ML19345F992
| ML19345F992 | |
| Person / Time | |
|---|---|
| Site: | Maine Yankee |
| Issue date: | 02/09/1981 |
| From: | Johnson W Maine Yankee |
| To: | Eisenhut D Office of Nuclear Reactor Regulation |
| References | |
| EMY-81-16, NUDOCS 8102190699 | |
| Download: ML19345F992 (4) | |
Text
s BAmEj' HAllHEE
' Amml0 POWER COMPAnh' *
,s,, wonces,en no,o rRAMINGH AM, M ASSACHUSETTS 01701 e~aiseeniso orricg
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617 872-810o U
G rebruary 9, 1981 v
ye A.C.2.1
-FMY 81-16 j
United States Nuclear Regulatory Commission Wash ington, D. C.
20555 Attention:
Office of Nuclear Reactor Regulation Q
Darrell G. Eisenhut, Director g
Division of Licensing
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]
Re ferences :
(a)
License No. DPR-36 (Docket No. 50-309)
(b) MYAPC letter to USNRC dated March 5, 1980 (WMY 80-39)
Subject:
Description and Schedule for the Upgraded Subcooling Margin Monitor Installation
Dear Sir:
The purpose of this letter is to inform your staff that the saturation monitor upgrading schedule will be delayed due to associated equipment delivery schedules, and the unavailability of qualified RTD's.
The installation of a primary coolant saturation meter was one of many short term TMI requirements.
Maine Yankee met this requirement by installing a dedicated CE subcooling margin monitor during the 1980 winter refueling outage.
The temperature inputs to the monitor were not safety grade at the time of the monitor installation; although Maf ne Yankee believed it wculd be possible to upgrade other input signals by January,1981, as detailed in Reference (b).
Recent information from the vendor indicates that the metal cabinets being fabricated to house the associated circuitry for the saturation monitor inputs will not be available for delivery until mid April, 1981.
Since the hardware delivery schedule will delay equipment installation until May, and the plant is scheduled for a refueling shutdown in May, Maine Yankee intends to upgrade the saturation monitor inputs during the spring 1981 refueling outage (see Attachment I).
This installation schedule will also alleviate the necessity to work in the main control board while the plant is at power.
The CE saturation monitor provides the operator with a continuous digital N
display of either the pressure or temperature margin to saturation conditions.
Furthermore, the plant computer displays the margin to saturation in tne control room using temperature and pressure inputs different from those used by the subcooled margin monitor. Maine Yankee is fully confident that continued operation with the present saturation monitor inputs, in conjunction with revised procedures and training, adequately meet the ooerator's needs; and that the pub 1'c health and safety will not be compromised, Maine Yankee is engaged in the pursuit of qualified replacement equipment, and when qualified RTD's become available they will be installed during the next scheduled maintenance outage following receipt of equipment.
81021 o o(A9 p
United States Nuclear Regulatory Commission February 9,1981 Darrell G. Eisenhut, Director Pa ge 2 We trust you will find this course of action satisfactory, however, should you have any questions, please do not hesitate to contact us at your convenience.
Very truly yours, MAINE YANKEE ATOMIC POWER COMPANY SA$
W. P( Johnson Vice President RHG/ dis
ATTACHMENT I Reactor Coolant System Subcooling Margin Monitor Back ground Our original plans for replacing the two incore T/C's with three qualified RTD's have proved unsuccessful due to the unavailability of qualified equipme nt.
In lieu of this Maine Yankee will provide inputs from the present RTD's in each hot leg, and will add two additlocal incore T/C's inputs to the saturation monitor; thereby providing incore tempercture indication from each q uadrant.
Although the present RTD's are believed to be reliable, Maine Yankee recognizes the benefits to be gained from the use of qualified equipment, and is actively engaged in the pursuit of qualified of replacement equi pment.
Design Dasis A continuous indication of reactor coolant system subcooling margin is provided in the control room and meets the following criteria:
0 1)
Measurement and indication is from 0 to 150 F subcooling margin.
0 2)
Accuracy requirements for the system is 1 12 F for the full range.
3)
Subcooling margin is displayed continuously in the control room.
System Description
The subcooling margin monitor receives both temperature and pressure inputs.
The temperature inputs are from one core exit thermocouple from each quadrant and one hot leg RTD from each loop (TE lllX, TE 121X, TE 131X). The 0
temperature transmitters are calibrated for a range of 0-750 F.
Since both the core exit thermocouples and the hot leg RTD's are non-Class lE they are electrically isolated from the subcooling margin monitor.
The pressure inputs are from pressurizer pressure channels PT 102X, PT 102Y (0-3250 psig), PT 103 (0-1600 psig) and PT 101X (1500-2500 psig). Since PT 103 and PT 10lX are non-Class lE they are also electrically isolated from the subcooling margin monitor.
A functional block diagram is provided as Figure 7-1.
Temperature and pressure analog signals are converted to digital signals through an analog-to-digital converter. These signals are interfaced to a The microcomputer contains steam tables and interpolation microc omputer.
routines for which a saturation temperature and pressure is calculated.
By comparing the saturation temperature and pressure to the actual coolant Either the temperature and pressure, a margin from saturation is calculation.
temperature or pressure margin can be displayed on the digital panel meter.
The margin is also compared to a setpoint for a low margin alarm. The margin may be compared to an additional setpoint for a desired protective action initiation through the auxiliary contacts.
Software diagnostics are periodically executed to detect observable software mal fun ctions.
A diagnostic failure is indicated by a flashing meter display.
4
, D'MA RTN
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VETER
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- u o 1 s.. m = :
- CR PRES $URE Pressure uAncir.
Process Signals N
P1 A. A t.ec
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lov Margin Alarn s
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.k T
(Annunciator Pl-5) stTI:r I
=cE,g'aYg; P 4 ---+
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Chance in Saturation p
-A 4
3
+ Condition (Annunci-J ator P4-5)
Te=rerature Process Signals
. tut crs:JAL Data Log Output T,1 *
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- To Plant Computer
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CONVIRTE:
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T 8 --->
Dic'?8 Data Log Outout To 4
% Strip Chart Recorder AN C-convERTES (Not Used)
FIGURE 7.1 RNCTIONAL BLOCK DIACRAM Process Sat. Monitor Process Signal Elect. Signal Channel Signal Range Range 1
PT-103 0-1600 psig 4-20 ma de 1500-2500 4-20 ma de 2
PT-101X ogg 1
f 3
T/C 0-750 F 1-5 vde 4
T/C 0-750 F 1-5 vde i
5 T/C 0-750 F 1-5 vde 6
T/C 0-750 F 1-5 vde 7
PT 102X 0-3250 psig 4-20 ma de 8
PT 102Y 0-3250 psig 4-20 ma de 9
TE 111X 0-750 F 1-5 vde 10 TE 121X 0-750 F 1-5 vde I
11 TE 131X 0-750 F 1-5 vde 12 0-750 F 1-5 vde l
- TE 131X Channel 11 paralleled to Channel 12 input.
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