ML20008D789
| ML20008D789 | |
| Person / Time | |
|---|---|
| Site: | Midland |
| Issue date: | 01/13/1969 |
| From: | CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | |
| References | |
| NUDOCS 8007300705 | |
| Download: ML20008D789 (4) | |
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APPENDIX lhA CHE4ICAL SPPAYS INTRODUCTION A chemical additive has been added to the reactor building spray for the purpose cf re=cving any radioactive iodine which cay be released folleving a less-of-coolant accident. The chemical spray solution is a boric acid solution containing sodiu= thiosulfate and enough sodiu= hydroxide to for=
an alkaline pH buffer with the %cric acid. This solution co= position is cc=-
=cnly referred to as " alkaline suw.u:.1 thiosulfate. "
The sodiu: thiosu] Nte in the alkaline sodium thiosulfate solution reacts rap-J idly, co=pletely, a irreversibly with iodine, and was, in fact, suggested by Griffith(1) in his 15c3 study en the use of sprays for re=oving iodine frc=
reactor building at=cspheres. The sodium hydroxide is not intended to play an active role in the absorption of iodine; its function is =erely to preserve the long-tem stability of the alkaline sodiu= thiosulfate solutien by =aintaining the desired pH.
Data p esently available (2-7) indicate that the alkaline sodiu= thiosulfate solution is satisfactory when used in a properly engineered syste=.
1 IODITE RD! OVAL EFFECTIVENESS ORNL has conducted a nu=ber of spray tests in the Nuclear) Safety Pilot Plant (NSPP) facility. These tests, as reported in ORNL h253(7, have de=enstrated that elemental radicactive iodine is rapidly recoved by chemical sprays.
Using an NSPP run =ade at accident conditions closely approxi=ating those pre-dicted for Midland Units 1 and 2, the =easured iodine half-life was 31 seconds; that is, half of the radioactive iodine was re=oved fro = the Jtea=-air atmos-phere in 31 seconds after starting the sprays. These data haw been scaled to the Midland Units 1 and 2 design. They result in an iodine h C life of 28 seconds with the full spray installed capacity operating (2350 sp=) and a half-life of 56 seconds at half capacity. The iodine half-life reported in Section 14.2.2 3 7 is 61 seconds at full capacity and 121 seconds at half capacity.
A large number of confirmatcry tests (T-12) have been =ade which demonstrate that che=ical sprays are effective for ied' 'e re= oval. These spray tests have been
=ade using a vide range of variables - spray distributions with droplet sizes ranging frc= 100 to 1200 =icrons, fall heights ranging from a few feet to approxi=ately 50 feet, temperature and pressure conditions varying from a=bient to =ax1=u= accident conditions, iodine concentrations ranging fro = 1 to 130
=g/ cubic ceter, single and multiple spray nozzle installations, spray fluxes ranging frec O.007 to 0.2 gra per square foot vessel cross section, and cen-densing and noncondensing conditions. With this vide range of confir=atory
. test conditions, we are confident that the Midland Units 1 and 2 che=im spray syste=s vill perfom as predicted, b.
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ORGANIC ICDINE i
The organic iodine consists pri=arily of = ethyl iodide but includes a s=all, al= cst insignificant, fraction of cther organic iodides.
i Experimental data obtained under a vide variety of conditions en the amount of
= ethyl iodide released frc= overheated fuel are repcrted in nu=ercus publica-tiens.
Iodine release experiments using irradiated Zircalcy-clad UO, fuel in a PWR accident environment show 1-ss)than the 5 percent organic 1 di?.e assu=ed in Section 1h.2.2 3 7 Six tests (13 were perfor=ed at Battelle "orthwest Laboratories.
They found that 1 percent er less cf airborne iodine (ggg in the organic for=.
Thirteen other experi=ents were perfor:ed in England
/; all but two shov less than 0.2 percent as = ethyl iodide. The highest result was 3 percent. There are a number of other experiments reported in the literature which deal with the a= cunt of nonreactive iodine released frc= overheated fuel.
1 Sc=e of these experiments have observed greater than 5 percent nonrecovable iodine; however, these experiments were conducted under conditions that are not applicable to the PWR accident environment.
It is en the basis of all the
}
data above that we concluded that 5 percent nonre=ovable iodine was a conserva-l tive value for use in the accident analysis.
Spray tests at Oak Ridge National Laboratcry(7,15) and Battelle-Northwest Laboratory (16) have de=enstrated that alkaline sodium thiosulfate spray is ef-fective for re= oval of methyl iodide. While the removal rate is not as dra:atic as that for ele = ental iodine, the methyl iodine re= oval rate is sufficient to I_
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=ake a significant reduction in the airborne iodine eencentration and thus in s_/
the off-site doses.
Spray test A-12 in the Contain=ent Systems Experiment (CSE)(16) de=cnstrated I
that alkaline thicsulfate spray re=cves methyl iodine fro = a stea=-air environment with a half-life of 80 minutes. Scaling this to Midland Units 1 and 2 predicts a methyl iodide half-life of 52 minutes.
PARTICUIATE IODINE i
A s=all fraction of the iodine assumed to be roleased folleving the LOCA may attach to particles and dust to for= particulane aerosols. Several studies have shewn that, should the particulate aerosols be for:ed, they vill be rapidly re-moved frc= the reactor building at=osphere.
Stinchec=be and Goldsmith (II' 16) have shown that sub=icron particles are re=oved with 95 to 99 percent efficiency by condensing steam. They clso show that the ther=al and vapor presse-e gradients, which exist in the condensing stea= envi-ron=ent, drive the sub=icron particles tevard the eccler surfaces where they are re=oved frc= the atmosphere with the condensing water vapor.
