ML20137K972
| ML20137K972 | |
| Person / Time | |
|---|---|
| Site: | Saint Lucie  |
| Issue date: | 08/26/1994 |
| From: | FLORIDA POWER & LIGHT CO. |
| To: | |
| Shared Package | |
| ML20137K821 | List:
|
| References | |
| FOIA-96-485 JPN-PSL-SEFJ-94, JPN-PSL-SEFJ-94-021, JPN-PSL-SEFJ-94-21, NUDOCS 9704070130 | |
| Download: ML20137K972 (12) | |
Text
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$ DESCRIPTION h 1 0 -[~..
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2.0 DESCRIPTICII'AND PURPOSE . . . . . . ........ 4 3.0 LICENSING REQUIREMENTS . . . . . ... . . . . . . . .5 4.0 ANALYSIS OF EFFECTS ON SAFETY . . . ..... . . . .6 5.0 FAILURE MODES AND EFFECTS ANALYSIS ..... . . . .8 6.0 PLANT RESTRICTIONS . . . . . . . . .. . . . . . . .8 7.0 EFFECT ON TECHNICAL SPECIFICATIONS . . . . . . . . .8 8.0 U'" XED SAFETY QUESTION DETERMINATION . . . . . .9 9.0 ACTIONS REQUIRED . . . . . . . . . .. . . . ... 11
10.0 REFERENCES
. . , . . . . . . . . . . ........ 11 ATTACEMENTS '
A. FS&R MAREED UP PAGES . . . . . . . . . . . . 3 Pages B. TECHNICAL SPECIFICATIONS MARKED UP PAGES . . . 2 Pages C. SIEMENS LETTER RIN:94:106 . . . . . ..... . 3 Pages D. SIEMENS LETTER JLE:029:94 . . . . . ..... . 3 Pages
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P The evaluation performed here supports an increase in the maximum l l
allowable Resistance Temperature Detector (RTD) response time for ;
i St. Lucie Unit 1 from 8 seconds to 14 seconds. St. Lucie Unit 1 1 W'/pA c.cuses RTDs which are Need and Rosemount types.
l c During the Loop l t .
Current step Response (LCSR) testing of'the RTDs in the past few
! years, the response times of these RTDs have been in tho' range of i 3 to 8 seconds. The need RTDs have averaged response times less l than 5 seconds, whereas the Rosemount RTDs have typically shown
! response times between 6 and 8 seconds.
L :
[ Due to difficulties associated with the removal and installation of l
RTDs, the RTD respon'se time has been of interest to Florida Power j & Light (FPL) Company and to the nuclear industry in ganeral.
i Relaxation of the RTD response time will allow greater operational l flexibility, that would prevent a sound RTD from being replaced j when it is otnerwise acceptable for use.
1
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An evaluation is conducted to assess the impact of increased RTD l respo.n ao limit on the safety analysis. The Basis to Technical Specificauon (TS) for the Thermal Margin / Low Pressure (TM/LP) trip (Reference 1) specifies an allowance of 30 psia to compensate for the associated time delays. The pressure bias factor of 30 psia bounds the present RTD delay time of 8 seconds. This bias term has been re-evaluated for the RTD response time of 14 seconds. The new bias term, calculaced to be 42 psia, has been accounted for in the .
current safety analyses which, therefore, remain unaffected. I 1
It should be noted that a similar change to increase the RTD l response time to 14 seconds was approved by the NRC in 1991 for St. j Lucie Unit 2 (Reference 2) . Relocation of tables of instrument response time limits to the Final Safety Analysis Report (FSAR) has j recently been approved by the NRC for the St. Lucie Units 1 and 2 l in Reference 3, in response to FPL's request for a license amendment (Reference 4) . The proposed change to the RTD response time limit is in accordance with 10 CFR 50.59 and F.nclosure 1 to Generic Letter (GL) 93-08 (Reference 5).
