ML20065T752
| ML20065T752 | |
| Person / Time | |
|---|---|
| Site: | Browns Ferry  |
| Issue date: | 12/21/1990 |
| From: | Wallace E TENNESSEE VALLEY AUTHORITY |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| RTR-REGGD-01.097, RTR-REGGD-1.097 NUDOCS 9012310095 | |
| Download: ML20065T752 (4) | |
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4 TENNESSEE VALLEY AUTHORITY f
CH ATTANOOC A, TENNESSEE 37401 SB Lookout P'. ace
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DEC 211990 U.S. Nuclear Regulatory Commission ATTN Document Control Desk Washington, D.C.
20555 i
Gentlemen:
In the Matter of
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Docket No. 50-260 Tennessee Valley Authority 1
BROWNS FERDY NUCLEAR PLANT (BFN) - REGULATORY GUIDE (RG) 1.97 EMERGENCY VENTILATION DAMPERS POSITION INDICATION As discussed during the NRC inspection on RG 1.97 of October 22-26, 1990, TVA has:been in the process of performing a review of all instrument loops related to RG 1.97 variables. The partial results of this review were provided to NRC in the letter of October 15, 1990,. prior,to the NRC-RG 1.97 inspection. This
. review is now complete and its associated documentation (engineering calculations) is in final. review prior to issuance.
TVA considers it necessary to clarify the information presented in previous submittals as it relates to the control room emergency ventilation (CREV) system damper position indication.
In a letter to NRC dated April 30, 1984, TVA indicated in Table D24 that six
.dampera associated with the CREV system were provided with status lights in the control room. This information was resubmitted in TVA's letter to NRC dated August 23,-1988..These~1ettera did not. clarify that'the status lights for six CREV system related dampers were not a disect indication of damper position.
The purpose of this letter is to notify NRC that TVA. considers the status light indication.and alarms provided for the.CREV system to be an a:ceptable alternative to direct position indication and to meet the guidance provided in RG 1.-97..The evaluation to support this alternative is provided in the enclosure to this letter.
l If you have= any questions, please contact Patrick P. Carler, Manager 'of Site.
Licensing, at.(205) 729-3570.
Very truly yours,
- TENNESSEE VptLEY AUTHORITY -
4C -.
E. G. Wallace, Manager Nuclear Licensing and Regulatory Affairs 0
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Enclosure.
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DEC 211990 U.S. Nuclear Regulatory Commission cc (Enclosure):
Ms. S. C. Black, Deputy Director Project Directorate II-4 U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike, Rockville, Maryland 20852 NRC Resident inspector Browns Terry Nuclear Plant Route 12, Box 637 Athens, Alabama 35609-2000 Mr. Thierry M. Ross, Project Manager U. S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike Rockville, Maryland 20852 Mr. D. A. Wilson, Project Chief U.S. Nuclear Regulatory Commission Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 l
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ENCLOSURE IRIRODUC110E In response to Regulatory Guide (RG) 1.97, TVA developed a list of emergency ventilation dampers which have status lights in the control room.
A revision of this list was provided in a letter to NRC dated August 23, 1988.
NRC's Safety Evaluation Report (SER), dated February 8, 1990, concurred with this list and found the proposed instrumentation acceptable for use with the emergency ventilation damper position indication variable.
Based on subsequent evaluation of RG 1.97 related instrumentation, TVA considets necessary the clarification of the previous submittal as it relates to six dampers associated with the control room emergency ventilation (CREV) system.
The six dampers are the normal ventilation system inlet and exhaust dampers and the emergency ventilation system inlet dampers. These dampers are type D variables as defined by RG 1.97 TVA's August 23, 1988 letter stated that status lights were provided in the control room for these siv dampers.
Although most status lights associated with erargency ventilation dampers provide direct position indication, the status lights associated with the CLEV system do not.
Instead, the status lights associated with the CREV system related dampers indicate that power has been applied to move the dampers to their emergency position.
In addition. two alarms are provided to alert the operators to failure of the CREV system. The first alarm is for high radiation in the normal ventilation system intake and the second alarm will alert the operators to a wide variety of abnormal conditions associated with the control bay ventilation bystems.
Based on the status lights, the additional alarms in the control room, and the evaluation presented in this enclosure, TVA considers the present system design to be an acceptable alternative to direct position indication and to meet the guidance provided in RG 1.97 EE.GEAIDELGUIDMCE RG 1.97 defines Type D variables as ".
those variables that provide information to indicate the operation of individual safety systems and other systems important to safety."
In addition, RG 1.97 states:
"To the extent practicable, monitoring instrumentation inputs should be from sensors that directly measure the desired variables.
An indirect measurement should be made only when it can be shown by analysis to provide unambiguous information."
The purpose for providing direct position indication is to allow operations to monitor the operation of the CREV system.
TVA considers that the CREV system design provides an adequate alternative approach to direct position indication. TVA's conclusion is based on use of status lights and annunciators in the control room and use of the alarm panel in the air conditioning equipment room.
These indications and alarms provide sufficient information to monitor operation of the CREV system.
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EXEIQi_XYALVATICE The CREV system is designed to provide filtered air and to pressurite the control bay during accident conditions. The filtering portion of the CREV system includes high-efficiency particulate air filters and charcoal absorbers.
Initiation of the CREV system results in isolation of the normal HVAC system whict. supplies the control bay under normal conditions and actuation of the emergency ventilation system which supplies the control bay during a radiological event.
Isolation of the normal HVAC system includes closing the inlet and exhaust dampers (FCO-31-150B, -150D, -1500, and -150F).
Actuation of the emergency ventilation system results in the opening of the emergency supply dampers (FCO-31-151 and s152) and starting the emergency supply f ans.
These actions will isolate the normal ventilation system and allow the CREV system to pressurite and control the control bay environment.
Operation of the CREV system is monitored three ways.
First, status lights are provided in the Unit 1 main control room (MCR) to show that the CREV system has been actuated.
Second, an annunciator is provided in the Unit 1 MCR to alert operations to a wide variety of abnormal conditions related to control boy ventilation. These conditions range from the loss of a normel chiller unit to inadequate control bay pressurisation.
In the event of an abnormal condition ant unciation, the alarm response procedure (ARp) directs the operators to an alarm panel in the air conditioning equipment room.- This panel provides an alarm to indicate low static air pressure on Elevation 617 of the control bay. The alarm panel is also located on Elevation 617 of the control bay and is within the control room habitability sone. The pressurisation and ventilation for this elevation is maintained by the CREV system during a radiological event.
Included on this elevation are the control rooms, the technical support center, and the air conditioning equipment room. The low'stntic air pressure alarm discussed above informs the operator that air pressure in the control bay is insufficient to ensure protection of plant personnel. The associated ARP will direct the operators to take the necessary actions to repressurise the control bay.
Finally, control room annunciation is provided to alert operations if high radiation has been detected in the normal ventilation system intake ducts.
One of the responses to this alarm is to verify that normal inlet and exhaust dampers (FCO-31-150D, D, E, and F) are closed and to manually close these dampers-if required. These dampers are also located in the control bay and operations personnel are not required to leave the protected environment to initiate these manual actions.
The status lights and annunciators discussed above provide tufficient
-information to monitor the operation of the CREV system.
CQHCLUEIQH Based on the above discussion of the existing plant indications, the alarm response procedures, and the guidance provided in RG 1.97, TVA considers the present CREV system des 3 n as it relates to the emergency ventilation damper 9
position indication to be an acceptable alternative to direct position
' indication and to meet the guidance provided in RG 1.07.
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