ML17202L259

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Rev 1 to Core Operating Limits Rept,Dresden Station Unit 2, Cycle 12.
ML17202L259
Person / Time
Site: Dresden Constellation icon.png
Issue date: 05/31/1990
From:
COMMONWEALTH EDISON CO.
To:
Shared Package
ML17202L260 List:
References
NUDOCS 9006060221
Download: ML17202L259 (26)
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Text

-..! *,

Core Operating Limits Report Dresden Station Unit .2 Cycle 12

  • Revision 1 May 1990
  • Issuance of Changes Summary Affected Affected Section Paa es Summarv of Chances Date All All Oriainal Issue 12/89 5.0 5-1. 5-2 5-4 Channel Bow MCPR Adiusment 5/90 Dresden Unit 2 May 1990

Table of Contents Page References ....................................... .'. . . . . . . . . . . . iii List of Figures ..... *...... ~ .................................... iv List of Tables ........................................*........ v 1.0 Control Rod Withdrawal Block Instrumentation (3/4.2.C) ... 1-1 1.1 Technical Specification Referen~e ................... 1-1 1.2 Description .......................................... 1-1 2.0 Average Planar Linear Heat Generation Rate (3/4.5.I) ..... 2~1 2:1 Technical Specification Reference ................... 2-1 2.2 Description ....................... ;.; ............... 2-1

2. 3 MAPLHGR Multipliers .................. .- ........ ~ . . . . . 2-1 3.0 Local Steady State LHGR (3/4.5.J) ........................ 3-1 3.1 Technical Specification Reference ................... 3-1 3.2 Description ........................................... 3-1 4.0 Local Transient LHGR (3/4.5.K) ... ~*********~******: ...... 4-1 4.1 Technical Specification Reference ................... 4-1 4.2 Description ........... *.* ............................ 4-1 5.0 Minimum Critical Power Ratio Operating Limit (3/4.5.L) .. , 5-1 5.1 Technical Specification Reference.: ................. 5~1 5.2 Description .. :'. .... : ...............*................ 5-1 Dresden Unit 2 ii May 1990

References

1. Commonwealth Edison Company Docket No. 50-249, Dresden Nuclear Power Station, Unit 2, Facility Operating License DPR-19.
2. Letter from D. M. Crutchfield to All Power Reactor Licensees and Applicants, Generic Letter 88-16; Concerning the Removal of Cycle-Specific Parameter Limits from Technical Specifications.

Dresden Unit 2 ii i May 1990

Li st of Figures Figure Title/Description Page 2.2-1 MAPLHGR Limit versus Bundle Average Exposure - 2-2 ANF 8x8 Fuel

  • 2 .2:...:2 . MAPLHGR Limit versus Bundle Average Exposure - 2-3 ANF 9x9 Fuel
  • 2. 2-3
  • MAPLHGR Limit versus Average Planar Exposure - 2-4 GE BXS lTAs 3~2-1 Steady State Linear Heat Generaiion Rate 3-2 Limit (SLHGR) vs. Pl~nar Exposure 4.2-1 . Transient Linear Heat Generation Rate Limit 4-2 (TLHGR) vs. Planar Exposure for ANF 8x8 Fuel.

4.2-2 Transient Linear Heat Generation Rate Limit 4-3 (TLHGR) vs. Planar Exposure for ANF 9x9 Fuel

.5.2-1 MCPR Limit vs Measured Scram Time to 90% 5-2 Insertion - Rated Flow Conditions 5.2-2 MCPR Operating Limit for Manual Flow Control 5-3 5.2-3 MCPR Operating Limit for Automatic Flow* Control 5~4 Dresden Unit 2 iv May 1990 I **

  • List of Tables Table Title/Description Page
1. 2-1 Control Rod Withdrawal Block Instrumentation 1-2 Setpoints 2.3-1 MAPLHGR Multipliers 2-5 Dresden Unit 2
  • v May 1990

1.0 CONTROL ROD WITHDRAWAL BLOCK INSTRUMENTATION 1.1 Technical Specification Reference Technical Specification 3.2.C - Control Rod Block Actuation

1. 2 Oescri pt ion The Rod Block Monitor Upscale Instrumentation Setpoints are determined from the relationships shown in Table 1.2-1.

