ML20029E050
| ML20029E050 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  |
| Issue date: | 05/12/1994 |
| From: | Feigenbaum T NORTH ATLANTIC ENERGY SERVICE CORP. (NAESCO) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML19304C121 | List: |
| References | |
| NYN-94059, TAC-M86959, NUDOCS 9405160171 | |
| Download: ML20029E050 (38) | |
Text
,.. _
W.,
Nortli North Atlantic Energy Service Corporation a
no. nex 3oo
/ Atlantic se-bre
- N " m 874 h
(603) 474M21, Fax (603) 474-2987 The Northeaat Utilities System Ted C. Feigenbaum NYN 94059 Senior Vice President &
Chief Nuclear Officer May 12,1994 United States Nuclear Regulatory Commission Washington, D.C. 20555 Attention:
Document Control Desk
References:
(a)
Facility Operating License No. NPF-86, Docket 'No. 50-443 (b)
North Atlantic letter NYN-93020, dated February 2,1993, " Request Ihr NRC Review and Approval of Analysis Methodologies to be Applied to Seabrook Station." T. C. Feigenbaum to USNRC (c)
USNRC letter dated March 10,1994, " Request for Additional infinmation: Core Thennal Limit Protection Function Setpoint Methodology (TAC M86959)"
Subject:
Response to Request for Additional intbrmation (TAC M86959)
Gentlemen:
North Atlantic Energy Service Corporation (North Atlantic) herein provides (see enclosures) additionalinformation regarding the application to Seabrook Station of Yankee Atomic Electric Company Report YAEC-IS54P, " Core Thermal I.imit Protection Function Methodology fbr Seabrook Station" This intbrmation was requested by the NRC Staff l Reference (c)].
Portions of the information enclosed is proprietary to Yankee Atomic Electric Company (YAEC).
North Atlantic therefore requests that it be withheld from public disclosure pursuant to 10CFR2.790.
North Atlantic has enclosed an affidavit, signed by Mr. Stephen P. Schulz, Vice President YAEC, in support of the request tbr withholding pursuant to 10CFR2.790. North Atlantic has also enclosed a Copyright Notice, signed by Mr. Schulz, which grants the NRC authority to make the number of copies of YAEC-1854P which are necessary Ibr its internal use and to fulfill its legal responsibilities as regards public disclosure The additional information is provided in both a proprietary version (Enclosure I) and a non-proprietary version (Enc!osure 2). The pages with proprietary infbrmation have been deleted from.
Should you have any questions regarding this matter, please contact Mr. Terry L liarpster, Director of Licensing Services, at (603) 474 9521, extension 2765.
Very truly yours,
/
9405160171 940512 Ted C. Feigenbaum p
PDR ADOCK 05000443 P
United States Nuclear Regulatory Commission May 12,1994 Attention:
Document Control Desk l' age two cc with enclosures:
Mr. Thomas T. Martin Regional Administrator United States Nuclear Regulatory Commission Region i 475 Allendale Road King of Prussia, PA 19406 Mr. Albert W. De Agazio, Sr. Project Manager l'roject Directorate 1-4 Division of Reactor Projects U.S. Nuclear Regulatory Commission Washington, DC 20555 Mr. Antone C. Cerne NRC Senior Resident inspector P.O. Ilox 1149 Seabrook, Nil 03874 cc without enclosures:
Ms. Ileidi Komoriya International Technical Services, Inc.
Suite 2545 420 Lexington Avenue New York, NY 10170-l
AFFIDAVIT PURSUANT TO 10 CFR 2.790 YANKEE ATOMIC ELECTRIC COMPANY
)
NUCLEAR SERVICES DIVISION
)
COMMONWEALTH OF MASSACHUSETTS
)
WOP.CESTER COUNTY
)
(1) I, Stephen P. Schultz, depose and say that I am Vice President of Yankee Atomic Electric Company (" Yankee"), duly authorized to make this affidavit, and have reviewed or cause to have reviewed the information which is identified as proprietary. I am submitting this affidavit to the Nuclear Regulatory Commission
(" Commission") in conformance with the provisions of 10 CFR 2.790 of the Commission's regulations for withholding this information from public disclosure.
(2) The information for which proprietary treatment is sought is contained in
" Response to Requests for Additional Information Review of YAEC-1854P" (62 pages). These responses to Requests for Additional Information (RAIs) provide technical descriptions of analytical methodology developed and employed by Yankee.
(3) Pursuant to the provisions of Paragraph (b) (4) of Section 2.790 of the Commission's regulations, the following is furnished for the consideration of the Commission in determining whether the information in the above documents should be withheld from public disclosure:
a.
The information sought to be withheld from public disclosure is owned and has been held in confidence by Yankee, b.
The information is of a type customarily held in confidence by Yankee and not customarily disclosed to the public. Yankee has a rational basis for determining the type of information customarily held in confidence which includes a procedure which determines whether to hold information in confidence. Under that procedure,information that is determined to have
" actual or potential commercial value," i.e., is potentially marketable or provides a potential competitive advantage,is held in confidence, c.
This information is being transmitted to the Commission in confidence under the provisions of 10 CFR 2.790 with the understanding that it be received in confidence by the Commission.
d.
