ML20011F749
| ML20011F749 | |
| Person / Time | |
|---|---|
| Site: | Salem  |
| Issue date: | 11/30/1989 |
| From: | Green L, Mutyala M, Vertes C WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP. |
| To: | |
| Shared Package | |
| ML18094B318 | List: |
| References | |
| WCAP-12452, NUDOCS 9003070381 | |
| Download: ML20011F749 (38) | |
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- I HESTINGHOUSE ELECTRIC CORPORATION lI l
Commercial Nuclear Fuel Division P. O. Box 3912
- Pittsburgh, Pennsylvania 15230 t
'I 11251:6-891122 . ~. . _-. - - - - . La ' AB'S TRACT JThis report proposes a relaxation of the Limiting Condition for Operation and Surveillance Requirements values of Moderator Temperature Coefficient for the end of tycle, rated thermal power condition. Relaxation is sought in order to improve plant availability and minimize disruptions to normal plant operation, while continuing to satisfy plant safety criteria. A methodology for ~_~ establishing Technical Specification en.d of cycle Moderator Temperature ; Coefficient values that are consistent with the plant safety analyses is ' described herein. Specific application of the methodology to Salem Units 1 and 2 provides Technical Specification Moderator Temperature Coefficient values which are proposed to replace the existing values. l m N l 11251:6-891122 1 i -, ?-: y -TABLE OF CONTENTS + k Section 11tle Egge
1.0 INTRODUCTION
1-1 r 1.1 Background 1-1 1.2 Basis of Current E0L MTC 1-l' LCO and SR Values 2.0 METHODOLOGY FOR MODIFYING MOST NEGATIVE HTC TECH SPEC VALUES 2-1 2.1 Conversion of Safety Analysis 2-l' MDC to Tech Spec MTC 2.2 Conservatism of the ARI to ARO 2-2 MTC Conversion 4 2.3 Alternative MTC Conversion 2-2
, Approach 2.4 Determining SR MTC from 4 1 LCO MTC l[
3.0 MOST NEGATIVE FEASIBLE MTC APPROACH APPLIED TO SALEM UNIls 1 and 2 3-1 3.1 Salem Units Accident Analysis 3-1 1 MDC Assumption 3.2 Determination of Most Negative 3-l' 1 Feasible MTC Sensitivities ; a 3.3 Maximum Allowed Deviations from 3-5 Nominal Operating Conditions i a 11
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TABLE OF CONTENTS (contd.) I Section^ Title Eagg ' 3.0 3.4 Overall " Delta MTC" Factor for =3-9 8 Salem Units 1 and 2 Reloads , I 3.5 Proposed Salem Units 1 and 2' Tech Spec E0L MTC LCO Value 3-11 i t 4.0 SAFETY ANALYSIS IMPACT OF MOST NEGATIVE 4 ' FEASIBLE MTC APPROACH 5.0 DETERMINATION OF MOST NEGATIVE FEASIBLE 5-1 MTC SURVEILLANCE VALUE I
6.0 CONCLUSION
S 6-1 I REFERENCES R-1 APPENDIX A DETERMINATION OF MOST NEGATIVE FEASIBLE MTC SENSITIVITIES A-1 A.1 MTC-Sensitivity to Moderator A-2' Temperature and Pressure Variation A.2 MTC Sensitivity to RCCA Insertion A-4 A.3 Sensitivity to Axial Flux A-4 : (Power) Shape A.4 Sensitivity to Transient Fission A-6 'l Product (Xenon) Concentration l l ll l ll? l 111 1' I 11251:6-891122
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LIST OF TABLES lahlt lltle Eage 4.1 FSAR Chapter 15 Events That Assume 4-2 , a Constant 0.43 Ak/gm/cc Value of MDC LIST OF ILLUSTRATIONS i Elgute- Title Eggg_ I
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A.1 Change in MTC with Increase in A-7 T-Average above Nominal T-Average A.2 Delta MTC versus Axial Flux Difference A-8 at EOL, HFP, ARO I. , .I I
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1.0, INTRODUCTION ~
1.1 Background
For FSAR accident analyses, the transient response of the plant is dependent on reactivity feedback effects, in particular, the moderator temperature coefficient (HTC) and the Doppler power coefficient. Because of the j sensitivity of accident analyses results to the MTC value assumed, it is important that the actual core MTC remain within the bounds of the limiting values assumed in the FSAR accident analyses. While core neutronic analyses ; will have predicted that the MTC is within these bounds, the Technical Specifications require that the core MTC also be confirmed by measurement, as
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verification of the accuracy of the neutronic predictions. These MTC j
] measurements are performed:
- l. At beginning of cycle, prior to initial operation above 57. rated thermal power, and
- 2. Within 7 EFPD after reaching an equilibrium boron concentration of 300 ppm.
J 1.2 Basis of Current EOL HTC LCO and SR Values In order to ensure a bounding accident analysis, the HTC is assumed to be at its most limiting value for the analysis conditions appropriate to each accident. ; Currently, the most negative MTC limiting value is based on E0L conditions (specifically with regards to fuel burnup and boron concentration), full power, with rods fully inserted.
; Most accident analyses use a constant moderator density coefficient (MDC) designed to bound the MDC at this worst set of initial conditions (as well as at the most limiting set of transient conditions). This value for MDC forms
] the licensing basis for the FSAR accident analysis.
J 11251:6-891122 1-1
w .. Converting the MDC used in the accident analyses to a MTC is a simple calculation which accounts for the rate of change of moderator density with temperature at the conditions of interest. In this report, the convention followed is to discuss the moderator feedback in terms of.MTC, rather than MDC. Nevertheless, it is important to note that the accident analyses actually assume a constant MDC value, rather than making any explicit assumption on MTC. Technical Specifications place both Limiting Condition for Operation (LCO) and , Surveillance Requirements (SR) values on MTC, based on the accident analysis assumptions on MDC described above. The most positive MTC LCO limit applies ! to Modes 1 and.2, and requires that the MTC be less positive than the -l specified limit value. The most negative MTC LCO limit applies to Modes 1, 2, and.3, and requires that the HTC be less negative than the specified limit ! value for the all rods withdrawn, end of. cycle life, rated thermal power condition.
