ML20093M905
| ML20093M905 | |
| Person / Time | |
|---|---|
| Site: | Byron, Braidwood, 05000000 |
| Issue date: | 10/15/1984 |
| From: | Tramm T COMMONWEALTH EDISON CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| 9305N, NUDOCS 8410230365 | |
| Download: ML20093M905 (16) | |
Text
,_
m-c.$,-
~
' f,.,N), Commonwealth Edison T f ;,,,
(
One First National Plazt Chicigo, Illinois F. :c r- =:
^; ~ 7 Addr;ss FLply to: Post Offica Box 767 N j' Chicago, Illinois 60690 October 15, 1984
.Mr.= Harold R. Denton, Director Office:;of Nuclear Reactor Regulation
~U.S.. Nuclear Regulatory Commission Washington, DC-20555 Sub ject:
Byron-' Generating-Station Units 1 and 2 Braidwood Generating Station Units 1 and 2 Inadequate Core Cooling-NRC Docket Nos. 50-454/455 and 50-456/457
Dear Denton:
'This letter provides updated information regarding the instrumen-tation'for the detection of inadequate core cooling at the Byron and Braidwood stations.
NRC review of this information is necessary to close Outstanding Item 9 of. the Byron SER.
_ Enclosed with this letter are-revised pages for section E.31 of the Appendix E.to Byron /Braidwood FSAR.
These pages have been updated'to correctly descriae the instrumentation for the detection of inadequate core cooling.
They will be incorporated into the FSAR in the next amendment.-
One signed original and fif teen copies of this letter and the enclosure are provided for.NRC review.
Very truly yours, W
t T. R. Tramm Nuclear Licensing Administrator 1m Enclosure 8410230365 041015 PDR ADOCK 05000 E
\\
9305N
1 B/B-FSAR BYRON /BRAIDWOOD STATIONS - UNITS 1 AND 2 INADEQUATE CORE COOLING DETECTION SYSTEM
SUMMARY
STATUS REPORT APRIL, 1982 Revised Oct. 84 9
0 e
9 m.
z.
B/B-FSAR TABLE OF CONTENTS l
Section Title ge,.
1.0 INTRODUCTION
E.31-p 1.1 Summary of Activities E.31-4 1.2 Basis for ICC Instrument Selection E.31-4 1.3 Description of Event Progression E. 31 -4 1.4 Summary of Sensor Evaluations E.31,8 2.0 SYSTEM FUNCTIONS DESCRIPTION E. 31-3 0 2.1 ' Subcooling and Saturation E.31-~10 2.2 Coolant Level Measurement in Reactor Vessel E.31-10 2.3 Fuel Cladding Heatup E. 31.11 3.0. SYSTEM DESIGN DESCRIPTION E.31-12 3.1 Sensors Design E. 31 -3 2 3.2 Signal-Processing and Display Equipment Denign E.31-19 4.0 SYSTEM VERIFICATION TESTING E.31-23 4.1 Pressure Sensors E.31-26 4.2 HJTC System Sensors and Processing E.31-26 4.3 Core Exit Thermocouples E.31-27
- 5. 0 SYSTEM QUALIFICATION E.31-28 6.0 OPERATING INSTRUCTIONS E. 31 -29 9
+
W E. 31-3
e
~~
^'
e.
B/B-FSAR 1.0 LINTRODUCTION 1.1 -
SUMMARY
OF ACTIVITIES This report responds to the requirements in Section II.F.2 of NUREC-07 37
.Ref.il).
The report describes.the status of design and development
(- activities being conducted by the C-E Owners Group as supplemented by plant specific ef forts by Commonwealth Edison' Company to define and implement a system of instrumentation to ho used to detect fundequate core cooling (ICC). The freport also provides information specirle to
. Byron /Braidwood Units 1 and 2 in order to demonstrate the applicability of the' generic activity to Byron /Braidwood Units 1 and 2.
'Results of initial studies by the.C-E Owners Gruup are documented in reports CEN-117 (Ref. 2) and CEN-125 (Ref. 3).
All studies have been based-on the requirement to indicate the approach to, the existence of, Jand the recovery from ICC.
The ICC system selected was specifically based on the results presented in CEN-185'(Reference 5).
The basis for the instruments selected is summarized
-below.
1.2 BASES FOR'TCC INSTRUMENT SEI.ECTION The ICC ' instrumentation sensor package described herein is designed to:
- 1) - provide the' operator'with an advanced wa rning of the approach to ICC cover the full range of ICC from normal operation to complete cure
- 2). uncovery.-
The ICC detection system that employs this sensor package and displays, trends and logs the sensor outputs, enabling the. reactor operator to monitor system conditions associated with tne approach to and tne recovery from Icr..
1.3.'
DESCRIPTION OF ICC EVENT PROGRESSION The~ instrument sensor package for ICC detection provides the reactor oper ator a continuous indication of the thermal-hydraulic state within the Reactor Pressure Vessel (RPV) during'the progression of an event Icading to'and away from ICC. The progression towards and away from ICC can be divided into intervals based on physicalfprocesses occurring within the RPV.
These are characterized as-follows:
Ur e
4
\\
0
7-e
~
t B/B-FSAR l'l Intervals Associated with the Approach to ICC Interval l' Loss of fluid subcooling prior to the first occurrence of sat ura-tion conditions in the coolant.
Interval 2 Decreasing coolant inventory within the upper plentuh, ( t rom t he top of the vessel to the top of the active fuel).
Interval 3 Increasing core exit temperature produced by uncovery of the core resulting from the drop in level of the mixture of vapor bubbles and liquid below the top of the active fuel.
Intervals Associated with Recovery f rom ICC Interval 4a-Decreasing core exit temperature resulting from the rising of the mixture level within the core.