The information, to the best of Yankee's knowledge and belief, is not available in public sources.
e.
The material contained in the RAI responses contains significant information and detail pertaining to the development of a methodology and/or data. This material, which is marketable in several ways, was obtained at considerable expense to Yankee and our sponsor companies.
The public release of this information, raaking it readily available to our w,
e
~
competitors, would diminish Yankee's ability to sell products and services involving the use of this information.
f.
The use of the information and data provided in this document by a competitor would put Yankee at a competitive disadvantage by reducing their expenditure of resources at the expense of Yankee and our sponsor companies.
(4) Yankee hereby grants the Commission the authority to make the number of copies of these RAI responses which are necessary for its internal use and to fulfill its legal responsibilities as regards public disclosure.
(5) This information is part of that which would enable Yankee to:
(a) establish methods for calculating operating limits for reload cores; and, (b) perform reload safety evaluations addressing the impact of the reload core on the plant safety analysis.
Public disclosure of this proprietary information is likely to cause substantial harm to the competitive position of Yankee because it would enhance the ability of competitors to develop similar methodologies without commensurate expenditures. Also, public disclosure of the information would enable others to use the information to meet NRC requirements for licensing documentation without purchasing the right to use the information.
Further the deponent sayeth not.
~Irh steplien P. Schultz d
Vice President Sworn to before me this 4 th day of April,1994 XcY~ hcLTAA
(
Kathryn Gatus, No'tary Public My Commission Expires January 24,1997 l
i
,. ~
~
Proprietary Information Notice Transmitted herew!th are two proprietary documents (RAI responses) furnished to the Nuclear Regulatory Commission (NRC) in connection with requests for generic and/or plant-specific review and approval.
In order to conform to the requirements of 10 CFR 2.790 of the Commission's regulations concerning the protection of proprietary information so submitted to the NRC, the information which is proprietary is enclosed in brackets ( [ ] ). Each page of these RAI responses containing proprietary information is stamped
" PROPRIETARY".
t' l
A n
North Atlantic May 12,1994 l
ENCL OSURE 2 TO NYN-94059 NON-PROPRIETARY l
i
'l j
u
t
'4 ltesponse to I(equest for Additional Information Review of YAEC-1854P Provide a flow chart depicting steps (including codes used) taken to determine OPAT and OT6T 1
tri;> setpcints. Indirote nn the chart which variables are transferred onto the next block. In addition, indicate on the diagram those steps which are cycle-dependent (redone with each cycle).
ItESPONSE TO QUESTION 1:
Figures 1-5 provide a flowchart depicting the steps taken to determine OPAT and OTAT trip setpoints, including analytical computer codes used and data transfers. Automated interfaces are used to process the large amount of data. Cycle-dependent process are described in process blocks with rounded Data Cycle-independent processes are described in process blocks with square corners.
corners.
transferred is described in I/O blocks (parallelograms).
\\ _
1 e
4 E'i g u r e 1 Core Lt. ding START J
Pattato I
4 r
3 Generate SIMULATE-3 Cross-section cross-section library for W f uel types in library using CASMO-3/ TABLES-3 core W
}
4
(
3 Develop SIMULATE-3 Core Model for SIMULATE-3 W
model Cycle Loading Pattern N
)
4 r
3 Determine F1 s
.k Pin-vise 3-D power distri utions core power IP(x,y,z)) using distributions GIMULATE-3
(
)
4 r
3 Candidate Identify candidate subchannel hot subchannel M
local power locations distributions
(
)
V r
m Identify limiting Local power hot subchannel distributions locations for each for limiting
/
3 4
typical and power distribution via closed-channel thimble MDNBR calculation subchannel locations
(
)
l
m i
l 1
I e
Figure 2 i
l l
Determine MSSV
/
Limit Line from H55V Limit
>{
hf reactor coolantand Line cain steam system parameters.
Determine Hot Leg Hot Leg Saturation Limit Saturation Lines from core limits power and coolant (AT,Taval flow rate versus Pressure v
Determine AT at OPAT C=an as a Data for AT function of Tave
---H" 6 OPAT Quam and pressure v
m r
m Determine Thermat Thermal limit Limit Lines for the data - ATo, Determine base OPAT Reference power T.ve, Pece, AI trip equation Ke for the and Ks coefficient 4
distribution set using VIPRE-01 MOD Reference values 2
power distributions
(
)
(
)
v
$[
Base OPAT trip setpoint equation (K.,K.)
v 3
h
- W
t Figure 3 Local power distributions for limiting
[
typical and thimble subchannel locations i
4 r
3 Determine (Po,AI) for nominal T-H condition for each W (Po,4I) data flyspeck power distribution using VIPRE-01 MOD 2 N
]
4
(
3 Limiting hot Select limiting subchannel power distributions power for each distrbution combination of time W
data for in core life, power selected level, and control flyspeck power bank position distributions
(
)
l 4
r 3
Thermal limit Determine Thermal data - Afo, Limit Lines for the T...,
Paes, AI selected power
- for the distributions using selected VIPRE-01 MOD 2 flyspeck power distributions
(
)
O b
e Figure 4
/
23 v
\\/
/
Local power distributions Base OPAT
/
for limiting trip typical and setpoint thimble equation subchannel (K4,Kel locations
\\/
%/
(
)
(~
)
(Po,AI) data Determine {Fa,4I) for normal Determine required
/
for each flyspeck
~~~)
flyspeck OPAT Fe(AI) i>/OPATFe(AI) power distribution power function distributions
(
)
(
)
if n
4 7
r Determine limiting flyspeck power distributions w/r/t Limiting Po within proposed power Al LCO band (e.g.