-The Technical Specification SR calls for measurement of the MTC at BOL of each l cycle prior to initial operation above 57. rated thermal power, in order to l
.: demonstrate compliance with the most positive MTC LCO. Similarly, to demonstrate compliance with the most negative MTC LCO, the Technical I Specification SR calls for measurement of the MTC prior to EOL (near 300 ppm equilibrium boron concentration). However, unlike the BOL situation, this 300. ppm SR HTC value differs from the E0L LCO limit value. Because the HFP MTC value will gradually become more negative with further core depletion and boron concentration reduction, a 300 ppm SR value of MTC should necessarily be less negative than the EOL LCO limit. The 300 ppm SR value is sufficiently less negative than the EOL LCO limit value to provide assurance that the LCO limit will be met when the 300 ppm surveillance criterion is met. S
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J 2,0 METHODOLOGY FOR MODIFYING MOST NEGATIVF MTC TECH SPEC VALUES j 2.1 Conversion of Safety Analysis MDC to Tech Spec MTC As stated previously, the FSAR accident analyses have assumed a bounding value lI of the moderator density coefficient (MDC) which ensures a conservative result for the transient analyzed. The process by which this accident analysis most positive MDC is transformed into the most negative MTC LCO value is stated in STS BASES section 3/4.1.1.3: ,I "The most negative MTC value, equivalent to the most positive moderator ' I density coefficient (MDC), was obtained by incrementally correcting the MDC used in the FSAR accident analyses to nominal operating conditions. g These corrections involved subtracting the incremental change in the MDC s associated with a condition of all rods inserted (most positive MDC) to an all rods withdrawn condition, and a conversion for the rate of change of moderator density with temperature at RATED THERMAL POWER conditions. This value of the MDC was then transformed into the limiting MTC value." I: In the process of converting the accident analysis MDC into the Tech Spec HTC, the conversion for the rate of change of moderator density with temperature at rated thermal power conditions involves conventional thermodynamic properties and imposes no undue conservatism on the resulting MTC value. The additional conversion made is to correct the above MDC (MTC) value for the change associated with going from a condition of ARI to one of ARO. That is, the
.f accident ana' lysis MDC (MTC) assumes a coefficient determined for a condition of EOL HFP 0 ppm with all control and shutdown banks fully inserted. This accident analysis MDC (MTC) is corrected back to the ARO condition, in order to produce a Tech Spec limit which permits direct comparison against measured values. The effect of the presence of all control and shutdown banks is to make the MTC markedly more negative than a MTC at the ARO condition, hence this conversion has a substantial impact.
I I I 11251:6-891122 2-1
2.2 Conservatism of the ARI to ARO HTC Conversion The use of a substantially negative MTC (positive MDC) value for the transient I. accident analyses is prudent, in that it produces a more severe result for the g transient, which makes the analysis inherently conservative. The drawback to 3 the ARI assumption is that when.the conversion to the ARO condition is made, the resulting Tech Spec MTC value is dramatically less negative than the value corresponding to the transient safety calculations, and is even less negative than expected best estimate values of E0L MTC for high discharge burnup reload cores. In the worst case, maintaining the EOL MTC Tech Spec Ilmit at its present value could result in requiring that the plant be placed in hot I shutdown when, in fact, there exists substantial margin to the moderator coefficient. assumed in the accident analyses. Such a situation is unnecessarily restrictive, and results primarily from the ARI to ARO I adjustment made between the accident analysis MDC value and the Tech Spec HTC value. I In addition to being unnecessarily restrictive, the HFP ARI assumption is inconsistent with Tech Spec requirements for allowable operation, wherein shutdown banks are not permitted to be inserted during power operation and
-control banks must be maintained above their insertion limits.
2.3 Alternative MTC Conversion Approach If the ARI to ARO basis for converting from the accident analysis MDC value to a Tech Spec LCO MTC value is overly restrictive, what would constitute a more meaningful, yet inherently conservative basis? The concept herein proposed as an alternative to the ARI to ARO conversion is termed the "Most Negative Feasible MTC" approach. This approach maintains the existing accident analysis assumption of a bounding value of moderator coefficient, but offers an alternative method for converting to the Tech Spec LCO MTC value. I; I I 11251:6-891122 2-2
The'Most Negative Feasible MTC approach seeks to determine the conditions for "which a core will exhibit the most negative MTC value that is consistent with
' operation allowed by the Tech Specs. As an example, the Most Negative
= Feasible MTC approach would not require a conversion assumption that all rods be fully inserted at HFP conditions, but would require a conversion assumption " that all control banks'are inserted the maximum amount that Tech Specs permit, J so as to make the. calculated E0L HFP MTC more negative than it would be for an - unrodded core.
] The Most Negative Feasible MTC approach determines E0L MTC sensitivity to those design and operational parameters that directly impact MTC, and attempts 7 to make this determination in a such a manner that the resulting sensitivity for one parameter is independent of the assumed values of the other
_ parameters. As a result, parameters which are mutually exclusive but i permissible according to the Tech Specs (such as an assumption of full power ! operation and an assumption of no xenon concentration in the core), and which serve to make MTC more negative, will have their incremental impacts on MTC combined to arrive at a conservative and bounding condition for the most negative feasible MTC. The parameters which are variable under normal l operation, and which affect.MTC are: o - soluble boron concentration in the coolant 2
- moderator temperature and pressure RCCA insertion j
- axial flux (power) shape ;
- transient fission product (xenon) concentration I
The Most Negative Feasible MTC approach examines each parameter separately, and assesses the impact of variation in that parameter on EOL MTC. The assessment is performed for multiple core designs that feature combinations of fuel design, discharge burnup, cycle length, and operating temperature expected to envelope future core designs of the plant of interest. i
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14 - LHhen the assessment is complete, the MTC sensitivity associated with each of the. above parameters has been identified. One then determines the maximum deviation I from " nominal" conditions (ARO, HFP, equilibrium xenon, Tavg on the reference temperature program) that the Tech Specs permit, and multiplies that deviation by the appropriate MTC sensitivity to arrive at a " delta MTC" factor associated with I
'the parameter.
For example, suppose it is determined that MTC becomes I pcm/*F more negative for - each 1*F increase in core average operating temperature above nominal (the MTC I
" sensitivity" is -1 pcm/*F/*F). If the Tech Specs permit a maximum increase in j Tavg of 4*F above_ nominal core Tavg, then the moderator temperature " delta MTC" 1 factor is:
(-1 pcm/*F/*F) x 4'F - -4 pcm/*F. I Bounding " delta MTC" factors are determined in this-way for each of the above parameters, and these factors are then added to arrive at an overall bounding
" delta MTC" factor. This overall " delta MTC" factor states how much more negative the MTC can become, relative to the nominal E0L HFP ARO MTC value, for normal operation scenarios permitted by the current Tech Specs. The conditions of moderator temperature, rod insertion, xenon,'etc., which defined the Most Negative Feasible MTC condition become the conversion proposed as a replacement for the ARI to ARO conversion of the current MTC Tech Spec. The conversion for the Most I- Negative Feasible MTC :ondition is applied in the same way that the current
. ARI-to-ARO conversion is applied, in order to arrive at an EOL ARO HFP MTC Tech Spec'11mit that remains based on the accident analysis MDC assumption.
