ML20092N569
| ML20092N569 | |
| Person / Time | |
|---|---|
| Site: | Mcguire, Catawba, McGuire, 05000000 |
| Issue date: | 06/27/1984 |
| From: | Tucker H DUKE POWER CO. |
| To: | Adensam E, Harold Denton Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML19269A303 | List: |
| References | |
| GL-84-04, GL-84-4, NUDOCS 8407030294 | |
| Download: ML20092N569 (9) | |
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DUKE POWER GOMPANY P.O. DOX 33180 CHAHLOTTE, N.O. 28242 IIAL H. TUCKER retzenoxz
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June 27, 1984 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. C.
20555 Attention: Ms. E. G. Adensam, Chief Licensing Branch No. 4
-Re: Catawba Nuclear Station Docket Nos. 50-413 and 50-414
References:
- 1) Letter from W. H. Owen (Duke Power Company) to W. J. Dircks (NRC), dated September 19, 1983
- 2) Letter from H. R. Denton (NRC) to W. H. Owen (Duke Power Company), dated October 17, 1983
- 3) Letter from H. B. Tucker (Duke Power Company) to H. R. Denton (NRC), dated November 18, 1983
- 4) Generic Letter 84-04, NRC, dated February 1,1984
- 5) Letter from H. B. Tucker (Duke Power Company) to H. R. Denton (NRC), dated February 29, 1984
- 6) Letter from H. B. Tucker (Duke Power Company) to H. R. Denton (NRC) dated June 18, 1984
Dear Mr. Denton:
References 1 and 3 informed the NRC that Duke Power Company was evaluating the technical feasibility and potential benefits of eliminating postulated pipe breaks in the Residual Heat Removal (RHR) Lines from the structural design basis of the Catawba Nuclear Station. As a result of efforts by yt Westinghouse, the NRC, and Duke Power, we have concluded that it is tech-nically feasible to eliminate these postulated pipe breaks.
In accordance ng g
with the statement in Reference 2 that applications related to the leak-
.og before-break pipe failure concept will be permitted prior to the NRC com-
$15 pleting all of the changes in regulatory requirements, this letter is ED a submitted.
g
.7 Duke Power herein requests an exemption from General Design Criteria 4 h
to apply the " leak-before-break" concept to the Catawba Nuclear Station to eA eliminate postulated pipe breaks in the Residual Heat Removal (RHR) Lines from the plant structural design basis. Additionally, a safety balance in h terms of accident risk avoidance versus safety gain will be demonstrated.
l The Westinghouse technical report (WCAP-10577) entitled " Technical Basis for Eliminating the RHR Line Rupture as the Structural Design Basis for fgf$MU
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- Mr. Harold R. Denton, Director June 27, 1984 3
Page 2 Catawba Units 1 & 2 and McGuire Units 1 & 2" is' included as Enclosure A Jto provide technical ~ justification for elimination of RHR line breaks
-for Catawba...Because of the proprietary nature of this-report, Enclosure
. A has been provided only to the addressee and Mr. James P. O'Reilly of the
-NRC.
A no.-proprietary version of the specific plant applicability report (WCAP-10576) is included as Enclosure B and has been provided to others on the attached distribution list.
As Enclosure A contains infonnation proprietary to Westinghouse Electric
. Corporation, it is suppo'rted by the attached letter (Attachment 1) and affidavit. signed by Westinghouse, the owner of the information. The affidavit sets forth the basis on which the information may be withheld from public disclosure by.the Commission and addresses with specificity the considerationslistedinparagraph(b)(4)ofSection2.790oftheCommission's
- regulations. _Acccedingly, it is respectfully requested that the information which. is proprietary to Westinghouse be withheld from public disclosure in
_accordince with 10CFR Section 2.790 of the Commission's regulations.
- Correspondence with respect:to the proprietary aspects of the Application
.for. Withholding or the supporting Westinghouse affidavit should reference
. CAW-84-55'and should be addressed.to R. A. Wiesemann, Manager, Regulatory and Legislative Affairs, Westinghouse Electric Corporation, P. O. Box 355, Pittsburgh, Pennsylvania 15230.
Exemption Request Pursuantto10CFR50.12(a),DukePowerCompanyherebyappliesinconnection with the Catawba Nuclear _ Station license for an exemption from the pro-
-visions to 10CFR Part 50, Appendix A, authorizing alternative pipe break analyses for the Catawba Nuclear Station Residual Heat Removal Lines. The requested exemption is based upon the application of advance fracture mechanics technology as evaluated in the Westinghouse technical report WCAP-10577,:(Enclosure A).
Specifically we-request the elimin'ation of postulated circumferential and longitudinal pipe breaks in the Residual Heat Removal Lines (from Reactor Coolant Hot Leg to first isolation valve) from consideration in the structural design basis of Catawba Nuclear Station. The impact on important design aspects of implementing leak-before-break on Catawba Nuclear Station has been evaluated by Duke Power and is summarized in Attachment'2. A detailed list of previously postulated pipe breaks and L
associated rupture devices is provided in Attachment 3.
w The bases for the requested exemption are as follows:
.'1.
