ML20237B474
| ML20237B474 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 08/13/1998 |
| From: | Terry C TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| TXX-98183, NUDOCS 9808180314 | |
| Download: ML20237B474 (7) | |
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Log # TXX-98183 v.
File # 10010 illELECTRIC 915 Ref. # 10CFR50, Appendix K
- c. t..c. wery Senior Vice President
& PrincipalNuclear Officer AUQUst 13,1998 U. S. Nuclear Regulatory Commission Attn: Document Control Desic Washington, DC 20555
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SUBJECT:
COMANCHE PEAK STEAM ELECTRIC STATION (CPSES)
DOCKET NOS. 50-445 AND 50-446 REQUEST FOR EXEMPTION FROM APPENDIX K TO 10CFR50 ECCS EVALUATION MODELS REF: TU Electric Letter, logged TXX-98180, from C. L. Terry to the NRC dated July 17,1998, submitting Caldon, Inc. Topical Report ER-80P, " Improving Thermal Power Accuracy and Plant Safety While Increasing Operating Power Level Using j
the LEFM/* System" j
Gentlemen:
Pursuant to 10 CFR 50.12, TU Electric requests an exemption from certain requirements applicable to F.CCS evaluation models performed in accordance with Appendix K to Title 10 of the Code of Federal Regulations Part 50 (10 CFR 50) for Comanche Peak Steam Electric Station (CPSES) Units 1 and 2. TU Electric seeks this exemption to the 2% uncertainty specified by Appendix K of 10 CFR 50 to support license amendments for modest increases of up to 1% in the licensed power levels for both unas. The license amendment request for j
Unit 2 is scheduled to be filed in December,1998, after initial NRC Staff review of this l
exemption request. This exemption is based on implementation of the feedwater flow
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measurement system manufactured by Caldon, Inc. (Caldon), fully described in the enclosure l
to the referenced letter.
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- u. o u a yo 9808180314 980813 PDR ADOCK 05000445 P
PDR COMANCHE PEAK STEAM EllCTRIC STATION P.o. Box HJ02 Glen Rose, Texas 7604bl002
TXX-98183 Page 2 ef 2 The regulatory basis supporting the request for exemption is provided in the attachment to th!s letter. If you have any questions regarding this request, please contact Mr. J. D. Seawright at 254/897-0140 or Mr. R. D. Walker at 254/897-8233.
This communication contains na new licensing basis commitments regarding CPSES Units 1 and 2.
Sincerely,
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C. L. Terr [
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c-E. W. Merschoff, Region IV J. l. Tapia, Region IV T. J. Polich, NRR Resident inspectors, CPSES Caldon, Inc.
Attn: Cal Hastings, CEO 1070 Banksville Avenue l
Pittsburgh, PA 15216
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Attachment to TXX-98183 Page 1 of 5 Regulatory Basis for Specific Exemption Regulatorv Provisions TU Electric requests an exemption from NRC requirements mandating consideration of an assumed reactor operating power level of 1.02 times the licensed power level in development of the Emergency Core Cooling System (ECCS) evaluation models as set forth in Appendix K of Part 50, which provides in applicable part:
[1]t shall be assumed that the reactor has been operating continuously at a power level of at least 1.02 times the licensed power level (to allow for such uncertainties as instrument error).'
This regulation imposes a 2% licensed power margin on ECCS evaluation models of light water power reactors licensed in accordance with the requirements of Appendix K, including CPSES Units 1 and 2. Based on the proposed use of the improved Caldon, Inc. (Caldon) instrumentation to determine core power level, TU Electric seeks an exemption to reduce the licensed power uncertainty required by 10CFR50, Appendix K, using the current NRC-approved methodologies. The basis for the exemption is that the Caldon instrumentation provides a more accurate indication of feedwater flow (and correspondingly reactor thermal power) than assumed in the development of Appendix K requirements. Complete technical support for this conclusion is discussed in detail in the Caldon Topical Report ER-80P, " improving Thermal Power Accuracy and Plant Safety While Increasing Operating Power Level Using the LEFM/"
l System", which was previously submitted to the NRC on July 17,1998 by TU Electric letter,
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logged TXX-98180, from C. L. Terry. The improved thermal power measurement accuracy
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obviates the need for the full 2% power margin assumed in Appendix K, thereby increasing the j
thermal power available for electrical generation, while improving the certainty that actual reactor thermal power remains at or below the value used to analyze ECCS performance during i
a LOCA.