2.4 Determining SR HTC from LCO HTC I Under the Most Negative Feasible MTC approach, the 300 ppm surveillance value is determined in the manner currently stated in the BASES for STS plant MTC Tech Specs:
"The MTC surveillance value represents a conservative value (with corrections for burnup and soluble boron) at a core condition of 300 ppm equilibrium boron concentration and is obtained by making these corrections to the limiting MTC LCO value."
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-That is,lthe 300 ppm surveillance lvalue is derived by making a. conservative-
-adjustment-to.the EOL ARO HFP MTC limit value that accounts for the; change to MTC with-soluble boron and burnup. Plant-specific examination of the I^, difference betweeni300 ppm HFP MTC and EOL (0 ppm) HFP MTC suggests that a smaller correction is justified th'an the 9 pcm/*F which has. historically-been; I applied to Mestinghouse-designed STS plants.
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.3.0 MOST NEGATIVE FEASIBLE MTC APPROACH APPLIED TO SALEM UNITS 1 AND 2 g 3.'l Salem Units Accident Analysis MDC Assumption.
.-= = The FSAR accident analyses upon which the Tech Spec EOL HFP LCO MTC limit is based have assumed bounding values of moderator density coefficient in order-
'to ensure a conservative simulation o'f plant transient response for the Salem
- Units. For those transients for which analysis results are made more severe
[ by. assuming maximum moderator feedback, a moderator density coefficient (MDC)
.of 0.43 Ak/gm/cc has been assumed to exist throughout the transient, g When discussing the Tech Spec E0L LCO limit on moderator feedback, it is simpler to talk in terms of moderator temperature coefficient (MTC) than MDC.
g For this reason, the Salem Units accident analysis MDC assumption of 3 0.43 Ak/gm/cc is converted to its equivalent MTC. This conversion depends on the density change-to-temperature change relationship which prevails for the-conditions of interest. For this discussion, the conditions of interest are the core temperature and pressure (hence, density) experienced under
] normal operation at which the MDC assumes its most extreme (positive) value.
These temperature and pressure conditions are the Salem Units rated thermal power (RTP), full flow vessel average nominal operating conditions of 577.9'F and 2250 psia, respectively. At these nominal RTP oper'iting conditions, the accident analysis MDC value of 0.43 Ak/gm/cc is equivalent to a HFP MTC of -52.6 pcm/*F. For simplicity, this value of MTC will often be referred to as the " accident analysis MTC", in a the discussion which follows. However, it should be remembered that the applicable accident analyses actually assume a constant MDC value of 0.43 Ak/gm/cc and make no explicit assumption about HTC. 3.2 Determination of Most Negative Feasible MTC Sensitivities As stated previously, there are a limited number of core operational parameters that directly affect MTC c.nd are variable under normal core operation. The list of parameters is as follows. il 11251:6-891122 3-1
- soluble boron concentration in the coolant
- moderator temperature and pressure
- RCCA insertion
- axial flux (power) shape
- transient fission product (xenon) concentration ,
The radial flux (power) shape can also vary under normal core operation and , will affect MTC. However, the operational activities that directly affect radial power shape de so through withdrawal or inseition of control rods ant' i through xenon r,oncentrattori; therefore, the impact of radial flux distributton variatfon on MTC w1H 71 an impiteit part of the MIC teasitivity to these other parameters. I S01uble boron concentration is certain1.1 variable under norme.1 core operation. However, it is elimtnsted as a source of sentitt6 ty for this analysis. This is because the EOL HfP ARO MTC Tech Spec H mit vr.lue is assumed to be essentially a O ppm limit by virtue of the definition of ECL. The most negative MTC value will always occur at a boron concentration of 0 ppm, and therefore, a O ppm boron concentration is assumed as the basis of the E0L MTC Tech Spec limit under the Most Negative Feasible MTC approach. For-the remaining parameters, sensitivity analyses were performed by perturbing the parameter of interest in such a way as to induce a change from I its nominal E0L value, and then performing a MTC determination with the parameter held in the perturbed state. A further perturbation was induced and the MTC calculation repeated.- This sequence was repeated untti sufficient MTC data values were generated to reliably determine the trend of MTC change with variation in the value of the independent parameter. In order to establish trends in HTC that a;; appropriate and bounding for the Salem reload cores, these sensitivities were determined for five different reload cores. These cores exhibit design features that are expected to be I incorporated in future Salem reload cores (such as increased discharge burnup, higher enrichment, longer cycles, and advanced fuel product features). I 11251:6-891122 3-2
o . A brief description of the five reload core designs follows:
- j. i RELOAD A: This is a reload core for a Westinghouse designed 4 loop plant ;
j similar to the Salem Units. It utilizes the Westinghouse 17x17 standard rod diameter fuel design, feeds 84 assemblies in a low leakage loading pattern (L3P) and assumes a region average I discharge burnup of 36000 MHD/MTV. This reload also has 448 r pyrex glass bas and a nominal cycle length of 15800 MHD/HTU. The cor. trol rod absorber material is hafnium. The nominal core average temperature assumed in this t'.talysis is 590.5'F. p :
. RELOAD B: This core extends the above design to higher hurnup and new l
product features. It is'an L3F destgr feeding 76 assemblies with axial blankets, approximately 4500 part-length IFBA, high 3 enrichments, and a region average discnarge burnup of 45000 { Mh0/HTU. The cycle length is 16500 MHD/MTU and all other core ; operating parameters are assumed to be the same as Reload A. l l RELOAD C: This reload is a conceptual equilibrium 24 month (21830 MHD/MTU) [ cycle design with advanced fuel product features including the features in RELOAD B plus Zr grids and Intermediate Flow Mixer I (IFM) grids. A thimble plug removal analysis is also assumed which increases the core bypass flow and raises the core average II moderator temperature to 591.3'F. t RELOAD D: This reload core is an annual cycle L3P design using the Westinghouse 14 foot length 17x17_ standard fuel rod diameter [ design. The discharge burnup for this design is necessarily low since this is the first reload core for this particular plant. I This design has 416 pyrex glass bas and uses hafnium as the control rod absorber material. The nominal core average moderator temperature of 596.5'F at full power. I f 11251:6-891122 3-3 L
