ML20247B190
| ML20247B190 | |
| Person / Time | |
|---|---|
| Site: | Grand Gulf  |
| Issue date: | 11/30/1988 |
| From: | Nir I MSU SYSTEMS SERVICES, INC. |
| To: | |
| Shared Package | |
| ML20247B179 | List: |
| References | |
| NESDQ-88-003, NESDQ-88-003-R02, NESDQ-88-3, NESDQ-88-3-R2, NUDOCS 8907240063 | |
| Download: ML20247B190 (15) | |
Text
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NESDQ-88-003 Revision 0
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GRAND GULF NUCLEAR STATION UNIT 1 REVISED FLOW DEPENDENT THERMAL LIMITS O
Nuclear Engineering Services Department MSU Systems Services, Inc.
November 1988 0
8907240063 890630 PDR ADOCK 05000416 P
e NESDQ-88-003 Revision 0 7(
GRAND GULF NUCLEAR STATION UNIT I REVISED FLOW DEPENDENT THERMAL LIMITS l
Prepared by:
M ir/9/ pg O
I. Nir Date V
Lead Nuclear Engineer Plant Systems Analysis Section
/>
//!') ed Reviewed by:
r F. H. Smi T Date Lead Nuclear Engineer Reactor Physics Analysis Section Approved by:
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T. L. Temple /
Date Manager Plant Systems Analysis Section
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11 L--_-____-____--__
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I 1
TABLE OF CONTENTS
?
. Section P3agg 1.0
-Introduction......................................,,,,,,,,,,,,
3 2.0 Current MCPR and MAPFAC.....................................
I f
f 3.0 Revised MCPRf and MAPFAC.....................................
2 f
4.0 One-Loop Flow Runout Core Flows..............................,
4 5.0 References.........................................,,,,,,,,,,,
7 1
l.
1 F
iii
- .z
.t:
)
- '6.-
LIST OF TABLES-L-
. Tables
- ~
pg
' I.- Core Flows for the One-Loop Flow Runout Event...................
8 1j 2.
Revised Flow-Dependent Thermal Limits...........................
9
- )
1 I
LIST 0F FIGURES Figures Page 1.
Revised Flow-Dependent.MCPR Limit...............................
10 2.
Revised Flow-Dependent MAPFAC Limit.................
10
'3.
Flow-Dependent MCPR Limits Comparison...........................
11
- 4.
Flow-Dependent MAPFAC Limits Comparison.........................
11
-O
' O iv w
__,._____.____a_-___,-_-_x__-__----------_A
A--
1.0 Introduction j
n l
-Q This report documents the rationale for the revised MCPRf and MAPFACf i
thennal limits for Grand Gulf Nuclear Station Unit 1 (GGNS-1).
These revised limits incorporate:
a.
The GGNiel specific analysis results calculated by the Advanced Nuclear i
Fuels (ANF),instead of the BWR generic analysis results generated by General Electric (GE),
b.
The inherent design features of the Loop Manual mode of operation which preclude a two-loop flow runout event from being a credible event, and c.
The maximum achievable core flow rate without taking credit for the i
operator-controlled core flow limiter.
The revised MCPR and MAPFAC thermal limits were derived from GGNS-1 f
f specific analyses performed by ANF for Cycles 2 and 3 (References 1 and 2).
Additional conservatism were imposed on the revised MCPR limits as an I
f allowance for future cycles.
The probability of future changes in the MAPFACf curve is low since it was statistically established based on varied operating conditions.
Therefore, no additional margin of conserva-limits.
tism is necessary for the revist.d MAPFACf 2.0 Current MCPR and MAPFAC f
7 The MCPR and MAPFAC thermal limits protect the plant from exceeding the f
7 MCPR safety limit and the 120% overpower
- line, respectively, in the event the recirculation flow control valves inadvertently open (loop flow runout event).
The limiting event for all modes of operation is the two-loop runout event.
The current limits are dependent on the opera;or-m
- ~
contro17ed maximum core flow limiter which is set to either 102.5% or 107%
of rated flow.
The MCPR lfaits are based on a BWR/6 generic analysis 7
performed by GE for Cycle 1 and confirmed for Cycles 2 and 3 by 'ANF.
.The MAPFAC limits for ANF fuel are_ based on GGNS-1~ specific analy-f sis performed by ANF for Cycle 2 and confirmed for Cycle 3.
1 3.0 Revised MCPR and MAPFAC f
f The revised MCPR7 and MAPFAC7 limit curves are constructed to bound the GGNS-1 specific two-loop flow runout analyses results detemined by ANF for Cycles 2 and 3.
To eliminate the dependence on the operator-controlled maximum core flow limiter, the revised curves conservatively assume a maximum core flow of 110%, Which bounds the maximum flow achievable for the limiting flow runout event (Reference 3).
These curves, labeled "Non Loop O
a i
< r acra e a>>rac r
h ri e 2.
P ctiv ix.
f f
and are applicable to all flow control modes of operation (the term Non loop Manual is used to differentiate from the specific Loop Manual mode which is addressed separately below).
The revised MCPR curve incor-f porates the margin gain from the GGNS-1 specific analyses over the BWR generic GE analysis.
