ML20213E963
| ML20213E963 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 11/10/1986 |
| From: | Whittier G Maine Yankee |
| To: | Thadani A Office of Nuclear Reactor Regulation |
| References | |
| GDW-86-267, MN-86-141, NUDOCS 8611130391 | |
| Download: ML20213E963 (17) | |
Text
m MAIRE HARHEE ATOMICPOWERCOMPARUe
,uavgr,Yl,*,Tg o",fe h
(207) 623-3521 e
November 10, 1986 MN-86-141 GDH-86-267 Director of Nuclear Reactor Regulation United States Nuclear Regulatory Commission Washington, D. C.
20555 Attention:
Mr. Ashok C. Thadani, Director PHR Project Directorate #8 Division of Licensing
References:
(a)
License No. DPR-36 (Docket No. 50-309)
(b)
MYAPCo Letter to USNRC dated September 15, 1986 (MN-86-ll8)
Subject:
Maine Yankee LOCA Analysis Gentlemen:
Representatives of Yankee Atomic Electric Company and Maine Yankee Atomic Power Company met with members of your staff on October 22, 1986 to provide additional information on the proposed method changes planned to regain the apparent lost margin reported in Reference (b). During that meeting, we described and provided a proposed schedule for a two phase program which involved the following elements:
Phase I -
Implementation of a more realistic delta P injection penalty for reflood.
Phase II -
Implementation of a revised steam cooling model.
He also described the method which would be used to select the limiting axial power shapes used in the LOCA analysis.
This letter provides (a) justification for a revised delta p injection penalty, and (b) a description of the method which will be used to select the limiting axial power shapes which we plan to use in Phases I and II. This l
information is being provided for your review and approval.
poh"iBBu Stha$r p'b e
i 8203L-GDH Rec)c) v[c+/ea f/
-oo
I
~
MAINE YANKEE ATOMIC POWER COMPONY United States Nuclear Regulatory Commission Page Two Attention: Mr. Ashok C. Thadani, Director MN-86-141 The proposed revised delta p penalty was described in detail during the meeting. He provided the results of the examination of the 1/14 and 1/3-scale steam-water interaction tests data which demonstrates that the pumped ECCS injection delta p penalty in Maine Yankee's reflood model can be reduced from 0.80 to 0.15 psid.
Such a change has been generically approved for Exxon LOCA models in 1979 and specifically approved for the Yankee plant LOCA model in 1985.
Further justification for this change is provided in Attachment A.
He also described the method which would be used to select the limiting axial power shapes used in the LOCA analysis. A discussion of the axial power shapes evaluated in the LOCA analysis is contained in Attachment B.
The attachment is formatted as a revised Section 3.4.5 of the FSAR, which discusses power distributions.
The section has been expanded to discuss power distribution monitoring and the radial and axial power distributions used in nuclear design.
The method is identical to that described to your staff during the meeting.
He request your review and approval of the revised delta p injection penalty and the method employed to select the limiting axial power shapes.
Your approval by mid-December is desirable since, as we discussed at the October 22, 1986 meeting, we plan to use them for the Cycle 10 LOCA an<'3 sis.
The results of this analysis will be provided in the Cycle 10 Core Performance Analysis Report which is scheduled to be submitted in mid January, 1987.
He currently plan to submit our proposed methods for the revised steam cooling model (Phase II) by February 1, 1987, as we discussed at the meeting.
This method change is desired to support operation during the second half of Cycle 10 (December 1, 1987).
An application fee of $150.00 is enclosed.
If you have any questions, please do not hesitate to call.
Very truly yours, MAINE YANKEE ATOMIC P0HER COMPANY
/
b
. Whittier, Manager Nuclear Engineering and Licensing GDH/bjp Attachments cc: Dr. Thomas E. Murley Mr. Pat Sears Mr. Cornelius F. Holden 8203L-GDH
V M AINE YANCIEE ATOMIC POWER COMPANV ATTACHMENT A JUSTIFICATION FOR A REVISED ECCS INJECTION DELTA P PENALTY DURING REFLOOD FOR MAINE YANKEE LOCA ANALYSIS I
INTRODUCTION Appendix K to 10 CFR 50 Requirement I.D.4 directs that the thermal-hydraulic interaction between steam and all Emergency Core Cooling (ECC) water shall be taken into account in calculating the core reflood rates.
For the calculation of reflood rates, the net effect of the interaction of ECC water with the steam can be represented by a pressure drop in the cold leg.
This pressure drop is superimposed upon the wall friction pressure drop and is termed as injection delta p penalty.