-Interval 4b Increasing inventory above the fuel.
Interval 4e Establishment of saturation conditions followed by an increase in fluid subcooling.
These intervals encompass all possible coolant states associated with any ICC event progression. Intervals 1 t!iru 3 refer to fluid situations that occur.during the approach to ICC.
Intervals 4a, 4b and 4e refer to fluid situations which occur during the recovery from ICC.
In order to provide indication. during the entire progression of an event, an ICC instrument system should consist of instruments which provide at least one appropriate indicator for each of the physical intervals described above.
Applying this description of the " approach to", and " recovery from" TCC to ICC instrument selection:
- 1) provides assurance t, hat the selected ICC system detects the entire progression.
2) demonstrates the extent of instrument diversity or redundancy which is possible with the available instruments.
.t.
Furthermore, by' defining the ICC progression on a physical basis the general labels of 'hpproach to", and " recovery f rom" ICC can now be associdted wi t h specific physically measurable processes.
(See Section 1.3.1 and 1. 3. 3)
\\
The inadequate core cooling instrument sensor package consists of (1) Reactor coolant system wide range pressure -sensers, (2) reactor vessel level monitors employing the HJ1C concept and (3) core ext t 1thermo-couples.
The signals -from the temperature and pressure sensors can he en.him-1 to indicate the loss of subcooling and occurrence of anturation (interval 1) and the achievement of a subcooled condition following core recovery (Interval 4c).
The reactor vessel level monitors provide information to the k
g- -
~2
'f*:
~
B/B-FSAR b
operator on the decreasing liquid inventory in the reactor pressure vessel I'
)T
.y (RPV) : regions above the fuel alignment plate, as well as the increasf ag HPV
' liquid inventory above the fuel alignment plate following core recovery (Interval 2 and 4b). The core exit thermocouples (CETs) monitor the increasing steam temperatures associated with core uncovery and the decreasing
. steam temperatures associated with core recovery (Interval 3 and 4a).
1.3.1 Advanced Warning Of The Approach To ICC The ICC ~ instrumentation provides the operator with an advanced warning of the approach.to ICC by providing indications of:
- 1) : the loss of subcooling.and occurrence of saturation (Interval 1) with a
-subC00 ling meter receiving input from primary systen temperature and pressure sensors.
h' '3 l2)' the loss of inventory in the RPV (Interval 2) with the RVLMS.
!3) the. increasing core coolant exit temperature (Interval 3 ) 'with CETs.
It should be noted that the RVLMS_ measures inventory (collapsed 11guld level) rather than tva-phase level. This measurement provides the operator with an
- f advanced indication of the coolant level should conditions arise to cause the two-phase froth to collapse via system overpressurization, or the losn of operating reactor coolant pumps.
1.3.2 Application Of The ICC Detection Ins truments h:
j Following an. event. leading to. ICC the ICC detection instruments will provide D
information to the reactor operator so that he may:
/
7 p.-
- 1) verify that the core heat removal safety function is being met.
- 2) establish the potential for fission product release.
.n ICC instrumsntation indications will be used to support the operator in helping to verify that the core heat removal safety function is.being met.
ICC instrumer.tation indications available to the operator are (1) a decreasinn core exit steam superheat, (2) an increasing Inventory above the fuel nlignment plate or (3) an increasingLsubcooling in the RPV or RCS piping.
The operator is informed about the progressica of an event by both static anet trend-displays. 'The trending of ICC information enables the operator to
- quickly assess the success of autopstically or manually perfonned mit igat inn
- actions. A chart indicating the ICC instrumentation trending during the variou's ICC progression intervals associated with the approach to and recover.-
-fron ICC is presented in Tdble 1-1.
1
na
'I.
. APPROACHING AN ICC. CONDITION
~
SUBCOOLING MEA-WATER INVENTORY MEA-COOLANT SUPERHEAT INTERVAL SURED BY SMM
.SURED. B7 I!JTC PROBE -
MEASURED BY CET 1
DECREASING CONSTANT
{ CONSTANT 2
CONSTANT '
DECREASING
' CONSTANT 3
CONSTANT CONSTANT NCREASING N.
M II.
RECEDING.FROM AN ICC CONDITION 4
w~
m b
.SUBCOOLING MEA-WATER INVENTORY MEA-COOLANT SUPERHEAT INTERVAL SURED BY SHM SURED BY !!JTC PROBE MEASURED BY-CET 4a CONSTANT CONSTANT DECREASING 4b CONSTANT INC REASING CONSTANT 4c INCREASING CONSTANT CONSTANT If l
o
-=
I
I I
- +
B/B-FSAR
- 1. 3. 3 INSTRUMENT RANCE
' In the ICC instrumentation sensor package saturation temperature and water inventory are used as indicators for the approach to and recovery f rom 'ICC when there is water inventory above the fuel alignment plate.
These measure-ments characterize, Intervals 1, 2, 4b and 4e of the ICC progression.
When the_two-phase, level is below the fuel alignment plate, of core exit fluid temperature represents a direct the-measurement indication of the approach to, and recovery f rom ICC (Intervals 3 and 4a). Therefore, the ICC sensor package is sufficient to provide information to the reactor operator on the entire progression of-an event with the potential of resulting in ICC.
1.4 _
SUMMARY
OF SENSOR EVALUATIONS
-Several sensors have been evaluated for use in an ICC Deteet ton Synt em.
Significant conclusions about each instrument are given below.
1.4.1 Subcooled Margin Monitor A subcooled Margin Monitor (SMM), using inputs from existing Resistance Temperature Detectors (RTD) in the hot and cold Icgs and from the Reactor Coolant System pressure sensors, is adequate to detect the initial
- occurrence of saturation during LOCA events and during loss of heat sink events.
