ST-HL-AE-5046, Application for Exemption from 10CFR50,App J, Primary Reactor Containment Leakage Testing for Water Cooled Power Reactors & Amend to Licenses NPF-76 & NPF-80,replacing Current Specified Intervals W/Ref to 10CFR50 App J
| ML20081D206 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 03/16/1995 |
| From: | Groth J HOUSTON LIGHTING & POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20081D212 | List: |
| References | |
| ST-HL-AE-5046, NUDOCS 9503200169 | |
| Download: ML20081D206 (17) | |
Text
__ _ _ _ _ _ _ . _ _ _ _ _ . _ _
,' i The Light c o m p a n ySeth Texas Project acctric Encrating P.Station O. Box 289 Wadsworth, Texas 77483 liouston Lighting & Power March 16, 1995 ;
ST-HL-AE-5046 q File No.: G21.02 10CFR50, Appendix J ];
US Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 South Texas Project Units 1 and 2 Docket Nos. STN 50-498, 50-499 Application for Exemption from 10CFR Part 50, Appendix J and Proposed Amendment to Technical Specification 4.6.1.2 Houston Lighting & Power Company requests a one-time exemption for South Texas Project, Unit 2 from the requirements of 10CFR50, Appendix J, " Primary Reactor Containment Leakage Testing for Water Cooled Power Reactors," regarding Integrated Leak Rate Test intervals.
This exemption would provide a one-time interval extension for the Unit 2 Type A test (containment Integrated Leak Rate Test) from the current scheduled 48 months to approximately 66 months. This extension would result in a delay of the Integrated Leak Rate Test currently scheduled for the Unit 2 fourth refueling outage (Fall,1995) until the fifth refueling outage (Spring,1997).
Houston Lighting & Power Company also requests a Technical Specification Amendment for South Texas Project Units 1 and 2 to replace the current specified intervals with a reference to 10CFR50 Appendix J. No new requirements are added, nor are any existing requirements deleted.
f Pi)DCCd 01(
9503200169 950316 l PDR ADOCK 05000498 P PDR '\
MISC-95\95-06"1.001 Project Manager on Behalf of the Participants in the South Texas Project
Houston Lighting & Power Company South Texas Project Electric Generating Station ST-HL-AE-5046 File No.: G21.02 Page 2 This exemption request cites 10CFR50.12 paragraphs (a)(2)(ii) and (a)(2.)(vi) as justification. This request points out that the existing Type B and C testing programs are not being modified by this request and will continue to effectively detect leakage through containment components as well as containment penetrations. It has been the consistent and uniform experience at South Texas Project Unit 2 during Type A tests performed in 1988 and 1991, that any significant containment leakage paths are detected by the Type B and C testing. The Type A test results have only been confirmatory of the results of the Type B and C test results.
Additionally, the exemption request meets the requirements of 10 CFR 50.12 paragraphs (a)(1) and (a)(2)(ii) for the following reasons:
. The historical Type A test results as set forth in the exemption request demonstrate that South Texas Project Unit 2 has a low leakage containment. Two Type A tests have been performed at South Texas Project Unit 2 with no failures, and the highest leakage rate of 0.0653% per day was well below the acceptance limit of 0.225% per day and the design limit of 0.3% per day.
- There are no mechanisms that would adversely affect the stmetural capability of the containment, which is the only leakage mode not captured by the Type B and C testing to be performed. Absent actual accident conditions, structural deterioration of containment due to temperature, radiation, chemical or other such effects is a gradual phenomenon requiring periods of time well in excess of the proposed interval extension and is subject to detection by periodic visual inspections. In fact, other than accident conditions, the only pressure challenge to containment is the Integrated Leak Rate Test itself.
= An assessment of the risk impact in the exemption request concludes that there is no undue risk to the public health and safety as a result of the proposed schedule extension of the Type A test.
Therefore, the requested schedule extension of one cycle for the performance of our Appendix J Type A test will not present an undue risk to the public health and safety, and is consistent with the common defense and security as required by 10CFR50.12 (a)(1).
Houston Lighting & Power requests that the effective date of this technical specification exemption and change be the date of Nuclear Regulatory Commission approval, but not later than August 31,1995, in order to facilitate scheduling for the outage in October,1995. Although this request is neither exigent nor an emergency, prompt review by the Nuclear Regulatory Commission is requested.
