ML20099D410
| ML20099D410 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 07/28/1992 |
| From: | Horn G NEBRASKA PUBLIC POWER DISTRICT |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20099D413 | List: |
| References | |
| GL-91-01, GL-91-1, NSD920528, NUDOCS 9208060008 | |
| Download: ML20099D410 (12) | |
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0 GENinAL Of flC[
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$i,D920528 July 28, 1992 11.S. Nuclear llegulatory Commission Attentlon: Document Control Deak Washington, D.C.
20555 Gentlemen:
Subj ec t. :
Proposed Change No. 109 to Technical Specifications Revision of Prenspie Temperature Litnitation Curves Cooper Nuclear Station, NRC Docket No. 50-298, DPR 4f, in accordance: with the applicable provisions specified in 10 CFR 50, the Nebraska Public Power District (District) requestu that the Cooper Nuc1 car Station (CNS) Technical Specifications be revised as specified in the attachment. The proposed changes validate the existing presouro vs.
temperature operating limit curves for CNS beyond the current 12 Effective Full Power Years (EFPY), and remove the vessel rnatorial surveillance capsule withdrawal schedule from the CNS Technical Specifications in accordance with the guidance in Generic Letter 91-01.
The District currently estimates that CNS will surpass '2 EFPY by early November, 1992; Therefore, new pressure vs.
temperature operating limit curves must be in place by that time.
Accordingly, the attached contains a description of the proposed change, the attendant 10 CFR 50.92 evaluation, and the CNS Technical Specification pages revised by the institution of this change.
This proposed changs has been reviewed by the necessary Safety Review Committees and incorporates all amendments to the CNS Facility Operating License through Amendment 152 issued March 11, 1992.
11y copy of this letter and attachment, the appropriate State of Nebraska official is being notified in accordance with 10 CFR 50.91(b)(1).
Copies to the NRC Region IV Of fice and the CNS Resident Inspector are also being sent in accordance with 10 CFR 50.4(b)(2).
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- Page 2 of 3 July 28,-1992 1
Should you have any questions or require any additional information, please contact me.
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w Ilorn N
ar Power Group Manager GRil/MJB Attachment I
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ll.R. Borchert Departinent of Ilealth State of Nebraska NRC Regional Adtninistrator Region IV Arlington, TX NRC Resident Inspector-Cooper Nuclear Station I
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U. S. Nuclear Regulatory Conuninsion Page 3 of 3 July 28, 1992 STATE OF NEBRA5KA)
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PLATTE COUNTY
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C. R.11orn, being first duly sworn, deposes and says that he is an authorized representative of the Nebraska Public Power District, a public corporation and political subdivision of the State of Nebraska; that he is duly authorized to submit this request on behalf of Nebraska Public Power District; and th.
the statements contained herein are true to the best of his knowledge and belief.
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. R llorn Subscr bed in my presence and sworn to before me thin 2 T) $ day of
, 1992.
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Attachment te NSD920528 Page 1 of 9 PROPOSED CllANGE NO. 109 TO Tile CNS TEClINICAL SPECIFICATIONS REVISION OF PRESSURE VS. TEMPERATURE OPERATION LIMITATION CURVES Revised Pages c
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JNTRODUCTIOli
'f Tho-Nebraska 'Public Power District (District) requests that the NRC approve the proposed changes to the Cooper Fuclear Station (CNS) Technical Specifications _ described, below.
The ' proposed changes validate the-i existing pressure tempe.roture operating lisait curves (PT curves) for CNS.
beyond the currer.t:12 Effective Full Power Yearu (EFPY), and remove the vessel material surveillance capsule withdrawal schedule from the CNS Technical Specifications in accorduice with the guidance in Generic Letter 91-01, -Tlie District currently estimates that' CNS will surpass 12 EFPY by early November, 1992; therefore, new PT curves must be in place by that time.
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Section -' 3.6. AL -_of the-CNS.. Technical ' Specifications,
" Tho rtaal and Pressurization Limits;" defines,- through Figure Nos. 3_.6.1.a 3.6.1.b. and 3;6.2, the: pressure and_ temperature boundaries within which CNS nuat be operated to ensure adequate margin exists against vessel brittic fracture.
