ML19312B807
| ML19312B807 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 10/26/1977 |
| From: | Thies A DUKE POWER CO. |
| To: | Case E Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML19312B808 | List: |
| References | |
| NUDOCS 7911190587 | |
| Download: ML19312B807 (6) | |
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Mr. E. Case Duke Power Company 10-26-77 Charlotte, N.C.
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- fo6NAL Ng(Agggpggg 3 Simmen Proposed tech spec revisions... 3P suc*.csu as
- sseservica Ltr notarized 10 2.6-77 requesting for andt to OL/ tech specs to delete Justification for proposed revision to tech the existing reactor core quadrant power specs...
3P tilt & control rod position limits &
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Dear Sir:
Pursuant to 10CFR50.90, an amendment is requested to Oconee Nuclear Station Facility Operating Licenses DPR-38, -47 and -55 to delete the existing reactor core quadrant power tilt and control rod posi-tion limits for Oconee Unit 1 specified in Technical Specifications 3.5.2.4.a and 3.5.2.5.c.
The attached Technical Specification revision pages indicate those more conservative limits which will be instituted. The justification for this action is provided in to this letter.
This change is requested on a prompt basis with approval requested by October 31, 1977.
Very truly yours, A. C. Thies ACT:ge Attachments 773000286
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October 26, 1977 Page 2 A. C. THIES, being duly sworn, states that he is Senior Vice President of Duke Power Company; that he is authorized on the part of said Company i
to sign and file with the Nuclear Regulatory Commission 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.
WS A. C. Thies, Senior Vice President Subscribed and sworn to before me this 26th day of October 1977.
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Notary Public My Commission Expires:
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ATTAC10!ENT 2 OCONEE NUCLEAR STATION JUSTIFICATION FOR PROPOSED REVISION TO THE TECFNICAL SPECIFICATIONS October 26, 1977 l
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JUSTIFICATION FOR PROPOSED REVISIONS TO THE OCONEE TECHNICAL SPECIFICATIONS Revisions to the Oconee Nuclear Station Technical Specifications were approved by the'NRC on October 4, 1977 to permit the operation of Oconee 1, Cycle 4.
Subsequent pre-critical control rod drive trip time tests and zero power critical boron concentrations, temperature reactivity coef ficients, and control rod group worth' measure =ents demonstrated that these parameters were within the established accep-tance criteria.
Ejected rod worth measurements were made of Group 6, rod 4 at core location N-12 which had been predicted to be the highest worth ejected rod.
The test showed this rod to have 38% less worth than predicted.
The established acceptance criteria for ejected rod worth is i 20% of the predicted value.
Three other Group 6 rods located sy= metrically to this control rod were then measured for ejected rod worth and all had greater worths than the rod in question, but all were still less than the predicted value.
The data from these measurements also indicated a difference in the worth of symmetric reds.
Another series of ejected red worth measurements were =ade for each location in the inner ring of Group 6 control rods and these indicated close agreement.
Since all other parameters were within the acceptance criteria and the ejected rod worth measurements were more conservative than predicted, power escalation. testing to further evaluate this situation was considered prudent and cafe.
At the first plateau at 15% full power a core tilt was observed on the out of core detectors. An incore power map was taken which indicated a tilt of approximately + 10% in the WX quadrant and -12%
in the YZ quadrant.
The positive tilt quadrant contains the rod of maximum measured ejected rod which is consistent with the presence of the tilt.
An evaluation of this situation was made co determine possible causes of the tilt. Power escalation to 40% full power was performed to obtain an accurate incore power map and to observe the effects of increased powar on the tilt.
The results of the powar map confirmed the presence of the tilt and showed that the magnitude decreased with power level and the tilt did not appear to be significantly axially dependent.
Numerous verifications have been performed to detect a misloaded fuel assenbly, control' rod, or orifice rod.
Testing has been accomplished designed to dctact an' uncoupled control red and/or missing pins Ed control rods with no significant findings.
The integrity of the control rods has been assured by the absence of silver concentrations in the reactor coolant.
Also, operation in an all rods-out configuration has not significantly reduced the magnitude of the tilt.
Reviews have also been conducted of-manufacturing and design records and of changes to the initially designed core and these have not revealed'the cause of the core tilt.
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.As permitted by the Oconce Technical Specifications, cont nued physics i
-testing at the 40 percent plateau in in progress.
Escalation to the 75 percent plateau is planned on October 28, 1977 to'obtain more informa-I tion on the core power distribution and 1x1 the power dependence of the tilt limitations as outlined in the attached Technical Specifications.
The operating limits provided in the proposed Technical Specification i
3.5.2.8 are based on both analysis and measured data.
The analyses which established the current quadrant tilt and rod position limits in Specifi-cations 3.5.2.4 and 3.5.2.5 were based on a maximum quadrant tilt of 3.41%, which would produce a maximum power peaking increase of 5.1%.
The provision to operate at up to 6.03% quadrant tilt would. produce a maximum-power peaking increase of 9.0",
or 4% more than originally con-sidered.
However, the imbalance limits in Specification 3.5.2.6 applicable i
to Oconee I, Cycle 4, for the period of 0-100 + 10 EFPD are quite conservative below 90% of full power.
Based on =aintaining the limits of 3.5.2.6 at 4
and below 75% of full power and on =aintaining the rod position limits ot 3.5.2.8, the maximum clad temperature in the event of a L.0CA will not exceed the Final Acceptance Criteria.
The rod position limits of 3.5.2.8 also provide that the shutdown =argin and ej ected red worth criteria are met.
The measured hot zero power values I
of the worth of banks 5-7 and the ejected rod were compared to' the predicted values, and the most conservative set of values were used to determine new shutdown margin and ejected rod worth insertion limits.
Figure 3.5.2-6Al-shows the interim-rod position limits and the shutdown and ejected rod worth insertion limits derived as described above.
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