ML19289F915
| ML19289F915 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 05/25/1979 |
| From: | Rib L NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| To: | Kelber C NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| Shared Package | |
| ML19289F911 | List: |
| References | |
| NUDOCS 7906210125 | |
| Download: ML19289F915 (2) | |
Text
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$ }*g % '[,}s NUCLEAR REGULATORY COMMISSION WASHINGTON. D. C. 20555
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!MY c, -a 3p-MEMORANDUM FOR: Charles N. Kelber, Assistant Director for Advanced Reactor Safety Research Division of Reactor Safety Research FRCf t:
Louis N. Rib, Soecial Assistant Advanced Reactor Safety Research Division of Reactor Safety Research SU5 JECT:
RESPCNSE'TO CCMMISSION REGUEST FCR INFOR"ATICN ON THE POTENTIAL FOR 0, ACCUMULATICN IN THE REACTOR VESSEL DURING THE TMI-2 ACCIDENT The response to this question is addressed in three parts:
(1) Net procuction by radiolysis in the reactor core of H, and 0, (2) the 2
effect of the environment (coolant chernistry, ccre pcwer, P,T) en 0, production; and (3) the potential for 0 build up in the bubble in the 2
reactor vessel.
1.
Net production.
In PWRs the net production from the radiolytic process is suppressed by maintaining a ccncentraticn of H2 gas in solution in the primary coolant.
In Reference 1 Hochanadel showed that H and 0, in water at 25 C to 7
250*C are recombined by gama radiatiog/Kg maintained 0
- Reference 2, p. 31, states that "H concentrations as lcw as 6 c:a concentrations 2
2 at 0.01 to 0.02 ppm with water temperatures in the range 300 to 3E0 F."
This temperature range is appropriate for the perind of the TMI-2 incident where the primary coolant temperature reading was 280'F and the "H
bubble" was of concern.
2 2.
Envircnmental effects.
Nevertheless, if one assumes: an openirg in the primary ccolant systen such that the water level in the reactor vessel was down to the outlet pipe; no H7 gas in solution, and, the. core is at a 10Mw(th) decay heat level, then, KAPL calculated a radiolytic gas (H and 0 ) generation 7
7 rate of less than 20 scf/ day (Reference 3). Therefore, this value represents a maximum generation rate since we are aware that an excess of He was actually present in the primary system.
If this quantity were genefated in a boiling region of the core, gas could be stripped out of soluticn. How2ver, above the boiling region, the gas may be redissolved, in which case the recocbinaticn wculd remove all the 0.
Or, 0, r.ight be removed frca the gas stream when the 0 sweptbyho! metal (Er) 2 surfaces.
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Charles N. Kelber M M 2 ~ 1373 3.
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2 If some of the 0 managed to reach the gas bubble at the top of the reactor,couldt$e0 concentration build up to approach the deflagration 2
or explosive limits? Aside from what the limits may be (this is addressed in the following section) KAPL evaluated the H and 0 reconbination 2
2 rate under the following conditions (Reference 3):
a gas phase containing H, 0, water vapor and a gamma field strength of 6,000 r/ hour at atmosphere 9
9 pressure. The calculated recombination rate is of the order of 1,000 scf/ day. The experimental data base for this calculation is given in References 3 and 4 It is expected that as pressure is increased from atmospheric pressure to 1000 psi, the recombinaticn rate will also increase. This assumption is based on data in reference a which shcws that increasing hydrogen concentration increases the H -0 rec mbination 7 2 rate. This assumption requires experimental verification. Another f actor which would increase the recombynation rate is the much larger gama field in the reactor vessel ( 10 r/hr). Therefore, the 1000 scf/ day recombination rate is considered to be a very conservative value.
The recrbination rate thus is much greater than the very conservative radiolysis rate. Therefore, any 0 which reached the gas bubble would disappear rather than concentrate.2 This conclusion precludes the possibility of a H explosion in the gas bubble region of the reactor 2
vessel.
I Louis N. Rib, Special Assistant Advanced Reactor Safety Research References 1.
C. J. Hochanadel, Proc. Intern. Conf. Peaceful Uses Atomic Energy,
- 1955, 7_, 521-25 (1956), "The Radiation Induced Reaction of Hydrogen and Oxygen in Water at 25 C to 250 C."
2.
ORNL-4173, " Water Chemistry in Pressurized and Boiling Water Pcwer Reactors," G. H. Jenks and J. C. Griess.
3.
KAPL - Evaluation of Radiolysis Concerns Associated with the Three Mile Island Unit-2 Incident, dated May 1979.
4.
C0010321, " Recombination of H and 0 in the Presence of Water 2
7 Vapo under the Influence of nadiation," Drs. Benjamin and Isbin, University of F.innesota, July 1965.
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