The current PT curves were developed based on the results from testing the
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- first vessel: nateriali surveillance capsule and - in accordaneo, wi.th tl.e.
.-guidance of Regulatory cuido 't.99_ Revision 1, which was :in offect at that time; The iirst surveillance caprule was removed during the Roload 9, Cycle 10
-refueling. outage in-1905.- and was irradiated an equivalent of approximate 1s 6,8 Effective Full Power Years (EFFY).
The turveillance Jcapteule war. ent to CE's Vallecitos Nuclear Center for testing and jo
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Fo11 ewing this testing and analysis, the District submitted Proposed Change No. 48 to the CNS Technical Specifications to revise the vessel PT curves to reflect the surveillance specimen test results.1 The PT curves were based on the Regulatory Guide 1.99 Revision 1 prediction methods; however, the Regulatory Guide 1.99 Revision 1 results were adjusted to account for the high transition tertperature shift ineasured during ter. ting of the surveillance specimens.
This was accomplished by mult iplying the Regulatory Guide 1.99 chemistry factor by the ratio of measured shift in RTu:,7 to that calculated by using the formula in Regulatory Guide 1.99 Revision 1.
The result was an adjusted reference temperature (ART -ini ti al RTup, plus shift) which was more conservative than the values resulting from Regulatory Guide 1.99 Revision 2.
Following several related communications, the NRC ist.ued Amendment No.120 to the CNS operating license to incorporcte the new PT curves.'
The NRC noted during tleir safety evaluation accompanying Amendment No. 120 that the original CNS surveillance program was based on the
,J initial assumptions that the increase in reference temperature at end oi y
life resulting irom neutron exposure would be less than 100"F and that the surveillance specimen exposure would he greater than the vessel wall.
However, analysis of the first surveillanco capsule indicated that the surveillance specimen fluence lags that of the vessel wall, and that the i nc re.a s e in reference temperature vould be greater than 100"F at end ci life. dJTM E-185 82 recenacends that the s.urveillance capsule lead f actors j
(the ratio of the instantaneous neutron flux density at the specimen location to the maximum calculated neut ron flux density at the inside surface of the reactor vessel wall) he in the ranc,n of one to three. ASTM C-185-82 also recoitmends a minimum number of four surveillance captulos to be included in the surveillance program for a predicted end of life transition temperature shift between lod"F and 200*F, with withdrawal schedules of three. nix, and fiftern EFPY for the first three capsules, with the lant capsuin t.o be removed,:t end of.1i f n.
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Based on the abtve, the NRC rotammended that to meet as closely as possible the intent of ASTM E 185-fs2, that the withdrawal schedule for the second capsule be accelerated to 12 EFPY, and the schedule for t.he third capselo ht determined based on the analysts of the srcond capsula The NRC also cecommended that the District cousider possli.le insertion of a fourtb capnole into tna CNS vessel, porsiviy with reconstituted specimenn from an earlier capau?e.
Following various cominunications, in 1991, the Di s t.ri c t c o.nai t t ed to: 1) remove the second surveillance capsult during
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1 Letter from L.
G. Munc1 (NPPD) to NRC dated October 28, 1987, "Propowd Change No. 48 to the Cooper Nuclear Station Technical Spec i f i c at t or.s.
- Le t t e r f rom k'. O. hung (NRL) to G. A. Trevors (NPPD) dated April 26, 1988, " Cooper Nuclear Station Amendment No. 120 to Fecility Operating License No. DPR-46 (TAC So. 65793)."
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1 Attachment to NSD920$28 Page 3 of 9 l
1 the Reload 14, Cycle 15 refueling outage during 1991 (following approximately 11 EFPY of operation), and 2) reconstitute the specimens from this capsule and re insert the reconstituted specimens during the Reload 15, Cycle 16 refuelir.g outage.' The District also indicated that i
the withdrawal schedule for the third capsule will he based on the results of testing the second surveillance capsule.
The second surveillance capsule was withdrawn during the Reload 14, Cycle 15 refueling outage in late 1951 and was shipped to the CE Vallecitos Nucicar Center where it is currently undergoing testing and analysis.
