ML20205T272
| ML20205T272 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 11/03/1988 |
| From: | Gridley R TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| TAC-R00052, TAC-R00496, TAC-R00497, TAC-R496, TAC-R497, TAC-R52, NUDOCS 8811140190 | |
| Download: ML20205T272 (8) | |
Text
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TENNESSEE VALLEY AUTHORITY CHATTANOOGA. TENNESSEE 37401 SN 1578 Lookout Place NOV 031988 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C.
20555 Gentlemen:
In the Matter of
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Docket Nos. 50-327 Tennessee Valley Authority
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50-328 SEQUOYAH NUCLEAR PLANT (SQN) - TEMPORARY EXEMPTION FROM ADMINISTRATIVE PROVISIONS OF 10 CFR 50.46
References:
1.
TVA letter to NRC dated September 19, 1988, "Sequoyah Nuclear P1M t (SQN) - Request for Temporary Exemption from Adm'.nistrative Provisions of 10 CFR 50.46" 2.
NRC 'etter to TVA dated October 26, 1988, "Temporary Exemption to 10 CFR 50.46(a)(1) - Sequoyah Nuclear Plant, Unit 1 (TAC R0052)"
Reference I transmitted a request for a temporary exemption from administrative provisions of 10 CFR 50.46 for unit 1.
As discussed in reference 1 and other correspondence, the temporary exemption was needed in support of a reduced minimum delivered upper head injection (UHI) water volume.
NRC approval of the temporary exemption for unit I was transmitted by reference 2.
This letter stated that ;he temporary exemption was granted provided:
1.
Heat flux hot channel factor (F.*t]) shall not exceed 2.15.
2.
Steam generator tube plugging sliall not exceed 5 percent, f
3.
TVA shall complete a revised plant-specific emergency core cooling l
system (ECCS) analysis and shall submit the results of such analysis no later thar, Hay 31, 1989.
SQN has administrative controls in place to satisfy conditions 1 and 2.
TVA has planned to have condition 3 satisfied through a contract with e
Westinghouse Electric Corporation (H) for the performance of a UHI evaluation model analysis.
However, TVA has reevaluated the resources necessary to perform this analysis and has determined that the performance I
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An Equal opportunity Employer
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. NOV 031988 U.S. Nuclear Regulatory Commission of the UHI analysis creates a significant hardship.
Resources directed toward the performance of a UHI analysis are inconsistent with TVA's plans to remove UHI at SQN.
TVA and H resources directed at the UHI analysis would delay the availability of resources needed to suppor': UHI
.l deletion and could delay the implementation of UHI deletion untti later outages.
Additionally, TVA u mits that the performance of the UHI analysis is a poor utilization of TVA and W resources, as well as NRC resources, because of the nodd's age. As was described in reference 1, the UHI evaluation model is not currently available for use and would require extensive resort;es tc, vertt., 'nd validate on the current W computer i
system. All resources directed at the UHI analysis would 6e directed 4
toward "old" ".;ethodologies and technologies.
It should also be noted 1
that SON 15 also the last conimercial plant utilizing the UHI design in j
this country.
This forces TVA alone to bear the burden for these J
resource expenditures.
l As an alternative to performing the UHI analysis, TVA proposes to direct its resources toward the deletion of UHI for both SQN units.
This effort i
would allow TVA to obtain a significant benefit from its resource expenditures.
TVA submits that this would also be a better utilization j'
of W and NRC resources because their efforts would be directed toward the j
newer r'thodologies and technologies of accident analyses.
SQN units 1 i
and 2 will restart from their respective cycle 4 refueling outages with i
the necessary analyses, modifications, and license amendments to support j
plant operation with UHI removed from service.
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Plant operating conditions will not be bounded by the analysis until i
restart from the cycle 4 refueling outage because the no1-UHI analysis
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will require plant modifications to be performed.
However, plant operation will be bounded throughout cycle 4 operations by the
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sensitivity studles that have already been performed based on previous performances of the UHI evaluation model.
Current 1.v. the units 1 and 2 i
cycle 4 refueling outages are scheduled for mld and late 1990, respectively.
TVA therefore requests that the temporary exemption to
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10 CFR 50.46, as granted in reference 2 be extended for the entire cycle l
4 operation of SQN unit I and that a like exemption be granted G e SQN unit 2 cycle 4 operation.
Proposed UHI level switch setpoint ano Fo(z)
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technical specification changes for unit 2 will be transmitted by separate correspondence.
These changes will be the same as those i
l tequested for unit 1 (88-20 and 88-28).
The justification for this request is further deta' led in enclosure 1.
TVA also believes that the r ;uested exemptions are justified based on hardship and on the basis that application of the requirement for a UH! evaluation model in addition to the currently performed evaluations is not necessary to serve i
tne underlying purpose of 10 CFR 50.46.
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i NOV 031988 U.S. Nuclear Regulatory Commistion f
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TVA believes that in iew of the special circumstances described above,
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the requested extension of the unit i exemption and the issuance of the unit 2 exemption are authorized by law and will not present undue risk to the public health and safety.