The currently approved ECCS Model(I) uses a delta p penalty of 1.5 psid during the accumulatory injection and 0.8 psid during the pumped ECCS injection period.
These two values were derived from the scarce data available at the time of model submittal (1979).
Because of the experimental evidence obtained since the approval of our model, the delta p penalty for the pumped ECCS injection can be changed to 0.15 psid. A justification for this change is given in the following paragraphs.
PROPOSED MODEL Since the delta p penalty model described in Reference (1) was approved, tests have been performed by EPRI to examine the effects of steam water interaction in PHR cold legs.
These tests were performed with 1/14 and 1/3 scale geometries and are described in References (2) and (3) respectively. A brief description of these tests and the results obtained from them is given in the following paragraphs.
In both series of tests, the cold leg was simulated by a horizontal pipe with an inlet chamber and an injection nozzle as shown in Figure 1.
The inlet flow chamber simulated a PWR pump, and the injection nozzle simulated a PHR ECCS injection nozzle. The instrumentation shown in Figure 1 is representative of the 1/14 scale tests, however, the configuration for 1/3 scale tests was approximately the same.
For each test, steam was directed from the inlet chamber into the cold leg where subcooled water was injected from the nozzle.
the pressure drops along the length of the cold leg were measured as the required data.
The measured pressure drop included the frictional loss as well as the impact of ECCS injection.
Exxon Nuclear Company has calculated the injection delta p by approximately removing the wall frictional losses.(4) Their results are shown in Figure 2, where injection delta p for all pumped ECC data is reported as a function of steam dynamic head at the inlet to the cold leg pipe.
The results in Figure 2 show that the delta p penalty can be bounded by 0.15 psid. Only one point out of 131 was above the 0.15 psid bound, the duplicate run for this point yielded a delta p penalty of 0.06 psid.
8203L-GDH
f MAINE YANKEE ATOMIC POWER COMPANY APPLICABILITY OF EPRI RESULTS TO MAINE YANKEE PLANT The range of parameters for the two series of tests is given in the first two columns of Table 1.
The last column of Table 1 lists the values of these parameters calculated for Maine Yankee. As shown in this table, all of the Maine Yankee parameters are within the range of test conditions.
Hence, the model derived from the experiments is directly applicable to Maine Yankee.
SUMMARY
AND CONCLUSION It is proposed that the current delta p penalty of 0.8 psid during pumped ECCS flow be replaced by a delta p penalty of 0.15 psid.
The use of the proposed delta p penalty is based on applicable experimental data and is, therefore, in compliance with Appendix K Requirement I.D.4.
REFERENCES 1.
XN-75-41 Supplement 5, Revision 1, " Exxon Nuclear Company HREM-Based Generic PHR ECCS Evaluation Model", October 3, 1975.
2.
" Mixing of Emergency Core Cooling Hater With Steam:
1/14 Scale Testing Phase", EPRI-294-2, Key Phase Report, January, 1975.
3.
" Mixing of Emergency Core Cooling Hater with Steam:
1/3 Scale Test and Summary" EPRI-294-2, Final Report, June, 1975.
4.
XN-NF-78-30, " Exxon Nuclear Company HREN-Based Generic PHR ECCS Evaluation Model Update, ENC-HREM-ITA", May, 1979.
8203L-G0H
(
MAINE YANKEE ATOMIC POWER COMPANY TABLE 1 Test Parameters and Their Ranges 1/14 Scale 1/3 Scale Maine Parameter Test Ranae Test Rance Yankee Cold Leg Pressure (psia) 20, 40, 60 22, 50 37 Injection Water Velocity (ft/sec) 4, 8, 12 1-16 12.87 (pumped injection)-
Injection Angle 90, 45 90, 45 90 Steam Temperature (*F) 350, 550 Sat, 500 530 1
Injection Water Temperature 80, 120, 150 80, 120, 150 110
(*F)
Approximate Range of 0.1 to 0.65 0 to 0.35 0.2 to 0.4 2
Dynamic Head of Steam (PSI)
(From Fig.
(From Fig.
2 attached) 2 attached) i i
O s
e dV s
C O
i*
T 1
g f
(
6 g
0 e
9 n
O r
o T
i 9
E t
8 R
a 1
c W
o Sg L
P p
a M
T i
e n
sa*
r at 8 s u
g 0
s 0 08 9
s 8,
- g s
e a
e 0
t8 r
e*
n P
4t 1
_ =
eC et E d
e 5 J n
wP ss
=
O I
WI t a
2 I
ee*f es y
f 3 O(
r 3
e e t
r e
ammt e
f at s m
E e
'8 p
s et s
l i o
3 es$
e
., V i s s s
a G
e v n a NeeG E
l e -
W 0 Cs e
n S
a o
M nr%
i tc
- g C
e g
W S
S L
t F
s e
1
,O T
W f
Lt i
E tC 1
+
f e f d
=
ai e
LS r
- 3
~ -
W8 u
S e
g
- 6 SM e
i
+
F c.