Ilowevet, because the results of this testing will not he available with sufficient lead time to revise the CNS PT curves in order to support continued operation, the District has reanalyzed the CNS PT curves in accordance with the Guidance of Regulatory Guide 1.99, Revision 2 and has determined, as discussed below, that the existing CNS PT curves are valid beyond the stated 12 EFPY.
.Th District will re-ovaluate the CNS PT curves upon conclusion of the L
te-ing and analysis ot the at cond surveillanco capsule, and propose l
appropriato changes to the surveillance capsule withdrawal schndule anri to the CNr. Technleal Specifications if warranted.
I11. D1S&l!SJJDH Regulatory Guide 1.99. Revision 2 provides a method aco<eptable to the NRC for predicting the ef tect of neutron radiation on reactor vessel raaterials as required by Paragraph V. A. of 10 CFR 50 Appendix G.
Itecause of the scatter inheront to Charpy test data, Reguintory Guide 1.99 Revision.2 requires at least tvo :redthie surveillance dar.a sets be available before i
using the reactor specific data to deterwine ART and the Chatpy upper-shelf energy of ranctor ' beltline matet!.als.'.As discussed Thore, the District currently !.as only one het ' of surveillance data available.
Thereforo, the District generated new ART predictions using the methods described in Regulatory Guide 1.99 Revision 2, using the CN3 beltline material chemistries, and the peak fitwnce at given EFPYs.
The CNS Technical Specifications contain three PT curves for operator use based.on -the corrasponding application.
Figure 3.6.1.a provides the
- 3, minimum vessel temperature vs. vessel pressure f or non nucloc
- heatup and n
i LetterL t' rom C. R. Horn (NPPD) to NRC date d June 7,1991, " Response h_
to Questions on 1.icense Extenulon to 40 Years fro.n Operating.
License. Issuance." (Note: thio letter was erroneously dated 1990)
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.Rer,tlatory Guide 1.99 defines " credible" surveillance data as a 0 P for welds and 17" F for at e.,dard deviation of no more than 28 base metal abour a best fit lino fitted as described in Regulatory l
Pouit ton 2.1 of Regulatory Guide 1.99 Ravision 2.
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Figure 3.6.1.b provides the minimurn vessel temperature vs. versel pressure for core operation (when the core is critical), and is also valid through 12 EFPY. Figure 3.6.2 provides the minimura vessel temperature vs.
vessel pressure for pressure tests such as that required by Section XI of the ASME c. ode; this figure provides three curves based on 8, 10, and 12 EFPY.
Three curves were gerierated for Figure 3.6.2 to provide greater operational flexibility while performing system pressure tests, depending upon vessel exposure. Each of there curves are based on a calculated ART for the limiting versel material for the given EFPY based on the application.
Tberefore, new ART calculations were performed using the 3egulator* Guide 1.99 Revision 2 Psthodology to validate the existing P1 curves beyond the current 12 EFPY.
The results of this analysis are shown in the table i
below for the each ART previously calculated and upon vbich the existing PT curves are based.
EXISTING CNS TECilNICAL REVISED CNS TECllNICAL-ADJUSTED REFERENCE SPECIFICATIONS VESSEL SPt:CIFICATIONS VESSEL TEMPERATURE (ART)
EXPOSURE (EFPY)*
EXPOSURE (EFPYP 93*F 8
13 102F 10 18 110*F 12 21 l
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. Based on Regulatory Guide 1.99 Revision 1 with surveillance test results adjustment b.
Based on Regulatory Guide 1.99 Revision 2 with no surveillance test results adjustment The District has therefore revised Figures 3.6.1.n, 3.6.1.b, and 3.6.2, 1
and the corresponding Bases discussion to extend their validit.y in accordance with the above table. The specific changes are described below in Section IV, " Description of Changes."
In addition, in accordance with Generic Letter 91 01, the District
- proposes removal of the vessel raaterial surveillance capsule withdrawal schedule from-the-CNS Technical Specifications.
. ptovides the guidance for remo M of the surveillance capsule withdrawal schedule as a line-item improve.ent to the Technical Specifications.
