ST-HL-AE-3283, Application for Amends to Licenses NPF-76 & NPR-80,revising Tech Specs to Extend Allowed Outage Times & Surveillance Test Intervals Based on PRA of Current Tech Specs
| ML20006D115 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 02/01/1990 |
| From: | Vaughn G HOUSTON LIGHTING & POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20006D116 | List: |
| References | |
| ST-HL-AE-3283, NUDOCS 9002120111 | |
| Download: ML20006D115 (12) | |
Text
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The Light L
company l-P.O. Box 1700 liouston. Texas 77001 (713) 228 9211 llouston Lighting & Power.
L February 1, 1990 ST llL AE 3283 File No.: G20.02.01 l-C2.05 10CTR50.90 L.
U. S. Nucicar Regulatory Commission L
Attention:
Document Control Desk
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Vashington, DC 20555 l
South Texas Project Electric Generating Station
-Units 1 and 2 Docket Nos. STN 50 498, STN 50 499 Proposed Amendment to the Unit 1 and Unit 2 Technical Snecifications Based on Probabilistic Risk Analyses
Reference:
ST llL AE 3217 dated August 31, 1989 Pursuant to 10CFR50.90, Houston Lighting & Power Coapany (HL&P) hereby proposes to amend its Operating Licenses NPF 76 and NPF-80 for the South Texas Project Electric Generating Station (STPEGS), Units 1 and 2, by incorporating the attached proposed changes to the STPEGS Technical Specifications.
These changes were submitted to the staff for preliminary review by the reference letter.
In this letter, llL&P also committed to formally submit the proposed changes to Technical Specifications by the end of, December, 1989. An extension to January 31, 1990 was discussed with Mr. G. F. Dick of the NRC staff.
The proposed changes consist of extended allowed outage times (A0T) and surveillanco test intervals (STI) for the 22 Technical Specifications shown in, based on a probabilistic risk analysis (PRA) of the current STPEGS Technical Specifications. This PRA based study of the Technical Specifications is provided as Attachment 3.
The significant hazards evaluation is provided as Attachment 1.
l STPEGS has three electrically independent and physically separate safety trains.- The current STPEGS Technical Specifications are generally based on the Standard Westinghouse Technical Specifications which were developed for Vestinghouse two train designs that preceded STPEGS.
Consequently, credit has not generally been given to STPEGS for the added safety of the three train design.
Based on a probcbilistic analysis of plant risk, the proposed changes will, when approved, more accurately reflect the A0Ts and STIs necessary to allow acceptable maintenance and surveillance durations and frequencies for the added equipment of the three train design and keep risk to an acceptably i
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low value.
In addition, a number of other related Technical Specification
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changes are proposed and evaluated which are also shown to have little or no impact. No changes to the bases for the affected Technical Specifications are i
required since the proposed changes do not affect analysis assumptions regarding the functioning of required equipment designed to prevent or
[h mitigate the consequences of accidents. The minimum requirements for equipment operability are not changed.
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Implementation'of the proposed changes will have a positive.effect which.
has not been included in the evaluation.
Longer A0Ts are expected to allow z
substantially increased actual maintenance times on equipment during planned l
outages without increasing r.nerall unavailability. This is expected to result in improved equipment perfctmance and reliability as well as reduced equipment j
unavailability due to human error.
lii4P has revi.ewed the attached propesed amendment pursuant to 10CFR$0.92 and determined that it does not involve a significant hazards consideration.
l The basis for this determination is provided in the attachments.
In addition, L.
based on the information contained in this submittal and the NRC Final Environmental Assessment for STPEGS Units 1 and 2, Hi4P has concluded that, pursuant to 10CFR51, there are no significant radiological or nonradiological impacts associated with the proposed action and the proposed license amendment will not have a significant effect on the quality of the environment.
The STPEGS Nuclear Safety Review Board has reviewed and approved the proposed changes..
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In accordance with 10CFR50.91(b), HIAP is providing the State of Texas with a copy of this proposed amendment.
If the NRC should have any questions concerning this matter, please contact Mr. A. W. Harrison at (512) 972-7298 or myself at (512) 972-7921.
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G. E. Vaughn l.
Vice President l
Nuclear Operations CEV/ RAH /n1 L
Attachments:
- 1. Significant Hazards Evaluation for Risk Based Changes to j.