However, the usefulness of the SMM can be significantly increased by using the, signals from the fluid temperature measurements from the HJTCS and the signals from selected. core exit thermocouples and by modifying the SMM to calculate and display. degrees superheat (up to about 1800'F) in addition _to degrees subcooling. The signals from the HJTCS temperature measurements provide information about possible local dif ferencer, in t emperat ure bet w.. n the reactor vessel upper-head / upper plenum (locatinn of the H.!TCS) and the-hot or cold legs (location of the wide range RTDs).
The core exit thermo-couples respond to the coolant temperature at the core exit and their signal indicates superheat af ter the coolant level drops below the top of the core and, thus, provide an approximate indication of the ' depth of core uncovery.
9
,~,,-
n="-
r B/B-FSAR With this. implementation, the SMM can be used for detection of the approach to ICC, namely Interval 1 (loss of subcooling), Interval 3 (core uncovery),
~
Interval 4b (core recovery) and Interval 4c (establishment of saturation conditions). Even with the modifications, the SMM will not be capable of indicating the existence of Interval 2 when the coolant is at saturation conditions and the level is between the top of the vessel and the top of the core.
The recovery. interval may occur at low system pressure and temperature.
Since the errors in the existing SMM calculations increase with lower temperature and pressure, required subcooling margins need to be revised for this situation.
1.4.2 - Resistance Temperature Detectors (RTD) g 1Rie RTD are adequate for sensing the initial occurrence of saturation.
Narrow range RTD are located in the hot and cold leg manifolds and the
' vide range RTD are located in the hot and cold legs of the reactor coolant piping..Either-of-the narrow or wide range RTD are sufficient to sense saturation for events initiated at power. The wide range RTD are suf fielent to sense saturation for events initiated f rom zero power or shutdown conditions.
The RTD range is not adequate DTn ICC indications during core uncovery.
For depressurization LOCA events, the core may uncover at low pressure, when-the saturation temperature is below the lower limit of the RTD.
-Initial superheat of the steam will therefore not be detected by the RTI).
As the uncovery proceeds, the superheated steam temperature may quickly exceed the upper limit of the RTD range.
In order to be useful during the Ecore uncovery interval, the range of RID would have to be increased to cover a temperature range from 100*F to 1800*F.
1.4.3 Heated Junction Thermocouple System (H.ITCS)
- The 'HJTCS is being designed 'to -show the liquid inventory of the mixture of liquid and vapor coolaht,above the core.
It is an instrument which shoe.
the approach to ICC and is the only one which functions in Interval 2, namely the period from the initial occurrence of saturation conditions unt il the start of core uncovery and Interval 4b, the period when inventory is increasing above thcl fuel alignment plate.
1.4.4
The core exit thermocouples are adequate to show the approach to ICC af ter core uncovery for the events analyzed, provided that the signal processing and display does not-add substantial time delay to the thermal delay at
?
w 0
B/B-FSAR the thermocouple junction. As mentioned above, the core exit thermo-couples respond to the coolant temperature at the core exit and indicate
-superheat af ter the core is no longer completely covered by coolant.
Except for a time delay, depending on event, the trend of the change in superheat corresponds.to the trend of core uncovery as well as to the accompanying. trend of the change in cladding temperature.
2.0; SYSTEM FUNCTIONAL DESCRIPTION In the following sections a functional description of the instruments of the ICC Detection System is given and the function of the instruments is related to the ICC intervals which were described in Section 1.0.
2.1 ~SUBC00 LING'AND 3ATURATION
~
T' 'he parameters measured to detect subcooling and saturation are the RCS coolant temperature and pressure.
The measurement range extends from the shutdown cooling conditions up to saturation conditions at the pressurizer safety valve setpoint. The response time needs to be such
-that the operator obtains adequate information during those events which proceed slowly enough for him to observe and to act upon the informat lon.
The information which'is derived from the reactor vessel temperature and pressure measurements is the amount of subcooling during the initial approach to saturation conditions and the occurrence of saturation during Interval one..During Interval four, the reestablishment of suh-cooled conditions is obtained.
2.2 COOLANT LEVEL MEASURDfENT IN REACTOR VESSI:L The Reactor Coolant System is at saturation conditions until sufficient coolant is lost to lower the two-phase level to the top of the active During this interval there are no existing instruments which would core.
measure directly the coolant inventory loss. A Reactor Vessel Level Monitoring System provides a direct measurement during this period. 1he parameter which is medsured is the collapsed liquid level above t he fuel alignment plate. The collapsed level represents the arount of liquid mass which is in the reactor vessel above the core. Measurement nf the collapsed water level was selected in preference to measuring two-phase level, bec.iune
. it is a direct indication of the water inventory while the two phase level is determined by water inventory and void fraction.
The' collapsed level is obtained over the same temperature and pressure range as the saturation measurements, thereby encompassing all operating and accident conditions where it must function. Also, it is intended to f unction during Interval four, the recovery interval. Therefore, it mu..
f survive the high steam temperature which may occur during the preceding core uncovery interval.
{
E.31-10 n
V-a
-B/B-FSAR The level range extends from the top of the vessel down to the top of the
-fuel alignment plate. The response time is short enough to track the
-level ;during small break LOCA events. "The resolution is sufficient to show the initial' level drop, the key locations near the hot Icg elevat ion
,and the lowest-Icvels just above. the alignment plate. This provides the operator with adequate indication to track the progression during Intervals' two and four and to detect the consequences of his mitigating actions or the functionability of automatic equipment.
-2.3.
-FUEL CTADDING HEATUP The overall _ int.ent of -ICC detection is understood to be the detection of the potential for fission product release from the reactor fuel. The parameter which is most directly related to the potential for fisulon product release is the cladding temperature rather than
- he uncover y or the core by coolant.