MISC-95\95-067.001
4 1
Houston Lighting & Power Company - .
j South Texas Project Electric Generating Station j ST-HL-AE-5046 :
File No.: G21.02 Page 3 -
As required by 10 CFR 50.91(b)(1), a copy of this application and the analysis concluding
- that the proposed changes do not constitute a significant hazards consideration have been provided . l' to the State of Texas.
Should you have. any questions regarding this matter please contact Mr. P. L. Walker at
, (512) 972-8392 or me at (512) 972-8664.
i
- 3. F. roth Vice President, Nuclear Generation PLW/lf
)
Attachments: 1) Safety Assessment
- 2) Proposed Technical Specification Changes i
i i
MISC-95\95-067.001
i Houston Lighting & Power Company ST-HL-AE-5046 South Texas Project Electric Generating Station File No.: G21.02 Page 4 c:
Leonard J. Callan Rufus S. Scott Regional Administrator, Region IV Associate General Counsel U._ S. Nuclear Regulatory Commission Houston Lighting & Power Company 611 Ryan Plaza Drive, Suite 400 P. O. Box 61067 Arlington, TX 76011-8064 Houston, TX 77208 Thomas W. Alexion Institute of Nuclear Power Project Manager Operations - Records Center U. S. Nuclear Regulatory Commission 700 Galleria Parkway Washington, DC 20555-0001 13H15 Atlanta, GA 30339-5957 David P. Loveless Dr. Joseph M. Hendrie Sr. Resident Inspector 50 Bellport Lane c/o U. S. Nuclear Regulatory Comm. Bellport, NY 11713 P. O. Box 910 Bay City, TX 77404-0910 Richard A. Ratliff Bureau of Radiation Control J. R. Newman, Esquire Texas Department of Health Morgan, Lewis & Bockius 1100 West 49th Street 1800 M Street, N.W. Austin, TX 78756-3189 Washington, DC 20036-5869 U. S. Nuclear Regulatory Comm.
K. J. Fiedler/M. T. Hardt Attn: Document Control Desk City Public Service Washington, D. C. 20555-0001 P. O. Box 1771 San Antonio, TX 78296 J. C. Lanier/M. B. Lee J. R. Egan, Esquire City of Austin Egan & Associates, P.C.
Electric Utility Department 2300 N Street, N.W.
721 Barton Springs Road Washington, D.C. 20037 Austin, TX 78704 G. E. Vaughn/C. A. Johnson .,
Central Power and Light Company i P. O. Box 2121 i Corpus Christi, TX 78403 )
I
UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION In the Matter of ) Docket Nos. 50-498
) 50-499
)
IIOUSTON LIGHTING & POWER )
etal )
l )
l South Texas Project )
Electric Generating Station )
Units 1 and 2 )
AFFIDAVIT I, J. F. Groth, being duly sworn, hereby depose and say that I am Vice President, Nuclear Generation, of Ilouston Lighting & Power Company; that I am duly authorized to sign and file with the Nuclear Regulatory Commission the attached request for exemption to 10CFR50 Appendix J nnd proposed changes to Technical Specification 4.6.1.2; that I am familiar with the content thereof and that the matters set forth therein are true and correct to the best of my knowledge and belief.
F. Grod ice Presider.t, Nuclear Generation STATE OF TEXAS )
)
)
Subscribed and sworn to before me, a Notary Public in and for the State of Texas, this
/@ day of N eA ,1995.
Y d e k bin b UMonmmHum ; Notary Public in and for the umwe. sun""" 9 State of Texas
! My Comemssam W# N
a ATTACIIMENT 1 SAFETY ASSESSMENT :
l i
l l
I i
l I
l l
i 1
)
I i
ST-HL-AE-5046 Attachment 1 DESCRIPTION OF PROPOSED CHANGES Ilouston Lighting & Power requests exemption from the following portion of Appendix J, !
Section III.D.I.(a), " Type A Periodic Retest Schedule," for Type A test intervals:
After the pre-operational leakage rate tests, a set of three Type A tests shall be performed, at approximately equal intervals during each 10-year service period. The third test of each set shall be conducted when the plant is shutdown for the 10-year plant inservice inspections.