distribution limiting initial identifiers power distributions for condition II cooldown events) j 4
(
h Determine perturbed Pin-wise 3D power distributions
. distribution power for Conditon II cooldown events data using 51MULATE-3
(
)
4 r
3 Determine Po and &!
{Ps,All data for Condition II for Cooldown cooldown power Event Power distributions Distributions
}
4 Figure 5 MSSV Limit h
Line Hot Leg
/
Saturation
' * ~
~**
limits g
(AT,Tavo) versus Pressure Base OPAT trip 3
setpoint equatton (K.,Ke)
T/
ir
%/
[
\\
Thermal limit data - 47.,
Determine the base T...,
P...,
AI 074T trip equation
- for the
?
Es, Ka, and K.
Reference coefficients power distributions
(
)
./
Base OT&T trip equation v
r 3
Thermal limit data - ATs, T...,
Paes, 41 Determine required nT&T rs(&I)
OT&T rs(All
- for the selected function flyspeck power distributions
(
)
A OPAT trip equation
)[
including e s a1) 1 1
Ilesponse to Request for Additional Information Review of YAEC 1854P 2
Statistical allowance for uncertainties is discussed only with respect to generation of the MSSV Limit Lines. In all other formulations, there was no mention ofany uncertainties. This stands in contrast to the approved methodology fwhich is proposed to simply be extended to Seabrook by this submittal) in which uncertainties were incorporated at each step. Discuss how uncertainties (and their sizes) are accounted for with each step in this proposed methodology.
RESPONSE TO QUESTION 2:
Consistent with the approved methodology, uncertainties are applied at each step of the Seabrook methodology. The steps in the Seabrook methodology at which uncertainties are applied are:
1) the determination of values of Pt Table 2-1 provides a summary of the uncertainties accounted for in determining values of Po and centerline melt related operating limits.
Items 1-5 are applied in the determination of the value of P for each flyspeck power distribution. The statistical t
combination of items 6-8 is applied to reduce the width of the Al LCO band as discussed in the response to question 14. Items 6-8 are also included with item 9 in the determination of the OPAT Channel Statistical Allowance (CSA).
2) the determination of values of Po Table 2-2 provides a summary of the uncertainties accounted for in determining values of Po. Since the values of Po are determined using the WRB-1/RTDP Safety Analysis Limits for thimble and typical channel MDNBR, the uncertainties included in the derivation of the Safety Analysis Limits (see Table 2-3) are also inherent in the calculated values of Po. Items 1-4,6,8,9; and 15 are applied in the VIPRE input used to determine Po for each flyspeck power distribution. Items 5,7,10 are included in-the WRB 1/RTDP Safety Analysis Limit determination. The statistical combination ofitems 1113 is applied to reduce the width of the AI LCO band as discussed in the response to question 14.
Items 11-13 are also included with item 14 in the determination of the OPAT Channel Statistical Allowance (CSA).
-7
~
... _ _ ~.-
Ilesponse to lleguest for Additional Information lleview of YAEC 1854P 3) the determination of the Reference TLLs and specific Flyspeck power distribution TLLs The uncertainties applied are the same as those listed in Tables 2-2 and 2-3, excluding those factors noted as being included in the OTAT Channel Statistical Allowance.
4) the determination of the MSSV Limit Line Table 2-4 provides a summary of the uncertainties applied in the generation of the MSSV Limit Line. These are the same global system parameter uncertainties included in the WRB 1/RTDP limit determination which also influence the locus of the MSSV limit line. The local effect of items 1-4 on the limit line are statistically combined using the Root-Sum-Square technique to determine a bias which is conservatively applied to the nominal limit line Item 5 is an additional bias which is applied to the Hot Leg saturation limit line.
5) the determination of the Hot Leg Saturation Limit Lines Table 2-4 provides a summary of the uncertainties applied in the generation of the Hot Leg Saturation Limit Lines.
These are the same global system parameter uncertainties included in the WRB-1/RTDP limit determination which also influence the locus of the Hot Leg Saturation limit line. The local effect ofitems 1-4 on the limit line are statistically combined using the Root-Sum-Square technique to determine a bias which is conservatively applied to the nominallimit line. Item 5 is an additional bias which is applied to the Hot Leg saturation limit line.
6) the determination of transient MDNBR values "
The uncertainties applied are the same as those listed in Tables 2-2 and 2-3, excluding the factors noted as being included in the OTAT Channel Statistical Allowance.
7) the determination of the AI LCO bandwidth 8-m,e>
~.
