L-76-401, Letter Supplements Information Repair Report CEN-38(f)-P, Rev. 1, and Documents Results of Recent Discussions with Staff. FP&L Concluded Additional Monitoring Using Traversing Incore Probes Would Not Be Appropriate

Letter Supplements Information Repair Report CEN-38(f)-P, Rev. 1, and Documents Results of Recent Discussions with Staff. FP&L Concluded Additional Monitoring Using Traversing Incore Probes Would Not Be Appropriate

ML18127B137
Person / Time
Site:	Saint Lucie
Issue date:	11/18/1976
From:	Robert E. Uhrig Florida Power & Light Co
To:	Stello V Office of Nuclear Reactor Regulation
References
CEN-38(f)-P, Rev 1, L-76-401
Download: ML18127B137 (9)

Text

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FLORIDAPOWER & LIGHTCOMPANY Re~ulatory

)jig CVr November 18, 1976 L-76-401 Office of Nuclear Reactor Regulation Attn:

Victor Stello, Jr., Director Division of Operating Reactors U. S. Nuclear Regulatory Commission Washington, D. C.

20555

Dear Mr. Stello:

Re:

St. Lucie Unit No.

1 Docket No.

50-335 Repair Report CEN-38(f)-P, Rev.

1 Su lemental Information Pp.

g This letter supplements the information contained in the subject report.

It also serves to document the results of recent discussions with members of your staff.

Section V of the subject report indicates that the startup test program include measurements of rod worths of CEA Group 1 and shutdown group B only if the measurements of CEA groups 7,6,5,4,3, and 2 differ from predictions by a significant variation.

Rod worth measurements are to be made with the following two objectives in mind'.

1)

To verify adequate shutdown margin as defined in Section 1.13 of the Technical Specifications.

2)

To compare to design calculations.

Measurements are generally expected to agree with design values within +10% or 0.1% hie/tc, whichever is larger.

To satisfy these requirements, the following rod worth measurements shall be performed during the startup physics tests.

CEA groups 7,6,5,4,3,2 will be measured and compared to design calculations as described in item 2) above.

If these measurements (7-2) fail the above acceptance

criteria, groups 1 and B shall also be measured.

If the sum of groups 7 through 1 and shutdown group B differ by more than 10%

from the design values, then the design calculations shall be reviewed.

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To:

Re:

Victor Stello, Jr.,

NRC St. Lucie Unit No.

1 Docket No. 50-335 Supplemental Information Re air Re ort CEN-38(f)-P, Rev.

1 November 18, 1976 Page Table 1 contains the design reactivity parameters associated with the calculation,,of shutdown margin.

Xt is seen that measurement of CEA groups 7-2 xepresents more than 85%

(5%

h,v/v less 10% for uncertainty +4.5S he/w) of the rod worth required to maintain shutdown margin (5.05% h,v/v).

Therefore, adequate margin would be ensured unless predictions of the worth of the remaining rods were in error by more than 80%.

However, the revised design, calculations demonstrate-'.that, the rod worths are essentially unchanged from beginning of life (BOL) and the BOL measurements of all rods (7-1, AGB) are in excellent agreement with the original predictions.

The following additional at power monitoring is to be performed if the excore mode described in paragraph 4.2.1.2 of the Tech-nical Specifications is used, and the core burnup is less than 10 GWD/MTU.

This core burnup ensures that, in the unlikely event of redistribution and. loss of the remaining boron in a fashion similar to that experienced with the original shims, the resultant axial and radial power peaks would be within the original design criteria.

This additional monitoring will be sufficient to ensure that if the anomaly were to reoccur, it would be detected prior to original design. criteria being exceeded.

1.

The axial peaking factor is to be monitored in the maximum number of bundles possible via fixed incore Rh detectors.

The surveillance period shall be sufficient to ensure that the axial peak increases less than 3% between" measurements based on the average growth rate from the most recent measurements, but not to exceed 7 operating days.

A 3% per day growth rate in the axial peak shall be assumed until measurements are available.

All measured growth rates shall be doubled to account for measure-ment and projection uncertainties.

2.

Core power maps are to be taken weekly (7 operating days) and compared with predicted distributions.

Additional monitoring using the traversing incore probes has been evaluated.

Design calculations and measurements with incore movable fission detectors demonstrate that boron loss and redistribution as experienced in the original pins do not cause local power perturbations that. can be detected at the

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To:

Re:

Victor Stello, Jr.,

NRC St. Lucie Unit No.

1 Docket No. 50-335 Supplemental Information Re air Re ort CEN-38(f)-P, Rev.

1 November 18, 1976 Page instrument thimble (both the Rh and fission detector thimbles are located in the center guide tube).

We have concluded, therefore, that additional monitoring using the traversing in-core probes would not be, appropriate.

Very truly yours, Robert E. Uhrig Vice President REU/NLR/hlc Attachment.

cc:

Norman C. Moseley, Region II Robert Lowenstein, Esq.

TABLE 1 DESIGN REACTIVITY PARAMETERS SHUTDOWN MARGIN CALCULATIONS Power Defect (Doppler + Moderator)

Transient Xenon CEA Bite 6 Boron Deadband P/L CEA Effects Shutdown Margin 6 Accident Analysis Allowance Total Reactivity Change (unrodded) 2.3

.1.2 0.0 2.45 5.05

%b,p Rodworth Rodworth Rodworth Rodworth CEA Groups 7-2 CEA Groups l&B CEA Group A

Stuck Rodi 5.0 1.1 4.1 2

% 7 1'odworth All Rods

'Stuck Rod 7.5 Measurement Uncertainty

.8 Available Rodworth less Uncertainty 6.8 Sb,p Rodworth Excess of Shutdown Margin less Measurement Uncertainty 1.0

%hp

• Preliminary calculations Revised calculations for individual bank worths are 40% complete.

These numbers are projected from the original values using the small differences seen in the revised values.

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