" Type A Tests" are defined in Appendix J,Section II.F as " tests intended to measure the primary reactor containment overall integrated leakage rate." The purpose of Appendix J leak test requirements, as stated in the Introduction to 10 CFR 50 Appendix J, is to " assure that: l (a) leakage through the primary reactor containment and systems and components penetrating primary containment shall not exceed , Nwable leakage rate values as specified in the technical specifications or associated bast.. and (b) periodic surveillance of reactor containment penetrations and isolation valves is performed so that proper maintenance and ;
repairs are made during the service life of the containment, and systems and components ,
penetrating primary containment."
The proposed Unit 2 exemption to 10 CFR 50, Appendix J.Section III.D.I.(a), would allow for a one-time extension of the interval between the first and second Type A test during the first ten-year service period. The extension would allow the Unit 2 Type A Integrated Leak ,
Rate Test to be performed at the fifth refueling outage instead of the fourth refueling outage as currently scheduled.
This exemption request concerns part (a) of the stated purpose of Appendix J. Part (b) of the stated purpose of Appendix J applies to penetrations and isolation valves, which are tested by Type B and C Local Leak Rate Tests.
The proposed amendment to the South Texas Project Technical Specifications would revise Technical Specification 4.6.1.2 such that it would reference 10 CFR 50, Appendix J directly, rather than paraphrase the regulation, and allow approved exemptions to the Integrated Leak Rate Test frequency requirements. This change is applicable to both Unit I and Unit 2.
- . , . , oi
l ST-HL-AE-5046 Attachment 1 ,
REGULATORY HASIS FOR SPECIFIC EXEMPTION l I
Pursuant to 10 CFR 50.12(a)(2), the Nuclear Regulatory Commission will not consider i granting an exemption to a requirement unless special circumstances are present. This exemption request meets the special circumstances of paragraphs (a)(2)(ii) and (a)(2)(vi) of 10 C R 50.12. The exemption request, as discussed below, demonstrates that the underlying purpose of the regulation is achieved [(a)(2)(ii)] and there are present material circumstances l not considered when the regulation was adopted ((a)(2)(vi)]. Granting this requested i exemption will not present an taidue risk to the health and safety of the public and is i consistent with the common defense and security.
HACKGROUNL) INFORMATION j The Nuclear Regulatory Commission is currently examining those regulations that may be j revised to reduce regulatory burden on licensees without a significant impact on safety. As l part of this effort, the Nuclear Regulatory Commission is currently processing a proposed !
revision to 10 CFR 50, Appendix J, " Primary Reactor Containment Leakage Testing for j Water-Cooled Power Reactors." The current proposal will provide a performance based !
option for leakage rate testing of containments of light-water-cooled nuclear power plants.
I he Nuclear Regulatory Commission published the proposed rule change for public comment j of February 21,1995 Therefore, licensees who have refueling outages scheduled prior to [
adoption of the rule will not be able to implement the revised rule to make use of the l performance-based option during these refueling outages. ,
The fourth refueling outage for South Texas Project, Unit 2 is currently scheduled to begin in I October,1995. Houston Lighting & Power requests a one-time exemption to the Type A test schedule, performing the Integrated Leak Rate Test during the fifth refueling outage instead of during the fourth refueling outage. t k
i 2
L r
I f
i unc mesmo 1-2
ST-HL-AE-5046 Attachment 1 DESCRIPTION OF CONTAINMENT (Applicable to Unit I and Unit 2)
The containment is a fully continuous, steel-lined, post-tensioned, reinforced-concrete structure consisting of a vertical cylinder with a hemispherical dome, supported on a flat foundation mat. The cylinder and dome are post-tensioned with high-strength unbonded wire tendans. The dimensions of the containment are: 150-foot inside diameter,239-1/4 foot inside height to the top of the dome, with 4-foot cylinder wall thickness,3-foot dome thickness, and 18-foot mu Gickness. The top of the foundation mat is 41-1/4 feet below grade.
A continuous welded steel liner plate is provided on the entire inside face of the Containment to limit release of radioactive materials into the environment. The nominal thickness of the liner in the wall ano dome :.s 3/8-inch. A 3/8-inch-thick plate is used on top of the foundation mat and is covered with a 24-inch concrete fill slab.
An increased plate thickness up to 2-inch is provided around all penetrations and for the crane girder brackets.
An anchorage system is provided to prevent instability of the liner. For the dome, the anchorage system consists of meridional structural tees, circumferential angles, and plates.
A system of vertical and circumferential stiffeners is provided for the cylinder, using structural angles, channels, and plates.