I An expeditious response to this proposal is requested because, at this tiAc, no W resources are being titrected at the UHI analysis.
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Enclosed is a check for the $150 fee required by 10 CFR 170.12 for review of this exemption extension.
Summary statements of comritments contained in this submittal are l
4 provided in enclosure 2.
Please direct questions concerning this issue
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to R. R. Thompson at (61f.) 870-7470, f
Very truly yours, j
TENNESSEE VAL EY AUTHORITY I
/
l R.
ridley, M ager I
Nuclear Licensing and i
Regulatory Affairs Enc:osures cc (Enclosures):
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Ms. S. C. Black, Assistant Director for Projects
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TVA Projects Division U.S. Nuclear Regulatory Commission
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1 One White Filnt, North 11555 Rockville Pike l
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Rockville, Maryland 20852 I
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l Mr. F. R. McCoy, A',sistsit Director for Inspectico Programs j
t TVA Projects Olvision U.S. Nuclear Regulatory C(m.ission Region II j
101 Harletta Street, NW, Suite 2900 t
Atlanta, Georgia 30323 L
t y
J Sequoyah Resident Inspector j
Sequoyah Nuclear Plant 2600 Igou Ferry Road j
Soddy Daisy, Tennessee 37379 t
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ENCLOSURE 1
.. ^0RARY EXEMPTION FROM ADMINISTRATIVE PROVISIONS OF 10 CFR 50.46 JUSTIFICATION FOR TEMPORARY EXEMPTION
^
By letter dated SepW.nber 19, 1988, TVA requested a temporary exemption from administrative provisions of 10 CFR 50.46.
This exemption was requested in support of a reduced minimum delivered upper head injection (VHI) water volume.
The Westinghouse Electric Corporation (W) UHI evaluation model is not currently available for use to provide computer generated results to bound SQN operating conditions.
Fsant operating conditions for cycle 4 operation for both units will be bounded by sensitivity studies that have already been pe'rformed based on previous performances of the UHI evaluation model.
The reliance on these sensitivity studies necessitated the need for the temporary i
exemption.
NRC granted the temporary exemption for SQN unit I b,v letter dated October 26, 1988. The temporary exemption was granted provided:
1.
Heat flux hot channel factor (F,[z]) shall not exceed 2.15, 2.
Steam generator tube plugging shall not exceed 5 percent.
3.
TVA shall complete a revised plant-specific emergency core cooling system (ECCS) analysis and shall submit the results of such analysis no later than May 31, 1989.
TVA has plarined to meet the third proviso by submitting the results of a revised UHI evaluation model to NRC no later than May 31, 1989.
TVA has reevaluated the resources necessary to meet this commitment and has determined that the performance of the UHI analysis creates a significant horasnip.
As an alternative to the UHI analysis, TVA proposes to meet the third proviso by performing a plant-specific ECCS analysis, which demonstrates the safe operation of SQN units I and 2 with UHI removed from service.
Because this analysis would require plant modifications to be performed, plant operating conditions will not be bounded by the non-UHI analysis until restart from the cycle 4 refueling outage.
Accordingly, TVA requests an extension of the temporary exemption granted j
October 26, 1988, for SQN unit I and the granting of a like exemption for SQN unit 2 cycle 4 operation.
The conditions in the proviso granting the exemption for unit I will be retained for each unit's cycle 4 operation, except that the third pr.vlso requiring a revised plant-specific ECCS analysis would be performed on a schedule supporting the cycle 4 refueling outage planning of each unit.
IVA believes the extension to be acceptable because the evaluations and operating restrictions eat ensure peak clad temperature (PCT) will not exceed the 2,200 degree fabri W it (F) limit (which was the basis for the current unit I temporary exrn
.n) will still be valid for the requested extension of the exemption.
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As discussed in the September 19, 1988 and October 26, 1988 correspondence, censervative evaluations have been performed that demonstrate that the limiting PCT is 2,198 degrees F for UHI delivered _ water volume ranging from 1,130.5 cubic feet to 850 cubic feet.
These evaluations are based on j
sensitivities developed from the UHI evaluation model.
PCT margin was l
obtained by reducing the Fo(z) limit to 2.15 and by reducing the steam generator tube olugging limit to 5 percent.
These operating restrictions provided limiting PCTs.with more than 100-degrees-F margin to the 10 CFR 50.46(b) criten Under this proposal, these operating restrictions j
would be imposed for a, of cycle 4 operation on uth units.
It is important to note that additional PCT margin will be obtained as core i
t burnup increases.
The limiting PCTs were determined assuming a Fo(z) of t
2.15 as described above.
In reality, a maximum Fo(z) of approximately 2.12 has been calculated for cycle 4 operation; and this value will decrease over i
core life.
This is the result the lowering of centerline fuel temperatures as core burnup increases.
