ML20082H798
| ML20082H798 | |
| Person / Time | |
|---|---|
| Site: | Duane Arnold  |
| Issue date: | 08/16/1991 |
| From: | Boger B Office of Nuclear Reactor Regulation |
| To: | IES UTILITIES INC., (FORMERLY IOWA ELECTRIC LIGHT |
| Shared Package | |
| ML20082H800 | List: |
| References | |
| NUDOCS 9108260277 | |
| Download: ML20082H798 (7) | |
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UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION in the Matter of IOWA ELECTRIC LIGHT AND POWER COMPANY Docket No. 50-331 CENTRAL IOWA POWER
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COOPERATIVE, AND
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CORN BELT POWER COOPERATIVE (Duane Arnold Er. orgy Center)
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EXEMPTION 1.
The towa Electric Light and Power Company, et al., (the licensee), is the holder of Facility Operating License No. DPR-49 which authorizes operation of the Duane Arnold Energy Center at power levels not in excess of 1658 megawatts thermal. The license provides, among other things, that it is subject to all rules, regulations and Orders of the Nuclear Regulatory Commission (the Connission) now and hereaf ter in effect.
The facility consists of a boiling water reactor located at the licensee's site in Linn County, Iowa, 11.
On November 19, 1980, the Commission published a revised Section 50.48 and a new Appendix R to 10 CFR Part 50 regarding five protection features of nuclear power plants. The revised Section 50.48 and Appendix R became effective on February 17, 1981.
Section 111 of Appendix R contains 15 9108260277 910016 PDR ADOCK 05000331 F
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' subsections lettered A through 0, each of which specifies requirements for a ' articular aspect of the fire protection features at a nuclear power plant.
One of the subsections, Ill.G, is the subject of the licensee's exemption request.
Specifically, Subsection Ill G, Part 2 requires a 3-hour fire 'sarrier 3r % her equivalent means of separating redundant trains of safe shutdown equipment to ensure that one train is free of fire damage.
By letter dated August 25, 1987, the Iowa Electric Light and Power Company (the licensee) responded to an unresolved item (50-331/86005-01) from an NRC fire protection program inspection conducted at the Duane Arnold Energy Center (DAEC) on February 24-28, March 12, April 22-23, and May 15, 1986.
The unresolved item was concerned with the potential for fire damage to redundant safe shutdown cables in penetrations passing through the expansion gap due to burning combustible foam material located in the expansion gap.
Boiling Water Reactor (BWR) Containments expand and contract with both the thernial and pressure changes which occur over the course of a normal operating cycle, in order to accommodate these dimensional changes, an
" Expansion Gap" of about 21 to 3 inchet is provided between the steel containment vessel (the drywell) and the reinforced concrete biological shield that surrounds the drywell. This Expansion Gap is built in by means of installing compressible plastic foam sheets around the outside of the steel drywell before pouring the concrete.
At Dresden Units 2 and 3, the plastic foam was covered with a glass-fiber mat which in turn was sealed with an epoxy resin 6nd left permanently in place after the concrete pours.
4 3
During flame cutting operations on January 20, 1986, and again on June 4, 1988, on certain nechanical penetrations at Dresden Unit 3, maintenance personnel allowed hot slag to drop down the annulus around the penetration.
The hot slag ignited the expansion gap material which smoldered for several hours and was difficult to extinguish.
Licensees with designs similar to Dresden have evaluated their particular construction designs and requested exemptions, as appropriate, from the requirements of Section 111.G.2 of Appendix R to 10 CFR part 50 as they apply to the expansion gap, in its letter dated August 25, 1987, the licensee requested an exemption from the Commission's regulations in 10 CFR part 50, Appendix R, Section 111.G.2 requiring a 3-hour barrier or other equivalent means of separating redundant trains of safe shutdown equipment to ensure that one train is free of fire damage.
Section 111.G of Appendix R to 10 CFR Part 50 provides different dcceptable methods of protecting safe shutdown capability from the effects of fire.- These different methods utilize various combinations of 3-hour and 1-hour fire-related barriers, automatic fire detection and fixed fire suppression capability, and spatial separation between redundant safe shutdo" components.
The licensee has requested an exemption from the specific requirements for 3-hour fire rated barrier so,,aration for the redundant safe shutdown train instrumentation and power and control cables located in containment penetrations where they pass through the expansion gap between the steel drywell and the concrete biological shield.
4 The technical information furnished by the licensee to support this I
requested exemption included the following:
A.
Unlike the Dresden construction, most of the foam material was removed from the expansion gap at DAEC following each concrete pour. The only combustible material remaining in the expansion gap at DAEC is elastic polyurethane circumferential strips 3 inches thick x 5 inches wide on 2-feet centers below elevatica 748 feet 9 inches and 3-feet centers above that elevation.
