ML19312B775

Forwards Justification for Full Power Operation in Unrodded Mode in Cycle 4 of Unit 1 & Proposed Tech Spec 3.5.2 Permitting Operation in Unrodded Mode.Requests Prompt Approval

ML19312B775
Person / Time
Site:	Oconee
Issue date:	11/09/1977
From:	Parker W DUKE POWER CO.
To:	Case E Office of Nuclear Reactor Regulation
Shared Package
ML19312B776	List: ML19312B775 ML19312B777
References
NUDOCS 7911190566
Download: ML19312B775 (9)

Text

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f DISTRI3UTION AFTER ISSUANCF~? OPERATING LICENSE q

U.C. NUCLEAR AGGULAToRY wJMMISSio OoCKET NUMO3 A j

.J RC Fccu.195 50-269

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NRC DISTRIBUTION pon PART 50 DCCKET MATERIAL iTO:

Mr. Edson G. Case FRCM: Duke Power Co.

CATE CF CCCUMENT 11/09/77

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Charlotte, N. C.

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William O. Parker, Jr.

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2CNcLAssiniso C C0" 3 </66)M auc csuas i:sscrirrioN Notorized 11/09/77...Trans The Consists of Oconne 1, Cycle 4 Just-Following:

ification For Full Power Operation In An Un-Rodded Mode and Revision request for Amendment to the Oconne Tech Specs which will permit opera _l tion of Oconne 1, Cycle 4 in the unrodded mode..

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G5iudDRY dom ta@py DUKE POWER COMPANY Powra BUILDING 422 SocTu CncHcu STREET, CluRWTTE, N. C. 28242 e ~K November 9, 1977 wiw-o. pan aca. a n.

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Y RE: Occaee Unit 1 Docket No. 50-269 coi g

Dear Sir:

My letter dated October 4, 1977 advised you of the results of the Oconee 1, Cycle 4 startup physics testing program.

A core tilt in excess of the Technical Specification limits for normal operation was observed at reactor power levels of 40 percent full power. Power escalation to the 75 percent plateau was planned te enable further physics testing to investigate the presence of the core tilt.

An amendment was requested to the Oconee Technical Specifications to permit continued operation with a core tilt in excess of the Technical Specifications limits at 75 percent full power with certain conserva-tive limits applied.

By letter dated October 31, 1977, these amend-ments were approved by the NRC.

The reactor has operated at 75 percent full power and the core tilt has decreased to near the original Technical Specification limit of 3.41%.

The cause of the core tilt has not yet been identified although investigations are continuing. Analyses have been performed, however, which demonstrate the capability for safe operation of the Oconee 1, Cycle 4 core at full power for 100 EFPD in an unrodded mode assuming a real core tilt of 6%.

Analyses for operation beyond 100 EFPD will be performed at a later date. A summary of these considerations is provided in Attachment 1.

Pursuant to the provisions of 10CFR50.90, an amendment is requested to the"Oconee Technical Specifications which will permit operation of Oconee 1, Cycle 4 in the unrodded mode. The requested revision is indicated in Attachment 2.

Although operation is currently permitted under the original Technical Specifications if the core tilt returns to less than 3.41% and power ascention testing is accomplished in the rodded mode, it is considered desirable and prudent to provide for continued operation in an unrodded mode. Therefore, it is requested that these amendments be approved on a prompt basis.

Ver truly yours,f

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&.... b. n y William O. Parker, Jt/

MST:ge 773410112 Attachments

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.J November 9, 1977 Page 2 i

WILLIAM 0. PARKER, JR., being duly sworn, states that he is Vice President of Duke Power Company; that he is authorized on the part of said Company to sign and file with the Nuclear Regulatory Comission this request for amendment of the Oconee Nuclear Station Facility Operating Licenses DPR-38, DPR-47, and DPR-55; and that all statements and matters set forth therein are true and correct to the best of his knowledge.

