05000369/LER-1981-178, Forwards LER 81-178/03L-0.Detailed Event Analysis Encl

Forwards LER 81-178/03L-0.Detailed Event Analysis Encl

ML20069B485
Person / Time
Site:	McGuire
Issue date:	12/11/1981
From:	Parker W DUKE POWER CO.
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20069B489	List: 05000369/LER-1981-178, Forwards LER 81-178/03L-0.Detailed Event Analysis Encl 05000369/LER-1981-178-03, /03L-0:on 811113,UHI Surge Tank Hi/Lo Pressure Alarm Received,Indicating Upper Head Injection Sys Pressure Increased to Setpoint of 1206 Psig.Probably Caused by Packaging Leakoffs from Four Uhi Block Valves
References
NUDOCS 8112240235
Download: ML20069B485 (3)

LER-1981-178, Forwards LER 81-178/03L-0.Detailed Event Analysis Encl

Event date:
Report date:
3691981178R00 - NRC Website

text

.

o DUKE POWER CO3WM

,' IR C n -

Powru UU11. DING 1 Sl -,, '

[.[/

422 SocTu Citrucu Srnrr.r Ciuur.orTE, N. C. una4.2

?O l0 il Q,

WILLI AM O. Pan R M E R, J R.

y v.y p.csa w December 11, 1981 r t c ~c ~ c. a.t.

e S e t.nn Poonococi.

3?3-4093 Mr. J. P. O'Reilly, Director U. S. Nuclear Regulatory Comission to(/

Region II y

,g 101 Marietta Street, Suite 3100 2

x 4

k, Atlanta, Georgia 30303 s-l}

Q' ' l s.,,

t Re: McGuire Nuclear Station Unit 1 Docket No. 50-369

/

's

/

s

/

Dear Mr. O' Reilly:

Please find attached Reportable Occurrence Report R0-369/81-178.

This report concerns T.S.3.5.1.2, "Each upper head injection accumulator shall be operable with:

...c.

The nitrogen bearing accumulator pressurized to between 1206 and 1264 psig." This incident was considered to be of no significance with respect to the health and safety of the public.

/

very truly yours, Q. i if, 3 William O. Parker, Jr.'

PBN/j fw Attachments cc: Director Records Center Office of Management and Program Analysis Institute of Nuclear Power Operations U. S. Nuclear Regulatory Commission 1820 Water Place Washington, D. C.

20555 Atlanta, Georgia 30339 Mr. P. R. Bemis Senior Resident Inspector-NRC McGuire Nuclear Station 8112240235 811211

}g -.EAL f OIT

{DRADOCK 05000369 PDR A

E O

/

9-

~

.w..

_m

~

O DUKE POWER COMPANY McGUIRE NUCLEAR STATION REPORTABLE OCCURRENCE REPORT NO.81-178 REPORT'DATE:

December 11, 1981 FACILITY: McGuire Unit 1, Cornelius, NC IDENTIFICATION: Upper Head Injection (UHI) Accumulator Pressure Decreased to Tech Spec Limit

INTRODUCTION

On November 13, 1981 the "UHI Surge Tank Hi/Lo Pressure" alarm annunciated in the control room. The alarm indicated that the UHI system pressure had decreased to the Technical Specification 3.5.1.2 setpoint of 1206 psig. The exact cause of the pressure decrease could not specifically be determined but contributing factors were the packing leakof fs from four UHI block valves on the UHI water accumulator. The nitrogen bottles were aligned to the UHI nitrogen accumulator, and the low pressure alarm was cleared. Prior to the incident, Unit I was at 48% power and the UHI surge tank level was approximately 50%.

EVALUATION: During plant operation, packing leakoffs on the block valves cause a level decrease in the surge tank and eventually a pressure decrease in the UHI system. Consequently, water is routinely added to *he surge tank to increase the level. Prior to the incident, it is possible that the UHI pressure was close to the alarm setpoint and the surge tank level decreased sufficiently-to cause the low UHI pressure alarm to annunciate.

It has been difficult to accurately monitor UHI system pressure because the 58 psig operating band (1206-1264 psig) must be read on a gage with a range of 0-2000 psig. After the alarm was received, the nitrogen system was aligned in preparation for repressurizing the UHI nitrogen accumulator.

No water was added since the surge tank level was approximately 50%.

CORRECTIVE ACTION

An operator immediately aligned nitrogen to the UHI system and repressurized the nitrogen accumulator. A subsequent investigation for leaks on instrument lines and from vent valves was hindered because the UHI ni*rogen accumu-lator is located in a presently roped off High Radiation Area. However, no nitrogen leaks were discovered on instrument lines on the UHI surge tank or.from vent valves on the piping containing the rupture diaphragm. Thus, it could not be determined specifically if the packing leakoffs on the block valves were the sole cause of the incident. The investigation will be continued when the nitrcgen accumulator is accessible.

In order to provide more complete indication of UHI system pressure in the control.

room, three modifications are planned: one is to provide an analog computer point for the UHI pressure.

If a UHI hi/lo pressure alarm should occur, the computer point will indicate exactly what the UHI pressure is.

Another changes the hi/lo pressure alarm setpoints from the present Tech Spec limits of 1206 and 1264 psig to 1215 and 1255 psig. This will give the operators sufficient time to adjust pressure without challenging the Tech Spec requirements. Finally, the range of one of the two UHI pressure gages in the control room will be changed from 0-2000 psig to 1000-1500 psig.

This will allow the control roon operators to more easily ascertain UHI pressure because of better gage resolution.

Report No.81-178 Page 2 l

VERIFICATION: Af ter the nitrogen was aligned to the UllI nitrogen accumulator, the l

pressure was returned to the normal operating band within approximately twenty min-utes. The implementation of the modifications will provide more complete UllI system pressure indication and enable the control room operators to more quickly react to abnormalities should they occur.

SAFETY AMAYLSIS: The UHI system is passive and would only be used if a large reactor oolant system break occurs. Even though the UHI pressure decreased to the Tech Spec low limit, the system was still operable and could have been used if an emergency had occurred. However, no break occurred and safe plant operation and the health and safety of the public were unaffected by this incident.

i.

{

I l

s y

a e

a l

l ek i

I.

g c-u.

g i

5

~

.~

4 s

r

~

Ye

~