ML19242C857
| ML19242C857 | |
| Person / Time | |
|---|---|
| Site: | Mcguire, Harris, Diablo Canyon, McGuire, 05000514, 05000515, 05000471, 05000516, 05000517, Atlantic Nuclear Power Plant, Perkins, Skagit, Black Fox, Green County  |
| Issue date: | 03/05/1979 |
| From: | Scinto J NRC OFFICE OF THE EXECUTIVE LEGAL DIRECTOR (OELD) |
| To: | Atomic Safety and Licensing Board Panel |
| Shared Package | |
| ML19242C850 | List: |
| References | |
| NUDOCS 7908140052 | |
| Download: ML19242C857 (1) | |
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- v. Am i'. 210'.. D. c. 7 ML p.. n. e t', arch 5,1979 BOARD f;3TIFICATION Re:
Black Fox Docket rio. 50-556/557 Diablo Canyon Docket tio. 50-275/323 f rip Dociet tio. STN 50-437 Greene County Docket t'o. 50-549 Jamesport Docket f;o. 50-516/517 ficGui re Docket No. 50-359/370 Pebble Springs Dor ' e t fio. 50-514/515 Perkins Dotiet fio. 50-403/489/a90 Pilgrim 2 Docket tio. 50-471 Shearon Harris Docket flo. 50-400/401/402/403 Skagit Docket fio. 50-522/523 Ladies and Centlenen:
.r Enclosed is a memorandum from the Staff dated October 17, 1978 discussing post-LOCA hydrogen generation from materials inside contain: cent.
Due to a misunderstanding of the ir.co:aing request, this information was thought to be applicable only to the Yellow Creek plant.
The Licensing Board considering the Yellow Crew plant was inferred of this on fiovember 6, 1978. Recently, we have recognized that the information, although developcd for Yellow Creeks is generic.
Accordingly, we are enclosing this information for the captioned proceeding.
Sincerely, Y.e
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Director, Hearing Division Enclosure As Stated 7 0 0 814 0?5~A
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N U C, L : A h M G U L A T O R Y C Of.'..'.10 sl O N V. ASHl'.G TUN. D C. 2035
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October 17, 1978 Boyd, Director, Division of -
Jet t i'.E!'.DRANDUM FOR :
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Roger J. Mattson, Director, Division of Systems Safety
SUBJECT:
POST-LOCA HYDR 0GEri PRODUCTIO'i FROM t'.ATERIALS If; SIDE C0 iTAli; melit
References:
(1) Memorandum to D. B. Vassallo from C. O. Thomas, "Reconmended Licensing Board I;otification - Post-LOCA Hydrogen Generation from Materials Inside Containment da+ed August 24, 1978; W) Memorandum for Robert L. Tedesco from ',1.
R. Butler,
" Post-LOCA Hydrogen Generation from Zinc," dated September 20, 1978; and g
(3) Memorandum for W. R. Butler from F. Eltawila through J. Kudrick, " Hydrogen Generation in Mark II Containment Due to Zinc Corrosion," dated September 20, 1978 In Reference (1) Mr. Thomas indicated that the post-LOCA hydrogen produc-tion due to corrosion of caterials inside the prir.ary containment, (such as aluminum and zinc) and the thermal, chemical, and radiolytic decomposition of organic cogonents in protective coating systems r.ay not have been adequately considered in the evaluation of combus tible gas control systems and recomended notification of appropriate hearing boards.
The effects of the matters discussed in Reference (1) have beca conservatively evaluated to assess the potential for significant hydro-gen generation due to the presence of the stated materials, i.e.,
conservative values were used for the hydrogen generation rates from gal-vanized steel and zinc-based coatings [provided by MIEB] in a post-LOCA environment and to evaluate the potential consequences on the design of hydrogen control systems in both BUR and PR containments.
A brief sum-mary of the effects of these aspects as potentially additional contribu-tors of hydrogen production follows:
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Es;er S. Loya October 17, 1978 DEC0". POSITION OF ORGANICS:
A substantial ar:Jnt cf organic materials is used in protective cca tirg systems, including th se over zinc-based primer paints inside PWR and 80 containments.
Wr.n exposed to the LOCA environment (high tuyerature, cher.ical, and radiation fielc's),
these organic niterials undergo a process of decomposition to form hyJrogen and hydrocarbons.