In accordance with the -guidance provided in Generic Letter 91 01, tho
. District has. updated the surveillance capsule withdrawal schedule with Revision 10 to the CNS USAR, dr;ch was submitted to the NRC prior to July _22, 1992.
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NSD920578 Page 5 of 9 The Bases section for therrnal and pressurization litnitations is revised to reference the location' of the surveillance capsule withdrawal schedule in the CNS USAR,. Finally, Section 4.6. A of the CNS Technical Specifications is revised to indicate'that the surveillance specimens shall be removed and exarnined to deterrnino changes in their raaterial properties as required by 10 - CFR 50 Appendix H.
These changes correspond to the guidance provided in Generic Letter 9101, and are detailed below in Section IV,
" Description of Changes."
Finally, this proposed change trakes an administrative par,ination change to relocate a blank pat,e to the cc.d of the 3/4.6 Bases section. This change
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is detailed in Section IV below.
IV, DESCRIPTION OF CHANGES, Page 132 - Section 3.6.A.3 is revised to change the figure 3.6.2 curve references from 8, 10, & 12 EFPY to 13,18, & 21 EFPY, In addition, the-statement indicating that the ART for the bottom head region is valid to 12 EFFY is deleted, as this curve is actually valid to end of 11fe, since the bottom head region is not expected to receive sufficient fluence to exhibit a shif t in les reference temperature. Additionally, Section 3.6. A.2 is clarified to rpecify that the temperature limits for non-nuclear -- heatup and for core cooldown following nuclear shutdown apply only when the reactor vessel head is tensioned.
Page 133 - The reactor vessel surveillance capsule withdraral schedule is deleted. Additionally, language is added to specify that the reactor vessel surveillance specimens wil1~be withdrawn and examined to determine changes in their material properties as required by 10 CFR 50 Append.x H.
Page 147 - The 3/4.6 Bases sect.lon is updated to describe the basis for the revised PT curves.
This sectica is also revised to reference the surveillance capsule withdrawal schedule in Section IV.2.7 of the CNS USAR.
I Pago-154 - This previously blank page is revised to become the new Figure l
3.6.1,a, "Minist.m Temper.:ture for Non Nuclec.r Heatup or Core Cooldown N11owing Nuclear ' Shutdown. "
In addition, this figure's period of validity is-revised from 12 to 21 EFPY.
Page 155 -- This page, previously Figure 3.6.1.a, is revised to become the new Figure 3;6.1.b, " Minimum Teinperature for Core Operation L
(Criticality)
Includes 40*?. Margin Required by 10CPR50 Appendix 0 In addition, this figure's period of validity is revised from 12 to 21 EFPY.
Page 156 - - This page, previously Figure 3.6.1 b, is revised to becorne the new Figure 3.6.2, " Minimum Temperature for Pressure Tests Such L
as Required by Section XI,"
In addition, this figure's period
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Page 157 - Thtse pages are combined into one " Intentionally Left Blank" 6 158 page.
V.
HIG{LFICANT llAZARDS DETEPMINATION 10 CFR 50.91(a)(1) requires that licensee requests for operating license amendments be accompanied by an evaluation of significant hazards posed by the issuance of the amendment.
This evaluation is to be performed with respect to the criteria given in 10 CFR 50.92(c). The following analysis meets these requirements, fvaluation of this Amendment with Respect to 10 CFR SO M The enclosed Technical Specifications change is judged to involve no nignificant hazards based on the following:
G o
1.
Does the proposad change involve a significant increase in the probability or ccreequences of an accident previously evaluated?
Evaluntion The proposed revisions to the existing Cooper Nuclear Station (CNS)
Technical Specifications pressure vs. temperature operating limit curves (PT curves) do not involve a significant increase in the y robability or consequences of an accident previously evaluated.