~ Since clad temperature is not directly measured, a pars.neter to which cladding temperature may be related is measured. This parameter is the fluid temperature at the core exit. After the core becomes uncovered, the fluid leaving.the core is superheated steam and the amount of super -
heat is related to the fuel length exposed and to the cladding temperature.
The ' amount of superheat -of the steam 1 caving the core will be measured by the core exit thermocouples. The time behavior of the superheat tempera-ture is, with the-exception of an acceptably small time delay, similar to the tine behavior of the cladding temperature. Thus, from the observaticu of the steam superheat, the behavior of the cladding temperature can be
. inferred. - Observation of the cladding tenperature trends during an accident is considered to be of more value to the operator than information on the absolute value of the cladding temperature.
The core exit steam temperature is measured with the thermocouples located at an elevation a few inches above the fuel alignment plate. Gener t e calculations of a similar installation for representative uncovery events show that the thermocouples respond suf ficiently fast to the increasin ;
steam temperature.
Tim required temperature range of the thermocouples extends frem the lowest saturation temperature at which uncovery may occur up to the maximum core average exit temperature which occurs when the peak clad temperature reaches 2200*F. The required thermocouple range is therefore
- 200*F to about 1800'F, which is the approximate upper service temperature limit. Thermocouples are expected to function with reduced accuracy at even higher temperatures, so the range for processing the thermocouple
/,
outpu.t extends to about 2300*F.
t
z.
=
B/B-rSAR 3.0 SYSTEM DESIGH DESCRIPTION The following sensors have been selected as the basic instruments to meet the functional requirements described in section 2.
l'.
The subcooled margin monitor (SMM) (Reference 1)
~
2.
The heated junction thermocouple (HJTC) system (Reference 2) and 3.
The core exit thereocouple (CET) system.
The conceptual design of each ICC instrument is desc'ribed in this section which addresses:
-1.
Sensors design-
- 2. ~ Signal processing and display design Figure 3-1 is the functional diagram for the ICC instrument systems.
The HJTC and CET instrument systems consist of two safety grade channels from
~
sensors through signal processing equipment. The outputs of processing equipment systems feeding the primary display are isolated to separate safety grade and non-safety grade systems. Channelized safety grade bach-up displays are included for the two instrument systems.
The SMM instrument system consists of various sensor inputs to the process computcr.
The generation and Jisplay of SMM is donc by the process computer and is non-safety grade. The following sections present details of the design.
3.1 SENSORS DESIGN 3.1.1 - Subcooled Marnin Monitoring Svstem The subcooled margin Sonitor design configuration being implemented is detailed in Section 3.2.4.1.
The sensor inputs to the SMM are:.
Input Range Reactor Coolant Loop Pressure (Wide Range, RC Hot Legs A & C) 0-3000 psig Average of the 10 highest CET 200-2300 F
i\\\\l
{
T w33$m t3 d Y<
l E
g8338u RB OO SR NP)
B E
E Y
B)
SPS L
O2 LS E
R(
CPA N
P T
A N
Y JO A
B A
CS H(
L H
TS
'L L
E C
JA N
E E
N I
I N
N N
N N
A A
A lC T
l C
H H
C C
J N
O I
I I
C T
x A
T T
T t
V
)
E E
J M.
t
,"6 s
C C
E
< i r
x L
o x
E s
r n
7 x
ER L
e x
(
a f L
s 6
n.x V
O E
S x
C S
x S
2 x
E i
h c
x R
L f
O C
T R
\\ #
C P
AE S
R Y
)
A O
5 L
6 NP P)
(
5 OS T(
II E
T TD C
E A
C TD)
NN2 EA 1
M F -
UGO3 RN TI 1 E SS R
NSTU IEE C CE T C
D NOil F ORS P
M P
IP(
U M
T P
U C,
CE L
N CS C
A I
R L
C P
P D
G
^
M S
,~
C E
S T
R R
S Z
Y O
R S
T C
P A
T E
N R
A LO B
A O
C G
G S
L S
R CR O
P TCAER B
A P
M P
U M
P U
P L
1 j
\\I l
0
7 e
e-h
'l g3y powg3 AUTILIART l MAIN TRAlif A ELECTRICAL I COWROL EQUIPMENT 8
]
IN ColGROL BOARD.
ROOM ROON e
LEVEL.luTC e
e putt (8) puTC/CET l
BACK.UP DISPEAT I
[
CHANNEL A i
l PROCESSOR e
I' (DICITAL)
I CASINET CET (33)
CHANNEL A l
8 8
I g
yggyggg ggg.cgy
,y gAcg.UP DISPLAT
- g l
CHANNEL A t
(DICITAL)
(
.IE/NON.!E ISotATION 4
10 TSC 1
s g
& E0P g
g PRIMARY DISPtAT a
I LEVEL.HJTC l
I e
TEMPERATURE.CET RCL(2)
IE/NON lf l
PROCESS a
P e
SUSC00 LED MARCIN Isot>T10N I
coppgTgg NOTE t l
8 u
l e
e 3
l l
l e
g g
l
~!
,~~
PRESS.RC WIDE RANCE 5.
...... 5 " FETE *.*P!.a, WTE 2
( A NA LOC) e 8
l T
T 8
i
~
~
o
~
g l
I I
- IE/NON.IE i '
l l
l ISOLATION g
Lgygl.guTC e
tWTC (8)
SAct.UP DISPLAT HJTt/CET PROCESSOR CHANNEL 8 e
CA8tNET CET (31)
CHANNEL S l
I g
1 l
TINPERAIURE.CET l
l g
)
8 BACK.UP DISPLAT l
ESP POWER l
CHANNEL 3 TRAIN B l
(DECITAL) g L.-.
