05000338/LER-1980-024-03, /03L-0:on 800304,during Testing,Heater for Train Safeguards Area Ventilation Sys Filter Failed to Energize Rendering Filter Inoperable.Caused by Dirty Hepa Filter Prefilter & Improper Location of High Side Sensor

/03L-0:on 800304,during Testing,Heater for Train Safeguards Area Ventilation Sys Filter Failed to Energize Rendering Filter Inoperable.Caused by Dirty Hepa Filter Prefilter & Improper Location of High Side Sensor

ML19309B896
Person / Time
Site:	North Anna
Issue date:	04/02/1980
From:	Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML19309B893	List: 05000338/LER-1980-024, Forwards LER 80-024/03L-0 05000338/LER-1980-024-03, /03L-0:on 800304,during Testing,Heater for Train Safeguards Area Ventilation Sys Filter Failed to Energize Rendering Filter Inoperable.Caused by Dirty Hepa Filter Prefilter & Improper Location of High Side Sensor
References
LER-80-024-03L, LER-80-24-3L, NUDOCS 8004070309
Download: ML19309B896 (2)

LER-1980-024, /03L-0:on 800304,during Testing,Heater for Train Safeguards Area Ventilation Sys Filter Failed to Energize Rendering Filter Inoperable.Caused by Dirty Hepa Filter Prefilter & Improper Location of High Side Sensor

Event date:
Report date:
3381980024R03 - NRC Website

text

_ _

NRC FORA 5 364 U. S. NUCLEAR CEOULATORY COMMISSION (7 77)

LICENSEE EVENT REPORT CONTROL BLOCK: l l

l l

l l

(PLEASE PRINT OR TYPE ALL REQUIRED INFORMATIOffl

% lV l Al Nl Al Sl Il@16 0l 0l -l 0l 0l 0l 0l 0 l -l O! Olh 4 l 1l 111! 1lh!

l lh 7

8 9 UCENSEE CODE 14 UCENSE NUMBER 26 26 LICENSE TYPE Jo 67 CAT 68 CON'T l'O] @l 0l 5 l 0l 0 l 0 l 3 l 3 l 8 @l 013 l 0 l 4 l 8 l 0 hl 0l 4 l 0 l 2 l 8 l 0 lg o i g

7 8

60 68 DOCKET NUMBER 68 68 EVENT DATE 74 7b REPORT DATE 80 EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h Ql On March 4, 1980, the heater for the Train A Safeguards Area Ventilation System (SAVSl) f5T51 I filter failed to energize during the performance of the monthly survallinca + ae I

o 4 l rendering the filter inoperable. Since the Train B SAVS filter remained operable l

lo g3; l and the Train A filter was restored to operable status within the 7 day ACTION l

f5Ts-] l statement, the health and safety of the general public were not affected. Per>ortable 1 [T]T] l pursuant to T.S. 6.9.1.9.b.

I 10181 l So 7

8 9 E

CO E SUB E

COMPONENT CODE SUSCOD'E SU E

8 l Al Al@ [fj@ [x_J@ Ir 11 lt I TI El al@ Iz_J@ L7J @

7 8

9 10 11 12 13 18 19 20 SEQUENTIAL OCCURRENCE REPORT REVISION LE R EVENT YEAR REPORT NO.

COD 8 TYPE NO.

@,ag/RO 181 01 l-J 1012 l 4 l [d

10131 Lt_J l-J LOJ g

_ 21 22 23 24 26 27 28 29 30 31 32 KN A T

M HOURS SUB T FORM 8.

U MA RER LC_J@lz_J@

Lz_]@

Lz_J@

10 10 10 10 I tr_J@

in_lO l.a_l@

Iv la I 91 91@

33 34 3b 36 37 40 43 42 43 44 47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h g l The heater failed to energize because air flow through the filter dropped below the l

setpoint of the heater flow sensor (pressure differential switch) due to a dirty Hepa l g

filter prefilter and also because the location of the pressure differential switch g

l high side sensor was such that it was not in the main channel of flow. Corrective l

gaction was to replace the prefilter and extend the high side sensor further into the l 80 9 suply air flow path.

7 8

'STA'S

% POWER OTHER STATUS ISCO R DISCOVERY DESCalPTION NA l { @l SURVEILLANCE TEST l

[ Ej@ l1 l 0l0 l@l i s A TIVITY C TENT RELEASED OF RELEASE AMOUNT OF ACTIVITY LOCATION OF RELEASE I

nA l

l "A

LzJ @ 1.1J@!

i s 7

8 9 _

10 11 44 46 80 PERSONNEL EXPOSURES NUMBER TYPE

DESCRIPTION

Li_LJ l I

I l@l2l@l

"^

l PERSONNEL %unS DESCRIPTION @

~uMylol@l R

"A I

I l

i R 7

8 9 11 12 80 LOSS OF OR DAMAGE TO FACILITY TYPE

DESCRIPTION

IZi@l l

NA i 9 7

8 9 to 80 PUBLICITY NRC USE ONLY

[,Njhl ESCRIPTION ISSUED D

NA l

l l l l l l l l l l l l l,-

2 O g

8004070 7

8 s l

W.

R. CARTWRIGHT 703-894-51;l o*

l NAME OF PREPARER PHONE:

1

' Virginia Electric and Power Company North Anna Power Station, Unit #1 Attachment: Page 1 of 1 Docket No. 50-338 Report No. LER 80-24/03L-0

Description of Event

on March 4,1980, during the performance of the monthly surveillance test, the heater for the Train A Safeguards Area Ventilation System (SAVS) filter failed to energize rendering the filter inoperable.

Probable Consequences of Occurence The purpose of the Safeguards area ventilation system filters is to clear any potentially contaminated primary plant exhaust system of airborne radio-activity prior to release to the atmosphere. Two filter assemblies are installed in parallel to provide redundancy in case one assembly becomes contaiminated, so that a filtration capability is maintained during a decay period for the radioactive assembly prior to filter replacement. Because the Train B SAVS filter remained operable and the Train A filter was restored to operable status within the 7 day time limit allowed by the ACTION statement of T.S.

3.7.8.1, the health and safety of the general public were not affected by this occurrence. There are no generic implications associated with this event.

Cause of Event

i A flow sensor (pressure differential switch) is installed in the heater control circuit to prevent the heater from being energized with an insufficient air flow present. The heater failed to energize during the periodic test because the flow through the filter was below the setpoint of the flow sensor due to a dirty Hepa filter inlet prefiltering pad. The problem was compounded by the fact that the pressure differential switch high side sensor was not located far enough into the supply air flow path thus preventing the sensor from sensing the maximum air flow pressure.

Immediate Corrective Action

When the problem was first encountered, the pressure differential flow switch was calibrated and found to be out of spec low but functioning properly.

The switch was set correctly and the dirty prefilter was replaced due to the low air flow present. When the heater still did not energize, the switch setting was rechecked and found to be satisfactory which resulted in the high pressure side sensor being extended further into the supply air flow path so that it could be subjected to the maximum flow available. The periodic test was then reperformed satisfactorily and the filter was declared operable.

Scheduled Corrective Action No scheduled corrective action is required.

Actions Taken to Prevent Recurrence All filter flow switches involved with heater control will be calibrated to verify proper heater operation at the correct switch setting. This action will ensure that present flow sensor locations are adequate enough to subject the sensors to sufficient air flow.

t s

- e e

r-,--

- e r -T v e.

---re

- tw -

e*-~*+*