ML20056H319
| ML20056H319 | |
| Person / Time | |
|---|---|
| Site: | McGuire, Mcguire  |
| Issue date: | 08/24/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20056H315 | List: |
| References | |
| NUDOCS 9309090147 | |
| Download: ML20056H319 (5) | |
Text
.
1 k;
.. t
[Q ggf[
E UNITED STATES NUCLEAR REGULATORY COMMISSION
.4y wasmuctow. o c. mss-v '.s ENCLOSURE 1 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATING TO BORON SYSTEM CONCENTRATION CHANGES FOR DUKE POWER COMPANY
?
MCGUIRE UNITS 1 AND 2 DOCKET NOS. 50-369 AND 50-370 l
l
1.0 INTRODUCTION
By letter dated July 13, 1993, the Duke Power Company requested NRC approval to increase the minimum Refueling Water Storage Tank (RWST) boron concentration to 2175 ppm, increase the minimum Cold Leg Accumulator (CLA) boron concentration to 2000 ppm and several other related changes. These changes are reflected in proposed Technical Specifications (TS) 3.1.2.5, 3.1.2.6, 3.5.1.1, 3.5.5, 3.9.1, 3.9.12 and 4.9.12 and the appropriate sections of the TS bases. The staff's safety evaluation of the proposed changes follows.
2.0 EVALUATION t
2.1 Chances to RWST Boron Concentrations i
In order to accomodate a core with a larger percentage of Mark-BW fuel in cycle nine and subsequent cycles, Duke's cycle 9 reload analysis showed that an increase in the minimum RWST minimum boron concentration was required in order to meet shutdown margin requirements. The proposed minimum RWST boron concentration is 2175 ppm and Duke states that their analysis showed that this concentration is sufficient to maintain long term sub-criticality following a Loss of Coolant Accident (LOCA).
In order to maintain a 100 ppm operating window, it is proposed to increase the maximum boron concentration to 2275 ppm. Duke's analysis of the above changes was performed with well established and NRC approved methods (ref.1) using appropriate conservatism.
9309090147 930824 PDR ADOCK 05000369 P
PDR; f
\\
t The staff finds these changes acceptable.
Several changes are proposed for Unit 1 in order to reduce the differences between the two unit's TS. These changes involve increasing the maximum RWST boron concentration from 2100 ppm to 2275 ppm and implementing the recirculation sump pH change discussed in the following section. Duke's analysis of the above changes was performed with well established and NRC approved methods (ref.1) using appropriate conservatism. The staff finds these changes acceptable.
The RWST boron concentration change has prompted Duke to make the following additional changes to the Unit 1 TS:
1.
It is proposed to increase the minimum boron concentration in the refueling canal and the spent fuel pool to 2175 ppm to ensure that the i
RWST boron concentration will remain within specification following refueling operations. The staff considers this change acceptable because it meets the shutdown margin requirements.
I r
2.
The minimum post-LOCA coolant pH has been revised from 8.5 to 7.5 due to i
the increased acidity of the water. The staff feels that this should not pose any additional threat of corrosion to the reactor vessel, piping, etc. because this pH value is above the minimum recommended value in the Standard Review Plan, Section 6.1.1 " Engineered Safety Features Materials." The staff, therefore, finds this change acceptable (Note that this change is also made to Unit 2 as previously discussed).
3.
To preclude boron precipitation at this higher concentration, Duke l
proposes to reduce the hot leg recirculation initiation time from 9 hours1.041667e-4 days <br />0.0025 hours <br />1.488095e-5 weeks <br />3.4245e-6 months <br /> to 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br />. Duke's analysis has shown this to be acceptable and I
the staff concurs in this finding.
l t
I r
i I
I
l:
- l t
2.2 Cold Leo Accumulator Boron Chance j
Duke's Unit 2, Cycle 9 reload analysis showed that in order to maintain post-l LOCA sub-criticality, the CLA minimum boron concentration needs to be raised j
from 1900 ppm to 2000 ppm.
Furthermore, Duke proposes to increase the maximum l
CLA boron corcentration from 2100 ppm to 2275 ppm to maintain an operating l
1 margin.
This change is also being applied to Unit 1 in order to maintain j
similar TS between the two units. The previously discussed changes to the i
post-LOCA pH and the hot leg recirculation initiation time are appropriate for these proposed CLA boron concentrations as well. The proposed CLA boron concentration changes were analyzed by Duke using well established and NRC approved methods (ref.1) and the staff finds them acceptable.
Duke also proposes to increase the volume weighted accumulator boron concentration from 1500 ppm to 1900 ppm for Unit 2 and from 1500 ppm to 1800 ppm for Unit 1.
This large change is necessary due to the fact that the minimum volume weighted boron concentration should have been increased to 1800 I
ppm for both units in their cycle 8 reload report, but, as Duke states,
...(was) inadvertently left out."
The proposed change from 1500 ppm to 1900
[
~
ppm boron will bring Unit 2 up to the value required for cycle 9 operation and I
an increase to 1800 ppm for Unit I will bring Unit I up to an acceptable value for its current cycle. The evaluation of the above changes was performed with l
well established and NRC approved methods (ref.1) and the staff finds them acceptable, f
i
3.0 CONCLUSION
S i
Based upon the above discussion, the staff concludes that the proposed
{
Technical Specification changes relating RWST and CLA boron concentrations are acceptable. The staff's conclusion is based upon the following:
1.
The referenced analysis used established techniques that were properly verified.
2.
The analysis was suitably conservative and bounding.
i 3
- i...~,_.,.__
]
1 l I 3.
The consequences of limiting accidents are acceptable.
4.
The proposed TS are consistent with the analyses provided.
i The staff has concluded, based upon 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 issuance of this amendment will not be inimical to the common defense and i
security.
l
4.0 REFERENCES
L 1.0 "DPC-NF-2010A, McGuire Nuclear Station / Catawba Nuclear Station Nuclear Physics Methodology for Reload Design," Duke Power Cor.ipany, June 1985.
[
I L
I I
i i
i i
k i
i
?
L
r i
4 I
SYSTEMATIC ASSESSMENT OF LICENSEE PERFORMANCE FACILITY NAME McGuire Unit 1 and 2 I
SUMMARY
OF REVIEW This SER reviews a request to increase the RWST boron concentration from 2000 ppm to 2275 ppm and to increase the CLA boron concentration Trom 1900 ppm to 2000 ppm. We find the criticality aspects of this request acceptable.
NARRATIVE DISCUSSION OF LICENSEE PERFORMANCE - SAFETY ASSESSMENT /0VALITY YE_RIFICATION The licensee's submittal was adequate to determine the criticality effects of the proposed changes. No additional information was necessary.
I AUTHOR:
T. ULSES DATE:
08/20/93