l- . RELOAD E: This reload is the actual core design for Salem Unit 2. Cycle 4. An L3P design is used for a cycle length of 17000 MHD/MTU and a region average discharge burnup of 38000 MHD/MTV. This design also feeds 84 assemblies and uses 1728 pyrex glass bas. The control rod absorber material is silver-indium-cadmium. The core I average moderator temperature is 575.3*F. These features are i typical of recent Salem designs. l Reloads A, B, 0, r,.nd E were used in the calculition of the sensitivities to l the four parameters describo previous)y. To pro 9tde Edditional information , regarding the effect of extrenely long cycles and high discharge burnups oh ! the MTC sentitivity to moderator temperature and pressure and xenon ! concentration, Reload C was also usort in the determination of those sensitivitter. { The core neutronic models of these five reload cores were derived using standard Hestinghouse procedures and computer methods. The ARK code, which has evolved from the LEOPARD (U and CINDER (2) codes, was used to perform , the fast and thermal spectrum calculations and is the basis for all cross sections, depletion rates, and reactivity feedback models. ANC(3) and PALADON(4) , nodal analysis theory codes used in two and three dimensions, were used for core neutronic calculations to determine MTC sensitivity for the five reload cores. APOLLO, an advanced version of PANDA (5) , was used as an axial neutronic model of the reload cores to determine MTC sensitivity to varying axial flux shape. The neutronic calculations and evaluations performed for the five reload core designs established MTC sensitivities for each of the parameters listed above. The description and results of this analysis are provided in Appendix A. I 11251:6-891122 3-4
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3.3 Maximum Allowed Deviations from Nominal Operating Conditions The concept of maximum allowed deviation from nominal operating conditions is employed to determine the extent to which reactor parameters can vary under normal operation so as to cause MTC to become more negative. This combination of parameter statepoints then defines the worst allowable initial condition for a transient that employs a most negative MTC (most positive HDC) assumption. It is also necessary to demonstrate that the parameter changes tb&t occer throughout the transient do not result in a MTC value which is unbounded by the moderktor coefficient assumption used in the accident analysis. The adequacy of the constant MDC accide1t analysis assumption to bound HTC values that occur throughout the transient is examined in Section 4. The bases for the ma<imum allowed deviation from nomina) operating conditions I are Technical Specifications that limit the extent of modurator temperature increase, PCCA insertion, and axial power skewing. The deviations permitted i by present Salem Tech Specs and possible future perturbations to those Tech Specs values are discussed in the following sections: I Moderator Temoerature and Pressure Deviationi I Tech Spec 3.2.5 establishes the LCO values of the DNB parameters reactor coolant system Tavg and pressurizer pressure. For both Salem Units, Tech Spec 3.2.5 states a minimum allowable indicated pressurizer pressure of 2220 psia, and the maximum allowable indicated RCS vessel average temperature of 582.0*F. There is an additional uncertainty of 15 psia applied to the pressure. Therefore, the maximum allowable RCS temperature and the minimum allowable pressure assumed in the safety analysis are 582.0'F and 2205 psia, respectively. Because the current nominal design RCS vessel average temperature for the Salem Units is 577.9'F, the 582.0'F safety analysis limit represents a 4.l'F maximum allowable Tavg increase over nominal conditions. The current nominal design pressure for the Salem Units is 2250 psta; I therefore, the 2205 psia safety analysis limit represents a 45 psi maximum reduction from nominal system pressure. 11251:6-891128 3-5 i
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Because Tech Spec 3.2.5 limits deviations from nominal condition RCS l temperature and pressure to 4.l'F and 45 psi, respectively, it also indirectly places a limit on the maximum allowable deviation of RCS moderator density j from nominal. These maximum temperature and pressure deviations are applied j to the MTC sensitivity to temperature and pressure, which is described in J Appendix A, to obtain a " delta MTC" factor associated with RCS moderator temperature and pressure deviations from nominal. The resulting " delta MTC" ; is [ f"'C pcm/*F. RCQLinsertl0RAdjtt10D , The no.?. int.1 cordition assurption for RCCA placement is complete withdrawat j I (ARO). This assumption is undersc'>ren by the requirement in Tech Spec 3.1.1.4 for Unit I and 3.'.1.lfor Unit 2 that tbo LCO value of EOL MTC is for the "all rods withcirawn" condition. Becaus9 snma RCCA insertion is allowed during full power operation, anJ becauw RCCA insertion w'.11 gtnerally cause MTC to i be mcre negative than it wocid be otherwise, the RCCA inserticn deviation is simply that maximum allowable RCCA insertion permitted by the Tech Specs. Tech Specs 3.1.3.4 and 3.1.3.5 place limits on allowable RCCA insertion. Tech Spec 3.1.3.4 precludes Shutdown RCCA insertion in Modes 1 and 2, and Tech Spec I 3.1.3.5 limits Control Bank insertion via the Rod Insertion Limits (RILs). Control rods can be inserted as a function of power level according to the i RILs, and all RCCAs can be inserted at HZP coincident with reactor trip. With greater RCCA insertion, MTC becomes more negative relative to the ARO MTC, all , other parameters being held equal. However, Tech Specs do not allow all other , parameters to be held equal. With deeper RCCA insertion, power must be reduced and Tavg will be reduced accordingly. The reduction in Tavg serves to make the MTC more positive, and at EOL 0 ppm conditions, this positive Tavg I effect will entirely offset the negative RCCA effect on MTC. For this reason, the maximum RCCA deviation from nominal conditions allowable by the Tech Specs needs to be assessed at only the HFP condition. I 11251:6-891122 3-6 I
O, e i E At full power, the RILs for the Salem units permit insertion of the lead control bank to 170 steps withdrawn. However, strict application of these current RIls in determining the " delta MTC" factor associated with RCCA I insertion may prove to be restrictive if minor changes to the RILs become necessary in the future. For this reason, the HFP RCCA inse, tion assumed for this analysis is [ f"'C steps withdrawn. This additional insertion is expected to bound minor RIL adjustment which may be necessary for optimizing core performance characteristics of future Salem reloads. However, applicability of the ultimate EOL MYC LCO value derived from these sensitivitie' ,will be confirmed on a cycle-by-cycle basis as part of the reloed design prot.est; therefore, a RIL adjustment to lead control br.nk insertion t'eyond [ f"'C steps withdrawn will not necessarily invalidate the revised IOL MTC LCO value. This limiting HFP RCCA insertion of i f"'S "teps withdrawn forms the basis of the deterM nation of MTC sensitivity to HFP RCCA insertion, which is descri'ced in Appendix A. The resulting " delta MTC" factor associated with
; RCCA insertion was determined to be ( pa,cpe,j.7, Axial Flux (Power) Shaoe Deviation I As indicated earlier, MTC is affected by the axial flux shape which exists in the core, primarily as a result of the influence that the axial flux shape has
;. on the rate at which the moderator is heated as it moves up the core. The detailed shape itself is not so important, but rather the " balance" of the flux shape, in terms of how much moderator heating occurs in the lower half of the core versus the upper half of the core. The influence which axial power shape has on MTC can, therefore, be captured by quantifying this axial flux
" balance", and this balance is best quantified by the core's Axial Flux Difference (AFD).