Response to Request for Additional Information Review of YAEC 185 tP The width of the Al LCO band is reduced on each side by 5% AI, which is the statistical combination of the following three uncertainties on indicated Al:
Excore Al Calibration 3.0% AI Accuracy of excore detector current vs Al fits 0.5% Al Uncertainty in predicted SIMULATE AI 4.0% Al This approach is consistent with the latest Maine Yankee methodology in which the efTects of uncertainties on the excore axial power shape measurement are statistically combined. It is also consistent with the Westinghouse setpoint methodology for protection systems, in which allowances for the uncertainties on the excore Al indication are included in the statistical combination of trip channel uncertainties which supports the Total Allowance value in Technical Specifications for the Seabrook OTAT and OPAT trips.
8) the determination of the Nominal K and K values.
i The Nominal value for the K. coeflicient specified in the plant Technical Specifications (or COLR)is a value less than or equal to the Safety Analysis Limit for K, reduced by.
the CSA. The value of the K and K. coeflicients derived by fitting the base OPAT i
and OTAT trip setpoint equations are referred to as the SAFETY ANALYSIS LIMIT (SAL) values. The. value of the K, and K, coeflicients specified in Technical Specification 2.2 are the Nominal values which must be set into the plant hardware.
The Nominal values are equal to the SAFETY ANALYSIS LIMIT value reduced by the Total Allowance (TA). The TA must be 2 the Channel Statistical Allowance, which is the statistical combination of the remaining trip channel input parameter process measurement uncertainties and allowances. with the instrument processing uncertainties and allowances.
9
.~.
l 1
Response to Request for Additional Information Review of YAEC-1854P increase in hot assembly enthalpy-rise determined from a cycle-specific assembly wise analysis of core inlet flow maldistribution.
4.
Technical Specification Table 4.31 requires recalibration of the excore AXIAL FLUX DIFFERENCE if incore to excore axial flux difference is 2 3%
e
[]
Proprietary Westinghouse Information.
I s
)
't
-k
Itesponse to llequest for Additional Information Iteview of YAEC 1854P 3
Since the statistical DNB methodology documented in YAEC-1869P is to be used in generation of TLLs, discuss thoroughly and quantitatively differences in the overall setpoints introduced by the use of the RTDP, in DNB analysis from the current setpoints being used.
RESPONSE TO QUESTION 3:
The current Seabrook OTAT setpoints were determined by Westinghouse Electric Corporation using the W-3 DNB correlation and deterministic application of uncertainties, per the approved method described in WCAP-8746, Design Bases for the Thermal Overpower AT and Thermal Overtemperature AT Trip Functions. As noted in YAEC-1869P, the proposed application of the RTDP is based on use of the WRB-1 DNB correlation, with Seabrook specific MDNBR limits for typical and thimble channel MDNBRs.
The OTAT setpoints are derived from Thermal Limit Line (TLL) data for the reference set of power distributions and the Flyspeck power distributions. The TLLs are determined by predicted values of Po, the core power level at which either the MDNBR limit or the coolant quality limit would be reached for a particular core power distribution. Due to the increased accuracy of predictions of critical heat flux associated with the use of a state-of-the-art correlation such as the WRB-1 DNB correlation, and the higher limit on allowable coolant quality of the WRB-1 correlation relative to the W-3 correlation limit, the values of Po determined using the WRB-1 DNB correlation are higher than the values of Pp which would be calculated using the W-3 DNB correlation. As a result, the TLLs computed for a particular Flyspeck power distribution using WRB-1 and the RTDP would be less
.f restrictive than those which would be calculated using the combination of W 3 and deterministic l
application of uncertainties.
Assuming the same reference power distributions (e.g. no increase in Fj), the reference set of thermal limit lines to which the base OTAT setpoints are fit w~ould also therefore be less restrictive when determined using WRB-1 and the RTDP, than those which would have been calculated using the W-3 DNB correlation and deterministic application of uncertainties. The application of WRB 1 and RTDP was intended to gain sufficient margin to allow an increase in FJ from the current 1.55 limit to 1.05.
The combination of WRB 1 and RTDP provides sufficient margin to accomplish this goal. The OTAT trip setpointa determined using WRB 1 and RTDP for the increased F5 provide similar operational margin to the OTAT trip se icint at nominal hot full power conditions as that provided by the existing 15
i Ilesponse to lleguest for Additional Information lleview of YAEC-1854P setpoints based on W-3 and deterministic application of uncertainties.
,*e b
e
}
-16 1
- ~- ~ - - -- --
Itesponse to Itequest for Additional Information Iteview of YAEC 1854P The formulation of the ' tent
- as shown in Figure 3-1 is based upon 23 data points. Justify that 6
this constitutes a complete set of cases to be considered for this purpose.
ILESPONSE TO QUESTION 6:
Figures 3-1 and 3 2 of YAEC-1854P are illustrations of the method and process used to derive the OI%T F (AI) function and do not show the complete set of points (power distributions) used to derive 2
the function. The Po data for the complete set of flyspeck power distributions described in Section 4.1.3 of YAEC-1854P (approximately 13,000 power distributions, corresponding to 22 combinations of core power level and control bank position spanning the complete range of power operation, allowable control bank position, and core average burnup) are used to determine the required F,(AI) function using the process illustrated in Figures 3-1 and 3-2. 1
. ~. -. - -
Ilesponse to Itequest for Additionni Informntion lleview of YAEC-1854P 7
Explain the method of determining the base Overpower Trip equation line on Figure 3-3.