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William O. Parker, Jr., Vice President Subscribed and sworn to before me this 9th day of November, 19'7.

hcdee hAs Notary Public My Comission Expires:

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ATTACHMENT 1 OCONEE 1, CYCLE 4 JUSTIFICATION FOR FULL POWER OPERATION IN AN UNRODDED MODE e

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J OCONEE 1, CYCLE 4 JUSTIFICATION FOR OPERATION IN AN UNRODDED MODE Power Peaking Conservatisms The power peaking analysis for Oconee 1 Cycle 4 operation from 0 to 100 EFPD in the unrodded mode was performed assuming the existence of a 6%

real quadrant tilt at all power levels.

This tilt was determined to cause a 9% increase in local peaking, based on two factors:

a) this represents the relationship between peaking and tilt established by many full-core PDQ calculations with induced tilts, and b) the comparison of calIculated and measured power distribution shown in Figures 1 and 2 at 40 and 75% of> full power show that a factor of 1.09, in conjunction with the standard total and radial nuclear uncertainty factors would be conservative.

All other peaking penalties normally included in the generation of Technical Specification operating limits were included in this analysis.

The present cycle 4 Reactor Protective System limits, Figure 2.1-2A, were shown to be valid under the above conditions.

i Table 1 provides a comparison of the total peaks calculated during each time step of the fuel-cycle through 100 EFPD.

Operation in the unrodded mode was found to provide reduced total peaks during the fuel cycle at all times after the 4 EFPD time step compared to rodded operation.

Since the base peaking is lower for the unrodded cores the perturbed peaking is also lower.

This is especially true when bank 7 is confined to the range of 295% WD to 274% WD at full power, as restricted by the proposed Figure 3.5.2-1A1.

Operating in the unrodded mode provides a means to restrict power peaking to nominal values.

This protection is gained at the expense of operational flexibility. With this mode of operation the plant has a greatly reduced maneuvering capability.

However, as stated above, the usual peaking factors due to xenon changes induced by normal maneuvering were included in the analysis, providing additional conservatism.

Ejected Rod Limits-The ejected rod worth insertion limits were determined based on using the hot, zero power measured values to correct for the quadrant tilt effects.

The resulting maximum ejected rod worth correction factor was over 50%.

This factor was used to adjust calculated efected rod worths for the exis-tence of the quadrant tilt.

The net result of this procedure is the decrease in the amount that the operating banks may be inserted to satisfy the criteria during a postulated ejected rod accident.

The resulting rod insertion limits-were less limiting than shutdown margin criteria at all power levels above O

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.J zero power. Thus only the zero power limit (30% withdrawn) is based on ejected rod criteria.

$hutdown Rod Insertion Limits The shutdown rod insertion limits were determined using standard techniques based on symmetric conditions and adjusting these calculations to account for the tilt.

The calculated stuck rod worths are increased over 50%. The measured values of banks, 5, 6 and 7 at HZP were also used to determine the shutdown margin rod insertion limits.

As an added conservatism the Boc j

calculated total rod worth was used at 100 EFPD to determine the limits at this time.

The result of this procedure is the conservative shutdown rod insertion limits shown in Figures 3.5.2-1A1 and 3.5.2-2A1.

Discussion The net effect of all these conservatisms is that the core is restricted in operating flexibility but allowed to operate at full power in a safe manner.

The current APSR position limits (Figure 3.5.2-5A1) and tabalance limits Figure 3.5.2-3A1) for 0 to 100 EFPD are more restrictive than necessary for the proposed mode of rods-out-operations.

This represents another conserva-tism La the analysis.

The rod position limits were determined based on the super-position of the most conservative calculated and measured data.

The limits are' clearly conservative.

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TABLE 1 FLAME Calculated Total Peaks For Unrodded And Rodded Operation i

Unrodded Rodded Time Max. Calc.

Max. Cal.

EFPD Total Peak Total Peak

% Difference 0

1.647 1.581 (4.17) 4 1.572 1.524 (3.15) 25 1.476 1.521 2.96 50 dr 1.424 1.481 3.85 100 1.393 1.455 4.26 1

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