2.0 DESCRIPTICE aED PURPOSI This evaluation proposes to increase the maximum allowable RTD response time for St. Lucie Unit 1 from 8 seconds to a value of 14 seconds. The ATDs at St. Lucie Unit I have shown response times approaching the present allowable limit of 8 seconds during the surveillance testing.
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- St. Lucie Unit i uses RTDs which are Need and Rosemount types.
l During the LCSR testing of the RTDs in the past few years, the
, response times of these RTDs have been in the range of 3 to 8
- j. seconds. The Need RTDs have averaged response times less than 5 i seconds, whereas the Rosencunt RTDs have typically shown response j' times between 6 and 8 seconds.
here is to'evaluste'the effects' ofiincreased R2D delay j '" time safety analyses. A similar change to increase the RTD ^
! response time to 14 seconds for the St. Lucie Unit 2, was approved i by the NRC in 1991 (Reference 2) . Generic Letter 93-08 allowed j relocation of the response time limit tables from TS to the FSAR.
l Enclosure 1 to GL 93-08 allows control of changes to the response D' time limits in accordance with the provisions o^ 10 CFR 50.59 without the need to process a license amendment request.
The FSAR Table 15.1.3-2 specifies RTD response time to be 1 8.0
! seconds. This time is changed to 1 14.0 seconds per this i evaluation as shown in Attachment A.
The proposed change also involves a ,-hange to the Bases of St.
, Lucie Unit 1 '" %nical Specifications as described below. The h marked up pag. , , . the Bases to Technical Specifications is in j' Attachment B.
! The bases for section 2.0, Safety Limits and Limiting Safety i
System Settings, require a safety analysis allowance of ag, Rait for TM/LP trip to account for time delays. This pressure bias term for the TM/LP trip is calculated to be 32, i D, ~ Baig in the re-analyses of the Control Element Assembly l x Nithdrawal event to support the proposed RTD response time o .of 14 seconds. The numerical value of the pressure bias tems
- is deleted from the Bases to the Technical Specifications.
I j 3.0 LIczasrae maccInzuzurs l l The proposed activity is related to the change in RTD response time
- limit specified in the instrument response times Table 15.1.3-2 in
/ the FSAR. Changes to the FSAR table are permitted if controlled in accordance with 10'CFR 50.59 (Reference 5). The proposed activity requires a change to the Basis of Technical Specification for TM/LP trip, which defines a value of 30 psia as a pressure allowance for time delays. The Basis to TS is changed to accommodate variations in the pressure bias term corresponding to changes in the RTD response time. The e;tual value is, therefore, deleted from the Basis to TS. This change does not reduce the margin of safety.
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l The Reactor Protection System, in the evaluation of the reactor j trip setpoints, uses the auctioneered higher of the ex-core power j' and the AT-power signals. The accuracy of RTDs to measure the p temperature during transients is deterninM by their response i
- times. The RID response time, thus affects the ability of the AT-l
' power c;alculator3to; The coldaccurately measure the core alsopower during power imput.jp@
transients? leg 22Ds measurement enters'as:an x (inlet temperature, T.) to the TM/LP trip calculation as shown
- below from Figure 2.2-4 of the Technical Specification.
Paa = 2061
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8950 l: .During fast power excursions, where the measured Reactor Coolant
? System (RCS) temperature lags significantly behind the actual RCS
! tempersture, a more accurate power measurement is provided by the i ex-core neutron power detectors. However, during very slow power
! excursions where large amounts of Control Element Assembly (CFA)
I notion are required to produce the power excursion, the ex-core detectors may be significantly decalibrated due to temperature shadowinn - rod shadowing effects. For these cases, the AT-power 4 calculu.. .sy provide a more accurate power measurement.