FES:
1.
THREE MONITOR $ AND PRINTERS, COMPUTit ORIVEN.
NON. DEDICATED FVR OPTIONAL ICC DISPLAT SUPPORT.
ICC DETECTION INSTRUMENTATION 2.
SIX ANALOC INDICAICRS, De CONTINUOUS PEN RECORDERS SENSORS, PROCES$1NC AND btSPLAT LND ONE PON!1DR, COMPUTER DRIVEN, ION. DEDICATED ftR (SHEET 2 CP I)
LPTIONAL ICC DISPtAT SUPPORT.
PICURE 3 1 i
g
'*e.
O
T k
n.
.$~,
,{
l 3
B /B-FSAR.
L 3.1.2 Heated Junction Thermocouple (HJTC) System -
The HJTC system measures. reactor coolant liquid inventory _with discrete llJTC Jsensors located at dif ferent levcis within a separator tube ranging f rom the top of the core'to the reactor vessel head.
The basic principic of system operation is the detection of a temperature difference between 3
- adjacent heated and unheated thermocouples.
As ' pictured in' Figure 3-2, the HJTC sensor consists of a Chromel-Alumel
~
. thermocouple near. a heater. (or heated junction) and another Chromel-Alumel
- thermocouple positioned away from the heater (or unheated junction).
In a fluid with relatively. good heat transfer properties, - the temperature dif-
. ference between the adjacent ' thermocouples is very small. In a fluid with relatively poor-heat _ transfer properties, the temperature dif ference between-the thermocouples is large.
Two design features ensure proper operation under all' thermal-hydraulle conditions. First, each HJTC~is. shielded to avoid overcooling due to
. direct water contact during two phase fluid conditions..The HJTC with the~ splash shield is referred ' to as the HJTC sensor (Sec Figure 3-2).
iSecond, a string of HJTC sensors is enclosed in a tube that separates the s
liquid and gas phases that surround it.
,v The separator tube creates a collnpsed liquid Icvel that the II.lTC sennor';
measure. This collapsed liquid Icvel is directly related to the averiw,"
liquid fraction of the fluid in the reactor head volume above the f uel alignment plate. This mode of direct in-vessel sensing reduces spurious L_
. effects due to pressure, fluid properties, and non-homogeneitics of the fluid medium. The string of HJTC sensors and the separator tube is L
e
[
referred to as the HJTC instrument.
F F
The HJTC System is composed of two channels of HJTC instruments.
Each IIJTC instrument is manufactured into a probe assembly.
The probe assembly in-cludes eight (8) HJTC sensors, a seal plug, and electrical connectors (Figure ' 3-3). The eight (8) HJTC sensors are electrically independent and r.
located at eight levels. from the reactor vessel head to the fuel alignment plate.
~
JThe probe assembly is housed in a stainicss stec] structure that protects the sensors ' from flow loads and serves as the guide path for the sensor:.
Figure 3-4 describes tho' locations of the lIJTC prohc assemh1les.
Innta!!a-
- tion arrangements have been. developed for Byron /Braidwood Units 1 and 2.
-3.1.3 Core Exit Thermocouple (CET) System
+
The design of the Byron /Braidwood Units 1 and 2 in-core instrumentation h
(ICT) nystem 'includen 65 Type K (Chromel-Alumel) thermocouplen. The t he rno -
couples are installed into guide tubes whleh penet rate t he reactor ve.iset head and terminate at the exit flow end of selected fuel assenbile<.
_n_
0
1 I
~
S Q.
Q h
i O
M m
l
',D I
L E
I H
S H
S A
LPS M
S IYA C
C L
C t
i D
D E
L T
E A
I I
M f
H M
g S
/
g 7
H S
a E
A
'~
N L
jA O
P Z
Tl S2 I
R
/ -
E C3 T
T A
JE E
HR e
H g#
l*
- G I
RF P
O S
]__
N E
S C
T J
H W1 M
N k
t N
O E I C T NA I
EC RO EL F
A C
E
/
R1 f
t l
j:
I!
i
)
%0 4
e
't g
t e
('
9
~
s 4
C3 m
W E"
Mut
-o z
>=
=
u i
e<a.
W e
M L,
(
b:
J b,
C O
l n, W
.I
- wa f* li *k b
e
- v. v, O V. V H<M H
U L2 O
- (. tc m w C b.
MM C
N H
Y=
I,f O
n-a D
Da b
a,J<
w
=
M g
E Q>uw I,a J
E=
2 E C O uy e'
.4 m 4M 5:! e aw
>= b W L.;
I
- i!
j
' b f**
/ Y)
/
9
\\
B/B-FSAR l
90' I
I i
i CONTR01. RVI) DI:! vt.
CET N0ZZLES (5)
MI'CIIAN !!;.'f OOOO p.
OOOO OO O
OO OO OO O
OOO O
s O
O o-OOOOOOO 180 O
OOO O
O O
OO O
OO OOOO d'
OOOOO o
G 1
LEVEL, f)l:TF.C10R PENETRATION 1.or:.\\ Tier:::
IN SPARI; Nuy.?.l.I's (2)
I' L
'~
HJTC HOLDER ASSEMBLY LOCATIONS REACTOR VESSEL Pl/sN
_A
1 s
'B/B-FSAR These core exit thermocouples (CET) monitor the temperature of the reactor coolant as it exits the fuel assemblies. The core locations of the thermo-
-couples are_shown in Figure 3-4A.
FSAR Subsection 4.4.6.1 and Section 7.7 describe the orcsont desien of the
, ~
CET system. The basic design of the CET system will not. change for the final ICC detection system; however, modifications will be performed to up-grade the CET to meet environmental qualification requirements.
(See Section 5.0).
