ML19098B439
| ML19098B439 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 04/01/1977 |
| From: | Stallings C Virginia Electric & Power Co (VEPCO) |
| To: | Reid R, Rusche B Office of Nuclear Reactor Regulation |
| References | |
| Serial No. 072/021577 | |
| Download: ML19098B439 (6) | |
Text
VIRGINIA ELECTRIC AND POWER COMPANY RIOHMOND,VIRGINIA 23261 April 1, l97T
- lll6UlAroRy DOCl(ff R.
Mr. Benard C. Rusche ff COPY Director of Nuclear Reactor Regulations
- u. s. Nuclear Regulatory Commission Washington, D. c.
20555 Attn: Mr. Robert W. Reid, Chief Operating Reactors Branch 4
Dear Mr. Rusche:
Serial No. 072/021577 PO&M/TAP:dgt Docket Nos. 50-280 50-281 License Noso DPR-32 DPR-37 This is in response to your letter of February 15, 1977, in which you requested additional infonnation regarding concerns of primary system overpressurization. Resolution of overpressure mitigating system specific design features that were addressed in your letter was incorporated in our design submittal of February *25, 1977. We would appreciate an appropriately expedited response to our design submittal so that we may proceed with the system's final design and procurement to allow a schedule to meet our commit-ment of system installation by December 31, 1977 *.
The additional infonnation which you requested is provided in the attachment; except for questions 3,4 and 5, which will be answered after the Westinghouse analysis has been completed and received. This is currently scheduled for completion the end of April.
Attachments cc: Mr. Nonnan C. Moseley
- -t":..
- 1:Jl i APR 4 PM l 05 r
1*,vi tc
- ~
.e ATTACHMENT ANSWERS TO REQUEST FOR ADDITIONAL INFORMATION FEBRUARY 25, 1977
- 1)
We were requested to *provide schematic piping and instrumentation diagrams which are not available. Therefore, we are including our flow diagrams and instrument block diagrams of the requested system.
- 2)
The failure mode and effects analysis is Table 1 *
. 3:1 These questions will be addressed when the Westinghouse analysis is completed.
- 6)
The degree of relief capa~ity installed in the RHR system that could provide additional protection in the event of an overpressure transient is one valve
- *in the discharge piping of the RHR pumps. The water relief capacity of the valve is 750 gpm at a back pressure of 5 psig. The RHR system is not auto-matically isolated on RCS high pressure (or any other signal) *. The RHR system relief valve is set at 600 psig and has no automatic isolation.
- 7) The instrumentation and alarms which are available to e.nable the operator to quickly terminate an overpressure event are:
- a.
Alarm - RHR Pump Discharge Hi Pressure/NDT Alarm (490 spig) actuates a_ cpJil.i:..r::ui.
I
- b.
Inst.rumentation - Two Narrow Range (0-1000 psig) Reactor Coolant Pressure c
- gages in control room - sensed at PI-458 and PI-403 from the Pressurizer and the "C" Loop Hot Leg, **re-spectively.
- One Wide Range (0-3000 psig) Reactor Coolant Pressure gage in the control room - sensed at PI-402 from the "C" Loop Hot Leg.
Pressurizer relief valve operation is indicated by temperature indication
. downstream of the power operated relief valves and. a high.
temperature alarm annunciator. Pressurizer Relief Tank (PRT) level, pressure and temperature indication also provides indication of relief valve operation.
RHR system relief valve operation also is indicated by the PRT level, pressure and temperature indicators and annunciators.
- 8) Removal of power from valve motor operators removes the power from the indica-ting lights. The SI Accumulator discharge valves have annunciators which alarm when the valves are closed. When power is removed from motor operators, it is accomplished by procedure which requires~placing the valve in the desired position and then opening the power supply breaker.
Removal of power from valve motor operators is accomplished by opening the breaker at the Motor Control Center.
Deenergizing or locking out power to a pump is accomplished from the Control
.e Room by placing the control switch to PULL-TO-LOCK position.
~.
1
> C I
e Page_ 1
- of 2
. TABLE 1 FAILURE MODE AND EFFECTS ANALYSIS Resultant.Effect on Operability RHR Failure Mode PORV 1 PORV 2 Relief Comment Failure of channel 1 component Not Op*
Op*
Op Note 1
- Failure of channel 2 component Op Not Op Op Note 2 Loss of channel 1 instrument Not Op Op Op Note 2 power (Vital Bus I)
Loss of channel 2 instrument Op No*t Op Op Note 2
-power (Vital Bus IV)
.Loss of PORV 1 battery Not Op Op Op
- ,Loss of PORV 2 battery Op Not Op Op Loss of instrument air Op Op Op Note 3
'1.oss off-sice
-~- -* *--- -*...
. ~---
I OJ:
power
- v_p
- vp VJ:'
ss of off-site power plus Not Op Op Op Note 2
.* loss of one diesel
-Loss of off-site power plus Op.
Not Op Op Note 2
- -~:.-*-,. loss of other diesel
.'"'~---
. '. __ ;: ~~-~.'Loss of letdown
- ..,..m Op_
Op Op Note 3
- solation of RHR Op Op Not Op
- Note 3
- closure of PORV l isolation Not Op Op Op
-valve
'Closur'1 of PORV 2 isolation Op Not Op Op
.. co:valve
- -~n--* *
- lnndvt!rtent SI Op Op Op Note 3
.-,r,..
anual starting of SIS pump Op Op Op Note 3 Manual starting of additional Op Op Op Note 3
--duu:gins-Pump. -*--------*--. -*- ------- ___
v,,*-.*.............._.
- ,.n
- r-
.. ~ -
Starting RCP Op Op Op Note 3
-i e
Page 2 of 2 Resultant Effect on Ooerability RHR Failure Mode PORV 1 PORV 2 Relief
- comment Failure to activate low Not Op Op Op Note ~
pressure setpoint channel 1 Failure to activate low Op Not Op Op Note 4 setpoint channel 2 pressure Problems with operation of Op Op
~Qt Op
- pressurizer relief tank Undefined common mode failure Not Op Not Op Op Note 5 of channels 1 and 2
-Testing of one channel leaves Not Op Op Op only one channel operable, but for the short period of time required for testing, a problem does not exist (per
.. IEEE, 279)
. ~...,'";_.,
... ::. -~-:
. NOTES
- Not Op denotes that this valve is not operable and not capable of performing its pressure relieving function.
Op denotes that this valve is operable and can perform its pressure relieving function.
- -Note 1
Channel component consists of _one of the following:
sensor, channel power supply, bistable to valve, or PORV.
Note 2
Note 3
Note 4
')i.*~--~;*-\\.
Vital Bus I is fed from emergency bus H Vital Bus IV is fed from emergency bus J For all possible causes of overpressurization, no failure o*f PORV 1 or 2 results.
Alarm will alert the operate~ to this condition.
Note 5
Common mode failure of channels 1 and 2 is considered incredible at the time of an overpressurization event, but this_shows that* pressure relief
-*-**--" *----
- is still available via the RHR relief valve.
- -*-* --*---~~*---------__, *-..,. --- --------* -*
'. /
..t