Explain thoroughly how K, was ' fitted' ILESPONSE 'lO QUESTION 7:
The base Overpower AT (OPAT) Trip equation line is a conservative bound to the locus of points of intersection of the reference Thermal Limit Lines (TLLs) witia curves delineating the indicated coolant loop AT at the maximum allowable overpower, Qm, as a function of coolant average temperature.
As shown below, the base OPAT setpoint equation takes the form of a constant multiple (N) of AT,,,
(the indicated coolant loop AT at the nominal HFP condition), and a term which reduces the setpoint by an amount proportional to the difference between the indicated coolant loop average temperature (T,,,), and T,,,,(the nominal coolant loop average temperature at HFP). The % term is zero for coolant loop average temperatures less than or equal to T,,,.
ATopa = N AT,a - % (T.,, - T,,,) AT,,,r Thus, the base OPAT trip equation defines two line segments as depicted in the bottom portion of Figure 3-3.
N is the "y"-intercept of the horizontal line segment, when the coolant loop AT is normalized to the value of AT,,,.
N is the absolute value of the slope of the line segment which begins at the reference average temperature.
E is set to a value s the ratio of the coolant loop AT on the curve of the locus ofintersection points at the selected value of T, to the value of AT,,, used in the OPAT trip. Referring to the bottom of Figure 3-3, the value of T,,,(the nominal HFP coolant loop average temperature)is 588.5 F. The value of AT from the curve of the locus of intersection points is 69.2 F. The value of AT,,, for the same volumetric coolant flow is 59.4 F. Thus, for this example, N would be set to a value s 69.2 / 59.4 =
1,165.,,. _.
~
i Ilesponse to llequest for Additional Information lleview of YAEC 1854P' i
8 Discuss andjustify the process used to determine a set of thermal hydraulic conditions used for the determination of Po ItESPONSE TO QUESTION 8:
The value of Po for any power distribution depends upon coolant flow, coolant temperature, and system pressure. In the approved Maine Yankee methodology, the P data is generated using the design o
minimum coolant flow rate, the design steady-state maximum coolant inlet temperature, and the design steady-state minimum system pressure. The methodology as applied to Seabrook takes into account the application of the RTDP. Thus, in generating the Po data for Seabrook the coolant flow is taken to be the Minimum Measured Flow (MMF). The MMF corresponds to the lower limit for nominal RCS flow measurements that will be specified in the Technical Specification 3.2.5 DNB_
Parametern as part of the implementation of RTDP, Similarly, consistent with the application of the RTDP, the coolant inlet temperature and system pressure are assumed to be the steady-state nominal values at 100<7c RTP, conservatively adjusted by allowances and uncertainties not included in the determination of the RTDP MDNBR limit.
h i
-25
Ilesponse to Itequest for Additional Information Iteview of YAEC 1854P 9
Ref. Figure 3.5.
The overpower AT line on the top Figure 3-5 appears to be a straight line.
Demonstrate that this line is equivalent to the line corresponding to the OPAT line on the bottom figure. In addition, discuss the difference between the OPAT lines on Figure 3 3 and 3 5.
RESPONSE TO QUESTION 9:
The OPAT line on the top figure of Figure 3-5 corresponds to the base OPAT trip setpoint expressed in terms of Qgxx, the maximum allowable overpower, which does not vary as a function of inlet temperature. For the purposes of this illustration, the value of Quix was set to 118 % RTP (the basis for the current OPAT setpoints). The OPAT line in the bottom figure is an illustration of the variation of the corresponding base OPAT trip setpoint with T va. As discussed in the response to Question 7, A
the base OPAT setpoint is a conservative " fit" of the indicated AT at Quix versus T vo for a range of 4
RCS pressure.
Figure 3 3 and Figure 3 5 were intended for illustration of different aspects of the setpoint methodology. Neither figure was intended to depict the actual base OPAT setpoint. The value of K4
- ATy used in the generation of Figure 3-5 was slightly smaller than that used in preparing Figure 3-3. -
-_ _. _ _ = -
~.
4 Ilesponse to Itequest for Additional Information Review of YAEC-1854P
. 1 l
3.
The MSSV Limit Line.
Cycle specific core power distributions have no effect on this limit. It is determined by the performance of the steam generators, reactor coolant pumps, and the MSSV valve setpoints and tolerances. The limit assumed is consistent with proposed Technical Specifications for RCS coolant flow, coolant average temperature, SG tube plugging, and MSSV setpoints, specified in the Technical Specifications. Operation of the plant in compliance with these Technical Specification assures that this limit continues to apply. The MSSV limit would be revised, if needed, to be consistent with the effect of any proposed changes to the associated Technical Specifications.
O.,,
Itesponse to itequest for Additional Information
-l Iteview of YAEC 1854P i
h 12 Discuss how three constant coefficients were fitted for the OTAT trip setpoint equation.
f IIESPONSE TO QUESTION 12:
The constant coeflicients of the base OTAT setpoint equation are determined using the same approach as that used to determine the constant coefficients (e.g. A, B, and C) of the Maine Yankee TM/LP base trip a Wion, namely by selecting the coefficients such that they result in a conservative fit of the reference set of Thermal Limit Lines.