Dresden Unit 2 1-1 May 1990

.e

.. Table 1.2-1 Control Rod Withdrawal Block Instrumentation Setpoints Trip Function - Trip Level Setting Rod Block Monitor Upscale (Flow Bias)

Dual Loop Operation Less than or equal to (0.65 Wd plus 45)

(See Note)

Single Loop Operation Less than or equal to (0.65 Wd plus 41)

(See Note)

Note: Wd - percent of drive flow required to produce a rated core flow of 98 Mlb/hr.

Dresden Unit 2 1-2 May 1990

2.0 AVERAGE PLANAR LINEAR HEAT GENERATION RATE 2.1 Technical Specification Ref~rences Section 2.2: .Technical Specification 3.5.1 - Average .Planar LHGR Section 2.3: See Table 2.3-1 2.2 Descriotion The Maximum Average Planar Linear Heat Generation Rate (MAPLHGR) versus Bundle Average Exposure for ANF 8x8 fuel is determined from Figure 2.2-1.

The Maximum Average Planar Linear Heat Generation Rate (MAPLHGR) versus Bundle Average Exposure for ANF 9x9 fuel is determined from Figure 2.2-2.

  • The Maximum Average Planar Linear Heat Generation Rate (MAPLHGR) versus Average Planar Exposure for the GE BXS LTAs is determined from Figure 2.2-3.

2.3 MAPLHGR Multipliers The appropriate multiplicative factors to apply to the base MAPLHGR l.imits specified in Section 2.2 are shown in Table 2.3-1.

Dresden Unit 2 2-1 May 1990

Figure 2.2-1

. MAPLHGR Limit vs. Bundle Average Exposure ANF 8x8 Fuel J

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  • ---.::::.- 2:.*-*.. --*.
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  • - I g *** I 5 10 15 20 25 - 30.

Bundle Average Exposure (GWd/LmJ)

The above graph is based on the following MAPLHGR summary for ANF' 8x8 fuel design.

. Exoosure CGWd/MTUl

  • Limit. Kw/ft

' 0 13.00 10 13.00 15 13.00 18 12.85 20 12.60 25 11.95 30 ' 11. 20 35 10.45 Dresden Unit 2 2-2 May 1990

Figure 2.2-2 MAPLHGR Limit vs. Bundle Average Exposure ANF 9x9 Fuel I

I

5. 10 15 20 25 30 35 40 Bundle Average Exposure (GWd/MTU)

The above graph is based on the following MAPLHGR summary for ANF 9x9 fuel design.

Bundle Average *MAPLHGR Exposure (GWD/MTU) Limit. Kw/ft 0 . 11. 40 5 11. 75 10 11.40 15 10.55 20 9.70 25 8.85 30 8.00 35 7.15 40 6.30 Dresden Unit 2 2-3 May 1990

Figure 2.2-3 MAPLHGR Limit vs. Average Planar Exposure GE axe LTAs 13

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, I

. "' ~~

I I I I I ~

8

~

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0 5 10 15 20 25 30 35 40 45 .*

Average Planer Exposure (GWd/St) l'.t The above graph is based on the following MAPLHGR summary for the GE LTA fuel design.

Average Planar

  • MAPLHGR Exposure CGWD/STU) Limit. Kw/ft 0.2 11. 5 1.0 11. 6 5.0 11. 9 10.0 12.1 15 .o* 12.1 20.0 11. 9 25.0 11.3 30.0 10.7 35.0 10.2 41.6 8.8 Dresden Unit 2 2-4 May 1990

Table 2.3-1 MAPLHGR Multipliers Multiplicative Factors Specification Title of TS Scenario ANF 8x8 ANF 9x9

  • 3.5.D.2 Automatic Pressure One Relief* 0.89 0.76 Relief Subsystems Valve Out of Service.

3.5.I and Average Planar LHGR Single Loop 0.91 0.91 3.6.H.3.f Recirc Pump Flow Operation .

Limitations 3.5. I. and . Average Planar LHGR Single Loop 0.89 0.76 3.6.H.3.f Recirc Pump Flow Operation and Limit at i ans One Relief Valve Out of Service.

Dresden Unit 2 2-5 May 1990

3.0 LOCAL STEADY STATE LHGR 3.1 Technical Specification Reference Technical Specification 3.5.J - Local Steady State LHGR 3.2 Description The Local Steady State LHGR (SLHGR} limit versus Average Planar Exposure for all resident fuel is determined from Figure 3.2-1.