4 3
- T D
4 k
- e r
f l3
/
i s
F
-s e
- s I
l i,
l
- i!i tl i ;i' j
1 I
I I
I i
..jg.
0.2 _
Upper Dound
=
m 3
0.1 a
e
=
o l
p
. + '
g
- s
=
0 c
~
.. =
o ga
+e g
" [*
a
="
"s o
=
3
-0.1
_=
= -
=
s
+
a a,
i
, :., =
l+
s w
E s
i A
a j
-0.2
- Duplicate Runs l
1/14 Scale Data 1/3 Scale Data t.
r
-0.3 I
I b
- e i
I i
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 2
pV s INLET STEAN DYNAMIC HEAD, 2g i
Figure 2.
Pressure Loss Due to Pumped Safety Injection
8 o
MAINE YANKEE ATOMIC POWER COMPANY ATTACHMENT B MAINE YANKEE PROPOSED FSAR SECTION 3.4.5 POWER DISTRIBUTIONS i
8203L-GDH
M AINE Y ANKEE ATOMIC POWER COMPM5Y 3.4.5 Power Distributions The power distribution in the core, and in particular the peak heat flux and enthalpy rise, is of major importance in determining core thermal margin. The full three-dimensional power distribution configurations of the core are a function of cycle burnup, power level, moderator temperature, CEA insertion, and xenon distribution. The effects of these independent variables on power distributions and the subsequent calculation of thermal limits are accounted for in the determination of Limiting Conditions for Operation (LCOs) and Limiting Safety System Settings (LSSSs) to assure that the Specified Acceptable Fuel Design Limits (SAFDLs) are not exceeded for the design basis events.
3.4.5.1 Power Distribution Monitorina The power distribution is monitored by both the incore nuclear instrumentation (Section 7.5.0 and the excore power range channel nuclear instrumentation (Sections 7.5.
- and 7.5.2.6).
The incore nuclear instrumentation provides measured flux c ta to generate three-dimensional power distributions by use of the INCA Program, which is described in Reference 50. The split excore power range detectors monitor the axial component of the power distribution and express it in terms of Symmetric Offset (S0).
The incore and excore detectors monitor the following parameters as LCOs:
TotalIntegratedRadialPeaking(Ff)
The unrodded, steady-state radial component of the power distribution is monitored by the incore detectors and compared to the limit, which is a function of cycle burnup.
The radial peaking limit, in conjunction with other LCOs and the Reactor Protection System (RPS) trips (Section 3.2.2.3),
assure that the SAFDLs are not exceeded.
Symmetric Offset (501 The symmetric offset is monitored by the excore detectors and compared to the limit, which is a function of core power level.
The symmetric offset limits, in conjunction with other LCOs and the RPS trips, assure that the SAFDLs are not exceeded.
Symmetric offset is both monitored as an LC0 and input to the RPS trips.
Linear Heat Generation Rate (LHGR)
The maximum local LHGR is monitored by the incore detectors and compared to the limit, which is a function of core height, cycle burnup, and fuel type.
Incore detector alarms are set based on the latest power distribution obtained from the incore analysis to provide a continuous monitoring capability.
The LHGR limits assure that the Loss-of-Coolant Accident (LOCA) analysis results are acceptable (Section 14.14).
8203L-GDH
MAINE YANKEE ATOMIC POWER COMPANY 3.4.5.2 Power Distributions for Nuclear Desian Radial r..id axial power distributions for nuclear design are provided each cycle for core thermal margin evaluations. Cycle burnup, power level, moderator temperature, CEA insertion, and xenon distribution are the independent variables which are evaluated due to their effect on core power distribution.
The nuclear design methods which generate these power distributions are discussed in Section 3.4.7.
3.4.5.2.1 Radial Power Distributions for Thermal Marain Evaluation The radial power distribution in the core is evaluated with core depletion for the current operating cycle in Appendix D.
The effects on the radial power distribution at beginning, middle, and end-of-cycle for the lead regulating group inserted are also provided in Appendix D.
Radial power distribution calculations are performed for all permissible at-power CEA configurations each cycle.