Leak chase channels and angles are provided at the bottom liner seams which, after construction, are inaccessible for leaktightness examination due to the 2-foot interior fill slab.
The cylindrical wall is reinforced with conventional steel reinforcing bars throughout the structure. The bars are placed in a horizontal and vertical pattem in each face of the cylinder wall. Additional bars are provided around penetrations and in the buttresses to resist local stress concentrations. Radial shear reinforcement is provided throughout, and tangential shear reinforcement is provided where required.
The reinforcement in the dome is provided in a meridional and circumferential pattern up to 45 degrees from the spring line, with the remaining area being reinforced using a grid pattern.
Reinforcement is provided on both faces of the dome wall. Radial ties are provided to both resist radial shear and prevent delamination of the dome under prestressing.
Further information on the containment design can be found in the South Texas Project Updated Final Safety Analysis Report.
wacwc au 1-3
ST-HL-AE-5046 Attachment 1 liistorical Tme A Testine Results 10 CFR 50. Appendix J Section II.K defines the acceptable leakage limit L, as "the maximum allowable leakage rate at pressure P, [ calculated design basis accident peak containment pressure] as specified for preoperational tests in the technical specifications or associated bases, and as specified for periodic tests in the operating license."
The South Texas Project Unit 2 Type A test history provides substantial justification for the proposed test schedule. As can be seen below, two Type A tests have been performed to date and considerable margin exists between the Type A test results and the Technical Specification 4.6.1.2 limit of 0.75% L,, where L, is equal to 0.3% per day sf containment atmosphere at the peak accident pressure. These test results demonstrate that South Texas Project Unit 2 has a low leakage containment and that the proposed 18-month extension would not jeopardize the ability of the containment to maintain the leakage rate at or below the required Type A limits.
Two different testing methods were employed in performing some of the tests: the mass point leakage rate method and the total time leakage rate method. When more than one method was utilized, the results of both tests arc reported. The results of the individual South Texas Project Unit 2 Type A tests follow:
Pre-operational Type A Test The pre-operational Type A test was successfully completed on September 27,1988 with the following results: 1) a mass point leakage rate of 0.034% per day, and 2) a total time leakage rate of 0.034% per day. Both values represent an upper 95% confidence limit. These results are well under the acceptance limit of 0.225% per day (0.75 L ). The test was performed at a pressure of 52.99 psia (approximately 38 psig).
The results of this test were provided to the Nuclear Regulatory Commission by 'etter dated January 30,1989 (ST-HL-AE-2969). >
First Periodic Type A Test The first periodic Type A test was successfully completed on September 23,1991, with the following results: 1) a mass point leakage rate of C.0653% per day, and 2) a total time leakage of 0.0569% per day. Both results are at the 95% upper confidence limit. The test was performed at a pressure of 44.6 psig, which represents an increase in the calculated accident pressure from the original test. These results are also well below the acceptance limit.
The results of this test were provided to the Nuclear Regulatory Commission by letter dated February 13,1992 (ST-HL-AE-3998).
m . .o i..
1
. i i
ST-HL-AE-5046 Attachment I ;
i DISCUSSION OF CHANGE Factors affecting leak tightness of containment may be categorized as: 1) active components l which are leak-rate tested by Type B and C tests, and 2) passive components which constitute !
the containment structure and are tested during the Type A test. i Active Components The purpose of containment leak testing is to detect any containment leakage resulting from l active or passive failures in the containment isolation boundaries before an accidept occurs. ,
The major containment leakage paths include: ;
- 1) Penetration Seal Leakage: Air lock door seals; doors with resilient seals or gaskets except for seal welded doors; penetrations whose design incorporates resilient seals, gaskets, [
or sealant compounds; piping penetrations fitted with expansion bellows; and electrical ;
penetrations fitted with flexible metal seal assemblies may all exhibit leakage. Type B tests :
cover this type of leakage and will not be affected by the proposed change in the Integrated Leak Rate Test schedule.
- 2) Containment Isolation valves: These valves provide either a potential or dimet :
connection between the inside and outside atmospheres of the primary reactor containment under normal operation, are required to close automatically upon receipt of a containment -
isolation signal in response to controls intended to effect containment isolation, and are ;
required to operate intermittently under post-accident conditions. Leakage through these -
valves can be caused by leaking valve seals, isolation valve closure failure, or failure to return ;
a penetration to its normally closed condition following maintenance. For all of these f initiating events, except post-maintenance / Local Leak Rate Test errors, this type of leakage is >
detectable by Type C local leak rate testing. Following maintenance on a Containment ,
Isolation valve, a Local Leak Rate Test is performed followed by an independent valve alignment verification to ensure that leakage remains within acceptable levels. Type C tests will not be affected by the proposed change in the Integrated Leak Rate Test schedule. i
- 3) Gross Contabment failure: This is a low probability event which is the single event j that will be uniquely detected by a Type A test.