Dresden Unit 2 3-1 May 1990

Figure 3.2-1 Steady State Linear Heat Generation Rate (SLHGR) Limit vs. Planar Exposure 16 ..... _....... _

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5 10 15

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4-0 o o I I 45

'I I I I 50 I I I I 55 Planar Exposure (GWd/MlU)

GE 8X8 Fuel ANF 8x8 Fuel ANF 9x9 Fuel Exposure LHGR Exposure LHGR Exposure LHGR 0.0 16.0. 0.0 14.5 0.0 13.4 14.5 45.8 13.4 25.4 14.1 5.0 42.0 9.3 25.2 10.8 48.0 7.2 3-2 May 1990 Dresden Unit 2

4.0 LOCAL TRANSIENT LHGR 4.1 Technical Specification Reference Technical Specification 3.5.K - Local Transient LHGR 4.2 Description The Local Transient LHGR (TLHGR) limit versus Average Planar Exposure for ANF 8x8 fuel is determined from Figure 4.2-1.

The TLHGR limit versus Average Planar Exposure for ANF 9x9 fuel is determined from Figure 4.2-2.

For core modeling purposes, the TLHGR limit versus Average Planar Exposure for the GE 8X8 LTAs is 1.2 * (SLHGR Limit). The SLHGR limit is determined from Figure 3.2-1 Dresden Unit 2 4-1 May 1990

  • Figure 4.2-1 Transient Linear Heat Generation Rate (TLHGR) Limit vs. Planar Exposure for ANF 8x8 Fuel 15 20. 25- 30. 35. 40 45 so_

Planar flposlrre (GWd/LflU)

Exposure

  • LHGR 0.0 19.2 25.4 16.9
43. 2 10.8 48.0 10.0 Dresden Unit 2 . 4-2 May 1990

l) 0 Figure 4.2-2 Transient linear Heat Generation Rate (TlHGR) limit vs. Planar Exposure for ANF 9x9 Fuel Planar Exposure (GWd/MTIJ) 111 Exposure lHGR 0.0 19.2 25.4 16.9 43.2 10.8 48.0 10.0 Dresden Unit 2 4-3 May 1990

5.0 MINIMUM CRITICAL POWER RATIO OPERATING LIMIT 5.1 Technical Specification References Technical Specification 3.5.L - Minimum Critical Power Ratio (MCPR) 5.2 Description

a. The MCPR Operating Limit at rated flow versus measured scram time is shown in Figure 5.2-1. The MCPR Operating Limit* is 1.45 or greater whenever the measured 90% insertion time is 3.50 seconds or less.
b. During Manual Flow Control, the MCPR Operating Limit at reduced flow rates can be determined from:
i. Figure 5.2-2 using the appropriate flow rate, .or ii. The rated flow MCPR Operating Limit determined via Figure 5.2-1, whichever is greater.
c. During Automatic Flow Control, the MCPR Operating Limit at.

reduced flow rates can be determined from Figure 5.2-3 using the appropriate flow rate and rated flow MCPR Operating Limit, which is obtained from Figure 5.2-1. Linear interpolation between the c~rves on Figure 5.2-3 is permi~sible.

Dresden Unit 2 5-1 May 1990

Figure 5.2-1 MCPR Limit vs. Measured Scram Time to 90% Insertion Rated Flow Conditions M

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R IMCPR LCO = 1.451 0

p 1.45 ~---....-----------------....;

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1. 35 '--------'-'_ __,,_;.___..___,_ _,_,_ __.___ _..._,- - . . : . ! . ' ' - - - - - '

2.70 .2.80 2.90 3.00 3.10 3.20 3.30 3.40 . 3.50 Measured Scram Time to 90% Insertion (seconds)

The above graph demonstrates the following dependence of the MCPR Operating Lim1t versus measured scram time to 90% insertion for all resident fuel types:

MCPR LCO = 1.45 Note that the MCPR Operating Limit is not a function of scram time assuming the Technical Specification scram time limit of 3.50 seconds to 90% insertion (3.3.C) is met.

Dresden Unit 2 5-2 May 1990

c.