In-shop, pre-service, and in-service inspections performed on piping for the Catawba Nuclear Station minimize the possibility of flaws existing in such piping. - The application'of advanced fracture mechanics has demonstrated that if such flaws exist they will not
. grow to a leakage crack when subjected to the worst case loading condition over-_the life of the plant.
4
Mr. Harold R. D;nton, Director
.Juns 27,1984 Pagt 3 2.
If one postulated a through-wall crack, large margins against un-stable crack extension exist for certain stainless steel piping when subjected to the worst case loading conditions over the life of the plant.
The application of advanced fracture mechanics technology has demonstrated that small flaws or leakage cracks (postulated or real) will remain stable and will be detected either by in-service inspection or by leakage monitoring systems long before such flaws can grow to critical sizes which otherwise could lead to large break areas such as a double-ended rupture of the RHR line. To date, use of this advanced fracture mechanics technology has been limited by the definition of a LOCA in Appendix A to 10CFR Part 50 as including postulated double-ended ruptures of piping regardless of the associated pro-bability. Application of the LOCA definition without regard to this advanced technology to large diameter thick-walled piping such as the Residual Heat Removal lines of a PWR imposes a severe penalty in terms of cost and occupat-ional exposure because of the massive pipe whip restraints it requires which must be removed for in-service inspections. This penalty is unreasonable because the;e pipes do not have a history of failing or cracking and are coriservatively designed. Accordingly, for design purposes associated with protection against dynamic effects, we request this exemption from the regulations to eliminate the need to postulate circumferential and longitudinal pipe breaks. This exemption request does not extend to speci-fying design bases for containment, the emergency core cooling system, or environmental effects.
We request that the exemption authorize, with respect to the plant structural
- design basis, the elimination of pipe breaks in the Residual Heat Removal lines. Thus, the use of advanced fracture mechanics permits a deterministic evaluation of the stability of postulated flaws / leakage cracks in piping as an alternative to the current mandate of overly conservative postulations of piping ruptures.
This exemption request if consistent with the provisions of footnote 1 to 10CFR Part 50, Appendix A, which refers to the development of "further details relating to the type, size and orientation of postulated breaks in specific components of the reactor coolant pressure boundary." The RHR line is a part of this boundary.
As support for this request, in addition to the previously specified infor-mation, we would request consideration of the following:
1.
Letter from Darrell G. Eisenhut (NRC) to E. P. R6he (Westinghouse) dated February 1, 1984.
2.
Memorandum from Darrell G. Eisenhut (NRC) to All Operating PWR Licensees, Construction Permit Holders and Applicants for Con-struction Permits dated February 1,1984 -
Subject:
Safety Evaluation of Westinghouse Topical Reports Dealing with Elimination of Postulated Pipe Breaks in PWR Primary Main loops (Generic Letter 84-04).
m
p Mr. Harold R. Denton, Director
.Jun2 27, 1984 Page 4 3.
CRGR resolution of generic issue A-2.
4.
ACRS letter dated June 14, 1983, re:
" Fracture Mechanics Approach to Pipe Failure."
5.
Memorandum from William J..Dircks, EDO, to ACRS dated July 29, 1983, re:
" Fracture Mechanics Approach to Postulated Pipe Failure."
6.
Memorandum from Harold Denton (NRC) to Murray Edelman (AIF),
dated May 2, 1983.
Safety Balance t
Further, pursuant to 10CFR50.12(a), we believe the requested exemption will not endanger life or property or the common defense and security and is in the public interest. The total increase in public and occupational accident t
exposure associated with omitting the Residual Heat Removal line whip i
restraints and jet deflectors is estimated to be less than.5 man-rem for the nominal case with 40-year plant life. This estimate is based on an analysis similar to that for the primary loop in the " Leak-Before-Break Value-Impact Analysis" of Enclosure 2 to Reference (4), but performed speci-i fically for the Residual Heat Removal lines. The major difference in the analysis is that a RHR line break will not contribute to asymmetric blcwdown; therefore, no LOCA is assumed to occur in the reactor cavity for the RHR line break. A reactor cavity LOCA leads to a majority of the potential accident risk for the primary loop; and thus, a Residual Heat Removal line break would result in a lower risk than a primary loop break.
The benefits in avoidance of exposure for Catawba Unit 2 associated with the requested exemption are estimated to be 146 man-rem of occupational exposure over plant life, based on Duke Power studies. This eliminated radiation exposure is related to pipe whip restraint inspection tasks, restraint disassembly / reassembly for pipe weld inspections, and improved personnel access for operation and maintenance. Consequently, the savings in exposure by granting the exemption far exceed the potentially small increase in public risk and occupationTl accident exposure associated with deleting restraint devices. Duke Power Company estimates cost savings for Catawba Nuclear Station, Unit 2 of at least 726,500 dollars as given in Attachment 4.
Benefits with regard to plant safety, operation, and design are given in.