The existing Type B and C testing programs are not being modified by this request and will .
continue to effectively detect containment leakage caused by degradation of active ]
containment isolation components (e.g., valves) as well as sealing material witnin containment l penetrations. Industry experience indicates that 9/% of the failures associated with Type A tests are found to be due to Type B and C-tested penetrations (Draft NUREG-1493, l
" Performance-Based Containment Leak Test Program"). The local leak rate testing j frequencies of these penetrations are not affected by this proposed change. Therefore, 1 continued overall leak tightness of the active containment components can be assured by the existing Type B and C testing program. '
une.sw ou !5 [
I l
ST-HL-AE-5046 ,
Attachment 1 Passive Structure l
Two mechanisms could adversely affect the passive structural capability of containment. The first is deterioration of the structure due to pressure, temperature, radiation, chemical, or other l such effects. Secondly, modifications can be made to the structure which,if not carefully controlled, could leave the structure with reduced capability.
Absent actual accident conditions, structural deterioration is a gradual phenomenon requiring periods of time well in excess of the proposed interval extension. Other than accident conditions, the only pressure challenge to containment is the Integrated Leak Rate Test itself.
10 CFR 50, Appendix J, Section V.A requires a general inspection of accessible interior and exterior surfaces of the containment structures and components. The inspection is to be performed prior to any Type A test to uncover evidence of structt.ral deterioration that may affect either the containment structural integrity or leak tightness. /u the South Texas Project, there has been no evidence of structural deterioration of Unit 2 cont. ament that would impact structural integrity or leak tightness.
Modifications that would alter the passive containment structure are infrequent and would receive extensive review to ensure containment capabilities are not diminished. The South Texas Project Unit 2 design change and 10 CFR 50.59 programs adequately address such safety significant modifications. In addition,10 CFR 50, Appendix J, Section IV.A requires Type A testing to be performed following any major modification to the primary containment boundary. This requirement will be maintained.
Misk Impact Assessment The risk impact of containment structural life is measured by a pathway created for radionuclides if the containment is challenged such as in a loss of coolant accident or severe accident. Such leakage does not create any new accident scenarios, nor does it contribute to initiation of any accident.
From a risk standpoint, the purpose of Appendix J leak testing is to detect containment leakage resulting from failures in the containment isolation boundary before an accident occurs. Such leakage could be the result of leakage through containment penetrations, through airlocks, or through containment structural faults. The Appendix J Type B and C tests, which are unaffected by this proposed change, will continue to detect leakage through containment valves, penetrations, and airlocks. The only potential failures that would not be detected by Type B and C testing are mechanical failures of the containment shell (i.e., resulting from degradations or modifications to the containment shell). Thus, the only potential effect of the proposed one-time change to the Type A test frequency is that containment structural leakage may go undetected between tests.
ST-HL-AE-5046 Attachment 1 The containment structure is passive. Under normal operating conditions, there is no signi6 cant environmental or operational stress present that could contribute to its degradation.
A review of modi 6 cations for potential effects to the antainment structure is described in the preceding section. Passive failures resulting in significant containment structural leakage are therefore extremely unlikely to develop between Type A tests. No such failures have occurred at South Texas Project Unit 2.
The South Texas Project Level 2 Probabilistic Safety Assessment and Individual Plant Examination has evaluated the impact of Large and Small Early Release Frequencies for failure of the containment given a core damaging event. The most important causes for a Large Early Release were found to be large containment isolation failures and phenomenological effects associated with severe accidents. The large containment isolation contributor includes failure to isolate the large supplemental purge penetrations in the unlikely event that a purge is in progress during the accident. The South Texas Project Probabilistic Safety Assessment does not model large pre-existing leaks because all lines greater than 3" are covered by autoclosure isolation valves and hence there is no credible mechanism for large pre-existing leaks. Therefore, this Technical Specification change would have no impact on the Large Early Release Frequency at the South Texas Project. Th,: SmaH Early Release Frequency evaluates the potential for a small pre-existing leak. The impact of this change would be a negligible increase to the contribution for a Small Early Release Frequency.