The power measurement is used as one of the inputs to the TM/LP trip, LPD (Local Power Density) t:cip and VIP (Variable Eigh Power) trip. The St. Lucie Unit 1 safety analysis methodology always uses ex-core neutron fluz power in the simulation of the transients
(
Reference:
6).A Although signals from the cold leg and the hot leg RTDs determina the AT-power, the effect of increased R2D response time on ATw; r,< therefore, does not ispect these transient simulations. - Thus,Yonly the safety analyses of the power escursion transients which do not reach the Eigh Power or the Righ Pressure trip, and require the TM/LP trip, are affected by the proposed RTD response time change. The only such transients requiring the TM/LP trip are the slow CEA Withdrawal events. Events tripping on High Pressure or High Power are not considered as they are unaltered by the change in the RTD response time. The RTD delay time increase has no effect on the TM/LP trip pressure bias previously calculated for the UFSAR Event 15.2.12, Inadvertent Opening of a Pressurizar Pressure Relief Valve (References 7, 8).
SIANI CEE WIvanamt AMELYSIS WITE 16 SEC RTD DEIAT TIME The safety analyses impacted by the proposed change to the RTD response time lir.it are the slow CEA Withdrawal events as discussed above. Numerous slow control rod withdrawal calculations have been performed by Siem6ns Power Corporation (SPC) for the St. Lucie Unit 1 Cycle 11 to determine a bias term for the TM/LP trip to account
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! for an increase. in the RTD response time from 8 seconds to is seconds (Reference ~1) . These calculations were performed to
,' justify any potential future need for relaxing the limit on the RTD response time, as done for the St. Lucie Unit 2 (Reference 2) . The pressure bias term from chose calculations (42 psia) is larger than the present value in the Basis to Technical Specification for TM/LP y c., .. .
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- The maximum bias of 42 psia, obtained from the slow CEA Withdrawal'~'
i calculations, has already been accounted for in the existing safety
! analyses in determining the TM/LP margin. The current analyses, therefore, remain unchanged.
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{ . The.VHP and LPD trips are not impacted by the proposed RTD response 1 time as the safety analyses ~for St. Lucie-Unit-1 use the ex-core -
- neutron flux power, and not the AT-power, in the simulation of transients as stated before.
i BZAS TERM Increased . Rv0 response time leads to the degradation of TM/LP performac . to increased lag in the cold leg temperature signal 1-to the TM/LP trip. The result of the calculations was a higher
) pressure bias term to compensate for the slower trip response due l
to the increased RTD response time from 8 seconds to 16 seconds.
/
The maximum bias was calculated as 1
Pen. = 15.85 * (TC2JmK - TDELAY),
l
- where, '
i TCIJmX is the pawi== cold leg teeperature, and i
TDEIAY is the RTD toeperature assuming a delay of 16
! seconds.
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2 The maximum bias teza from numerous calculations performed for i
Cycle 11 was 42 psia. This value remains unaffected and valid for
) Cycle 12 (Reference 8) . The TM/LP trip bias term is thus increased l
by 12 psi compared to the existing value of 30 psia in the j Technical Specification basis.
- The present safety analyses using' 42 psia bias tern have shown that
) with the proposed 14 seconds RTD delay time the safety limits for i
the limiting event will not be violated.
I
! RfD RESPONSE TIan '"JP 14.0 SECCEDS 4
) The maximum pressure tias term calculations for 16 seconds RTD i delay time include en additional 1 seconds delay in the response i time giving a total delay of 11 seconds. Also, the analysis bounds i
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i the inclusion of a La second trip delay time (Raference 9) . The l TM/LP margin analysis of the CEA Withdrawal event also has
- additional conservative assumptions,- such as a 2*F penalty on the s
inlet temperature and minimum Technical Specification flow correar am ag to an uncertainty of ~44.
The analysis, therefore rts a total. delay.of about 13, seconds
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"" without vial =**=*4 ga" and-isafetyP11mits.~ - Allowing l - conservatively" a~ ' delay 'of -5' seconds corresponding to the l time values for 145R accuracy and aging / electronic l
drift / repeatability, as done for St. Lucie Unit 2, a RTD response time of H seconds fit - 5 = 141 is well justified from safety considerations. A 14 seconds limit is, therefore, proposed for the RTD response time for St. Lucie Unit 1.