With these benefits and with a net reduction of radiation exposure of 146 man-rem, a net safety gain has been demonstrated for Catawba Unit 2.
- Also, a' cost savings of at least 726,500 dollars has been shown, and a technical basis for elimination of RHR line breaks has been demonstrated.
Implementation of the leak-before-break concept will thus be cost-effective as well as technically justifiable while resulting in improved overall plant safety.
Therefore, Duke Power Company hereby requests NRC approval of an exemption to GDC-4 in order to rpply the leak-before-break concept to Catawba Nuclear Station to eliminate postulated pipe breaks in the Residual Heat Removal
'line frcn the plant structural design basis.
~. -
4.. ~ Mr. Harold R.-Dinton, Director
. June 27, 1984
- Page'5-Enclosure.C of Reference 5) consisted of the revised Catawba FSAR pages associated with elimination of pressurizer surge line breaks.
In addition, Attachment 5 of Reference 6) included additional information pertaining to the elimination of Class.1 ~ Accumulator Injection line breaks. Attachment 5 to this letter includes additional changes to the FSAR associated with the elimination of the Residual Heat Removal line
- breaks. 'These_. changes will be included in a future revision to the FSAR.
This current request is for implementation on Unit 2 only; Duke Power will submit additional information prior to implementation on Unit 1.
Construction completion of the Residual. Heat Removal line devices at Catawba Unit 2 is on hold pending an NRC ruling on this proposal. We
. request.a resolution concerning'this matter prior,to July 30, 1984.
If I can 'be of further assistance, or if a meeting with the staff is
~
- deemed beneficial for a final resolution of this matter, please contact me.
.Very.- truly 'you rs,
. g g [ca Hal-B'. Tucker
[
t ROS/rh's~. ' Attachments f
cc: Mr. James P. O'Reilly, Regional Administrator I
U. S. Nuclear Regulatory Commission Region II 101 Marietta' Street, NW, Suite 2900 i
-Atlanta, Georgia =30303 L
NRC Resident Inspector-Catawba Nuclear Station Mr.- Robert Guild, Esq.
I Attorney-at-Law 7
P. O. Box 12097 L
Charleston, South Carolina 29412 Palmetto Alliance 21351 Devine Street Columbia, South Carolina 29205 Mr. Jesse L. Riley.
Carolina Environmental Study Group 854 Henley Place Charlotte,. North Carolina 28207 i
ATTACHMENT 2 Impact of Elimination of Postulated Circumferential and Longitudinal Pipe Breaks in the Residual Heat Removal Lines
- Structures, Systens, Components, Programs Considered for Impact Impact Residual Heat. Removal Line Pipe Deleted from Design Whip Restraints and Jet Barriers Primary Shield. Wall / Crane Wall /
Reduction in pressurization Operating Floor / Refueling Canal loading Wall RCE. Pressure Boundary Leakage No Change Detection Systems-Environmental Qualification No Change Program b
.)
L ATTACHMENT 3 Postulated Residual Heat Removal Line Pipe Breaks and Associated Rupture Devices.
Erection Status Postulated Break' Location Devices Associated with Break Catawba Unit 2
- 1. Terminal end at Hot
- 4. Pipe Whip Restraints Not Installed.
. Leg 28.
- 2. Terminal end at Hot 4 Pipe Whip Restraints Not Installed.
Leg 2C.
The total number-of devices being deleted is 8 pipe whip restraints.
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m ATTA iT 4 Summary of l its from the Elimination of:Res Heat Removal Line Pipe Breaks on Cataw clear Station Unit 2
- Category Benefit 1.
Design, material and erection
$368,000
- costs associated with 8 rupture devices.
2.
Plant design aplifies overall plant design
'limination of potential inter-nes with piping, hangers,
)
' tubing, etc.
3.
Relief of congestion, improving 146 man-rem reduction in radiation access for operation and main-exposure over life of Unit 2 tenance.
($358,500).
4.
Reduction in piping heat loss at Not quantitatively assessed.
whip restraint locations.
Insulation can be installed on piping at current locations of Residual Heat Removal Line pipe whip restraints.
5.
Improvement in overall plant Improvement in ISI quality.
_ safety (NUREG/CR-2136).
Elimination of potential for restricted thermal or seismic movement.
- Current (1984) Dollars I'
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ATTACHMENT 5 Table 3.6.1-4 Piping Systems For A) plication of
" Leak Before Brea(" Concep_t_
System Math Model Line Description Reactor Coolant Reactor Coolant Loops Reactor Coolant.
NC-201 Pressurizer Surge Line Safety Injection NI-204 10" Accumulator Injection Line-Loop A (Class 1)
Safety Injection NI-205 10" Accumulator injection Line-Loop B (Class 1)
Safety; Injection NI-206 10" Accumulator Injection Line-Loop C (Class 1)
Safety Injection NI-207 10" Accumulator Injection Line-Loop D (Class 1)
Residual Heat Removal ND-201 12" Residual Heat Removal Line-Hot Leg 2B Residual Heat Removal ND-202 12" Residual Heat Removal Line-Hot Leg 2C 4
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