The OTAT trip setpoint equation is:
1+tsi ATour=1K -K -
(T,.,-Tm) + K,(P-Ps) - F (AI) 1 AT,,,
i 2
i 1+Ts 2
where, K, K,, and K are constant coeflicient settings; ti and t, are the time constants of a Lead / Lag i
3 controller which provides dynamic compensation of the trip setpoint; T,.r is a constant reference average temperature; Puis a constant reference pressure; and AT,,,is the value ofindicated AT at hot full power. The F (AI) function modifies the trip setpoint for axial power distributions more severe -
i than the axial power shape assumed.for the set of reference power distributions used to derive the reference TLLs.
The constant coeflicients (K, K, and K ) of the base OTAT trip setpoint equation are selected to result.
i 2
2 in a conservative fit of the reference set of Thermal Limit Lines, in the region bounded by the High Pressurizer Pressure Trip setpoint, the OPAT trip setpoint, the LO-LO Pressurizer Pressure Trip setpoint, and the MSSV Limit Line. The value of the F (AI) term for the axial power shape assumed i
in the set of reference power distributions used to derive the reference TLLs is zero.
Response to Request for
. Additional Information Review of YAEC-1854P The K, coefficient is determined by the desired value of AT,,,,,, at the reference pressure and temperature conditions (e.g. at T.., and P,,,J. The IQ coefficient is determined from the slope of AT,,,ym with respect to changes in T,., at a constant pressure. The value of K coeflicient represents the 3
sensitivity of AT,,,, to variation in pressurizer pressure, and an initial guess for this value is the maximum rate of change in AT,,y, with pressure over the range of pressures to be fit.
These coefficients are adjusted to assure that the value of AT,,,,,is conservative with respect to each thermal limit line in the region to be bounded. A check is nerformed to assure that this fit also bounds the Hot Leg Saturation Limit Lines. Figure 3-8 of the report provides an illustrative comparison of the trip setpoint with the limit lines.
I e '
e i
i l
llesponse to llequest for Additional Information Iteview of YAEC 1854P 13 Provide a detailed discussion of how the coefficients are reduced to account for the power overshoot.
ILESPONSE TO QUESTION 13:
As discussed in Section 3.3 of the report, power overshoot is minimized by the dynamic compensation of the trip setpoint. If an overshoot of the static conditions used to determine the required trip setpoints is found, the trip setpoints are modified in the following manner, With respect to the OPAT trip, the N coefficient is reduced as follows. The maximum difference in the indicated coolant loop AT between that corresponding to the maximum allowable power level, Qm, and the maximum allowable power level minus the power overshoot within the range of pressures bounded by the High Pressurizer Pressure reactor trip setpoint and the LO-LO Pressurizer Pressure
]
trip setpoint is determined. The value of & is then reduced by an amount equal to the ratio of this
-1 maximum difference to AT,,,. For example,if the value of % prior to consideration of power overshoot is 1.165 for AT,,, = 59.4 F, and the maximum difference in indicated AT is determined to be 1 F. N is
)
1 reduced to be 1.165 - 1.0/59.4 = 1.148. This assures that the value of the OPAT trip setpoint is reduced by an amount 2 the effect on indicated AT of the maximum power overshoot of the static trip setpoint. This assures that the OPAT trip will occur prior to core power level exceeding the maximum allowable power level, and that the maximum allowable power level is not exceeded during the power increase which occurs during the trip delay and time for control rod insertion.
J The same process is used to determine the required reduction of the OTAT % coefficient.
1.
P llesponse to Itequest for Additional Information lleview of YAEC 1854P 14 Explain thoroughly how the uncertainties in delta-l measurements are accounted for in the development of the delta.1 LCO band (p. 641.
ILESPONSE TO QUESTION 14:
As described on p. 64, the analyses of the various Condition 11 events which determine the allowable Al LCO band are conducted without consideration of Al uncertainties. Once the allowable Al band has been determined, the width of the band at all power levels is reduced by reducing the absolute value of the coordinates for the l>oundaries of the allowed Al LCO band by the statistical combination of the Al uncertainties. The Al uncertainties included are a 3% allowance for difference in incore to excore Al indications (specified in Tecimical Specification Table 4.3-1 as the threshold for recalibration of the excore Al indication), a 0.5 % Al allowance for the accuracy of excore detector current vs Al fits, and a 4% At allowance for uncertainty in SIMULATE-3 prediction ofincore al for flyspeck power distributions. These t.hree uncertainties are combined using the Root-Sum-Square approach, resulting in a 5% Al overall uncertainty which is subtracted from the absolute values of coordinates for the boundaries of the nominal adowable Al LCO band at each power level.
e t
l l
l'
4 llesponse to llequest I
for Additional Informa tion lleview of YAEC 1854P 1
17 Discuss the method and the codes used to simulate the multi dimensional core physics due to rodposition when determining the LCO band.
ILESPONSE TO QUESTION 17:
The simulation of the three dimensional power distributions is performed by the SIMULATE-3 code.