Technical Specifications
- 2. Mark-ups of Proposed Changes to Technical Specifications l
- 3. Risk-Based Evaluation of STPEGS Technical Specifications A1/045.NL9 l
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ST.HL AE 3283 Houston tighting & Power Company File No. : 020.02.01, G2.06 South Texas Project Electric Generating Station Page 3 cc:
Regional Administrator, Region IV Rufus S. Scott Nuclear Regulatory Commission Associate General Counsel
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611 Ryan Plaza Drive, Suite 1000 Houston Lighting & Power Company
. Arlington, TX 76011 P. O. Box 61867 l
Houston, TX 77208 George Dick, Project Manager U.S. Nuclear Regulatory Commission INPO o
i Washington, DC 20555 Records Center 1100 circle 75 Parkway.
J. I. Tapia Atlanta, CA 30339 3064 L
Senior Resident Inspector
-c/o U. S. Nuclear Regulatory Dr. Joseph M. Hendrie Commission.
50 Be11 port Lane P. O. Box 910 Be11 port, NY 11713 Bay City, TX-77414 i
D. K. Lacker
.J. R. Newman,' Esquire Bureau of Radiation Control Newman & Holtzinger, P.C.
Texas Department of Health 1615 L Street, N.W.
1100 West 49th Street Washington, DC 20036 Austin, TX 78704 D. E. Ward /R. P. Verret Central Power & Light Company P. O. Box 2121 Corpus Christi, TX 78403 J. C. Lanier L
Director of Generation l
City of Austin Electric Utility
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721 Barton Springs Road 1
Austin, TX 78704 L
R. J. Costello/M. T. Hardt l'
City. Public Service Board l
P. O. Box 1771 San Antonio, TX 78296 l
t Revised 12/15/89 LA/NRC/
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n, UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION In the Matter
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Houston Lighting & Power
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Docket Nos. 50-498 Company, et al.,
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50-499
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. South Texas Project'
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Units 1 and 2
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APFIDAVIT G. E. Vaughn being duly sworn, hereby deposes and says that ho is Vice
' President, Nuclear Operations, of Houston Lighting & Power Company; that he is duly authorized to sign and file with the Nuclear Regulatory Commission the proposed risk-based changes to the STPECS Technical Specifications shown in of
- ; is familiar with the content thereof; and that the matters set forth therein are true and correct to the best of his knowledge and belief.
M G.
E.
Vaughn
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Vice President, Nuclear Operations i
STATE OF TEXAS )
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Subscribed and sworn to before me, a Notary Public in and for The State J d w a h, 1990.
of Texas this Mt day of l
- ler, SHARON DONAHY f
gffg, hug /
Notary Pubhc STAYL OF TEXAS i
Notary Public in and for t $
State of Texas l
}# My Comm. Exp. Apt,6,1991 L
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l ATTACHMEKi
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i ATTACHMENT 1 i'
SIGNIFICANT HAZARDS EVALUATION FOR RISK-BASED CHANGES TO TECHNICAL SPECIFICATIONS l
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L ATTACHMENT 1 SIGNIFICANT HAEARDS EVALUATION FOR RISK-BASED CHANGES TO TECHNICAL SPECIFICATIONS l
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Backcround The proposed changes to STPEGS Technical Specifications are extended allowed outage times (AoT) and surveillance test intervals (STI) for selected systems evaluated on a risk basis for STPEGS (Attachment 3).
The baseline for this evaluation is the " South Texas Project Probabilistic Safety Assessment (PSA)," and other supporting material submitted by letters ST-HL-AE-3059 and i
ST-HL-AE-3137 from H. A. McBurnett to the Document Control Desk dated April 14, 1989 and June 15, 1989, respectively. The PSA was rebaselined for i
.this evaluation due to changes in modeling for the Auxiliary Feedwater (AFW)
System.
i For systems important in mitigating core damage (CD), the risk-based evaluation computes system unavailability and core damage frequency (CDF) using the proposed A0Te and STIs in Attachment 2.
The result is then compared to the rebaselined PSA values,to determine a change in system availability and a change in CDF for each corresponding Technical Specification change proposed. The lengths of A0T and STI extensions are justified by small percentage changes in CDF and changes in CDF to an already low absolute value.
i For systems having Technical Specifications which are not modeled in the PSA and which are not important for mitigating CD, a qualitative justification l
explains why these systems do not impact CDF and should have AoT or STI extensions.
STPEGS has three electrically independent and physically separate safety trains as compared to two safety trains for the standard Westinghouse plants.