10 CFR 50.12 states that the Commission may grant an exemption from requirements contained in 10 CFR 50 provided that: 1) the exemption is authorized by law,2) the exemption j
will not result in an undue risk to the public health and safety,3) the exemption is consistent with the common defense and security, and 4) special circumstances, as defined in 10 CFR 50.12(a)(2), are present. The exemption requested by TU Electric to use the Caldon calorimetric instruments in CPSES Units 1 and 2 satisfy these requirements as supported by the Caldon Topical Report ER-80P (ses ;etter TXX-98180 dated July 17,1998) pnd as generally.
described below.
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10 CFR Part 50, Appendix K, Section I.A.
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i Attachment to TXX-98183 Page 2 of'5 1.
The reauested exemotion is authorized bv law The installation and use of calorimetric instrumentation implementing new and improved technology is not prohibited by any law. The particular equipment TU Electric intends to utilize in CPSES Units 1 and 2 has a demonstrated measurement accuracy superior to
' the installed venturi devices. TU Electric's proposed use of the improved instrumentation accuracy associated with the LEFM/* without reanalysis of ECCS performance in accordance with 10CFR50.46 is consistent with the Commission's intention to allow licensees to use recent information and technologies to avoid unnecessarily restricted operation resulting from the overly conservative assumptions in Appendix K. As the Commission noted in the Statement of Considerations for the 1988 amendment to 10 CFR 50.46, Appendix K is conservative to a degree unnecessary with new and refined technology and calculational methods.2 The Commission stated that " improvements are expected in analytical techniques, and experimental programs are expected to provide increased and improved knowledge about ECCS performance."8 Further, the Commission has indicated that it expected the Staff to consider new technology applicable to ECCS evaluations as it became
-te available.'
It is apparent that the Commission expected new technology to be considered for implementation as it was developed. This expectation is consistent with permitting use, in the ECCS performance evaluations required by 10CFR50.46, of the improved accuracy of the new technology reflected in Caldon's feedwater flow device. TU Electric submits that its proposed approach to implementing the technology, including this request for an exemption and the associated license amendment, is reasonable and consistent with the Commission's intentions to integrate new technology and to eliminate unnecessary operating restrictions. This exemption is authorized by law and fully contemplated by the Commission.
2.
No Undue Risk to Public Health and Safety The proposed exemption satisfies the requirements 10 CFR 50.12(a) in that it does not present an undue risk to the public health and safety. Specifically, granting the proposed exemption is consistent not only with the intent of Appendix K requirements, but is consistent with the ECCS performance criteria set forth in Section 50.46(b). The
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analyses provided in the Caldon Topical Report (ER-8CP) demonstrate that use of the j
53 Fed. Reg. at 35996 (1988).
3 36 Fed. Reg. at 12248 (1971).
4 6 AEC 1085,1123 (1973).
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Attachment to TXX-98183 Page 3 of 5 improved calorimetric instrumentation results in a greater likelihood, relative to conventional venturi flow measuring devices, of operating within the power limits during steady state operations as assumed in the existing ECCS performance analysis.
Implementation of this exemption thus results in an actual increase in the overall level of protection to the public health and safety, even with a higher licensed power level.
3.
The reauested exemotion will not endanaer the common defense and security The Caldon ultrasonic instruments perform the same function as conventional venturi flow measuring devices. The equipment will be procured, handled and controlled in accordance with appropriate procedures applicable to these type of devices. Use of the new equipment will not affect the operation of CPSES Units 1 or 2 or endanger the common defense and security.
4.
Special circumstances are cresent which necessitate the reauest for an exemotion to the requirements of Aooendix K to CFR Part 50.
10 CFR 50.12 requires that any of the several special circumstances listed are present as a prerequisite for granting the exemption request. Those special circumstances -
applicable here are discussed below:
(i)
Application of the regulation in this particular circumstance will not serve *the underlying purpose of the rule and is not necessary to achieve the underlying purpose. [10 CFR 50.12(a)(2)(ii)]
l The underlying purpose of Appendix K is to assure ECCS evaluation models properly j
account for plant conditions so that calculated performance following a postulated LOCA conforms to the criteria set forth in 10 CFR 50.46(b). Appendix K requires specific calculational methods and assumptions of key parameters to assure that the calculated ECCS performance is conservatively described. One of the specific requirements is for an assumed initial reactor power level of 1.02 times licensed power level to allow for uncertainties in the calculation of reactor power.5 ECCS performance will conform to 10 CFR 50.46(b) criteria, and therefore satisfy the underlying purpose of Appendix K, as long as reactor power at initiation of a LOCA is at or below 102% of the maximum licensed power level assumed in the Appendix K analyses.