  • Figure 5.2-2 MCPR Operating Limit for Manual Flow Control 1.70 1.60 "-

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~ 1.40

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40 60 70 l'.9 80 90 100 1U11L CO![ nD'f (I PJJm. 98 ~)

The above curve is based -On the following MCPR operating limit summary for Manual Flow Control and all fuel types:

Total Core Flow

(% Rated) MCPR Operating Limit*

100 1.10 90 1.16 80 1.23 70 1.30 60 1.39 50 1. 51 40 1.65 Dresden Unit 2 5-3 May 1990

Figure 5.2-3 MCPR Operating Limit for Automatic Flow Control 2.00 Notes:

1.90 1----~~--1-----+---1) tt L!C'R Operoting Limit= 1,4,;>---+---~

at Rated Conc6tians. l

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~ 1.80 t-----i"oc,.......,,.--.~i-----+---2) tt Ma' R Operating Limit= 1.39_ _+ - - - - - '

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at Rated CcncfitDis. l 3} tt lrlO'R Operating Limit =1.35

~ 1.70 t-----+--~~-~~1--~

0 atRatedCcncfiticns.--+-----+---~

ct:

~ 1.60

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~1.50 t..)

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: See Note 1

§ 1.40 See Nate 2

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See Note 3

~

~ 1.30 1.20 1.1~0 40 50 60 70 80 90 100 IDTAL CORE FLOW(% PJ.TED, 98 MLB/HR)

The above curve is based on the following MCPR operating limit summary for Automatic Flow Control and all fuel types:.

Total Core Flow MCPR Operating Limit*

{% Rated) 1.35 1.39 1.45

  • 100 1.35 1.39 1.45 90 1.40 1.44 1.50 80 1.44 1.48 1.54 70 1.50 1.54 1.60 60 1.56 1.61 1.67 50 1.66 1.70 1.76 40 1.81 1.86 1.92
  • Column Headers are MCPR operating limits at rated flow.

Dresden Unit 2 5-4 May 1990

  • a ATIACBMENT 2 e DRESDEN UNIT 2 CYCLE 12 MCPR ADJUSTMENT SAFETY EVALUATION

Background

Conunonwealth Edison (CECo) recently completed its review of NRC Bulletin 90-02 (Reference 1). The bulletin requested that all BWR licensees address the effect of channel bow on thermal margin in Boiling Water Reactors (BWRs),

particularly the bow of channels that are being reused for a second bundle lifetime. Such reuse may result in high channel exposures, leading to excessive channel bow and an increase in the assembly wide-wide water gap.

This additional thermalization increases the peaking of .the fuel pins near the control blade, thereby potentially decreasing thermal margin.

The CECo. evaluation determined that the full flow operating MCPR limit for Dresden Unit 2 may not be sufficient to bound the effects of chanqel bow in the current operating cycle (Cyele 12). An appropriate adjustment to the MCPR operating limit was administratively implemented at that time based on an analysis by the fuel vendor (Reference 2). Edison committed to incorporate this MCPR limit adjustment in the Dresden 2 Core Operating Limits Report (COLR) by May 31, 1990 (see Reference 1). The following discussion provides the. bases for the MCPR limit adjustment _and an evaluation of its safety implicatibns.

  • Dresden 2 Cycle 12 has a significant number of reused channels as a result of CECo.' s channel management strategy in the early to mid 1980s.

During the Cy.cle 9 and Cycle 10 refueling outages, fresh reload fuel assemblies received channels with one or two prior cycles of irradiation*. A total of 303 reused channels remain in Dresden 2 Cycle 12. The remaining. 421 assemblies do not have reused channels.

Channel exposures were compiled *and projected to the end of Cycle

12. Of the 303 reused channels, 194 will exceed 40 GWd/MTU exposure and 28 will surpass 50 GWd/MTU prior to shutdown for refueling which is currently scheduled for September 1990. Essentially all of the reused channels, 297 out of 303, were manufactured by Carpenter Technology. These channels exhibit less irradiation induced growth than GE channels of the same vintage.

MCPR Limit Adjustment For Dresden 2 Cycle }2 In light of the high channel exposures, Advanced Nuclear Fuels (ANF) has completed a cycle specific analysis for Dresden Unit 2 Cycle 12 to assess the impact of channel bow on thermal margin for the current operating cycle (Reference 2). Using the end of Cycle 12 channel exposure projections, the CASM0-3G lattice physics code, and the ANFB critical power correlation, ANF has determined the impact of CPR using a procedure similar to that outlined in Reference 3. ANf' s generic channel bow methodology, currently *under NRC review, statistically accounts for the effects of channel bow by an adjustment to the MCPR Safety Limit; however, an equivalent adjustment to the MCPR operating limit provides the same level of thermal margin protection.