These calculations provide the radial components of the power distribution for s:/nthesis of the full three-dimensional power distribution in the RPS setpoint analysis, described in Reference 7, to assure maintenance of the SAFDLs discussed in Section 3.2.2.3.
The radial component of the power distribution is verified by the monitoring of the total integrated radial peaking as an LCO.
3.4.5.2.2 Radial Power Distributions for LOCA Evaluation
-The maximum allowable total integrated radial peak pin power during the cycle and the maximum assembly integrated radial power corresponding to the same time in life are used as input to the LOCA analysis. All uncertainties are applied to the radial components of the peaking. Maximizing the radial peaking component results in maximum integrated power and maximum enthalpy rise in the hot pin and assembly in the LOCA analysis, resulting in the most limiting allowable LHGR versus core height.
3.4.5.2.3 Ayial Power Distributions for Thermal Marain Evaluation The axial power distributions in the core are extensively evaluated each cycle as part of the RPS setpoint analysis described in Reference 7.
Three-dimensional xenon oscillation cases at beginning, middle, and end-of-cycle examine the effects of power level, moderator temperature, CEA insertion, and xenon distribution as independent variables affecting core power distribution.
These cases, synthesized with the radial peaking components, provide power distributions for evaluation of thermal margin as a function of core power and peripheral symmetric offset, as discussed in Section 3.2.2.3.
8203L-GDH
M AINE Y ANKEE ATOMIC POWER COMPANY o
4 3.4.5.2.4 Axial Power Distributions for LOCA Evaluation The axial power distribution evaluations for the RPS setpoint analysis cases are used to define an envelope which contains all near full-power axial shapes which are permitted within the positive symmetric offset LOO limits. This envelope is shown in Figure 3.4-6 to cover the Cycles 8, 9, and 10 envelopes of all permitted axial shapes from zero symmetric offset to the positive symmetric offset LCO. This envelope is one limit on the possible area for peaking of axial shapes for evaluation in the LOCA analysis in Section 14.14.
t The area for possible peak power shapes is illustrated in Figure 3.4-7 and is limited by both the LCOs due to the positive symmetric offset envelope (Figure 3.4-6) and the permissible LOCA LHGR limits versus core height. The LOCA LHGR limits are determined by varying the axial shapes and peaking factors until the Peak Clad Temperature (PCT) limit is reached at each of the selected core heights evaluated. The axial peaking factor is the only free variable provided to adjust the local LHGR at the peak location sinct the maximum integrated radial power with uncertainties is input in the LOCA analysis. This maximum integrated radial power is illustrated by the shaded area in Figure 3.4-7 and represents the total power which is redistributed axially within the defined area for allowable peak power shapes.
4 Four core heights are selected for LOCA evaluation of peak axial shapes, at approximately 52, 65, 73, and 85 percent of active core height.
The 52 percent elevation LHGR limit is applicable to the lower core heights.
The 85 percent elevation represents the maximum elevation of axial peaking near full power within the positive symmetric offset limits.
For each core height, two classes of axial shapes are examined.
Each class maximizes a characteristic which is detrimental to the LOCA analysis. The classes of axial shapes are illustrated in Figure 3.4-8.
Class l_- Maximum Intearated Power Up to Peak Power Location This class of axial shapes maximizes the enthalpy rise up to the axial peak location. This is most directly achieved by flattened, symmetric axial shapes which rise rapidly to the desired axial peak power and maintain the peak power up to the desired axial elevation (Figure 3.4-9).
These shapes are realistic and typical of fresh assemblies near middle-of-cycle.
Class 2 - Maximum Power From Peak Power to Peak Clad Temoerature (PCT)
Locations This class of axial shapes maximizes the power after the peak power location, up to the PCT location, which is typically above the peak power location. This is achieved by minimizing the power fall-off after the peak to the top of the core, keeping it parallel to the LOCA limit line while staying within the positive symmetric offset limit envelope (Figure 3.4-10).
These shapes are realistic and typical of xenon oscillation cases near middle-of-cycle.
8203L-GDH
^
MAINE YANKEE ATOMIC POWER COMPANY
. Examination of these two classes of axial shapes provides an evaluation of these key characteristics to identify the most limiting LOCA LHGR limit for each core elevation.
The typical axial shapes in Figures 3.4-9 and 3.4-10 are mathematically defined by combining straight-line segments and parabolas. Mathematically defined shapes are adjustable to achieve the desired axial peaking, core elevation of peak, and class characteristics.