As discussed fully in the Caldon Topical Report (ER-80P), the Caldon instrumentation system TU Electric intends to use for calorimetric measurements provides a more accurate indication of reactor thermal power than the conventional venturi flow measuring devices. Use of the Caldon system satisfies the underlying purpose of Appendix K through better measurements with improved accuracy.
i 10 CFR Part 50, Appendix K, Section 1.A.
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l Attachment to TXX-98183 Page 4 of'5 l
The proposed implementation plan, including this exemption and the associated license j
l amendment, is consistent with the regulatory intent of the power margin requirement.
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This requirement has served as a conservative tool to assure uncertainties in the l
measurement of reactor core power level are bounded by the licensed ECCS performance model. The Staff has acknowledged this purpose in Regulatory Guide i
1.49' and Standard Review Plan section 15.2.1.7 Consistent with these statements, and I
as discussed more fully in the Topical Report ER-80P, Caldon compared the probability
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of exceeding 2% licensed power to the probability of exceeding 1% licensed power with the LEFM/5, both under the currently licensed ECCS model. Caldon determined that, during steady-state operation, the probability of actual power being at or below the core power level assumed in the licensed ECCS evaluation model is actually improved. As a result, there is greater assurance that the relevant event acceptance criteria will be i
satisfied with the exemption than as currently licensed, even with a higher licensed
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power level.
l (ii)
The exemption will result in benefit to the public health and safety that i
compensates for any decrease in safety that may result from the grant of the j
exemption. [10 CFR 50.12(a)(2)(iv)]
i The public benefits from the proposed exemption are 1) more cost efficient generation of electricity from an existing plant and 2) increased health and safety from more accurate measurement of reactor power and the resulting higher probability that, should a LOCA occur, the actual reactor power will be at or below the value assumed in the ECCS performance analyses.
l The Commission has previously pointed out that increases of up to 5% reactor power have an insignificant effect on risk.' Further, with the Caldon system in operation, there is a higher probability that actual reactor power at the onset of a LOCA will be at or i
below the analyzed power level than with the current venturi instrumentation at the current, lower power level. The overall result is, therefore, a benefit to the public health j
and safety.
(iii)
There is present a material circumstance not considered when the regulation
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6 "Some of the analyses in support of the proposed licensed power level are made for a l
slightly higher assumed power level to allow for possible instrument errors in determing (sic]
l that power level. The Regulatory staff has determined that a margin of two percent of licensed j
power is adequate for this purpose." Regulatory Guide 1.49, Revision 1 (December,1973).
i The value is "to account for a 2% power measurement uncertainty." Standard Review Plan, Section 15.2.1.
8 53 Fed. Reg. at 36003 (1988).
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Attachment to TXX-98183 Page 5 of 5 was adopted for which it would be in the public interest to grant an exemption.
[10 CFR 50.12(a)(2)(vi)]
At the time of adoption of Appendix K, the technology incorporated into the Caldon system was not available for use in the nuclear industry. As discussed above, the i
Commission has acknowledged the regulation's reliance on conservative assumptions in assuring adequate ECCS performance to bound the lack of technological capability.
Improvements in technology have materially changed the need for, among other things, an assumed reactor power measurement uncertainty of 2%. Instrumentation technology, digital data processing, and decades of reactor operating experience now l
exist that were not available at the time Appendix K was adopted. Improvements in reactor power measurements, such as those provided by the Caldon system, will result in increased generation with a higher degree of safety when incorporated into present
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plant operations. This clearly is in the public interest.
l Period of Exemotion TU Electric requests this i.xemption on a permanent basis. No undue risk to the public health and safety is presented by this request.
Related Staff Acorovals TU Electric is seeking approval of Caldon, Inc. Topical Report ER-80P, " improving Thermal Power Accuracy and Plant Safety While Increasing Operating Power Level Using the LEFM/
System" submitted in the July 17,1998 TU Electric letter, logged TXX-98180, from C. L. Terry to the NRC.
Upon implementation of the LEFM/
system, TU Electric is also seeking approval for the continued use of topical reports identified in CPSES Technical Specification 6.9.1.6b. These topical reports describe the NRC-approved methodologies used to support the CPSES safety i
analysis, including the analyses of the small break and large break loss of coolant accidents. In j
many of these topical reports, reference is made to the use of a 2% uncertainty, consistent with Appendix K, to be applied to the reactor power. TU Electric requests that approval be provided l
for the use of these topical reports consistent with this exemption request (up to a 1% power uncertainty), and further, the acknowledgement that the change in the power uncertainty does j
not constitute a significant change as defined in 10CFR50.46 and Appendix K.
j Subsequent Staff action on a future license amendment request for power uprate, as well as this exemption request, is required for TU Electric to implement a power increase.
CONCLUSION l
For the above reasons, the Staff should grant this request for permanent exemption.
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