch in 1980, I was a member of the Accident Analysis Branch. Within that branch my duties included the identification and evaluation of hazards to the safe operation of nuclear power plants due to accidents external to those plants, and aspects of other risk evaluations susceptable to stochastic methods.
Risks from such external hazards for which I have performed or participated in analyses include munitions rail traffic near Braidwood, Illinois, tanker traffic near Waterford, Mississippi and Salem, New Jersey, and military aviation near Seabrook, Massachusetts, Boardman, Oregon, Douglas Point, Maryland and Palo Verde, Arizona.
I was responsible for-assessing the risks to proposed nuclear power plants from explosives, flammable gases, aircraft, and other missile impacts.
I have rer>3sented the Nuclear Regulatory Commission in discussions of flammable gas hazards amongst member nations of the Organization of Economic Cooperation and Development.
o I was born in Maywood, New Jersey, in 1935, and received an A.C. from Princeton in 1957 (physical chemistry), an M.S. from Yale in 1958 (statistical mechanics), and a Ph.D. from Yale in 1962 (chemistry and physics).
I was employed at Oak Ridge National Laboratory during the summers of 1956 and 1957, and held post-doctoral appointments at Columbia University and the Nevis Synchrocyclotron Laboratory between 1961 and early-1964.
I taught several courses in chemistry at fairleigh Dickinson University, part-time during 1962 and 1963 and full-time during 1964.
From late-1964 to 1974, I was enployed by the Lawrence Livermore Laboratory, in the Radiochemistry Division prior to 1971 and in Special Projects Division thereafter.
From 1966 to 1974 I held an appointment as Lecturer in the Department of Applied Science, Graduate School of Engineering, University of California.
During 19/3 and 1974 I was on detached assignment to the U. S. Atomic Energy Commission headquarters, under a contract between the Commission and the Regents.
I resigned from the Labora-tory and the Department on November 4,1974, to assume my present position.
My baccalaureate thesis was a sutdy of high temperature electrochemistry.
At Yale, I studies optical rotation of polarized light by molecules.
My eventual doctoral thesis was a study of the mechanisms of the nuclear reactions of heavy ions, and my post-doctoral studies concerned proton-induces nuclear spallation reactions, and the creation of computer programs to calculate the probabilities of rare nuclear interactions. While at the University of California's Lawrence Livermore Laboratory, I studied deuteron-indurad nuclear reactions, and was involved in research in nuclear fission and fusion devices.
My duties included supervision of radiochemical analysis and responsibility for the radiochemical diagnostics of certain prototype weapons.
I wrote the Monte Carlo code used to reduce the data from the Grome " neutron wheel" experiment, and performed the 2
search for neutron-rich silicon isotopes on the Hutch Event.
I was, for several
~
years, a participant in the U. S. - U. K. Joint Working Group in Radiochemistry, I
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-I am a member of the American Chemical Society and Sigma Xi.
I have i
served on the Board of Abstractors, in French and English, of the American Chemical Society and the American Association of University Profeners.
I have authored or co-authored articles in Physical Review and Journal o_f I_norganic and Nuclear f
Chemistry, papers presented before the American Nuclear Society, the American l
Chemical Society, and the International Union of Pure and Applied Chemistry, and numerous technical reports.
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