) 5.0 FAZIMtB tet3 DES AMD EFFECTS AFALYSIS l The proposed activity does not change any system configuration or
- structures and, therefore, does not create any additional failure j modes. The changes proposed to the FSAR Table and the Basis to TS
- have b- shown not to violate any safety analysis limits as descru... .a Section 4.0.
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l g.p. There are no plant,, restrictions related to the proposed change. z l
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.ggethe RTDs during.;survai"*Wa=*iag.Qjp9y 9 .
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l The Basis to St. Lucie Unit 1 Technical Specification for TM/LP
{ trip specifies an allowance of 30 psia to compensate for time i delays. This allowance has been calculated to be 42 psia in l i support of the proposed increase in the RTD response time froe 8 i
- seconds to 14 seconds. Consistent with the relocation of i instrument response time limit tables from the TS to the FSAR (Reference 3), the value for pressure bias term is deleted from the
! Basis to TS for TM/LP trip. The margin of safety defined in the TS 1 Basis is, however, not reduced. Changes to the response time i limits in accordance with the provisions of 10 CFR 50.59 are
{ allowed per F.nclosure 1 to the Generic Letter 93-08.
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1 10 CFR Part 50.59 permits the holder of an operating license to make changes to the facility and procedures as described in the FSAR and to conduct tests or experiments not previously described j in thw FSAR without prior NRC approval, provided they do not
- involve an unreviseed safety question and do not require a change j ,g ' to thopTaahaiaalt specificat;.ons.
3 i In accordance with 10 CFR Part 50.59, the following evaluation serves to determine whether this modification constitutes an unreviewed safety question:
, 8.1 Does .the proposed change increase the probability of l occurrence of an accident previously evaluated in the FSAR7 i The proposed change affects only the slow CEA Withdrawal
! events analyzed in the FSAR. The initiation of these events j is independent of the RTD response time. The probability of
- occurrence of such events is, thus, unaffected by the j proposed activity.
I Th.. . e, the probability of occurrence of an accident t
prenously evaluated in the FSAR is not increased.
8.2 Does the proposed change increase the consequences. of an j accident,previously evaluated in the FSAR? -
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e@M proposed. change will allow longer RTD response , time,
! g.jsfuhichivill affect the pressure bias term used in deta=iaiaa 1 .
ENu_" nd iwirths.
Min theTitcurrent /LP margin.slowThe new higher pressure biastoteria is used I
gD3 .
CEA Withdrawal the increased ItTD delay time. Thus the consersaae== of thnam events coeph for.
events remain unchanged.
4 Therefore, the consequences of an accident previously evaluated in the FSAR are not increased.
1 8.3 Does the proposed change increase the probability of an j , occurrence of a malfunction of equipment important to safety j previously evaluated in the FSAR?
j 1 The proposed change allows an increase in the response time i limit (from 8 sebonds to 14 seconds) to be met during i surveillance testing of the RTDs. This change has no effect i on the malf inction of any equipment or system important to j safety as evaluated in the FSAR, nor does it create any new
{ fallure modes.
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l Therefore, the probability of occurrence of any equipment 1
malfunction important to safety previously evaluated in the j FSAR will not increase.
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! 8.4 Does the proposed change increase the consequences of a i
malfunction of equapment important to safety previously i
evaluated in.the FSAR?
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W4The proposed' change does not adversely affect the performance "J j
of any safety related equipment.
l Therefore, the consequences of a malfunction of equipment
- important to safety previously evaluated in the FSAR are not j increased.
i j 8.5 Does the proposed change create the possibility of an j accident of a different type than any previously evaluated j in the FSAR?
a l The proposed change is an increasts in the RTD response time i limit and a compensating change in the pressure bias term.
