ML20137B515

Forwards Exemption from Requirements of 10CFR50.44(c)(3) (Iii),Re Installation of Reactor Vessel Head Vent Based on Verification That Noncondensible Gas Bubble Can Be Safely Removed Via Hot Leg High Point Vents,Per 850412 Request

ML20137B515
Person / Time
Site:	Rancho Seco
Issue date:	12/24/1985
From:	Stolz J Office of Nuclear Reactor Regulation
To:	Reinaldo Rodriguez SACRAMENTO MUNICIPAL UTILITY DISTRICT
Shared Package
ML20137B520	List: ML20137B515 ML20137B531 ML20137B542
References
TAC-57558, TAC-65453, NUDOCS 8601150533
Download: ML20137B515 (6)

Text

,

q 0h December 24, 1985 Docket No. 50-312 DISTRIBUTLON SMiner Grr File Kclet File GKalman

'Hr.nstein NRC-P OELD EBrach L PDR EJordan Mr. Ronald J. Rodriguez PBD-6 Rdg BGrimes Assistant General Manager, Nuclear HDenton JPartlow Sacramento Municipal Utility District DEisenhut TBarnhart-4 6201 S Street FMiraglia ACRS-10 P. O. Box 15830 GHolahan CMiles Sacramento, California 95813 Ringram RDiqqs

SUBJECT:

GRANTING 0F EXEMPTION FROM 10 CFR 50.44(c)(3)(iii), REACTOR VESSEL HEAD VENT On July 25, 1983, we issued a temporary exemption to the Sacramento Municipal Utility District which granted a schedular delay, until December 31, 1985, from the requirement to install a reactor vessel head vent at the Rancho Seco Nuclear Generating Station. The exemption was based on information presented to the NRC by your letters dated July 2,1982, and March 15, 1983, and on a requirement to conduct confirmatory integral system tests.

By letter dated April 12, 1985, you provided the results of the integral system tests along with a discussion of the applicability of the tests to the Rancho Seco reactor. Based upon this information, you requested that the exemption from the subject requirement be made permanent.

We have reviewed your request and found that.you have demonstrated that a noncondensible gas bubble in the reactor vessel can be safely removed via the hot leg high point vents; even with a noncondensible gas bubble in the reactor vessel head, natural circulation will be maintained while the plant is cooled and depressurized to the Decay Heat Removal System entry conditions. While a residual gas bubble would still remain in the reactor vessel head following the plant cooldown, the gas bubble would not interfere with the maintenance of core cooling and could be slowly removed thereafter j

by various means.

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8601150533 951224 DR ADOCK O 32

Mr. Rodriguez ;

We conclude that an exemption to 10 CFR 50.44(c)(3)(iii) can be granted. The Exemption.is enclosed; a copy of it is being filed with the.0ffice of the Federal Register for publication. Also enclosed is our Safety Evaluation supporting the Exemption.

Sincerely,

%WIGl:LG EIGO 3{

- JOUR F. SA%y John F. Stolz, Director PWR Project Directorate #6 Division of PWR Licensing-B

Enclosures:

1.

Exemption 2.

Safety Evaluation cc w/ enclosures:

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DOCKET No. 50-312 MXMQ4MQMSXE John Philips, Chief, Rules and Procedures Branch MfVeVt4UsHEY44MBERE Division of Rules and Records MEMORANDUM FOR:

v Office of Nuclear Reactor Regulation FROM:

RANCHO SECO HUCLEAR GEf ERATING STATION

SUBJECT:

One signed original of the Federal Register Notice identified below is enclosed for your transmittal to 6 ) of the Notice are enclosed for your u>e.

Register for publication. Additional conformed copies (

Notice of Receipt of Application for Construction Permit (s) and Operating License (s).

Time for Submission of Views O Notice of Receipt of Partial Application for Construction Permit (s) and Facility License (s):

on Antitrust Matters.

U Notice of Consideration of issuance of Amendment to Facility Operating License.

U Notice of Receipt of Application,for.Eacility License (s); Notice of Availability of Applicant's Environm j

Notice of Consideration of issuance of Facility License (s) and Notice of Opportunity for Hearing.