I Particles greater than 0.2 =icron size are re=oved efficiently by impac+. ion with the reactor building spray; these particles less than 0.2 =icron size are not.
However, the s= aller particles serve as condensation nuclei which grow until gravitational and inertial forces result in rapid deposition of these par ticles. (17, 19) The absence of particles, after aging, de=enstrates the effee-g "'
tiveness of this removal =echanis=.
Idkevise, ve; r s=all thermal gradients act r
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a l driving forces which caus9 migration of particles to the spray drop surfaces and thereby enhance removal.l 7) l 00&&
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l High concentrations of small(eO, 21) particles are very unstable and rapidly agglet-j erste into larger particles.
These are effectively removed by impac-tien with spray drops, by washout frc: the ecndensing stea=, and by settlement.
As a result, nearly all particulates are expected to be removed frc: the re-actor building atmosphere.
Experiments in the CSE(0) have de=enstrated rapid re= oval of particulates by I
spraying. These tests indicate removal rates in a condensing stea: enviren-cent - similar to that in the reactor buildi:2g following an LCCA - of cne third to one half as fast as for elemental iodine.
-f HY?cICDCUS ACID Hypoicdous acid is a product of elemental iodine hydrolysis by alkaline aqueous solutions.(22) The addition of sodium thiosulfate to an alkaline solution pre-cludes formation of hypoiodcus acid in any significant a: cunt. Sodium thio-l sulfate reacts instantaneously with elemental iodine, reducing the iodine to i
iodide. Thus, no ele ental iodine is available for hydrolysis to the hypc-iodcus form.
REFERENCES (1) Griffith, V., The Removal of Iodine Fro the Atmosphere by Sprays, AHSB(S)R h5, 1963, pp 7-12.
i (2) Cottrell, W.
B., ORNL Nuclear Safety Research and Develop =ent Program, Bicenthly Report for July-August 1967, OR%-TM-1986, p 35 (3) Cottrell, W.
B., ORNL Nuclear Safety Research and Develop =ent Program, Bimonthly Report for March-April 1968, ORNL-TM-2230, p 81.
(4) Cottrell, W.
B., ORNL Nuclear Safety Research and Develop =ent Prcgram, i
Bicenthly Report for May-June 1968, ORNL-m-2283, pp 6h-73 i
(5) Cottrell, W.
B., ORNL Nuclear Safety Research and Develop =ent Program, i
Bicenthly Report for July-August 1968, ORNL-m-2368, Section 3 5 (6) Cettrell, W.
B., ORNL Nuclear Safety Research and Develop =ent Program, Annual Report for 1967, ORNL-h228.
(7) Parsley, L. F. and Franzreb, J.
K., Re cval of Icdine Vapor From Air and Stean-Air At=cspheres in the Nuclear Safety Pilot Plant by Use of Sprays, f
ORNL h253, June 1968.
(8) Nuclear Safety Quarterly Report; November, December 1967, January 1968; for Nuclear Safety Branch of USAEC Divisicn of Reactor Develcirent and Technology, b.v the Staff of Battelle-Northwest, BNWL-816.
i (9) Nuclear Safety Quarterly Report; February, March, April 1968; for Nuclear Safety Branch of USAEC Division of Reactor Develop =ent and Technology, by the Staff of lattelle-Northwest, BNWL-885 l
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I (10)
Sodium Thiosulfate Sprays, CRW.-h076, p 169 Parker, W.,
Reaction of Molecular Iodine and of Methyl Iodid j
e With (11)
Nishizava, Y., et al., "A Study of the Re= oval of Iodine F phere by Sprays,' Journal cf the Japan Society of Nuclear Pever rem the Atmos-No. 11, November 19eo, pp 590-oC2.
, Vol 8, (12) Maekava, T.,
et al.,
I - Removal of Iodine by Sprav Under Atmospheric Press Ja9n Society of Nuclear Power, Vol 7, No.10, pp 563 569 ournal of the
, 1905 (13)
Centainment Behavior of a Simulant With Fission K.,
Coleman, L. F. and McCor:ack, J. D., Co parison
~
s of the Irradiated "C, ENL-581, March 1968, Table h, p A.5 2
ased From (lk)
Behavior of Gas-Borne Iodine, TRG-R-983(W) UKAEAC J., Some Experiments Relating to the April 1965
, Windscale, England, (15)
Parker, G. V., Creek, G.
E., and Horton, N. R., Dissolutio Progress Report for Period Ending Decemberof Methyl Iod n and Hydrolysis ram Annual 31, 1967, CPlTL-h228, April 1968.
(16)
Nuclear Safety Quarterly Report; May, June, July 1969 Branch of USAEC Division of Reactor Development and Technol, for Nu
(
. published).
ogy (to be (17) by Condensing Steam," AERE-M-121h.Stinchcombe, R. A. and P.,
" Removal of Iodine From Atmosphere (18)
Stea=," Journal of Nuclear Energy Parts A/B, Vol 20St P., " Removal of Iodine From Condensing
, pp 261-275, 1966.
(19)
Vapor Syste=s," Aerosol Science, C. N. Davies, EdGo G., "Diffusiophoresis and Themophoresis in Water New York, New York, pp 163-194 (1 % 6).
., Academic Press, Inc.,
(20)
Collings, D. A.,
et al., " Experience in Trapping Iodine 131 Fission Products Released From AGR-Type Fuel Elements " TID 76 and Other (21)
, p 113 Ke11holtz, G. W.,
Safeguards in Nuclear Installations," 0RNL-NSIC-13" Filters eered
, p 139, October 1966.
(22)
Parsley, L. F. and Wantland, J. L., " General Considerati Use of Sprays," pp 256-26h, Nuclear Safety Program Annual P for Period Ending Dece=ter ons I.garding the 31,1968, ORNL-4373 rogress Report 00043
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