-I-The discussion of the MTC sensitivity to axial flux (power) shape presented in Appendix A establishes that the more negative the AFD becomes, the more negative the MTC will become. The axial flux (power) shape deviation is, therefore, determined by how negative the AFD is allowed to become under normal full power operating conditions.
g 11251:6-891122 3-7
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W The Salem units employ a CAOC Tech Spec which sets the allowable full power ~ AFD limits at +6% and -9%. To assign a " delta HTC" factor attributable to axial flux shape, one need only examine the HTC effect associated with the -9% I " deviation" from a most negative expected target AFD value of approximately [ )+"'C%. However, to account for possible future changes in the most negative HFP AFD limit, an AFD value of ( 3+"'C% is selected as the basis of the axial flux (power) shape deviation. This [ 3*"'C% AFD deviation is applied to the HTC sensitivity to axial flux (power) shape, which is described in Appendix A, to obtain a " delta MTC" factor associnted with AFD deviation from a perfectly belarce.1 axial flux s%pe. The resulting "3etta HTC" factor is [ ]+Cpcb/'F, p,nslept Fission Produci_i)(enon) Concentration Otviation Xenon is the most significant transient fission product in terms of effects on coie reactivity and flux distributica; therefore. its possible impact on MTC are investigated to compute the final " delta HTC" factor to inclaje in the Host Negative Feasible HTC approach. While Tech Specs place no limitations on either xenon distribution or overall concentration, the AFD limits discussed above, in effect, place a limitation on the amount of axial xenon skewing that can occur, and the physics of xenon buildup and decay place practical limits I on the concentration. Because axial xenon distribution directly impacts axial flux shape, this aspect of xenon effect on HTC is implicitly included in the axial flux (power) shape deviation discussed above. What. remains to be quantified is the impact of the overall xenon concentration in the core. Taking the EOL HFP ARO equilibrium xenon concentration to be the nominal xenon condition for the core, it was determined for low leakage core designs of the type characteristic of Salem reloads, that the HTC becomes more negative with a reduced xenon concentration. Accordingly, the most negative HTC results when there is no xenon in the core. 11251:6-891122 3-8
I i It was established in the discussion on moderator temperature and pressure
' deviation and on RCCA insertion deviation, that the condition for the most l I negative HTC requires maximum allowable temperature (minimum allowable density) and, therefore, occurs at full power conditions. While the assumption of achieving full power operation with no xenon in the core is '
I certainly a conservative assumption, the possibility of steady power escalation after an extended shutdown period presents a reasonable scenario for full power operation with a comparatively low xenon concentration in the ' core, for this reason, the " xenon deviation" to be used in conservatively , osteraining the ' delta MTC" factor attributable to transient fission product ; is' a change frcm FFP ARO quilibrium xenon to no ::enon in tM core. The res01 ting "dvita NTC" factor b [ pa.c pg,j.p, 3.a overall "Delte, MTCa Factor for Salen, Units 1 and 2 Roioads
-The preceding sectic/a has concluded that the most adverse opert. tion possible, in terms of achieving the most negative EOL MTC under current Salem -
Units 1 and 2 Tech Specs, would feature the following values of key parameters: I - Core Moderator Temperature: 4.I'F above HFP nominal
- Core Moderator Pressure:
I - HFP RCCA insertion: 2205 psia [ f"'C steps withdrawn pa,c%
- HFP most negative AO: [
- HFP xenon concentration: 0%
When these maximum allowable deviations from a nominal condition of EOL HFP l AR0, with equilibrium xenon, and 0 ppm boron are applied to the individual > parameter sensitivities discussed in Appendix A, the overall " delta MTC" factor is determined. This overall factor for the Salem units is computed as follows: I I . I I 11251:6-891122 3-9
- Core Moderator Temperature and Pressure Factor: ( )+a,c pg,f.7
]+a,c pcm/*F I -
HFP RCCA Insertion Factor: Axial Flux (Power) Shape Factor: [ [ ]+a,c pcm/*F Xenon Concentration Factor: ( pa,c , f.E I Overall " Delta MTC" Factor: [ f"'C pcm/*F The interpretation of this overall " delta MTC" factor is as follows. The Tech Spec LCO value of EOL MTC.is based on the explicit conditions of unrodded full power operation. This is an appropriate condition for performing a HTC experiment and obtaining results that can be traaningfully compared to design predictions. It is not, however, the cordttion under which the MTC can . achieve its most negative value under normal operation scenarios permitted by the Tech Specs. The conservative " delta MTC" formulation has concludea that I the actual core MTC can be as much as ( t'e pa,c pcm/~r more neghtive than n EOL HTC LCO value defined by the Tech Specs. J I The individual components of this [ pa c pg,j.F overall " delta MTC" factor have been determined on a conservative basis and are expected to bound the values predicted for Salem reload cores in the future. While an I individual component could conceivably exceed the value cited above, such an occurrence would not invalidate the Most Negative Feasible MTC approach, as pa,c long as the total of all the components remains bound by the [ pcm/*F overall " delta MTC factor, Implementation of a revised E0L MTC Tech Spec based on the Most Negative Feasible MTC approach will require that any l reload core's overall " delta MTC" factor be demonstrated to be bounded by the Itcensing basis value, rather than specifically addressing the individual components. Such validation of the Most Negative Feasible MTC approach on a cycle-specific basis would be performed as part of the reload core design process described in Reference 6. I I I 11251:6-891122 3-10
n 3.5 Proposed Salem Units 1 and 2 Tech Spec EOL MTC.LCO Value As was pointed out in Section 3.1, Salem units FSAR accident analyses have I assumed a MDC value which, when converted to a MTC at nominal HFP conditions, is equivalent to a MTC of -52.6 pcm/*F. At no time may the actual core be I allowed to experience a MTC more negative than -52.6 pcm/'F, as this would invalidate an assumption of the accident analyses. The Most Negative Feasible MTC approach guarantees that such a situation will not occur by subtracting from this -52.6 pcm/'F MTC value the [ f"'C pcm/'F " delta MTC" factor detertained for both Salem units. The resulting value of I pa.c pg ,f.p u is the Tech Spec EOL LCO value of MTC under the Most Negative Foasible MIC approach. As an additional measura of conservatism, this value is forther increased to -44.0 pcm/*F, and proposed t.s the EOL HTP ARO Tech Spte MTC LCC value for botn Sai n, reload cores, replacing the current LCO value of- l
-38 pcm/'F for Unit 1 and -40 pcm/'F for Unit 2.