The Loop Manual mode is an operating mode tehich provides for independent manual control for each of the two recirculation flow control valves.
Credit is taken for the fact that a two-loop flow runout event is not
- redible in the Loop Manual mode.
In this mode, the flow control valves are controlled independently with no single failure or single operator action capable of inadvertently opening both valves simultaneously
^ (Reference 4).
- Yhus, in the Loop Manual mode, the limiting credible core 2-
y 7. '
e flow increase event is the one-loop flow-runout event.
Table 1 provides
/N-the initial and final core flows for the one-loop flow runout event.
The-Nd final core flows. are conservatively calculated to bound the maximum achievable
- core flow rates for the one-loop flow runout event (see 1
Section 4.0).
l Separate MCPR and MAPFAC limit:, applicable only when the plant is in the f
7 Loop Manual mode. are constructed based on ANF analyses results for Cycles 2 and 3 using the consenative flow rate increases of Table 1 for a one-loop flow runout event. These limits, labeled " Loop Manual", are shown on Figures 1 and 2 for MCPR and MAPFAC. respectively.
f f
A numerical tabulation of the Non Loop Manual and the Loop Manual MCPR f
q and MAPFAC revised limits is. provided in Table 2.
operating limit at rated power and flow (1.18) is. retained with the revised i
MCPR limits.
f The revised MCPR and MAPFAC limits are compared in Figures 3 and 4 to the f
f current GGNS-1 limits which were used during Cycles 2 and 3.
The re-vised MCPR limit for Non Loop 'danual operations is approximately equal or f
more limiting than the current 102.5 % maximum enre flow MCPR limit. The f
revised MAPFAC limit for Non loop Manual operations is more limiting than f
both the current 102.5% and 107.% maximum co' e flow MAPFAC limits.
The f
revised MCPR and MAPFAC limits for Loop Manual operations, as ex-f f
- pected, provide for operating flexibility as a result of the inherent design characteristics (i.e.,
independent control of the flow t.ontrol valves) of the Loop Manual operating mode. --- - --
l
'e 4.0 One-Looo-Flow Runout Core Flows During a one-loop flow runout event, a flow increase to maximum loop capacity occurs in one recirculation loop.
The flow increase is caused by the inadvertent opening of the recirculation flow control valve (FCV) to the full open position.
The position of the FCY in the other loop remains unchanged.
In order to evaluate the effect on the CPR and LHGR during a one-loop flow runout event, it is necessary to establish the maximum core flow increase (i.e., final core flow rate minus initial core flow rate) for different initial core flow rates.
The total core flow rate is equal to the sum of the individual loop flow rates (the loop flow is defined as the loop jet pump flow).
The loop flow rate is. regulated by the rectreulation FCV by adjusting the pressure drop across the loop.
Under symetric loop conditions (i.e., same flow rates in both loops) the FCV position can be directly correlated with the core flow rate.
For the limiting two-loop flow runout event, the maximum open FCV 4
position corresponds to a core flow rate that has been determined to be less than 110% of rated flow (Reference 3). The term " indicated loop flow" rate is defined as that loop flow rate which would result from a specific FCV position under symmetric loop conditions.
For asymmetric loop conditions, the FCV position does not uniquely determine the loop flow rate because the loop flow rate is also affected by the flow rate of the other loop.
Under asymmetric loop conditions the actual loop flow rate may be different from the indicated loop flow rate, and therefore, the actual core flow rate may r.at equal the sum of the O
4-
]
4 indicated loop flow rates.
For the limiting one-loop flow runout event, I
the affected loop FCV is opened to the maximum open position.
This position corresponds to the maximum indicated los flow rate.
The indicated loop flow rate of the other loop is unchanged since the FCV position remains the same.
l Under asymetric loop conditions following a one-loop runout event, the i
loop with the larger flow rate will have an actual flow rate higher than the indicated flow rate. This difference results because of the lower exit pressure exerted by the other loop in the lower plenum.
The loop with the smaller flow rate will have an actual flow rate lower than indicated as a result of the higher exit pressure exerted by the other loop.
Since the core flow rate is the sum of the actual loop flow rates, a relationship between the actual core flow rate (i.e., sum of the actual loon flow rates)
V to the inaicated core flow rate (i.e.,
sum of the indicated loop flow rates) is required in order to analyn the c e-loop flow unout event.
A conservative and simple relationship, applicable to all final core flow
- rates, is established by using the indicated core flow rate instead of tbr actual core flow rate.
This relationship is used in evaluating the core flow increase following a one-loop runout event.
This relationship is conservative (maximizes flow increase] since the indicated final core flow always bounds (i.e., is higher than or equal to) the actual core flow.
The difference between the indicated and actual core flow rates is zero for the symetric loop conditions and increases with an increasing degree of i
asymmetry.
This relationship has been demonstrated by a GGNS plant startup
(
test (one recirculation pump trip, Reference 5). This relationship is also E,, -
{
1 p-l e
supported by analysis using a computer model which has been validated 0
in t asas i ri a
- t <>t o
With 'the above relationship between the indicated loop and actual core flow-
- rates, the change in the core flow rate during a one-loop runout event can be bounded for any set of initial conditions. The following steps are used to establish a cortservative flow rate increase for the one-loop flow runout event:
a.