/103.6T3

ANF has evaluated the CPR degradation based on the actual Dresden 2 Cycle 12 loading pattern and projected end of cycle exposure conditions. The calculated CPR adjustment for channel bow is partially offset by the inherent conservatism of the XN-3 CPR correlation (the current thermal margin licensing basis for Dresden) relative to the ANFB correlation. ANF has discussed this inherent XN-3 conservatism with the NRC and transmitted the supporting documentation via Reference 4. The results of the Dresden Unit 2 channel bow analysis are summarized below:

(MCPR 01) + (CPR Bow Penalty) - (XN-3 Conservatism) = (New MCPR 01) 1.39 0.15 0.09 1.45 Revision 1 to the Dresden Unit 2 Cycle 12 COLR (Attachment 1) reflects this change in the full flow MCPR operating limit as well as the corresponding change to the reduced flow MCPR limits for Automatic Flow Control operation (COLR Figure 5;2-3}.

Safety Evaluation CECo has performed a safety evaluation of this adjustment to the MCPR limit and has concluded that no unreviewed safety questions exist for reasons described below.

(a) The primary concern with excessive channel bow is loss of thermal margin. Because of the large number of highly exposed channels in Dresden 2, an appropriate MCPR Operating Limit adjustment has been implemented and included in the attached Core Operating Lim~ts Report to ensure protection of the safety limit for fuel integrity. Future reload analyses will explicitly account for channel bow effect's. It is anticipated that the effect will decrease because. Commonwealth Edison's current channel management strategy prohibits the reuse of channels on new fuel assemblies. Additionally, stringent as-built channel bow criteria have been established to maintain bow levels to a minimum. For these reasons, the probability of occurrence or the consequences of an accident or malfunction of equipment important to

  • afety previously evaluated in the FSAR is not increased.

(b) By accounting for the effects of the channel bow, the safety limit for fuel cladding integrity remains protected and no new accident scenarios are created. CECo has also determined that channel bow will not significantly affect the performance of any safety related system. Since the characteristic deformation at*high channel exposures is oriented such that the channel bows away from the control rod, CRD system capabilities (scram times, normal insert and withdraw functions, etc.) are not adversely impacted. While there may be some effect on in-core neutron monitor indications, Traversing In-core Probe (TIP) asymmetries measured at BOC and periodically during Cycle 12 have been verified to be within the assumptions of licensing analyses. For these reasons, the possibility for an accident or malfunction of a different type than previously evaluated in the FSAR is not created.

/1036T4

(c)

CECo has ensured the margin to the MPCR Safety Limit .is maintained at a level sufficient to withstand any limiting operational occurrences; therefore, margin of safety as defined in the bases for any Technical Specification is not reduced.

In sununary, CECo has evaluated the effects of channel bow and has determined that no unreviewed safety question exists for D2Cl2 operation with a full flow MCPR operating limit of 1.45 or greater (as described in Reference 1). However, until NRC review of the vendor's generic channel bow methodology is complete, Staff concurrence with this interim limit adjustment for D2Cl2 (and a similar adjustment for D2Cl3, if needed) should _be obtained.

/1036T5

'

  • References *
1. Letter, M.H. Richter to USNRC, "Dresden Station Units 2 and 3, Quad Cities*

Station Units 1 and 2, LaSalle County Station Units 1 and 2 Response to NRC Bulletin 90-02, NRC Docket Nos. 50-237/249, 50-254/265 and 50-373/374", dated April 26, 1990.

  • 2. ANF proprietary docwnent "CECo Channel Bow Analysis Results" (Attachment B to Reference 1), April, 1990.
3. ANF-524(P), Revision 2, Supplement 1, "Advanced Nuclear Fuels Corporation Critical Power Methodology for Boiling Water Reactors - Methodology for Analysis of Assembly Channel Bowing Effects", November 1989.

4*. Letter, R.A. Copeland (ANF) to R.C. Jones (USNRC), "Loss of Thermal Margin Caused by Channel Box Bow", dated April 9, 1990.

/1036T6

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