Notice of Availability of NRC Draft / Final Environmental Statement.

U Notice of Limited Work Authorization.

O Notice of Availability of Safety Evaluation Report.

Notice of issuance of Construction Permit (s).

Notice of issuance of Facility Operating License (s) or Amendment (s).

Order, h Exemption.

U Notice of Granting of Relief.

U Other:

Division of PWR Licensing-B Office of Nuclear Reactor Regulation

Enclosure:

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December 24, 1985 Docket No. 50-312 DISTRIBUTION SMiner Gray File Docket File GKalman

~H0rnstein NRC PDR OELD EBrach L PDR EJordan Mr. Ronald J. Rodriguez PRD-6 Rdg BGrimes Assistant General Manager, Nuclear HDenton JPartlow Sacramento Municipal Utility District DEisenhut TBarnhart-4 6201 S Street FMiraglia ACRS-10 P. O. Box 15830 GHolahan CMiles Sacramento, California 95813 Ringram RDiqqs

SUBJECT:

GRANTING OF EXEMPTION FROM 10 CFR 50.44(c)(3)(fii), REACTOR VESSEL HEAD VENT On July 25, 1983, we issued a temporary exemption to the Sacramento Municipal Utility District which granted a schedular delay, until December 31, 1985, from the requirement to install a reactor vessel head vent at the Rancho Seco Nuclear Generating Station. The exemption was based on information presented to the NRC by your letters dated July 2,1982, and March 15, 1983, and on a requirement to conduct confirmatory integral system tests.

By letter dated April 12, 1985, you provided the results of the integral system tests along with a discussion of the applicability of the tests to the Rancho Seco reactor. Based upon this information, you requested that the exemption from the subject requirement be made permanent.

We have reviewed your request and found that you have demonstrated that a noncondensible gas bubble in the reactor vessel can be safely removed via the hot leg high point vents; even with a noncondensible gas bubble in the reactor vessel head, natural circulation will be maintained while the plant is cooled and depressurized to the Decay Heat Removal System entry conditions. While a residual gas bubble would still remain in the reactor vessel head following the plant cooldown, the gas bubble would not interfere with the maintenance of core cooling and could be slowly removed thereafter by various means.

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Mr. Rodriquez We conclude that an exemption to 10 CFR 50.44(c)(3)(iii) can be granted. The Exemption is enclosed; a copy of it is being filed with the Office of the Federal Register for publication. Also enclosed is our Safety Evaluation supporting the Exemption.

Sincerely,

>siclaut nam:nsg

• 30tE 1 7J054';.

John F. Stolz, Director PWR Project Directorate #6 Division of PWR Licensing-B

Enclosures:

1.

Exemption 2.

Safety Evaluation cc w/ enclosures:

See next page i

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Mr. R. J. Rodriguez Rancho Seco Nuclear Generating Sacramento Municipal Utility District Station

'cc:

Mr. David S. Kaplan, Secretary Sacramento County and General Counsel Board of Supervisors Sacramento Municipal Utility 827 7th Street, Room 424 District Sacramento, California 95814 6201 S Street P. O. Box 15830 Ms. Helen Hubbard Sacramento, California 95813 P. O. Box 63 Sunol, California 94586 Thomas Baxter, Esq.

Shaw, Pittman, Potts & Trowbridge 1800 M Street, N.W.

Washington, D.C.

20036 Mr. Robert B. Borsum Babcock & Wilcox Nuclear Power Generation Division Suite 220, 7910 Woodmont Avenue Bethesda, Maryland 20814 Resident inspector / Rancho Seco c/o U. S. N. R. C.

14410 Twin Cities Road Herald, California 95638 Regional Administrator, Region V U.S. Nuclear Regulatory Commission 1450 Maria Lane, Suite 210 Walnut Creek, California 94596 Director Energy Facilities Siting Division Energy Resources Conservation &

Development Commission 1516 - 9th Street Sacramento, California 95814 Mr. Joseph 0. Ward, Chief Radiological Health Branch State Department of Health Services 714 P Street, Office Building #8 Sacramento, California 95614 I

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