Assume an initial mismatch of 15 of rated flow between the two loops based on the GGNS Technical Specifications, Section 3.4.1.3 (I M was assumed for all initial core flows even though the Technical Specifica-tions limit the mismatch to 5% above 7M core flow).
b.
Assume that the loop with the lower initial flow rate will be the affected loop (maximizes flow increase).
c.
Assume a maximum indicated loop flow rate of 11 % of rated for the affected loop, following the runout event.
d.
Establish the final core flow rate as the sum of the individual indicated loop flow rates.
a.
Increase the final total core flow rate calculations (a 2.5% conservative bias in flow rate).
The individual core channel flow rates are not affected by unequal loop flow rates.
This is consistent with t-assumption of complete lower 1
plenum mixing which was employed by GE in their GGNS-1 single loop operation analysis and has been accepted by the NRC (Reference 6).
As
)
i q 1
1
lower plenum mixing is governed by vessel
- design, the validity of this assumption will not be affected by the insertion of ANF fuel bundles.
The one-loop runout event final flow rates for various initial flow rates analyzed are presented in Table 1.
These flow rates were calculated using the above five steps and represent a conservative upper bound to the actual flow rates ' expected following the one-loop runout event.
5.0 References 1.
" Grand Gulf Unit 1 Cycle 2 Reload Analysis", XK-NF-86-35, Rev.
3, Exxon Nuclear company, Inc., Richland, WA, August 1986.
2.
" Grand Gulf Unit Cycle 3 Reload Analysis". ANF-87-67 Rev.
1, Advanced Nuclear Fuels Corporation, Richland, WA, August 1987.
i 3.
Smith. A.
R.
(GE) to J.
G..Cesare (SERI), "GGNS Maximum Core Flow Capability",SEGE-87/125,11/87.
4.
NEDE-24011-P A-4US, Appendix 8.
O 5.
Kingsley, O.
D.
(SERI) to Grace, J. N. (NRC), " Final.Sumary Startup Test Report 12', AECM-8610066, 2/86.
6.
Kingsley, O.
D.
(SERI) to Denton, H. R. (NRC'), PCOL-86/05, AECM-86/0092, 3/86 ("GGNS Single Loop Operation Analysis",
GE, 2/86 attached). l
(
Table 1 Core Flows for the One-Loop Flow Runout Event Initial Core Final Core Flow Increase Flow (%)
Flow (%)
(5 of Rated) 100 110 10 90 105 15 80 100
'20 70 95 25 60 90 30 50 85 35 40 80 40 30 75 45 l 0
('
s.
ID.
(I Table 2 Revised Flow Dependent Thermal Limits Non Loop Loop Non Loop Loop Core Manual Manual Manual Manual Flow (%)
MCPR MCPR MAPFAC MAPFAC f
f f
f 105 1.18 1.18 1.0 1.0 91.0 1.0 90 0.992 86.3 1.18 84.3 1.0 80 1.212 0.904 0.977 73.4 1.18 t
70 1.271 1.193 0.827 0.928 60 1.345 1.243 0.757 0.880 50 1.441 1.314 0.695 0.837 40 1.566 1.414 0.638 0.794 30 1.727 1.545 0.586 0.752' I
O
Un wy b ~
. FIGURE 1:'-
e
~
REVISED FLOW DEPENDENT MCPR LIMIT
.A
- j
- i.s0-l 70-
-+- NON LOOP M ANUAL-LOOP NANUAL 1;60-
' 1.~ 5 0 -
E1.40-M 1.30-1.20-1.10-1.00 i.
i 20 30 40 50 60 70 80 90 100 110
'120
' CORE FLOW (!)
FIGURE 2 REVISED FLOW DEPENDENT MAPEAC LIMIT 1.10 1.00-0.90-W to.s0-E 0.10-LOOP WANUAL 0.60-
-*- NON LOOP WANUAL O.50 i
20 30 40 50 80 70 80 to 100 110 120 CORE FLOW (!)
i O
c 1
FIGURE 3
' FLOW DEPENDENT MCPR LIMITS r.0MPARISON N
1.80 U.
1.70-
- - NON LOOP-WANUAL LOOP WANUAL 1.50-N N
-+- T/ S 10 7 N
1.50-s'Ns s
-+- T/ S 102. 5
$1.40-
'N N
N 1.20-N 1.20-7'-
1.10-1.00 i
i i
i i
i i
i i
20 30 40 50 50 70 80 90 100 110 120 CORE FLOW (1)
FIGURE 4 FLOW DEPENDENT MAPFAC LIMITS COMPARISON 1.10 1.00-
/ /
/,
0.90-l/
s's !
s u
$0.80-
,/,/
a
,r','s e
-+- NON LOOP WANUAL sj,I' 0 10" LOOP MANUAL
,-f,'
1/5107 0.80-r
-+- T/S 102.5 0.50 i
i i
i i
i i
20 30 40 50 60 70 80 90 100 110 120 CORE FLOW (!)