Flattened symmetric, flattened top-peaked, and double-humped axial shapes are defined to represent the types of axial shapes present in the core. The particular axial peak and location defines what types of shapes are reasonable, based on an examination of axial shapes and envelopes from the RPS setpoint analysis.
The use of mathematically-defined axial shapes permits the design of realistic axial shapes with the desired characteristics to evaluate sensitivities within the constraints of existing LCOs.
REFERENCES 7.
YAEC-Il10, Maine Yankee Reactor Protection System Setooint Methodoloav, P. A. Bergeron, D. J. Denver, September 1976.
- 50. CENPD-145-P, INCA - Method of Analyzing Incore Detector Data in Power Reactors, T. G. Ober, H. B. Terney, G. H. Marks, April 1975.
8203L-G0W
MAINE YANKEE ENVELOPE OF AXIAL POWER SHAPES FOR NEAR UMmNG ASSEMBUES TOP PEAKED SHAPES FROM ZERO SYMMETRIC OFFSET TO POSITIVE SYMMETRIC OFFSET UMITS AT FULL POWER 1.6
~~~
,ge g~~e = 6 @ ~g%'ps, 1.5 -
{w 1.4 "
A d
1.3 -
3 1.2 -
/
a\\
1.1 H b
1.0 -
ej
\\
3
'6 o
i o
0.9 +
A o
\\
O_
1 o
\\
0 f
g\\
g 0.8 +
F 0.7 -
i a = CYCLE 8
^
= CYCLE 9 LU 0.6 -
'O o = CYCLE 10 e
o 0.5 +
A 0.4 -
0.3 -
23 0.2 "
i o
E O.1 -
0.0 1O 2O 3O
/0 SO 6O 7O dO 9O 100 g
PERCENT OF CORE HEIGHT s
L-tT 3800ld UNEAR HEAT GENERATION RATE (KW/FT) vetteey?ep499f?99990 o
[
%M('q j
i Ni!!!%lln
,!il A
5s o
O Og 5 g.
y 4
i i
8-B
,I 8
@l o
e
MAINE YANKEE CLASSES OF AXIAL POWER SHAPES FOR LOCA ANALYSIS 1.6 1.5-I l*4 "
CLASS 1 SHAPE CLASS 2 SHAPE MAXIMUM POWER MAXIMUM POWER 1.3 H UP TO PEAK FROM PEAK TO PCT LOCABONS LOCABONS 4
,a*,
-~~------------ -
1.2 -
i 1.1 -
/
Z
\\
Lu 1.0 PEAK
\\
3 LOCATION 2
08" f
\\,
W O.8 -
/
\\
l
\\
F 0.7 j
g 3
s W
0.6 -
/
\\
Z
/
LOCATIONS
\\
0.5 -
/
\\
/
\\,
0.4 -
0.3 -
21 0.2 +
o E
0.1 "
m 0.0 g
0 10 20 30 40 50 60 70 80 90 100
-4 i
PERCENT OF CORE HBGHT 00
3 MAINE YANKEE AREA OF POSSIBLE PEAK POWER SHAPES COMPARED TO CLASS 1 FLAT, SYMMETRIC POWER SHAPES 20 l9~
MAXIMUM POWER -
18-LOCA UMITS MAXIMUM POWER -
O (TYPICAL)
POSITIVE S.O. UMITS n-
's y
is-s M
15 -
\\
r/
w N
'4 ~
_ /7'/
A h m.
[
13-
,\\'-
z 12-
\\
O
$3_
~
Q 10-
\\
i b
g.
f 8-1 o
7-I Q
6-I 5-oc
]
4-5
)
N
_n O
2-T 1-O b
1O IO IO MD NO NO 7O N0 80 1d0 i
PERCENT OF CORE HEIGHT e
i
1 l
MAINE YANKEE AREA 0F POSSIBLE PEAK POWER SHAPES COMPARED TO CLASS 2 FLAT, TOP-PEAKED POWER SHAPES WITH HIGH POWER AFTER PEAK 20 I~
MAXIMUM POWER -
18-LOCA UMITS MAXIMUM POWER -
POSITIVE S.O. UMITS O
(TYPICAL) h 16-
- \\- - - - -/- - - -
'I s
q.
\\
15 -
/
~ Nh
\\
14-f
\\
[
13-Z 12-
\\
O gj_
- 10-l 9-i b
8-g O
7-I y
Q 6-I 5-Of
]
4-n 5
3-J O
2-C
- D 1-0 b
1O 2O 3O 4O 5O 6O 7O 8O 9O 1d0 o
1 PERCENT OF CORE HEIGHT O