ML19290E115
| ML19290E115 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear  |
| Issue date: | 02/22/1980 |
| From: | Trimble D ARKANSAS POWER & LIGHT CO. |
| To: | Reid R Office of Nuclear Reactor Regulation |
| References | |
| 1-020-17, 1-20-17, NUDOCS 8003040290 | |
| Download: ML19290E115 (3) | |
Text
E}
l dS ARKANSAS POWER & LIGHT COMPANY POST OFFICE BOX 551 LITTLE ROCK. ARKAf JSAS 72203 (501)371-4000 February 22, 1980 1-020-17 Director of Nuclear Reactor Regulation ATTN:
Mr. R. W. Reid, Chief Operating Reactors Branch #4 U. S. Nuclear Regulatory Commission Washington, D. C.
20555
Subject:
Arkansas Nuclear One - Unit 1 Docket No. 50-313 License No. DPR-51 Reactor Building Purge System (File:
1510)
Gentlemen:
In response to your request of January 3, 1980, the following is provided.
1.
ECCS ACTUATION The emergency core cooling actuation system is composed of three re-dundant analog subsytems and two redundant logic subsystems.
Each aralog subsystem contains two channels of information for initiating pmtective action when low RCS pressure or high reactor building pressura exceeds its assigned limit.
The trip signals from the three analog subsystems are simultaneously applied to two identical digital subsystems whose functions are as follows:
a.
Combine the' trip signals from the analog subsystems and initiate a trip to the final action units when any two of the three analog subsystems call for a trip.
b.
Provide a sealing feature in the event of an output trip signal until operator intervention cancels it.
The operator can cancel or reset the trip only after the trip initiating conditions have disappeared from the system.
c.
In the event of a loss of coolant accident allow the operator complete maneuverability by enabling him to inhibit or energize, individually, any of the final action units to meet the require-ments of the immediate situation.
P
-- --- -*o o s o 4 0 29o
1-020-17 February 22, 1980 d.
Provide the operator with a reliable means of manually tripping a channel.
e.
Provide for complete on-line testing of each component including the final action unit itself and not cause a false trip nor in-hibit a valid trip during the test interval.
Each analog subsystem contains one bypass bistable which allows con-trolled bypassing of the trip bistable to prevent actuation of the high and low pressure injection, isolation, and cooling systems during a normal shutdown.
These bypasses are automatically removed on plant startup at
= 250 PSIG above the trip bistable setpoint.
2.
SYSTEM MONITORING The analog subsystems are housed in separate analog cabinets.
Within each cabinet, each analog input is displayed on indicators.
Lamps in-dicate the state of each bistable, contact buffer, and logic buffer.
An indicating panel at the top of each cabinet is easily visible.
Lamps on this panel give quick visual indication of the trip status of the analog channels contained in that cabinet.
In addition, visual indication of cabinet fan and pressure trip bypass status is provided.
All odd channels' 2-out of-3 logics and their associated unit control modules are located in the same actuation cabinet (s), and the even channeh' 2-out-of-3 logics and their associated unit control modules are located in the same cabinet (s).
Within each cabinet, lamps indi-cate the trip state of each 2-out of-3 logic and each unit control module.
Each of these cabinets has an indicating panel at the top, which is easily visible at all times.
Lamps on this panel give quick visual indication of the trip status of each 2-out-of-3 logic input.
Cabinet fan and actuation channel trip status is also indicated.
3.
REACTOR BUILDING ISOLATION Our response to IE Bulletin 79-05A (dated April 16, 1979) committed us to provide diverse actuation signals of high reactor building pressure and low RCS pressure for reactor building isolation.
Both of these signals are derived from safety grade equipment.
Reactor building isolation on high radiation is not required and is not pro-vided in our design.
No modifications are necessary to this isola-tion signal due to the small numbers and low probability of events which might lead to high radiation prior to high reactor building pressure or low RCS pressure.
4.
Our response of January 31, 1979, to your generic letter of November 28, 1978 (with regard to bypasses), is clarified as follows:
"Our review of safety actuation signal circuitry has not revealed any manual over-ride features on the system level which unintentionally disable addi-tional safety actuation signal circuits."
1-020-17 February 22, 1980 FSAR Section 7.1.3.2 discusses a block action provided by the unit controller (UC).
The UC is employed to couple the trip signal from the trip bus to the safeguards device (pump, valve, etc.) and, there-fore, is available tc return individual components to manual control following an ESAS.
As a result of reviews performed to meet the re-quirements of IE Bulletins 79-05,79-05A and 79-05B, we have ensured that sufficient phycical features are provided to facilitate adequate administrative control and that the use of each individual component's manual ove' de is indicated at the component level.
Very truly yours, b & P. 7%d6 David C. Trimble Manager, Licensing DCT: ER6: s km