Based on information provided in Draft NUREG-1493, the increased risk of population dose attributable to extending the test interval by one refueling cycle would be extremely small.
Draft NUREG-1493 includes the results of a sensitivity study performed to explore the risk impact of several alternate leak rate testing schedules. " Alternative 4" from this study examines relaxing the Integrated Leak Rate Test frequency from 3 in 10 years to 1 in 10 years. Using best estimate data, the draft NUREG concludes that the increase in population ,
exposure risk to those in the vicinity of the five representative plants ranges from 0.02 to 0.14% This very low impact on risk is attributable to: 1) the effectiveness of Type B and C tests in identi4ing potential leak paths (about 977o), 2) a low likelihood of Integrated Leak Rate Test-identified leakages in excess of 2 times allowable, and 3) the insensitivity of risk to containment leak rate (e.g., no discernible increase in population dose risk with containment leak rates 100 times greater than currently allowed). This led the authors of draft NUREG-1493 to conclude that even increasing the Integrated Leak Rate Test frequency to once per 20 years would " lead to an imperceptible increase in risk."
The exemption requested for South Texas Project Unit 2 is concluded to be bounded by the analyses of draft NUREG-1493 because the requested exemption would result in a one-time test interval of approximate 5-1/2 years. Houston Lighting & Power believes that there is sufficient information in the Draft NUREG-1493 to conclude that the risk increase from the requested exemption is low and that the value, in terms of enhanced public safety, of f performing the Integrated Leak Rate Test in Fall 1995 is extremely low.
I user ow mu i-7
.. \
i ST-HL-AE-5046 - !
~
Attachment 1 l BASIS FOR EXEMPTION ,
The proposed Unit 2 interval extension meets the criteria for special circumstances as described in 10 CFR 50.12(a)(2)(ii) and (vi).
50.12(a)(2)(ii) Application of the Regulation is not Necessary to Achieve the Underlying Purpose of the Rule i i
The underlying purpose of 10 CFR 50, /.ppendix J is still achieved. Appendix J states that :
the leakage test requirements set fonh in this appendix provide for periodic verification by ;
tests of the leak tight integrity of the primary reactor containment. The appendix further states that the purpose of the tests is to assure that leakage through the primary reactor i containment shall not exceed the allowable leakage rate values as specified in the technical speciGcations or associated bases. ;
10 CFR 50, Appendix J, Section III.D.I.(a) states that a set of three periodic tests shall be performed at approximately equal intervals during each 10-year period and that the third test ;
shall be conducted when the plant in shutdown for the 10-year plant inservice inspections.
This exemption would delay performance of the second Type A test during the first ten-year ,
interval. The methodology, acceptance criteria, and technical specification leakage limits for .
the perfomiance of the Type A test will not change.
The testing history, structural capability of the containment, and the risk assessment discussed ;
previously establish that South Texas Project Unit 2 has had acceptable containment leakage rates with considerable margin, that the structural integrity of containment is assured, and that there is negligible risk it ' pact in changing the Type A test schedule on a one-time basis.
Experience at South Text 4 Project Unit 2 during the two Type A tests conducted in 1988 and 1991 shows that excessive containment leakage paths are detected by the Type B and C testing. The Type A test results have only been confirmatory of the Type B and C test results. t This exemption request does not affect the periodic schedule for Type B and C tests which will continue to be performed in accordance with Appendix J and approved exemptions. j Demonstrated operability of the associated components and penetrations through Type B and C tests adds assurance that the overall Type A leakage rates remain satisfactory. No significant leakage trends have been identified which threaten the overall containment leakage speciGcations. There is no significant change in the types or increase in the amount of any .
effluents that may be released offsite due to extension of the performance of the second Type A test during the first ten-year interval. This one-time change does not impact the design basis of the plant and would not affect the response of containment during a design basis accident, ,
Thus, there is significant assurance that the extended interval between Type A tests will continue to provide periodic verification of the leak tight integrity of the containment.
unewan i.s
.: i
, t ST-HL-AE-5046 l Attachment 1 }
50.12(a)(2)(vi) Presence of Material Circumstances Not Considered When the Regulation '
was Adopted Certain material circumstances were not considered when the regulation was adoped. The benefit of time has produced experience and information that provide a better perspective ,
about containment integrity. Two important material circumstances are testing history and ,
development of probabilistic risk assessments.