Since the STPEGS Technical Specifications are based on this standard two train design, credit has not generally been given for the added safety of the STPEGS design. Based on probabiliotic plant risk, the proposed changes will more accurately reflect the nocessary AOTs and STIs for a three safety train design.
In addition, a r. umber of other related Technical Specification changes are proposed and evaluated.
Other proposed Technical Specification changes based on probabilistic risk analyses were approved for the Seabrook, Byron, Brunswick, Hatch, and other l
nuclear plants.
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Proposed chance The proposed changes are primarily extensions of AoTs from three to ten days and STIs from monthly to quarterly.
Table I summarises the proposed changes to STPEGS Technical Specifications. Markups of the proposed changes are shown in Attachment 2.
No changes are proposed to the bases of the Technical Specifications because the minimum requirements for equipment operability are not altered as a result of the proposed changes.
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ATTACHMENT 1 Safety Evaluation The proposed changes are evaluated in a risk-based analysis using the rebaselined PSA as a basis for comparison. 'The rebaselined PSA is representative cf plant design and operational status as described in the Final Safety Analysis Report and other licensing basis documents. The risk-based evaluation of STPEGS Technical Specifications (Attachment 3) concludes that the proposed changes in CDF are acceptable and that scheduled maintenance and testing would be reduced as allowed by the longer AOTs.
Changes are proposed to the 22 Technical Specifications which are summarized in Table 1 of this attachment. The proposed changes have been evaluated quantitatively and/or qualitatively using the PSA as the basis.
Change in calculated CDP is used as the figure of merit.
The effect of each change is calculated individually in the case of 16 changes and is evaluated j
qualitatively in the case of six of the changes. Attachment 3 contains the l
qualitative and quantitative assessments.
Although the systems evaluated qualitatively are modeled in the PSA, the Technical Specifications under evaluation for these systems are not modeled.
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.The proposed changes, when considered individually, affect the calculated CDF from zero percent up to approximately 30%.
The resulting changes l
in CDF are not additive due to the interdependencies of plant systems in preventing core damage. Core damaga -
- occur as the result of the j
unavailability of several systems <
.ed by separate Technical Specification L
' requirements. All changes when es fed together affect the calculated CDP by l
increasing the mean frequency from "x10 to 2. 7 5x10~', a change of I.
approximately 69%.
The effect of the che
- posed to the STPEGS Technical Specifications are small when,
dered in comparison to the overall uncertainty in the calculated core damage frequency. The overall uncertainty in CDF is in excess of a factor of ten.
Therefore, the impact of the proposed changes is not considered significant.
Implementation of the proposed changes will have a positive effect which
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has not been quantified.
As the result of the longer AoTs, scheduled maintenance, which is currently performed approximately quarterly, can now be L
performed approximately semiannually in equipment outages of longer duration.
l Actual time spent in performing scheduled maintenance on equipment each year is expected to increase since less time will be lost in disassembling, assembling, L
testing, and returning the equipment to service. This is expected to result in is improved equipment performance and reliability as well as reduced equipment l
unavailability due to human error.
The STPEGS PSA is currently under review by the NRC and its contractors.
This PSA has been completed using a very conservative methodology, approach and data base.
It is expected that the NRC's review will confirm this result.
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ATTACHMENT 1 Determination of Sionificant Hazards Pureuant to 10CFR50.91, this analysis provides a determination that the-proposed changes to Technical 3pecifications do not involve any significant hazards consideration as defined in 10CFR50.92.
(1)
The proposed changes do not involve significant increases in the probability or consequences of accidents previously evaluated.
The proposed changes result in small calculated numerical changes in CDF
-(increases of 30% or less each over 1.63 x 10" events per year)..In the context of the uncertainty in estimating CDF, as has been done for STPEGS and many other nuclear plant's PRAs, these proposed changes in CDF are not significant. Since CDF is not changed significantly by the i
proposed changes, the probability of previously evaluated accidents is not increased significantly.
Since the proposed changes to AOTs and STIs do not alter equipment or assumptions made in accident analyses, the consequences of previously evaluated accidents are not increased.
(2)
The proposed changes do not create the possibility of a new or different kind of accident from any accident previously evaluated.
The proposed changes affect only the AOT and STI of the systems identified by the marked-up Technical Specifications. As indicated above, the proposed changes do not involve the alteration of any equipment nor do they allow modes of operation beyond those currently allowed. Therefore, implementation of these proposed changes does not g
create the possibility of a new or different kind of accident from any l
accident previously evaluated.