SIMULATE-3 is a two group, advanced nodal code, capable of determining detailed pin by pin power distributions for steady state and xenon transient conditions. All cross section data for SIMULATE-3 is given by CASMO-3 infinite lattice calculationc. CASMO-3 uses neutron transport methods in forty neutron groups and collapses the results into two neutron group cross sections and t.iscontinuity factors.
Both codes have been extensively benchmarked and proven accurate in cu rent safety analysis calculations performed at Yankee and other utilities. Generic approval of both (. odes for this type of work was granted in YAEC-1363-A for CASMO-3 and YAEC-1659 A for SIMULATE-3.
Power distributions and local peaking actors are the result from SIMULATE-3 calculations. Core conditions such as: control rod position, power level, and other parameters, are explicitly modelled within SIMULATE-3. The code uses the plant operating history, cross sections from CASMO-3, core conditions and control rod position to start the neutronic calculations. An industry standard advanced nodal technique is used to determine the incore flux and power distribution for each of nearly 20,000
^
nodes. Each node is defined as a quarter of an assembly in the radial direction and six inches in the axial direction. SIMULATE-3 has pin power reconstruction capabilities which will determine the power of each pin within each node.
i in the power distribution flyspeck analysis, a comprehensive set of control rod and core power level
- l m
-n-<-
e w
~
e-am n --
m v
m ><
1
. l i
l i
I(esponse to Itequest for Additional Infor: nation Iteview of YAEC 18511' conditions are modelled at many xenon conditions. The results are sorted and power distribution 3
innfoi, nation is c!cctronically transferred for analysis in determining the plant metpoint.a and M I,CO operating band.
I P
P b
r h
l
~
1..
r
Itesponse to itettuest for Additional Information lieview of YAEC 185 iP 18 Provide the details of(D the RETRAN auxiliary DNBR calculation as used by YAEC and (2) modelinx vi'the drapped rad reactivity insertion.
RESPONSE TO QUESTION 18:
YAEC-1854P was written prior to YAEC's transition from a single mainframe computing environment to a distributed workstation environment. Our intent was to use the RETRAN auxiliary DNBR calculation to determine the approximate time of occurrence during the event at which the thermal-hydraulic conditions are most adverse with respect to margin to DNBR, in order to minimize the number of static VIPRE calculations required to determine the actual MDNBR following the drop.
The increased computing capacity of YAEC's current distributed computing environment made it possible to utilize a series of static VIPRE cases to identify the limiting point in time during the event.
The RETRAN auxiliary DNBR calculation was not used in the Cycle 4 analyses, and will not be used in future analyses.
1 The RETRAN simulations of the RCCA drop event use the point kinetics model, with three axial core
']
nodes. The reactivity inserted by the dropped RCCAs is modelled by a RETRAN trip reactivity table j
)
which linearly inserts the dropped rod reactivity worth over a one second interval. One second represents a conservative lower bound on the measured control rod drop times.' Since the limiting thermal-hydraulic conditions occur at the point in time of maximum power overshoot, which typically
)
occurs more than 60 seconds after the drop, the transient response is not sensitive to the assumed.
.j RCCA drop time.
-43
I h
Figure 1-I Overpower Delta-T Trip Model INPUT (constant =
SUM Coolant Loop T-avg 1.0)
Tref 3/
SUM v
DER F6 RATE-LAG compensation v
v K5
$UM LAG K4
-1.0 v
M SUM LLC Coolant Loop Delta-T Trip setpoint v
i
-1.0 SUM
's Trip Comparator - output monitored by RETRAN trip l
l hno-
Figure 1-2 Overtemperature Delta-T Trip Model
- WPUf SUM INPUT
{ constant 1.0)
Coolant Loop Tavg - Tref Pressuriser Pressure V
v i
LLC Dynamic compensattori j
s SUM l
K2 V
v I
E3
$UM-SUM El i
SUM 4
Trip Setpoint Coolant Loop Delta-T v
i i
-1.0
?
SUM Trip Comparator LLC o
l h
Output monitored by j
RETRAM trip l
O
-l 1
-.f / -
c:
4-
\\
Figure 1-3 Loop Temperature Measurment Modelling Lumped Loop S!ngie Loop 15PUT INPUT INPUT INPUT Teold Thet Tcold Thot U
u LAC LAG LAG LAC RTD RESPCNSE T!NE 6 PHOCES$1NG DELAY TIME V
v y
OLT DLY DLY DLY INPUT INPUT INPUT INPOT CCNSTANT CONSTANT CONSTANT CONSTANT I
Apply measure uncerta U
u y
M
$UM W
SUM W
$0H 4
$UN I
I l
l INPUT INPUT INPUT INPUT CONSTANT CONSTANT CCNSTANT CONSTANT Process Scaling U
u SUN SOM M
SUM 4
$UM e
Loop temperature inputs to af and Tav. modelling
) b~
~
it I
i5 ro t
ta s
g n
n e
i l
p a
m c
o S
C e
s t
s n
e a
co n
r y
P D
ro a
d t
n s
d a
g n
r a
l e
a a
n p
T d
T m g
A o
i t
o v
P m
a O
a P
T c.