Since the promulgation of 10 CFR 50, Appendix J, in 1973, more than 2.0 years of nuclear power plant operating history have been obtained. A review of industry data did not find any !
instances where a Type A test failed to meet Appendix J acceptance criteria as a result of a containment structurs! leak not due to initial fabrication or a plant modification. This j additional operating history provides a significant indicator that containment structural integrity (passive) is not a significant safety conce;a.
Plant specific probabilistic risk assessments were not available and therefore were not I considered when the regulation requiring compliance with Appendix J (10 CFR 50.54(o)) was adopted. Overall plant risk due to containment leakage is relatively small, given the small probability of containment leakage itself. The predominant contributor to the Large Early !
Release Frequency is failure to isolate the large supplemental purge penetrations in the unlikely event that a purge is in progress during the accident. This contributor would not be impacted by this Technical Specification change. Moreover, the increase in the Small Early i Release Frequency due to the testing interval increase is negligible. j Additionally, the exemption request meets the requirements of 10 CFR 50.12 paragraphs !
(a)(1) and (a)(2)(ii) for the followmg reasons:
i
- The historical Type A test results as set forth in the exemption request demonstrate that South Texas Project Unit 2 has a low leakage containment.
Two Type A tests have been performed at South Texas Project Unit 2 with no failures, and the highest leakage rate of 0.0653% per day was well below the acceptance limit of 0.225% per day and the design limit of 0.3% per day. ,
1
- There are no mechanisms that would adverselj affect the structural capability of the containment, which is the only leakage mode not captured by the Type B and C testing to be pe cformed. Absent actual accident conditions, structural deterioration of containment due to temperature, radiation, chemical or other such effects is a gradual phenomenon requiring periods of time well in excess of the proposed interval extension and is subject to detection by periodic visual inspections. In fact, other than accident conditions, the only pressure challenge to containment is the Integrated Leak Rate Test itself.
- An assessment of the risk impact in the exemption request concludes that there is no undue risk to the public health and safety as a result of the proposed ,
schedule extension of the Type A test. !
Therefore, the requested schedule extension of one cycle for the performance of our Appendix 1 J Type A test will not prescia an tmdue risk to the public health and safety, and is consistent i with the common defense and security as required by 10 CFR 50.12(a)(1).
amressetun 1-9
ST-HI-AE-5046 Attachment 1 DETERMINATION OF NO SIGNIFICANT HAZARDS CONSIDERATION j An evaluation of the proposed exemption to 10 CFR 50, Appendix J requirements and the ;
proposed administrative Technical Specification change has been performed in accordance t with 10 CFR 50.91(a)(1) regarding no significant hazards considerations using the standards in 10 CFR 50.92(c). A discussion of these standards as they relate to this exemption and amendment request follows:
i Criterion 1: Does Not Involve a Significant Increase in the Probability or Consequences of an Accident Previously Evaluated.
The proposed change specific to Unit 2 will provide a one-time exemption from the 10 CFR '
50, Appendix J Section Ill.D.I.(a) leak rate test schedule requirement. This change will allow for a one-time test interval for Type A Integrated Leak Rate Tests of approximately 66 :
months. :
Leak rate testing is not an initiating event in any accident; therefore, this proposed change does not involve a significant increase in the probability of a previously evaluated accident.
Type A tests are capable of detecting both local leak paths and gross containment failure paths. Experience at South Texas Project Unit 2 demonstrates that excessive containment leakage paths are local leakage detected by Type B and C Local Leak Rate Tests.
Administrative controls govern maintenance and testing of containment penetrations such that the probability of excessive penetration leakage due to improper maintenance or valve misalignment is very low. Following maintenance on any containment penetration, a Local Leak Rate Test is performed to ensure acceptable leakage levels. Following a Local Leak Rate Test on a containment isolation valve, an independent valve alignment check is i performed. Therefore, Type A testing is not necessary to ensure acceptable leakage rates through containment penetrations.