' hhe CETs-have a usable temperature range from 200'F to up to 2300'F
' (reference 4) although accuracy is reduced at temperatures above 1800'F.
The signal processing and display for the CET portion of the ICC detection instrumentation is described in paragraph 3.2.4.3 below.
3.2 SIGNAL PROCESSING AND DISPLAY EQUIPMENT DESIGN The processing and display hardware depicted in Figure 3-1 includes two subsystems of hardware - a qualified, safety related subsystem of ICC inst rumentation and an unqualified, non-safety subsystem of ICC inst rumenta-
-tion.
The equipment subsystems process and display the ICC detection sensor inputs as well as sensor inputs to meet other NRC requirements. The back-up displays for reactor. level and core exit temperature are safety grade wh fit-the primary displays are non-safety grade. Human factors engineering reviews are applied to both types of display. The design objective for the equipment is to address the NUREG-0737, Item II.F.2.
3.2.1 Backup Displays As depicted in Figure,3-1, the backup displays for reactor Vessel level and core exit temperature sre driven by a two channel system. Both the ll3TC anel CET systems use microprocessor based designs for the signal processing function in conjunction with main control room indication, digital and analog, respectively. Each channel will accept and process ICC input signals, and provide outputs to the channel. related indicator and the plant process computer.
The backup displays are designed to give information to the operator in the remote chance that the primary display becomes inoperah16 and to confirm primary display information. Speci fic display descript funn for each ICC detection instrument are included in Section 3.2.4.
3.2.2 Primary Displays The primary displays for ICC detection are generated by the plant procesu computer using isolated outputs f rom the HJTC and CET processor cabinets
.and NSSS protection system cabinets (for reactor coolant system pressures).
The main control room primary displays for ICC detection are part of the SPDS A complete description of the SPDS is included in Section E.17 for NUREG-0737 Item I.D.2.
A description of specific ICC displays is included in Section 3.2.4.
m.;--
\\
B/B-FSAR O
O O
O O
O O
O O
O O
O O
O O
O O
O O
O O
O O
O O
O O
O O
O O
O O
O O
O O
O O
O O
O O
O O
O O
O O
O O
O O
O O
O O
O O
O O
O O
O O
O THERMOCOUPLE LOCATION CORE EXIT THERM 0 COUPLES CORE LOCATIONS FICURE 3-4A n
7-e.
t
~-
B/B-FSAR 3.2.3 Cabling Systems g
l'/
The'in-containment cabling system for the CETs and HJTCs uses environmentally
-qualified cabling and Class IE connectors.
Qualified containment penet rat Inns route 'the CET and HJTC signals through the containment wall to the aux 1]Iary building.'
Separation of the two CET/HJTC channels.is initiated below the. missile shield and mainta'ined to the signal processing equipment in accordance with the requirements of Regulatory Guide 1.75.
Section 5.0 discusses the
. qualification testing of the cabling.
The SMM inputs are routed from the sensors to the processing equipment via existing safety grade cabling and containment penetrations and signal isolation hardware.
3.2.4 Processing and Display Description The following sections describe the processing and display for each of the ICC detection instruments.
3.2.4.1 subcooled Margin Monitor The SMM functions performed by the process computer are as follows:
1.
Calculate the subcooled margin.
The saturation temperature is calculated from the average reactor coolant loop pressure input (wide range).
The saturation pressure is calculated from the average of tem hottest core exit thermocouples.
The temperature subcooled margin is the difference between the saturation temperature and the hottest temperature input noted above.
The pressure subcooled margin is the difference between saturation pressure and the average pressure input.
2.
Process all outputs for display.
The SMM processes the temperature and pressure inputs over the following CET temperatures from 200 to 2300 F, and reactor coolant loop-ranges:
pressure from 0 to 3000 psig.
The saturation temperature and pressure are calculated from a saturation curve and an interpolation routine.
d
?
"Q
, w B/B-FSAR The following information,is presented on the primary ' display:
1.
. Temperature margin to saturation 2.
Trends of pressure or temperature margin to saturation
~
Additional infomation regarding the primary display, safety parameter display system (SPDS) is included in Section E.17.
. Backup displays are not provided :for the SPMi however a procedure has been developed for operator use utilizing the safety grade backup instrumentation to determine subcooling margin.
~
3.2.4.2 _ Heated Junction Thermocouples - Reactor VesiE3 level The processing equipment for the HJTC Rcrforms the following functions:
1.
Determine if-liqu'id' inventory exists at the HJTC positions,
.The heated and unheated thermocouples in the HJTC are connected in e
such a way that absolute and differential temperature signals are available.
This is shown in Figure 3-5.
When water surrounds the thermocouples, their temperature and voltage output are approximate 1v equal..V(A-C) on Figure 3-5 is, therefore,' approximately zero.
In the absence of liquid, the thermocouple temperatures and output voltages become unequal,* causing V to rise.
of'the individual HJTC rises above(A-C)
When Vg.c) predetermined setpoint, liquid inventory does not exist at this HJTC position.
.2.
Process all nputs and calculated outputs for display.
3.
Provide an alarm output to the plant annunciator system.when any of the
'HJTC detects the absence of liquid level.
- 4. - Provide control of-heater power for proper HJTC output signal level.
Figure 3-6 shows a single channel design which includes the heater power controller, 5.=. ' Provide an input to the process computer for % liquid inventory level above the--
. fuel alignment plate.
This output is an isolated signal.
The following information is presented on the primary display:
1.
Liquid level inventory above the fuel alignment plate.
- 2.. Trends of liquid -level inventory.
.._.m.,,,_
,_..,,,m,_
.-...,_.,._,,_.,_m_..n._m,,,,_,,.,,,,,._,,,,_,_.-____m.___._,.,y,,._..