The -44.0 pcm/'F prerosed limit provides relief over the limit associated with the current Tech Spec AP.0-to-ARI conversion requirement, yet still represents a conservative formulation. The scenario of deep RCCA insertion, coupled with high Tavg, low system pressure, and no xenon, represents a compounding of worst case events which can be considered independent, yet are not treated as I such in the Most Negative Feasible MTC formulation. Determination that the core MTC is less negative than -44.0 pcm/*F at EOL HFP ARO conditions provides assurance that the assumption on initial condition MTC made in the plant accident analyses remains bounding. Additional assurance that the MTC (MDC) will not become more limiting at any time during a transient is also needed, in order to demonstrate that the accident analysis conclusions remain valid. This additional assurance is the primary subject of Section 4.0. I lI 1 11251:6-891122 3-11 i
'f i .
4.0 SAFETY ANALYSIS IMPACT OF..MOST NEGATIVE FEASIBLE MTC APPROACH I The accident analyses conservatively model the various reactivity coefficients to produce a bounding analysis. As discussed in Section 3.1, the applicable analyses assume a constant MDC of 0.43 Ak/gm/cc to bound the predicted I moderator reactivity insertion. The events which assume this value for EOL HDC are listed in Table 4.1. I The Most Negative Feasible M1C approach determines the conditions for which a core will exhibit the most negative NTC value that is censistent with
. operation allowed by the TNb Specs. Thus, the value for the Most Negative Feasible ATC provides the basis for a conservative initial cenottion I assumption.
Changes in the parameters identified in Section 2.3 could take place during a transient in such a urc/ as to make the MlC rare negative than that altowed ! l under norm;l operation. However, the most aoverse ronditions seen in inese events will not result in a reactivity insertion that would invalidate the conclusions of the FSAR accident analyses. Therefore, the 0.43 ok/gm/cc assumption used as the basis for the Most Negative Feasible MTC Tech Spec will not change. As discussed in Reference 6, the reactivity coefficients assumed can have a strong influence on accident analysis results. Since the moderator coefficient can be affected by a reload, the conservative nature of the l accident analysis assumption must be confirmed on a cycle-specific basis using the methodology discussed in Reference 6. This includes verification that the most adverse accident conditions discussed above do not invalidate the conservative nature of the accident analysis assumption. This process ensures the ability to verify that the applicable safety limits are met for each I reload design and, consequently, that the Tech Specs are met. I I I 11251:6-891122 4-1
P TABLE 4.1 FSAR Chapter 15 Events That Assume A Constant 0.43Ak/gm/cc Value of MDC 1
'Section Event 15.2.2 Uncontrolled Rod Cluster Control Assembly Bank Hithdetwal at Power 10.2.6 Startup of an Inkttive Reactor Coolant Pomp 15.2.7 Less of External Electrical Load 15.7.7 Turbine Trip 15.2.10 Excessive Heat Removal Due to Feedwater Syttem Malfunctions 15.2.11 Excessive Load Increase Incident 15.4.3 Major Rupture of a Main feedwater Line i
i I 11251:6-891122 4-2 ;
W,' W 5.0 DETERMINATION OF MOST NEGATIVE FEASIBLE MTC SURVEILLANCE VALUE F Section 1.3 pointed out the potential conservatism in the separation of - 9 pcm/*F between the Tech Spec 300 ppm MTC SR value and the EOL HFP ARO MTC LCO value for both Salem units. Typical 17x17 reload designs exhibit a predicted difference between the 300 ppm HFP design MTC and the EOL HFP ARO design MTC which is much less than 9 pcm/'F. However, in order to justify the use of a value which is smaller than 9 pcm/'F for a given plant, the specific design predictions of the plant must be examined. Design predictions for recent Salem reload r. ores were reviewed in order to determine the differerce bctween the predietJ1 300 ppm HFF fiTC and the predicted EOL HFP MTL, The magnitude of the difference showed little variation, tarying from 5.6 to a n.aximum of 6.1 pcm/*F. In reviewir.g the differencos tietween 7.edicted 300 ppm and EOL MTC values for the relcad corts of 4 loop plants which are similar to the Salem enits, an important trend was discerned. It was observed that the higher core average enrichments associated with increasing discharge burnup tend to decrease the magnitude of MTC difference. As future Salem reload cores area expected to increase enrichment and fuel discharge burnup levels, it is anticipated that I the difference between the HFP 300 ppm MTC and the HFP EOL MTC will become less in the future. This [ ]+"'C pcm/*F should, therefore, bound the 300 ppm MTC-to-EOL MTC differences for future Salem reload cores. The proposed Tech Spec SR value for both Salem reload cores is -37.0 pcm/'F.
= This value is 7.00 pcm/*F less negative than the EOL LCO MTC value proposed in Section 3.5. The 7.00 pcm/*F was chosen to bound the maximum ( )*"'C pcm/'F difference observed for recent Salem reload cores, yet afford relief from the 9 pcm/*F difference applied by the current Tech Specs. While the I -37.0 pcm/*F 300 ppm Tech Spec SR value is expected to be bounding for future Salem fuel management, the validity of this SR value will be confirmed on a cycle-by-cycle basis, as part of the reload core design process described in Reference 6.