T p
l h
O A
M M
C p
M o i T
d U
A L
o i U
V t
r l
M U
S S
L t
r S
t U
e S
t tu T
t d
p u T p
A o
p n
T o
o n
T I
O L
I O
M t,
?
r a
T lo o
C a
0 d
t e
1 p
4l m
u d
e L
lo 1D t
o 2n T
M Ua M
v U
Pt U
S e&
Ns S
I no r
c ug gv ia F -
s T
ro I
d t
d n
a n
s p
a r
a l
a o
T p
g e
t A
m y
T d
o o
P o
a A
o T
T P
m h
O c
A M
O L
T M
G p
M M
U v
U v
U 4
L o
p U
S L
t i
o i t
r R
r S
t t
t t
t u
u T
n p
p T p
A o
n A
n T
a o
I T
I O
L O
l t
o na o
lo C
o C
0 e
1 l
g n
d l
i S
o t
o Tn T
g Ua v
g M
Pt s
U Ns S
I noc
)
[
t i
l
Ilesponse to Supptrnental Request f
for-Additional Information j
Iteview of YAEC 1854P i
1 3
Discuss in detail how the axial power distribution compensation is performed, RESPONSE TO ATTACHMENT QUESTION 3:
The OTAT trip setpoint equation is:
1+Ts 3
ATora=( K - K --- (T,,cT r) + Ks(P-P r) - F (AI) ] AT r i
2 o
a i
o 1 + t:5 where, K, K,, and K. are constant coeflicient settings; t and t, are the time constants of a Lead / Lag i
i controller which provides dynamic compensation of the trip setpoint; T.,is a constant reference average temperature; P ris a constant reference pressure; and AT ris the value ofindicated AT at hot o
o full power. The F (AI) function provides compensation of the OTAT setpoint for cycle-specific power i
distributions where the combination of the FJ and axial power shape are more limiting than those included in the set of reference power distributions used to derive the base OTAT trip. The setpoint is reduced by an amount equal to F (AI)
- ATo3 i
To determine the required F (AI) function, limiting flyspeck power distributions are identified from Po vs axial offset plots for each cotr.bination of control bank position and iniaal core power level.
Thermal Limit Lines (TLLs) are computed for each limiting power distribution. The TLLs are then compared to tha OPAT trip setpoint, the base OTAT trip setpoint, and the MSSV limit line to determine if the thermallimit for any power distribution would be reached prior to reaching either trip setpoint or the physicallimit on achievable plant conditions represented by the MSSV limit line. l l
e m
i Itesponse to Supplmental Itequest for Additional Information Review of YAEC 1854P Compensation of the base OTAT setpoint is required in the situation where any portion of a TLL for a particular power distribution is mero limiting (e.g. more restrictive in AT versua T,.yo space) than both the OPAT trip and the base OTAT trip at a physically achievable plant condition (e.g. the AISSV limitline is not crossed). Figure 3-1 provides an example of such a case. No compensation is required in the case where all the TLLs for a particular power distribution are less limiting than either the OPAT trip setpoint, or the base OTAT setpoint, over the range of physically achievable plant conditions (e.g. the region to the left of the MSSV limit line on a plot of AT versus Tavo). Figure 3-2 provides an example of this situation.
When the need for compensation is indicated, the amount of compensation required is determined by computing the value of the difference between the AT from the TLL, ATu, and the value of the base OTAT trip setpoint, ATour, at the same pressure used to compute the TLL, and at the same value of T o. This difference is then normalized by ATazr, to obtain the required F function value.' The i
AV required compensation is determined over the full span of AI. The computed values for required F (AI) are accumulated on a single plot of F (AI) versus AI, as illustrated in the example plot of required Fi i
versus Al is provided in Figure 310 of the report. As noted on Figure 310, upper bounding line segments are then drawn to separately envelope the data for positive and negative values of AL The F (AI) function coeflicient settings are defined by the slopes and baseline intercepts of the bounding 3
line segments.
m,
m w.
O Figure 3-1 00 Base Overtemperature AT Trip Setpoint for pressure indicated tl%$
0'S 80 -
4 y
-o G,
w 7
9 6
e,y Y
70 -
Overpower AT Trip uno s,
g g
s s
's, 60 -
's i
's
's
's i
g
's i
's,
's t;
s,
\\
2400 PSIA 50 -
i, i,
\\.
i, g
i
' 2250 PStA s
40 -
i Thormal Umit Unos 2125 SIA for pressures Indicated i
30 -
^
Stoam Generator Safety Valvo Opons dne /
20 540 560 580 600 620 640 660 T (*F) 6l
e-Figure 3-2 i
90 j
Base Overtemperature AT Trip Setpoint i
for pressure indicated N
1 *3,
@_ k p$
p S
80 -
4 in in 7
9 9
70 -
Overpower AT Trip Une i,
i
\\.
i s
g
's, 60 -
\\
e
's i,
L F<-
i.
i.
s
's.
50 -
i 2400 PSIA
\\
\\.
' 2250 PSIA '
ThermalUmit unes 40 -
i 1
2125 'SIA for pressures indicated i
\\.
4 1960 SIA 30 Steam Generator Safety Valve Opens Line s
s s
n n
s 540 560 580 600 620 640 660 20 To(*F)
.