(The equator of the spherical portion of the drywell is at elevation 766 feet.)
B.
The strips are manufactured of plastic material that is classed as "self-extinguishing" in accordance with ASTM D 1692.
C.
Because of the geometry (long narrow circumferential strips separated by 0 feet on centers from below the equator of the bulb) and the self-extinguishing characteristics of the plastic material, any fire that might occur is expected to be limited to the area of ignition and would not spread to other strips.
D.
The steel drywell itself will serve as a large heat sink to further assist in cooling and aiding he self-extinguishing characteristics of this material should it become ignited.
E.
Maintenance work on containment penetrations is administrative 1y controlled.
In addition to fire watches, precautions include filling the annulus space with noncombustible material prior to any operations which might produce hot slag or sparks.
The staff has evaluated the technical information furnished by the licensee to support its requested exemption. On the basis of that evaluation, the staff concludes that the likelihood of fire occurring in the expansion gap foam material is slight.
Further, if the material should become ignited, the staff concludes thai. the fire would be localized and would not endanger ce nonents of redundant safe shutdown trains passing through the drywell.
i
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5-On this basis, the staff finds that the licensee has demonstrated, as required by 10 CFR 50.12(a)(2)(ii), that the subject redundant safe shutdown train instrumentation and power and control cables located in containment penetrations where they pass through the expansion gap between the steel drywell and the concrete biological shield need not have a 3-hour fire barrier to achieve the underlying purpose of the rule (i.e., achieve and maintain safe shutdown) in that the geometry, construction techniques, and self-extinguishing characteristic of the foam material in the expansion gap will maintain the tempereture increase in the cables below the damage threshold.
111.
In sunmary, the NRC staff finds that the licensee has demonstrated that there are special circumstances present as required by 10 CFR 50.12(a)(2).
Further, the staff also finds that, for this exemption request, the fire protection provided by the licensee will not present an undue risk to the public health and safety.
Accordingly, the Coumission has determined that, pursuant to 10 CFR 50.12, the exemption as described in Section 11 is authorized by law and will not endanger life or property or the common defense and security and is otherwise in the public interest and hereby grants the exemption to the requirements of 10 CFR Part 50, Appendix R, Section III.G.2.
Pursuant to 10 CFR 51.21, 51.32, and 51.35, an environmental assessment and finding of no significant impact has been prepared and published in the Federal Register (56 FR 32229, July 15,1991).
- Accordingly, based upon the environmental assessment, the Commission has determined that the granting of the exemption will not have a significant effect on the quality of the human environment.
This Exemption is effective upon issuance.
FOR THE NUCLEAR REGULATORY COMMISSION eng nalY900d DY i
Bruce A. Boger, Director Division of Reactor Projects Ill/lV/V Office of Nuclear Reactor Regulation Dated at Rockville, Maryland this 16th day of August 1991.
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UNITED STATES 3
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.. t ej August 19. 1991
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DOCKET No. 50-331 Regulatory Publications Branch MEMORANDUM FOR:
Division of Freedom of Information and Publications Services Of fice of Administration and Resources Management FROM:
Office of Nxtear Reactor Regulaton IOWA ELECTRIC LIEHT AND POWER COMPANY. CENTRAL IOWA suaxCT:
POWER COOPERATIVE, AND CORN BELT POWER COOPERATIVE _ DUANE ARHOLD One signed original of the Federa1 Register Notice identified below is enclosed for your transmittal to the Of fice of the Federal Register for publication. Additional conf ormed copies ( 6
) of the Notice are enclosed for your use Notice of Receipt of Application for Construction Permit (s) and Operating License (s)
Notice of Receipt of Partial Application for Construction Permit (s) and Facility License (s): Time for Submission of Views on Antitrust Matters.
Notice of Consideration of issuance of Amendment to Facility Operating License.(Catt with _ day insert date).
Notice of Receipt of Application for Facilitv Licensets); Notice of Availability of Applicant's Environmental Report; and Notice of Consideration of issuance of Factiny License (s) and Notice of Opportunity for Hearing.
Notice of Availability of NRC Draf t/ Final Environmental Statement.
Nott:e of Limited Work Authorization.
Notice of Availability of Safety Evaluation Report Notice of issuance of Construction Permit (s),
Notice of lasuance of Facility Operating License (s) or Amendment (s).
- Order, Exemption.
Notice of Granting Exemption.
Environmental Assessment.
Notice of Preparation of Environmental Assessment.
Receipt of Petition for Director's Decision Under 10 CFR 2.206.
Issuance of Final Director's Decision Under 10 CFR 2.206 Other:
Jo;in N. Hannon. Director Project Directorate III-3
Enclosure:
As stated contact:
P. Kreutzer Phone:
49-21392 ormr
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