11251:6-891122 5-1
6.0 CONCLUSION
S The present Salem Tech Spec values of -38 pcm/'F and -40 pcm/*F for the EOL I HFP ARO MTC LCO, and of -29 pcm/*F and -31 pcm/'F for the 300 ppm HFP ARO SR for Units 1 and 2 respectively, conservatively reflect the FSAR accident
- analysis MDC assumption. However, they are considered to be overly restrictive by potentially requiring repeated deviation from nominal plant operation. An alternative adjustment procedure is proposed which is based on a conservative determination of the extent to which a nominal EOL HFP ARO MTC '
value can be made more negative under the most extreme values of certain cperational parameters that are permitted by other Tech Specs. This Most Negative Feasible !ATC approach assumes that these largely indeper. dent extreme situations cccur s*multaneously, and in the worst case, serve to make the EOL HFP MTC [ pa,c penf.F more negative than it would be at neminhl
~
conditions. When this value is subtracted from the MTC equivalent of the _ accident analysis assumed MDC salue, the resulting MTC is [ pa,c prm/ 'f . The sM ghtly note conscrvative vhlbe of -44.0 ccm/'F ts, proposed as i tht 1.0L liFC MTC Tech Spec LCO limit under the F.ost Negative Feasible MIC approach. Examination of the difference between the 300 ppm HFP equilibrium boron I concentration MTC value and the E0L HFP MTC values concluded that a bounding expected difference between these two MTC values for both Salem reload cores is -7.0 pcm/'F. This difference is subtracted from the proposed -44,0 pcm/'F EOL HFP MTC Tech Spec limit to arrive at a proposed Tech Spec 300 ppm HFP MTC SR value of -37.0 pcm/'F. It is concluded that the Tech Spec EOL MTC LCO and 300 ppm SR values proposed under the Most Negative Feasible MTC approach do not impact conclusions of FSAR accident analyses, because they do not affect the accident analysis I assumption of MDC. In addition, the validity of the above-stated LCO and SR HTC values, as well as the plant's ability to comply with them, will be I examined for each reload cycle as part of the normal reload design process.
-I 11251:6-891122 6-1
- e The new EOL MTC LC0 and 300 ppm SR MTC values and the revised basis for adjuttment overcome the problems inherent with the present version of Tech )
Spec 3/4.1.1.4 for Unit 1 and 3/4.1.1.3 for Unit 2, yet still afford protection. These Tech Specs continue to require that surveillance be ! performed, so that any deviations between the operating core and design I predictions that might threaten the validity of accident analysis assumptions can be detected, and continued surveillarge and appropriate action undertaken, j I ! I
~
I I : I : I . I lI lI I I 11251:6-891122 6-2 4
REFERENCES
- 1. Barry, R. F., " LEOPARD - A Spectrum Dependent Non-Spatial Depletion Code for the IBM-7094." HCAP-3269-26, September 1963.
- 2. England, T. R., " CINDER - A One-Point Depletion and Fission Product Program," HAPD-TM-334, August 1962. x
- 3. Liu, Y. S., et al., "ANC: A Westinghouse Advanced Nodal Computer Code,"
WCAP-10965-P-A, September 1986.
- 4. Camden, T. M., Kersting, P. J., Carlson, H. R., "PALADON - Hestinghouse p L
. tiodal Computer Code," WCAP-9485-P-A, December 1978, t
g b B. 5. Barry, R. F., "The PANDA Cods," WCAP-7048, April 1967. ~= . " 6. Davidson, S. L., Kramer, H. R., ed., "Westinghoust Reload Safety y Evaluation Methodology," HCAP-9272-P-A, July 1985. -I L I
-I I
LI , I I I , I sizsi:e-e94i22 R-> y
k 5 a E g APPENDIX A "6
-I DETERMINATION OF MOST NEGATIVE FEASIBLE 3
MTC SENSITIVITIE5 =E is I I il
=
;I I:
,8 I
I
' 11251:6-891122 A-1
.. o Investigation of the sensitivity of HTC to core operational parameters that
" are variable under normal core operation is a fundamental requirement of the Most Negative Feasible MTC approach. Of the parameters discussed in Section 3.2, those that required detailed evaluation are:
- moderator temperature and pressure
- RCCA insertion
- axial flux (power) shape
- transient fission product (xenon) concentration For each of these parameters, the sensitivity analyses were performed by perturbing the_ parameter in such a way as to induce a change from its nominal EOL value, and then performing a MTC determination with the parameter held in the parturbed state. A further perturbation was induced and the MTC calculation rep uted. This sequence was repeated until sufficient data was obtained to reliably determine the trend of MTC change with variation in the valur of the parameter. The sensitivity analyses were performed for t recent t.vpical Salem reload, as well as four adMtional reload cores. These cores
} exhibit destyn features that rny be in:orporated into future Salem reloads, such as increased discharge bernup, high 2r,richments, longer cycles and advanced product features. Neutronic calculations and evaluations were performed for each of these core designs to establish bounding sens'.tivities to each of the above parameters. The following sections provide a brief 1 description of these calculations, and the " delta MTC" factors obtained. A.1 MTC Sensitivity to Moderator Temperature and Pressure Variation The decrease in moderator density which accompanies moderator heatup has the effect of reducing neutron moderation. With a low soluble boron concentration in the moderator, this results in a negative moderator temperature I coefficient. I 11251:6-891122 A-2
.. .i Since water density changes more rapidly with increasing temperature, and because of additional spectrum hardening effects, the MTC becomes progressively more negative with increasing temperature. The sensitivity of l MTC to increasing temperature was determined for each of the reload cores by j , increasing core reference moderator temperature slightly above the nominal HFP :
value, while holding pressure constant at 2250 psia, and then performing a MTC -[ calculation that induced small changes in core K-effective via changes in ! moderator temperature and density about the reference values. The effects of changes in moderator temperature and density were considered together. After ! the MTC value was computed, core reference moderator temperature was further ; increased, and another MTC calculation performed. This process was repeated , until the trend of MTC with increasing core reference moderator temperature was clearly established. i Results were recorded for the five reload cores in terms of change in MTC from the nominal HFP MTC as a function of increase in reference moderator [
- teinperature above the nominal HFP moderator temperature. The results are sSown ir Figure A.I. As expected, Reload D exhibits the strongest sensitivity cf MTC to increases in moderator temperature, due to its higher nominal HFP reference temperature. A curve which concervatively bounds the MTC '
senst'civity results of the five reloads is also shown in Figure A.I. This bounding curve is used in determining the " delta MTC" factor. ; To use the bounding MTC sensitivity information of Figure A.1, the maximum , allowable temperature and pressure (and, therefore, density) deviations f permissible under operation that complies with Tech Specs must also be , determined. These deviation values, presented in Section 3.3, are combined with the sensitivity data to arrive at' a " delta MTC" factor associated with moderator temperature and pressure (and, therefore, density). For the 4.1'F temperature deviation cited in Section 3.3, figure A.1 indicates that the corresponding " delta MTC" due to temperature increase is [ ]+a,c a pcm/*F. This was increased to ( 3 ,c pcm/*F to cover the difference I between the nominal core design temperature of 581.8'F and the actual core operating temperature of approximately 575'F. The " delta MTC" due to the 45 psi pressure deviation cited in Section 3.3 was conservatively determined to not exceed [ ]+a c pcm/*F. The combined " delta MTC" factor is, therefore [ ]+a c pcm/*F.