The existing PT curves, approved with Aniendment No. 120 to the CNS operating license, were developed based on Regulatory Guide 1,99 Revision 1,
the NRC guidance in effect at the time of their
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revision, and were ccuservatively adj us ted to account for the results from testing the initial vessel :naterials surveillan.:e capsule withdrawn. Since that time, the NRC issued Regulatory Guide 1.99 Revision 2, which describes the current methods acceptable to the NRC for predicting the shift in nil-ductility transition temperature (RTn37) of the vessel beltline materials. The proposed revisions to the CNS PT curves are based on the recommendations in Regulato*y Guide 1.99 Revision 2, and are therefore in accordance with the latest NRC guidance.
In
- 1985, the District removed the first vessel materials survei11ance capsule for testing and analysis.
This testing displayed an RTu37 shift greater than had been previously expected.
Accordingly, the District revised the CNS PT curves based on the guidance in eifect at that time, Regulatory Guide 1.99 Revision 1, but conservatively adjusted the results to account for the RTm shift exhibited during the testing of the first surveillance capsule.
As a result, the Regulatory Guide 1.99 Revision 1 chemistry factors used to determine the Adj us ted Reference initial RTu3, plus the shift in RT due to Tennerature (ART g37
Attechment to NSD920528 Page 7 of 9 neutron irradiation) were multiplied by an adjustment factor equal to the ratio of the measured RTm at 6.8 Effective Full Powee Years
. (EPPY) to the expected RTm at 6.8 EFPY using Regulatory Guide 1.99 Revision 1 methods.
This methodology resulted in estimated APT values that were overly conservative, when compared to Regulatory Guide 1.99 Revision 2 predictions.
The proposed changes to the CNS PT curves are based on the motbods described in Regulatory Guide 1.99 Revision 2.
Because of the data scatter inhetent to Charpy testing results, absent additional justification, P.egulatory Guide 1.99 Revision 2 requires that at least two sats of credible surveillance data be available to develop a
vessel-specific transition temperature shift correlation; otherwise, the methods of Regulatory Guide 1.99 Revision 2 should be used. Currently, the District has only one set of surveillance data available. The second CNS surveillance capsule was removed during i
the Reload 14, Cycle 15 Refueling outage in the it.te fall of 1991; however, the results of the. second capsule testing will not be available on a schedule that will support this proposed change. The District has therefore recalculated the ART based on the method described in Regulatory Guide 1.99 Revision 2.
The results of these calculatio-validato the pres.ont CNS PT curves through 21 EFPY of operation, which represents an ART of 110*F as calculated using the Regulatory Guide 1.99. Revision 2.
These include Figure 3.6.1.a, "Minimam Temperature for Non Nuclear Heatup or Cooldown Following Nuclear Shutdown, Figure 3.6.1.b,
" Minimum Temperature for Core Operation (Criticality) - Includes 40"P Margin i
..l' Required by' 10CFR50 % pendix G " and -Figure 3.6.2,
" Minimum Temperature for Pressure Tests Such as Required by Section XI."
Additionally, the three separate curves ara retained in Figure 3.6.2 to provide operational flexibility. These curves correspond to ARTS of 93'F, 102'F, and 110*F which are valid for 13, 18, and 21 EFPY respectively based on Regulatory Guide 1.99 Revision 2 calculations.
Other than the extension of their period of validity by using the calculation methods.of Regulatory Guide 1.99 Revision 2, no other changes are proposed to - the CNS PT curves.
Accordingly, the y
proposed revision to the CNS PT curves are based on an NRC-accepted means of ensuring protection against brittle reactor vessel failure,
-and compliance with 10 CFR-' Appendix G will be -maintained.
Therefore, this _ proposed change will - not involve a significant increase _in the probability. or consequences of an accident previously evaluated.
The changes proposed to remove the reactor vessel surveillance capsule withdrawal schedule from the CNS Technical Specifications are in accordance with ~ the guidance provided in Generic Letter 91-01.
As discussed -in Generic Letter 91-01, licensee vessel surveillance programs are controlled by 10 CFR Appendix H, which 1
requires licensee submittal. of and NRC approval of the proposed surveil 3.ance capsule withdrawal schedule prior to implementation.
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_._...._.___-._._.._..__._.____.___.m Attachment to NSD920528 Page 8 of 9 In addition, with Reviulon 10 to the CNS Updated Safety Analysis -
Rtport (USAR), the District will update the surveillance withdrawal schedule as described in the NRC Safety Evaluation accompanying Amendment No.143 to the CNS Operatin;g License, dated July 5,1991.