Additional confidence in the available PCT margin can be drawn from che new t
Appendix K rule and from the loss-of-fluid tn t (LOFT) results. A summary of the rule changes as printed in the September 16, 1988 Federal Register.
i acknowledged that "... the existing evaluation models are known to contain a large degree of overall conservatism..." The LOFT results indicated that PCT margin on the order of hundreds cf degrees existed between predicted and l
experimently measured PCTs.
l A plant-specific ECCS evaluation model will be completed during cycle 4 j
operation of SQN.
TVA would direct 8 to complete the non-UHI evaluation well in advance of the outages to support the planning and scheduling of modifications and license amendments necessitated by the non-UHI analysis.
i All necessary analyses, modifications, and license amendments to support plant j
operation with UHI removed from service would be completed before restart from l
e j
the cycle 4 refueling outages, i
Additionally, TVA believes the exemption for cycle 4 operation of both units is justified under 10 CFR 50.12(2)(11) because the performance of the UHI i
j analysis is not necessary to demonstrate that ECCS performance will meet the i
criteria of 10 CFR 50.46(b). As discussed above, conservative evaluations have been performed that meet the Intent of the rule. Operating restrictions have been imposed that provide additional PCT margin, further ensuring that criterton (1) of 10 CFR 50.46(b) is satisfied.
Finally, core behavior over cycle life provides even more margin.
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The exemption for the duration of cycle 4 operation is also justifiable under 10 CFR 50.12 (2)(111) because of (1) the unavailability of the 8 UHI evaluation model; (2) the cost of verifying and validating the UHI evaluation model solely for TVA's use (i.e., the cost could not be shared among several utilities), which would only be applicable for a short period of time; and (3) the resulting conflict between the development of UHI and non-UHI evaluation j
models for SQN.
The result would be undue hardship and costs significantly in excess of those contemplated when the rule was adoptej and significantly in t
excess of those being incurred by other licensees.
_3 The cost to TVA of performing the UHI analysis 10 expected to exceed
$1.1 million.
This is in addition to approximatel; $670 thousand that will be spent to perform the non-UHI analysis.
The performance of the UHI analysis will provide no significant benefit.
It will serve only to confirm the results of the conservative sensitivity studies, which NRC has already found would not present undue risk to the pubilc health and safety. On the other hand, performance of the non-UHI analysis would support plant operation with UHI removed from service, which would result In significant operation and maintenance improvements for TVA.
The additional cost of performing the UHI e glysis, which will provide no significant benefit to TVA, demonstrates the
..dship associated with performing the UHI analysis.
Previous UHI evaluations performed when the model was available f.ost approximately
$500 thousand, lending further justification to the hardship argument.
ENVIRONMENTAL ASSESSMEN(
Identification of Proposed Action:
The exemption will permit the utilization of evaluations based on sensitiv'ity studios to demonstrate that calculated PCTs remain below the acceptance criteria of 10 CFR 50.46.
Provisions of 10 CFR 50.46 require that ECCS performance be calculated with an acceptable evaluation model. An Appendix K evaluation will not be completed by W in support of the current cycle 4 schedules.
Therefore, a temporary exemption is needed from certain provisions of 10 CFR 50.46(a)(1) until the analysis can be completed.
The Need for the Proposed Action:
The proposed temporary exemption is needed to permit plant operation without being in violation of 10 CFR 50.46 requirements.
Environmental Impact of the Proposed Action:
The proposed temporary exemption is from certain administrative provisions of 10 CFR $0.46(a)(1).
The intent of those provisions is to ensure that the PCTs during a postulated accident do not exceed 2,200 degrees F.
As described above, W calculations have been performed that demonstrate that the limiting PCT resulting from the reduced minimum delivered UHI water volume is below the regulatory limit.
- Also, operating restrictions have been imposed to provide additional PCT margin of 4
greater than 100 degrees F.
This margin offsets any uncertainties of the sensitivity studies and ensures compliance with the 10 CFR 50.46(b) PCT r
criterlon. Consequently, the radiological releases will not be greater than i
previously determined nor does the proposed exemption otherwise affect radiological plant effluents.
Therefore
't is concluded that there are no signift: ant radiological environmental impacts associated with this proposed i
l exemption. With regard to potential nonradiological impacts, the proposed exemption does not affect nonradiological plant effluents and has no other environmental impact.
Therefore, it is concluded that there are no significant nonradiological environmental impacts associated with the proposed exemption.
l Alternative to the Proposed Action:
The alternative to the proposed action would be to delay cycle 4 operation until the Appendix K analysis is completed.
This would result in a significant loss of generation capability to TVA with no benefit to safety.
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Alternate Use of Resources:
This action does not involve the use of resources not previously considered in connection with the "Final Environmental Statement Related to the Operation of Sequoyah Nuclear Plant, Units 1 and 2 "
dated July 1974.
CONCLUSION TVA believes that in view of the special circumstantes described above, the requested extension of the un'.t i exemption and the issuance of the unit 2 exemption are authorized by law and will not present undue risk to the public health and safety.
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ENCLOSURE 2 SON units I and 2 will not restart from their respective cycle 4 refueling outages unt' the necessary modifications, license amendments, and evaluation models rey red by 10 CFR 50.46 have been completed to support plant operation with UHI re.aved from service, t
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