ML20136F595
| ML20136F595 | |
| Person / Time | |
|---|---|
| Site: | Saint Lucie  |
| Issue date: | 05/16/1995 |
| From: | NRC |
| To: | |
| Shared Package | |
| ML20136C539 | List:
|
| References | |
| FOIA-96-485 NUDOCS 9703170010 | |
| Download: ML20136F595 (5) | |
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UNITED STATES ye j
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%, *****o ENCLOSURE 1 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATING TO TECHNICAL SPECIFICATION CHANGE TO RELOCATE H-CORE INSTRUMENT RE0VIREMENTS FLORIDA POWER & LIGHT COMPANY ST. LUCIE UNITS 1 AND 2 j
DOCKET N0. 50-335 AND 50-389
1.0 INTRODUCTION
By letter dated January 20, 1995 Florida Power & Light Company requested changes to the Technical Specifications for St. Lucie Units 1 and 2.
These proposed changes would eliminate Technical Specification 3/4.3.3.2 and relocate the limitations on the use of the Incore Instrument (ICI) System to the St. Lucie Updated Final Safety Analysis Report (UFSAR) for each unit.
Also, the uncertainty factors specified in Linear Heat Rate (LHR) Surveillance j
Requirement (SR) 4.2.1.4.b that are associated with the incore detector Local Power Density alarm setpoints will likewise be relocated.
The ICI system at St. Lucie Unit I consists of 45 neutron detector strings positioned in the center of selected fuel assemblies.
St. Lucie Unit 2 has 56 similar neutron detector strings in the ICI system.
Each detector string consists of 4 rhodium neutron detector segments located at 20, 40, 60, and 80%
of core height. The neutron flux indicated by the detector segments is processed by a full-core power distribution system to determine the peak linear heat rate, peak pin power, radial peaking factors, and azimuthal power tilt for comparison to the Technical Specification limits. Thus the In-Core i
Instrumentation system is directly used to verify important safety parameters, 2.0 EVALUATION i
Essentially all PWR Technical Specifications contain a requirement for operability of 75% of the incore detector locations for mapping of the core 3
9703170010 970301 PDR FOIA BINDER 96-485 PDR
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2 power distribution.
In-core detector data is used to calculate power peaking factors which are used to verify compliance with fuel performance limits.
While relocating the ICI System operability requirements is not a concern, the possibility of changing the number and/or distribution requirements is of great concern.
On a number of occasions, for various reasons, failures of detector strings in operating PWRs have approached or exceeded 25%, and relaxation of the 75%
requirement has been permitted for the duration of the affected operating cycle. This relaxation was justifiable because the reactor had started the cycle and performed the physics startup tests with at least 75% of the incore detector locations operable, general trends for the cycle had been established and the system would be restored to full (or nearly full) compliment before beginning the next cycle.
In addition, the uncertainties on the measurements was increased to account for fewer operable detectors.
A significant safety concern relating to degration of incore mapping ability is the ability to detect anomalous conditions in the core. One of these is the inadvertent loading of a fuel assembly into an improper position. Since this is a loading problem, it is of great concern if long-term operation with fewer than 75% of the detectors is considered.
It is not of as much concern when relaxation of requirements is considered for only the remainder of an operating cycle.
The current Technical Specification 3.3.3.2. requires at 75% of all incore detector locations to be operable and a minimum of two quadrant symmetric incore detector locations per core quadrant. A minimum of three of the rhodium detectors on a detector string must be operable for the string to be operable. These requirements were established to ensure adequate core coverage. Changes to these requirements must be carefully reviewed and justification provided to specify how adequate core coverage would be maintained and how anomalies would be detected.
The licensee has stated that changes to the requirements on number and/or distribution of operable incore detectors will be evaluated under CFR 50.59 or
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3 by license amendment.
In order to change the requirements concerning the number and location of operable detectors a rigorous evaluation and justification is required. The following considerations must be included in a 50.59 evaluation if changes to the requirements for the ICI system are proposed:
- 1) how an inadvertent loading of a fuel assembly into an improper location will be detected,
- 2) how the validity of the tilt estimates will be ensured,
- 3) how adequate core coverage will be maintair.ed,
- 4) a list of the measurement uncertainties and why the added uncertainties are adequate to guarantee that measured peak linear heat rates, peak pin powers radial peaking factors and azimuthal power tilts will meet Technical Specification limits, and
- 5) how the ICI system will be restored to full (or nearly full) service before the beginning of each cycle.
3.0 TECHNICAL SPECIFICATION CHANGES i
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Section 3/4.3.3.2 - This section will be eliminated and the limitations on the t
use of the ICI System will be relocated to the Updated Final Safety Analysis Report (UFSAR). This is acceptable as discussed in Section 2 above.
Surveillance 4.2.1.4.b - Remove the uncertainty factors applied to the ICI System and relocate them to the UFSAR. This is acceptable as discussed in Section 2 above.
INDEX Pages IV and V - delete "Incore Detectors" and the associated page reference.
TS 4.10.2.2, 4.10.4.2 (PSL2 only), and 4.10.5.2 will be revised to delete reference TS 3.3.3.2 and include reference TS 4.2.1.4 (LHR).
Bases Section 3/4.2.1 - Revise to. delete the numerical values listed for the i
uncertainty allowances.
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Bases Section 3/4.3.2 - replace with the word "DELEATED".
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4.0 CONCLUSION
Based on the staff evaluation in Section 2.0 above, the staff concludes that eliminating Technical Specification 3/4.3.3.2 and relocating the limitations i
on the use of the ICI System to the UFSAR is acceptable. However changes to the number and distribution of incore detector measurements necessary to j
measure the core power distrfhution limits require rigorous evaluation and justification as detailed in Section 2 above. The staff emphasizes that it 4
would be prudent to restore the ICI system to a full or nearly full complement of detectors at the beginning of each cycle.
We have concluded, based on the considerations discussed above, that: (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, and (2) such activities will be conducted in compliance with the commission's regulations, and j
issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public.
5.0 REFERENCES
1.
Florida Power & Light Company to NRC, letter dated January 20, 1995.
Principle Contributor:
M. Chatterton l
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.r ENCLOSURE 2 SYSTEMATIC ASSESSMENT OF LICENSEE PERFORMANCE FACILITY NAME St. Lucie Units 1 & 2
SUMMARY
OF REVIEW The proposed Technical specification change to eliminate Technical Specification 3/4.3.3.2 and relocate the operability requirements of the ICI System to the St. Lucie Unit 1 & 2 Updated Final Safety Analysis Report was reviewed. As expressed in the SER, elimination of the Tech Spec and relocation of the operability requirements is not of great concern, however changes to the operability requirements is of great concern and conditions were detailed in Section 2 of the SER.
NARRATIVE DISCUSSION OF LICENSEE PERFORMANCE -
SAFETY ASSESSMENT /00ALITY VERIFICATION The submittal was well reasonably written and fairly complete.
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AUTHOR:
M.Chatterton[/5' DATE:
05//6/95 1