There are no changes to the plant configuration. No new systet system interactions are involved that adversely affect equipment or systems important to safety.
Therefore, the proposed ah= v does net create the possibility of , an _ accident of a <!ifierent' type than any
- ~ previous
"' 1, evaluated in the rosa.
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.;::l.nE possibility of ' a*wj?h.D; F. rpropond change create the "I
+ 9;g lmalfunctica er previously equipmentevaluated importantintothe safety of a different
_w type't2aan any FSAR? .
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The aham proposed allows longer RTD response times and does not adversely affect any safety related equipment.
Additionally, there are no changes to any system configuration or equipment important to safety.
Thus, the possibility of a malfunction of equipment important to safety of a different type than any previously evaluated in the FSAR is not increased.
8.7 Does the proposed change reduce the margin of safety as !
defined in the basis for any Technical Specification?
The Basis to Tei'hnical Specification for TM/LP trip specifies ,l an allowance of 30 psia to account for time delays. The i value for this pressure allowance changes to 42 psia ;
corresponding to the proposed RTD response time of 14.0 !
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! seconds. The increase in the pressure bias term from 30 psia
{ to 42 psia, used in the current safety analysis, compensat e j for the effects of proposed increast in the RTD response
- time. The margin of safety is, thus, not reduced. The NRC
! has approved the relocation of the response time tables from
! the TS to the FSaR (R6ference 3) .
! Therstore, the propuc4ed change does not reduce the margin of i . safety .as defined in the bases for the Technical l
Specifications.
j CouCLUSIcars
' The above discus.<, ion justifies that there is no unreviewed safety question associated with the proposed increase in the i RTD response timai limit.
4 9.0 ACTICES REQUIRED i The following documents are affected 'and should be changed to
! reflect the changes proposed. ,
3
} 1. 15hd (See Attachment A) j 2. Technical Specification Bases (See Attachment B)
The IEC Procedure 1-1400162A (RTD Time Response Test Data Collection) should be changed as necessary to reflect the revised l
RTD response time limit of 14.0 seconds.
1 l 10'.0 REFERENCES
- 1. St. Lucie Unit 1 Technical Specifications, Amendment 128,
- //12/94
Unit 2 - Issuance of Amendment RE: Resistance Temperature Detector Delay Time (TAC No. 69863), May 23, 1991 j
- 3. USNRC Letter J.A. Norris to J.B. Goldberg (FPL), St. Lucie Units 1 And 2 - Issuance of amanuements RE: Relocation of Tables of Instrument Response Time Limits (GL 93-08) (TAC Nos. N88974 And N88975), July 12, 1994
- 4. FPL Letter I-94-031 (10 CFR 50.90), D.A. Sager to USNRC, St.
Lucie Unit 1 and Unit 2 Docket Nos. 50-335 and 50-389 Proposed Lh~ense Amendments Relocatton of Tables of instrtnnent Resoonse Time Limits tGL 93-08) . February 22, 1994
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! JPN-PSL-SIFJ-94-021 Rev 0 Page 12 of 12
- 5. 08nRC Generic Letter 93-08, Relocation of Technical BPecification Tables of Instrument Response Time Limits Siemens Letter RIn:94:106, R.I. Wescott to E.R. Knuckles y 6.
1 (TEL), Verifica tion of Power Input Assumptions for
[ slaulations, August 26, 1994
- 1. Steanna Report sne-91-150, St. Lucie Unit 1 Cycle il Safety AnalyeLa Report,. September 1991 .
l S. Siemens Report ENF-93-020, St. Lucie palt 1 cycle 12 Safety Analysis Report, unsch 1993
- 9. Siemens Letter JLE:029:94, J.L. Rola to E.R. Knuckles (FPL),
Confirmation of . Totsi . Delay . time Assumed _ in Slow _CEA*
Withdrawal R4ent for S'.:. Lucie Unit 1, Janunty 27, 1994 7
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