Therefore, no loss of NRC regulatory control of the surveillance capsule withdrawal schedule occurs as a result of this proposed change, and rernovs1 of the surveillance capsule does not involve a significant increase in the probability or consequences of an
-accident previously evaluated.
The changes to Section 3.6.A.2 which clarify that the temperature limits apply only when the reactor vessel head is tensioned are condistent with the_1986 ASME code, and are - therefore consistent with 10 CFR 50 Appendix G.
This is referenced in Section IV.2.6.3.2 of the CNS USAR.
Therefore, these clarifications do not involve a si nificant increase in the probability or consequences of an 6
l necident previously evaluated.
Finally, the-repagination does not involve a significant increase in the probability or consequen< 3s of an accident previously evaluated,
't as_this is a purely administrative change.
2.
Does thu proposed chano,e create the possibility for a new or different kind of accident from any acciderit previously evaluated?
Evalurtion The proposed changes update existing vessel _ pressure - temperature l-operating liinits to correspond with the current NRC guidance. These changes are necessary to. pertait operation beyond 12 ETPY.
The proposed changes do not involve any plant design changes nor any new mode of operation. These changes only demonstrate compliance with the -brittle fracture prevention requirements of 10 CFR 50 L
_ Appendix G, and therefore do not create the possibility for a new or differcat kind of accident from any accident previously evaluated.
3.
.Does the proposed change create a significant reduction in the margin of safety?
Lyaluatioil L
. The __- proposed changes to the CNS PT curves do not create a significant reduction in the margin of safety. The proposed chenges revise ( the. existing CNS PT curves to be consistent with the recommendations'of Regulatory Guide-1.99, Revision 2, the current NRC guidance;given to encure compliance with 10 CFR Appendix G.
As discussed above, the existing - CNS - PT curves were developed by using the guidance of Regulatory Guide 1.99 Revision 1 with adj us tment factors to account for the greater than expected transition temperature shift exhibited during testing of the first set ~of vessel meterial surveillance specimens withdrawn in 1985.
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This methodology introducen excessive conse Natism compared tn the results using he methods of Regulatory Guide 1.99 Revision 2.
The proposed revision of the CNS PT curves rernovos the excessive conservatir. n contal ed in the existing PT curves which were developed using guidance which is now outdated.
The proposed revision to the PT curves does utilize the roost current NRC guidance 4
for compliance with 10 CFR 50 Appendix 0.
Therefore, this proposed
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change..does not result in a significant reduction in the margin of safety.-
Tre changes to Section 3.6.A.2 to clarify that the vessel ternparature liraits apply only when tho reactor vessel head is tensioned do not involve a significant reduction in the margin of safety.
These changes only clarify the requirements of 10 CFR 50 Appendix G, and makes the CNS Technice'l Specifications consistent with ti.e CNS USAR.
The proposed change to remove - the vessel material surveillance espsule withdrawal schedule from the CNS Technical Specifications is in accordance with the. guidance contained in Generic Letter 91 01.
In. addition, 10 CFR 50 Appendix H requires licenseen to obtain-NRC approval of _any changes to who surveillance capsule withdrawal schedule; therefore, including the schedule in the Technical Specifications represents redundant control mechanisms.
- surveillance capsule withdrawal schedule in accordance with conunitments made during approval of Amendment No. 143 to the CNS Operating License..Therefore, removal of the surveillance capsule withdrawal schedule does not constitute a reduction in the rargin of safety.
VI.
CONCIMSIDA d-The i)1 strict has evaluated thc proposed changes -described above againen l
the criteria given in 10 CFR 50.92(c) in accordance with-the requirements of 10 CFR-50.91(a)(1). This evaluation has determined that this proposed change will ng.t 1) involve a significant increase-in the probability or consequences of~ an. accident previously evaluated, 2) create-- the possibility for a new or different kind of accident from any - accident previously evaluated, or 3) create a significant reduction in the margin of safety.
Therefore, for the reasons detailed above, the District requests NRC approval of Proposed Change No. 109, f
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