.o-
~
'b COPPER IMCT.NFL S
~ W h%~ +--- -
CHROMEL ALUMEL A
ALUMEL 3
CHROMEL COPPER
.W
- ,.'A..M a aCTU AL TEMPER ATURE, UNHEATED JUNCTION V (C.El = ACTUAL IHMER ATURE. HEATED JUNCTION V i4 i- : lE FE RfMTIAL (E"PERATURE e
e D
i
', t w
e
,, - - - -., - - -. ~, - -,,
,,.r.___.,
C SENSOR 1 TH F.%'G H SIGNAL PROCESSOR
~ '
U II3U N #
C LOGIC AND CHANNEL BACKUP CONTROLS OlSPLAY
- ALARM FCWER FO'uE R CCNTROL UlGNAL o
HEAT POWER CONTROLLER' 4P
?
i o
j P0'NERTO HEATERS I
l
,e.
/,
I
[
HJTC SYSTEM PROCESS NG CONF!OURATION j
(CNE CHANNEL SHOWN) i FIGURE 3 6 t
i o
Yi~
7.:
' ~ ;. -
- t
- .7 ;, -
B/B-FSAR Additiona1'information regarding the primary display, safety parameter display system (SPDS) is included in Section E.17.
The following information'is presented on the backup 11JTC display:
'1.
% liquid inventory level above the fuel alignment plate derived from the eight discrete HJTC positions.
Unheated junction temperature at eight positions.
- 2. z.
- 3. - ' Heated j unction _ temperature at cight positons.
3.2.4.3 Core Exit Thermocouple System The processing equipment for the CET will perform the.following functions:
1.
Process all core exit thermocouple inputs. Processing of 33 CET inputn
.will be performed by Channel A and 32 CET inputs by Channel B. to the back up displays.
2.
Calculate the average of the ten highest reading CET for display on backup display.
3.
Provide data link outputs to the process computer for all 65 therreo-
. couple inputs. These outputs are. isolated signals.
These functions are intended to meet the design requirements of NUREr.-0737',
II.F.2 Attachment 1.
The following information is represented on the primary display.
~1. ' A 'spacially oriented core map inuicating the temperature at each of the CET locations.
2.
A core exit temperature representative of the CET inputs.
3.
Trends of core exit temperature.
Additional information regarding the primary display, safety parameter
' display system (SPDS) can be found in Section E.17.
The following information is availabic on the backup dispinys:
1.
Selectable temperatures of 6 core exit thernoccupies, 33 on Channel A and 32 on Channel'B.
4.0 SYSTEM VERIFILATION TESTING This section describes tests and operational experience with ICC Just runwor e.
5
7-4
~~
B/B FSAR 4.1 PRESSURE SENSORS The wide range Reactor Coolant Sys.
pressure sensors are standard NSSS instruments which have well known responses. No special verification tests have been-performed nor are planned for the future.
These sensors provide basic, pressure inputs which are considered adequate for use in the SMH and other additional display functions.
4 4.2 HJTC SYSTEM SENSORS AND PROCESSING The HJTC System is a new system developed to indicate liquid inventory above the core. Since it is a new system, extensive testing has been performed and further tests are planned to assure that the li.ITC Syst en will operate to unambiguously indicate liquid inventory above the core.
The testing is divided into three phases:
Phase 1 - Proof of Principle Testing (Reference 6)
- Phase 2 - Design Development Testing (Reference 7)
Phase 3 - Prototype Testing The first phase consicted of a series of five tests, which have been completed. The testing demonstrated the capability of the ll.ITC Instrinent design to measure liquid level in simulated reactor vessel thermal-hydraulic conditions (including accident conditions).
Test 1 Autoclave test to show HJTC (thermocouples only) response to water or steam.
In April 1980, a conceptual test was performed with two thernocouples in one sheath with one thermocouple as a heater and the other thernot onple as the inventory sensor. This configuration was placed in an autoclave (pressure vessel with the capabilities to adjust temperature and pre:.nure).
The thermocouples were exposed _ to water and then steam environmentn.
Th.-
results demonstrated E significant output dif ference between steam and water conditions for a given heater power level.
_ Test 2 Two phase flow test to show bare llJTC sensitivity to voids.
In June 1980, a HJTC (of the present dif ferential thermoeuuple design) was placed into the Advanced Instrun:entation for Ret'lood St udie. (A11 S) test facility, a low pressure two phase flow test facility at Oak Ridge Naticaal Laboratory (ORKl.). The HJTC was exposed to void fractions at various heater power icvels. The results demonstrated that the bare HJTC output was virtually the same in two phase liquid as in subcooled liquid. The HJTC did generate a significant output in 1007. quai tty steam.
l l
I
i c
B/B-FSAR Test =3 Atmospheric air-water test to show the effect of a splash shield ALsplash shield wcc' designed to increase the sensitivity to voids.
The splash shield prevents direct contact with the liquid in the two phase fluid. The !!JTC output changed at intermediate void fraction two phaw fluid. The results demonstrated that the HJTC sensor (heated junction thermoccuple with the splash shicid) sensed intermediate void fraction fluid conditions.
Test 4 High pressure boil-off test to show HJTC sensor response to reactor thermal-hydraulic conditions In! September 1980, a C-E HJTC sensor (HJTC with splash shield) was installed and tested at the ORNI. Thermal-Hydraulics Test Facility (111TF).
The. HJTC sensor was subjected to various ~ bio phase fluid condi tions a t reactor temperatures and pressures.- The results verified that the ll)TC sensor is a device dbat can sense liquid inventory under normal and accident reactor vessel high pressure and temperature two phase condi-tions..
Tes t 5 Atmospheric air-water tes t to show the effect of a separator tube A separator tube was added to the HJTC design 'to fonn a collapsed liquid
' level so that the HJTC sensor directly measures liquid inventory under all simulated two phase conditions.