-11251:6-891128 A-3 L
l"
\ \
A.2 MTC Sensitivity to RCCA Insertion i With constant moderator temperature, pressure, and boron concentration, ) insertion of control rods makes MTC more negative. As indicated in Section 3 the most negative MTC situation will always exist at HFP, with RCCA's inserted I to tne extent allowed by the HFP insertion limits. i To calculate the EOL HFP MTC sensitivity to RCCA insertion, the reload core ' rrodels had the lead control bank inserted the maximum appli n P e amount ! l determined from Section 3.3 ([ ]+"'C steps withdrawn), at HfP, with no soluble boron in the core. The MTC value for this condition was then determined by inducing small changes in core K-effective via changes in
- moderator temperature and density about their reference vs.!ves. This MTC value was compared to the MTC determined at the same conditions, but with all I RCCAs removed from the core.
Of the five reload corns analyzed, it was determined that the niaximum change to t~.e EOL 0 ppm HFP A90 MTC which occurred as a result of HFP RCCA insertion ! to a depth of I ]***C stops withdrawn was [ ]**'C pcm/*F. because wne minor r.djustment to RILt ma,v be @sirable for optimization of future core , I 6esiges, it vas considored prudent to further increase this MTC sensitivity factor. An increase of [ ]+a,r, is considered sufficient to bound HFP RCC/s ' worth changes that would accompany anticipated RIL changes, therefore, the I bounding " delta MTC" factor associated with allowable HFP RCCA insertion
]+a.c pg,f.7, becomes [
A.3 Sensitivity to Axial Flux (Power) Shape I MTC is not so much directly affected by axial flux distribution itself, but is affected via the impact which the axial flux distribution has on the rate at which the moderator is heated as it moves up the core, and via the importance weighting which the axial flux shape imparts to different regions of the core. I lI 11251:6-891122 A-4
T . l In general, the accumulated burnup in the bottom half of the core exceeds that in ;che top half of the core. Other things being equal, higher burnup results l i in a more regative MTC as a result of isotopic impacts on flux spectrum. A i more negative axial flux (power) shape allocates a greater "importance - weighting" to the lower regions of the core where burnups are greater, thereby I accentuating this effect. It may also be shown that, in general, as the power distribution becomes more bottom skewed, the average moderator temperatura increases for a constant core temperature rise. Therefore, both the importance weighting effe'et and the moderator axial heating rate effect indicate that a more negative Axial Flux Difference results in a more negative MTC. This effect was investigated for four of the reload cores at E0L HFP O ppm I conditions with no xenon in the core (xenon was removed so as to not complicate flux skewing strategy). A specific axial flux shape was induced and then, holding this flux shape approximately constant, the HTC was determined by observing the small changes in core K-effective which resulted .l from vertation in moderator tcmperature and density about their reference y values; A different axial flux shape was induced, and the HTC calculation repeated. This process was repeated until the behavior of MTC with variation in axial flux shape (as quantified by Axial Flux Difference) was clearly identified. Curves of " delta MTC" as a function of Axial Flux Difference (AFD) for the four reload cores are shown in Figure A.2. Note that a zero AFD is taken as the reference point, therefore, " delta MTC" is fixed at zero for an AFD of
- zew. Because more negative AFD values result from RCCA insertion, this axial flux shape MTC sensitivity implicitly captures part of the RCCA HTC sensitivity not included in the " delta MTC" factor of the previous section.
Section 3.3 concludes that a negative value of HFP AFD that is expected to I bound future Salem reload cores is [ J+a,c%. Using a value which bounds the most conservative trend of Figure A.4, the " delta MTC" factor corresponding to [ ]+a,c% AFD is [ ]+a,c pcm/'F. I ! 11251:6-891122 A-5
5 up A4 Sensitivity to Transient Fission Product (Xenon) Concentration i Xenon is the most significant transient fission product in terms of effects on E core reactivity and flux distribution, therefore, its possible impacts on MTC
- were investigated to compute the final " delta MTC" factor to include in the E Most Negative Feasible MTC approach. While Tech Specs place no limitations on e
either xenon distribution or overall concentration, the AFD limits discussed R in Section 3.3, in effect, place a limitation on the amount of axial xenon g skewing that can occur, and the physics of xenon buildup and decay place practical limits on the concentration.
?
5 Because axial xenon distribution directly impacts axial flux shape, this E aspect of xenon effect on MTC is implicitly included in the Axial Flux Shape
" delta MTC" factor discussed in Section A.3. What remains to be determined is ~I the sensitivity to overall xenon concentration in the core. Calculations to determine this sensitivity were performed.
For all five reload cores, it was fcuno that the raost negative MiC resulted when all xenon was remcVed froin the core. The largest " delta" from the i reference (equilibrium xenon) MTC that occurred when all uenon was remove') was l pa.c pcm/*f. This value becomes 'ho final " delta MTC" fartov attributable to xenon. No further entertainty is added, simply because the scenario of operating at full power with no xenon in the core is itself 4 sufficiently conservative as to be bounding. 5 I
- I
=I
=I
- I
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11251:6-891122 A-6
.e- . ;
Figure A.1 Change in MTC With Increase in T-Average Above Nominal T-Average I 0 =-
+a,c I
I -1 I I _ (-2 _ 1 w E I i I h I - I ~4 I I ~5
~
l , INCREASE IN T-AVG AB0VE hP(OF) NOWINA I 11251:6-891122 A-7
,'.i Figure A.2 Delta MTC Versus Axial Flux Difference At EOL, HFP, ARO I
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