While Type A testing is not necessary to ensure acceptable leakage rates through containment ,
i penetrations, Type A testing is necessary to demonstrate that there are no gross containment failures. Structural failure of the containment is considered to be a very unlikely event, and in fact, since South Texas Project Unit 2 has been in operation, it has successfully passed each Type A Integrated Leak Rate Test. Therefore, a one-time exemption increasing the interval for performing an Integrated Leak Rate Test results in a significant decrease in the '
confidence in the leak tightness of the containment structure. Therefore, this change does not involve a significant increase in the consequences of an accident previously evaluated. ;
t urer ew et ! to i
i i
I ST-IIL-AE-5046 Attachment 1 :
i The proposed amendment revises Technical Specification 4.6.1.2 to reference the testing !
frequency requirements of 10 CFR 50, Appendix J, and to state that Nuclear Regulatory l Commission approved exemptions to the applicable regulatory requirements are permitted.
This portion of the proposed change is applicable to Unit I and Unit 2. The current language i of Technical Specification 4.6.1.2 paraphrases the requirements of Section III,D.I.(a) of Appendix J. The proposed administrative revision simply deletes the paraphrased language t and directly references Appendix J. No new requirements are added, nor are any existing requirements deleted. Any specific changes to the requirements of Section III.D.I.(a) will require a submittal from Houston Lighting & Power under 10 CFR 50.12 and subsequent review and approval by the Nuclear Regulatory Commission prior to implementation.
The proposed amendment, in itself, does not affect reactor operations or accident analysis and has no radiological consequences. The change provides clarification so that future Technical Specifications changes will not be necessary to correspond to applicable Nuclear Regulatory ,
Commission-approved exemptions from the requirements of Appendix J.
Therefore, this proposed amendment does not involve a significant increase in the probability or consequences of any accident previously evaluated.
Criterion 2: Does Not Create the Possibility of a New or Different Kind of Accident i from any Previously Evaluated.
i The proposed Unit 2 exemption request does not affect normal plant operations or i configuration, nor does it affect leak rate test methods. The proposed change allows a one- ;
time test interval of approximately 66 months for the Integrated Leak Rate Test. Because the test history of South Texas Project Unit 2 demonstrates no Type A test failures during plant lifetime, the relaxation in schedule should not significantly decrease the confidence in the leak -
tightness of the containment.
The proposed Technical Specification amendment for Units 1 and 2 provides clarification to a i specification that paraphrases a codified requirement. !
Since the proposed change and amendment would not change the design, configuration or method of operation of the plant, they would p_ot create the possibility of a new or different kind of accident from any previously evaluated.
MMC WWp ? lRfl l*'l l
l ST-HL-AE-5046 Attachment 1 l
Criterion 3: Does Not Involve a Signincant Reducticn in the Margin of Safety l 1
1 The purpose of the existing schedule for Integrated Leak Rate Tests is to ensure that release 1 of radioactive materials will be restricted to those leak paths and leak rates assumed in accident analyses. The relaxed schedule for Integrated Leak Rate Tests does not allow for j relaxation of Type B and C Local Leak Rate Tests. Therefore, methods for detecting local containment leak paths and leak rates are unaffected by this proposed change. A one-time increase of the South Texas Project Unit 2 test interval does not lead to a significant probability of creating a new leakage path or increased leakage rates because the test history for Integrated Lean Rate Tests shows no failure during plant life. The margin of safety ;
inherent in existing accident analy:", is maintained. l The proposed Technical Specification amendment for Units I and 2 is administrative and .
clarifies the relationship between the requirements of Technical Specification 4.6.1.2, ,
Appendix J, and any approved exemptions to Appendix J. It does not, in itself, change a safety limit, a Limiting Condition of Operation, or a surveillance requirement on equipment l required to operate the plant. Nuclear Regulatory Commission approval of any proposed !
change or exemption to III.D.l.(a) of Appendix J will be required prior to implementation. l Therefore, this change and amendment do not involve a significant reduction in the margin of j safety,
)
Conclusions l Ilased on the Safety Assessment, Ilouston Lighting & Power concludes that: (1) the proposed ,
changes do not constitute a significant hazards consideration as defined by 10 CFR 50.92; and (
('.) there is reasonable assurance that the health and safety of the public will not be j endangered by the proposed change. Since this action does not involve a significant hazards l consideration, it will not result in a condition which significantly alters the impact of the !
station on the environment as described in the Nuclear Regulatory Commission Final l
Environmental Statement.
The proposed changes have been reviewed by the South Texas Project Plant Operations i Review Committee and the Nuclear Safety Review Board which concur that the requested l changes do pg involve a significant hazards consideration. i
\
l l
1 nmcw en i . 12 i