In October, 1980, atmospheric air-
- water tes ts were performed with HJTC sensor and the separator tube.
1he Lresults demonstrated that the separator tube did form a collapsed liquid Icvel and'the HJTC output did accurately indicate liquid inventury.
This. tes t verified diat the HJTC ins trument, which includes the IIJTC, the splash shield, and. the separator tube, is a viable measuring device
. for liquid inventory.
The Phase 2 test program consisted of a series of steady state and transie nt tests under single phase and two phase fluid conditions with an HJTC pruhe assembly. Fluid. conditions that the probe might be opposed to were simulated.
The Phase 2 ' tes ts verified that the llJTC probe assembly is capable of measuring, water' inventory in a reactor vessel.
The Phase 3 test program will consist of high temperature and pressure testing of the manufactured prototype system HJTC probe assembly and processing electronics. Verification of the itJTC system prototype will be the goal of this tes t program. The Phase 3 test report will be publinhe<!
in 1982.
4.3' CORE EXIT THERMOCOUPLES No verification testing of the CETs is planned. A study at ORNL was
/,
performed to test the response of CETs under simulated accident conditions (Reference 4).
This test showed that the ins truments remained functional up to 2300*F.
This test along with previous reactor operating experiener verifies the response of CETs.
O
es
_.g S,;
~
f'_
.w
[ Q; 9.
- ~
B/B-FSAR 5.0 SYSTEM QUALIFICATION The qualification program for the ICC detection system Instrumentation has not been completely defined..However, plans are being developed
. based on the' following categories of ICC instrumentation:
- 1. - Sensor instrumentation within the pressure' vessel.
jg 2.
Instrumentation components and systems which extend from.the
- primary pressure boundary up to and including the primary display
-isolator and including the backup displays.
A preliminary outline of a qualification program for each classification is given below.
The in-vessel sensors will meet. the NUREC-0737, Appendix B ' guide to ;
insta11' the best. equipment available consistent with qualification and.
schedular requirements. _ Design of the equipment will be consistent with the guidelines of Appendix B as well as. the clarification 'and Attachment I a
to Item II.F.2 in NUREC-0731. Specifically,: instrumentation will be
' designed such that they meet appropriate stress criteria when snh,lecteil to normal _ and design basis accident loadings. Seismic qualification to safe shutdown conditicas will verify function af ter helnn nobleer ed to the'scismic loadings.
The out-of-vessel instrumentation system, up to and including the primary
-display. isolator, and the backup displays will be environmentally qualifi..d in accordance with IEEE-323-1974._ Plant-specific containment temperature and pressure ' design profiles wil1~ be used where appropriate in theAe
- tests. This equipment will also be seismically quallfied according to IEEE-STD-344-19 75.
CEN-99(S),'"Scismic Qualification of NSSS Supplied Instrumentation Equipment. Combustion Engineering Inc." (August 1978) lescribes the methoda used to meet the criteria of this document for the
-h.ated junction thermocouple system.
1 Cons' stent with Appendix B of NUREC-0737, the out-of-venscl equipment under procurement is the best available equipment and will be qualified to meet the~ requirements of NUREC-0$88.
The primary display will not be designed as a Clans TI'. systen, bn' will be designed for high reliability; thua it will not be quallfled envirno-
. mentally or seismically to Class IE require.aents nor will it meet the
?
single failure criteria of Appendix B, Item 2.
Post-accident maintenance L
accessibility will tne included in the design. The quality assurance L
provisions of Appendix B, Item 5 do not apply to the primary display according to NUREC-0737.' However, the computer driven primary display l
system will'be separated from the Class IE sensors, processing und back-
/,
up display equipment by means of isolation devices which will be qualified to Class IE criteria.
1 GV,
~
.,=
B/B-TSAR Verification and Validation of the SPDS sof twa're for the primary ICC display will be performed. Additional information regarding the SPDS can be found_in Section E.17.
~ 6. 0 _OFERATING INSTRUCTIONS Plant specific emergency operating procedures for use of' the Information from the ICC instrumentation system will be developed taking into account recommendations from the C-E generic procedures and from the West lur,how e-Owners Group Ceneric Procedures.
The Byron /Braidwood operator trainin;;
program will be modified to include material associated with the use of the ICC instrumentation system.
6 O
4 0
e f
=
p' '
l g; m e-cg p
j.
^
-s.
B/B-FSAR
' REFERENCES 2.
NUREG-0737, " Clarification of IM1 Action Plan Requirements," U.S.
Nuclear Regulatory Commission, November,1980.
2.~ 'CEN-ll7, " Inadequate Core Cooling - A Response to NRC I E Bulletin 79-06C, ~ Item 5 for Combustion Engineering Nuclear Steam Supply Systems," Combustion Engineering, October,1979.
3.
CEN-125, " Input for Response to NRC Lessons i. earned Requirements for Combustion Engineering Nuclear Steam Supply Systems," Combur.tlon Engineering, December, 1979.
' 4.
Anderson, R. L., Banda L. A., Cain, D. G., "Incore Thermocoupl e Performance Under Simulated Accident Conditions," 1EEC Nuclear Science Symposium, Vol. 28, No.1 Page 773, Figure 81.
- 5.. CEN-185, '" Documentation of Inadequate core Cooling Instromontat ton for Combustion Engineering Nuclear Steam Supply Systems," Combustion Engineering, September, _1981.
6.
CEN-185, Sup.1, "HJTC Phase 1 Test Report," Combustion Engineering, November. 1981.
7.
CEN-185P, Sup. 2-P, "HJTC Phase 2 Test Report," Combustion Engineering.
November, 1981.
I a
E. 31-30