The Accident Analysis Branch (DSE) has estimated the resul tant hydrogen and hydrocachon concentra tions resulting from the radiolytic deco:positian of org. nics ar.d the thermal a
and chemical reaction of organic coatings on ccncrete surfaces.
Assuming a conservatively integrated radiation exposure of 103 rads, the Accident Analysis Branch (IGB) estimates the hydrogen concentration due to radiolytic deconposition of crganic coatings to be less than 0.4% for PWR ' s a nd l e s s t h a n 0. 26 f o r B.'-lR ' s.
For hydrogen genera tion due to thennal and chemical reaction of organic coatings on painted concrete surfaces the AAS esticates the resultant hydrogen concentra tion to be less than 0.3% for PWR's and less than.2L for E',;R's.
If we sum these hydrogen contributions from organic raterials v hich were heretofore not included in our analyses, the additional hydrcgen represents roughly a 6
10% increase in the hydrogen genercted from cl1 sources previously considered; i.e., zirconium water reaction, radiolysis of water, and oxidation of zinc with its organic topcoat during the post-LOCA period.
Since there will be a large amount of water, relative to the amount of organic materials, it can be concluded that the hydrogen gas generated from radiolysis of water should do.ainate that from decomposition of the organic materials.
CORROSION OF ZINC IN PRESSURE S'JPPRESSION CONTAIhMENTS:
The hydrogen generation from galvanized steel and zinc-based primers is a strong function of the containTent troperature history following a LOCA.
For ice pressure suppression containments, the post-LOCA tenpera ture profiles have been found to be suf ficiently low that the hydrogen genera tion from zinc-rich coatings does not jeopardize the capability of the hydrogen reco7biner systems.
Furthermore, for E',;R containments, where the hydro-gen concentration is predicted to peak within a few hours af ter accident initiation, there is not suf ficient time for the hydrogen generation from the zinc-rich coatings to cause the hydrogen concentration to exceed the 4% flagnabie limit before recombiner actuation or shortly thereaf ter.
CORROSION OF ZINC IN DRY CONTAINMENTS:
Becaut e of the uncertainty in the hydrogen generation rates, calculations were perfonntd to deten7ine the impact of the uncertainty on the recoabiner systems for several PWR plants (see Enclesure '.).
The hydrogen genera tion rate curve for galvanized steel (provided by MfEB) was increased by a factor of 2.0 to hound the available experimental da ta for galvanized steel.
This increase in the
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i.c,;n 5. E:/d October 17, 1976 corresicn rate would only result in a very slight increase in the hydro;cn c ncentration slightly in e< cess of 40 concentration but wculd yield a H for Yellow Creek.
In c.ost cases,2the recccbiner systems had the capability of mair,taining the hydrogen concentration below the 4% flammable limit by actuating earlier in the post-LOCA period.
In the analysis performed for the Yellow Creek plant, the hydrogen concen-tration would reach a peak value of about 4.13P.; hewever, giving credit to the diluting effect of the steam in the containnent atnosphere following a LOCA shcws that the hydrogen concentration would not exceed the 4%
flammable limit.
While it is our view that no safety concern is involved as a result of our using the updated hydrogen generation rates for zinc-rich coatings, we find that there is suf ficient justification to warrant further staff effort toward examining the generation of hydrogen from zinc-rich paints and organic materials.
A more refined knowledge of the behavior of these materials would increase our confidence in this area of review.
We plan to prepare a User's Request to have R5R ur,derL3 ke studies in such areas as:
- 1) the impact of uncertainties in the hydrogen generation rates on the analyses of hydrogen accumulation in PWR dry containments including an assessment of the inherent conservatisms in such analyses (see Enclosure 3); and 2) the relative importance of the decomposition of organic materials as a source of hydrogen in containments.
In surr.ary, we find that the effects evaluated regarding post-LOCA genera-tion of hydrogen in both BNR and FWR pressure suppression type containz.ents do not lead to new significant safety concerns not already being considered in our current safety reviews.
Since this matter was not explicitly considered in our reviews until reccntly, I agree that notification of appropriate licensing boar ds may be appropriate.
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- s. y Roger J. Mattson' Director Division of Systems Safety Office of Huclear Reactor Regulation
Enclosures:
As Stated cc:
See page 4 7
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H. Denton R. l'attson R. DeYoung V. Stello D. Eisenhut B. Grimes J. Knight R. Tedesco J. Glynn
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W. Bu tler C. Thomas J. Kudrick
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