(3)
The proposed changes do not involve significant reductions in the margin of safety.
The licensing basis for the plant assumes a minimum set.of equipment which is unaffected by the proposed changes. The proposed changes do not affect analysis assumptions regarding the functioning of' required equipment designed to prevent or mitigate the consequences of accidents.
In addition, the reverity of postulated accidents and any resulting radiological effluents are not impacted by the proposed changes. As noted above, the impact of the prop' sed changes are not significant since the impact on CDF is small cu.. pared to the uncertainty in CDP H
results and since the calculated CDF is already at a low absolute value.
It is concluded that there is no significant reduction in the margin of safety.
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Conclusion!
As reflected by the risk-based evaluation of the STPEGS Technical
-Specifications, ML&P concludes.that the proposed extension of allowed outage times and surveillance test intervals are not significant contributors to plant' risk and do not involve any significant hazards consideration.
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ATTACHMENT l ST HL-AE 3GM3 p,
PAGE _(p_ 0F _.b ATTACHMENT 1 Table 1 Summary of' Proposed Technical Specification Changes CURRENT PROPOSED Technical AOT STI ACT STI
% CHANGE F-SpecificadQD System (Days),(Jlay,d (Days)
(Days)
IN RISK 3.1.2.4 Chemical and volume-3 N/C 10 N/C
-0.7 (B) control (i.e. Charging Pumps)
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4.3.1 Reactor Protection N/C 62 N/C 92 0.2
- 4.3.2 Engineered Safeguard N/C.
62 N/C 92 0.0 Features Actuation l
3.4.2.2 Preasurizer Safety 15 min N/C 1 Hour N/C Valves 3.4.4 Pressurizer PORV's 1 Hour N/C 6 Hours N/C 3.5.1 Accumulators 1 Hour N/C 12 Hours N/C 0.3 3.5.2 Emergency Core 3
N/C 10 N/C 1.3 Cooling 3/4.5.6 Residual Heat Removal 3
92 10 184 0.0 4.6.1.7 Containment N/C 31 N/C 92 Ventilation 3/4.6.2.1 Containment Spray 3-92 10 184 0.0 3.6.2.2 Containment Spray 3
N/C 10 N/C 0.0 Additive 3/4.6.2.3 Reactor Containment 3
31 10 92
-0.1.(B)
Fan Coolers 3.6.3 Containment Isolation 4 Hours N/C 24 Hours N/C 3.7.1.1 Steam Generator 4 Hours N/C 24 Hours N/C Safety Relief Valves 3/4.7.1.2 Auxiliary Feedwater 3
31 10 92 30.4 3.7.3 Component Cooling 3
N/C 10 N/C 1.4 (A)
Water l
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ATTACHMENT 1 Table 11 Summary of Proposed Technical Specification Changes CURRENT PROPOSED t
% CHANGE' SDecification' System (Days)
(Days)
(Days)
(Days)
IN RISK 3.7.4 Essential Cooling-3 N/C 10 N/C 23.8.(A)
Water 3/ 4 ~. 7. 7 Control Room HVAC (1) 31 (2) 92 0.5 4.7.13 Electrical Auxiliary N/C 12 Hours N/C.
24 Houre Building HVAC 3.7.14 Essential Chilled 3
N/C 10 N/C 0.7 Water 3/4.8.1.1 Diesel Generators (3)
.N/C (4)
N/C 24.8 3.8.2 DC Electrical Sources (5)
N/C (6)
N/C 1.6 NOTES:
~ N/C
'No Change proposed (1) 7 days for the first inoperable train of control room HVAC and 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> for the second train of three (2) 10 days for the first inoperable train of control room HVAC and 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> for the second train of three (3) 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> for the first inoperable standby diesel generator and.
2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> for the second diesel ~ generator
.(4).
10 days for the first inoperable standby diesel generator and 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> for the second diesel generator (S) 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> for channels I and IV battery chargers; and 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> for any battery and Channels II and III chargers A1/045.NL9
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ATTACHMENT 1 i
Table l= Summary of Proposed Technical Specification Changes f
NOTES-(Cont.):
1 (6) 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> for any battery charger and-24 hours for any battery Denotes that a qualitative analysis is performed (A)
Includes a corresponding increase for all dependent systems (B)
The reduction of risk indicated reflects a minor modeling change in addition to-the proposed Technical Specification Change l
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