ML20248H281

Special Rept:On 890902,area Temp Found Greater than 120 F for Duration Greater than 8 H.Caused by Personnel Error Due to Shift Personnel Failure to Adequately Track Temp Excursion.Revised Thermal Life Calculations Performed

ML20248H281
Person / Time
Site:	Millstone
Issue date:	10/02/1989
From:	Scace S NORTHEAST NUCLEAR ENERGY CO., NORTHEAST UTILITIES
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
MP-13572, NUDOCS 8910110249
Download: ML20248H281 (2)

Text

mg . , , _ w. 2.- - .a. - . - -- -

a i 14 l

• pe.e , q j

. NORTHEAST ImLITIES *a-a' om= San S=2 "" co"""

I w sfeYn aYs"ac sett ecNecoEanY P.O. BOX 270 g '

tWne*as te rv Sany HARTFORD. CONNECTICUT 06414-0270 Northeast Nuclear Energy Company (203)665-5000 October 2, 1989 {

MP-13572 Docket No.: 50-423 Re: 10CFR50.36 f

1 U. S. Nuclear Reculatory Commission Attn: Document Control Desk Washington, D. C. 20555 Gentlemen:

a .

MILLSTONE NUCLEAR POWER STATION. UNIT NO. 3 AREA TEMPERATURE MONITORING - Main Steam Valve Building (MS-01)

' This Special Report is being submitted pursuant to Technical Specifications 3.7.14b,

" Area Temperature Monitoring" and 6.9.2, "Special Reports." The area being dis-cussed is zone MS-01, the 71 foot elevation of the Main Steam Valve Building (MSVB),

which is monitored by temperature element 3ECS-TE119. Technical Specification 3.7.14b requires that a Special Report be submitted, if the Main Steam Valve Building MS-01 temperature limit exceeds 120 degrees Fahrenheit, longer than 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />.

On September 2,1989 at 1724 hours0.02 days <br />0.479 hours <br />0.00285 weeks <br />6.55982e-4 months <br />, with the plant in Mode 1 at 100% power,586 degrees Fahrenheit and 2250 psia, 3ECS-TE119, indicated an area temperature greater than 120 degrees for a duration greater than 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />. Area temperature was monitored and verified less than 140 degrees - the temperature at which equipment in the area must be declared inoperable in accordance with the plant's Technical Specifications. Opera-tors verified proper ventilation alignment and no leaks were identified in the area. At 0127 hours0.00147 days <br />0.0353 hours <br />2.099868e-4 weeks <br />4.83235e-5 months <br /> on September 3,1989, area temperature at the 71 foot elevation went below 120 degrees. The duration of the temperature excursion was approximately 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br />.

The maximum indicated temperature during the excursion was 124.2 degrees, occurring at approximately 1500 hours0.0174 days <br />0.417 hours <br />0.00248 weeks <br />5.7075e-4 months <br />.

Temperature oscillations at values around the Technical Specifications temperature limit for the 71 foot elevation of the MSVB began on August 29,1989. Excursions above the temperature limit were not sustained until the evening of September 2,1989. Mainte-nance on a Main Steam System Pressure Control valve was ongoing until the end of day on September 1,1989. The ong ventilation system and resulted m,oing madequate cooling maintenance in the area. Also, aactivities may failed tempera- have shor ture controller in one of the two inlet ventilation dampers was discovered during the morning of September 3,1989. The actual time of the temperature controller failure .

could not be determined. The controller failure in conjunction with high outside air  !

temperatures around the same time frame may also have contributed to the temperature 7 excursion above the Technical Specification limit. Based on the ongoing investigation, ,

firm evidence to substantiate these conclusions has not been obtained.

I 8910110249 891002 i PDR ADOCK 05000423 ,

S PDC ,

i ]

'.O

w -

O 2 ;,;

• g .- @ - 2.-

["

t .

1 Although the aforementioned abnormal operating experiences may have contributed to -

the temperature excursion in the MSVB, the root cause of this event was personnel error.

Shift personnel failed to adequa,tely track the temperature excursion and failed to initiate compensatory measures to mitigate the excursion in a timely manner. No action was o taken to provide increased ventilation in the area when the temperature excursion was 1- initially identified.

The focus of concern over the temperature excursion and the basis for the Technical  ;

t Specification temperature limit is to ensure that the anticipated life-times for the envi-ronmenfally quahfied equipment in the area is not significantly. degraded. l 1

Revised thermal life calculations have been performed for the environmentally qualified i equipment located inside the area monitored by 3ECS-TE119. The results of these . q L calculations indicate no significant impact on the thermal life characteristics of the '

equipment and demonstrate continued operability of the associated equipment. Proce-P dural guidance to on shift personnel has been strengthened to include increased temper-

. ature monitoring and corrective action response for areas which exceed their alert (5 degrees below Technical Specification) temperature limit.

' Special Report /LER 86-050-03, " Area Temperature Monitoring - MS-01," submitted on September 30,1989, discussed the successful implementation of the " spot cooling" ventilation modification. As part of this modification, cooling ducts were installed in the

-vicinity of environmentally qualified equipment. The effectiveness of this " spot cooling" l

modification has been supported by continued operation throughout the past two sum-mers, without temperature excursions until this event. Based on the investigation of this excursion, no evidence to indicate shortcomings of the modification was identified.

The licensee contact for this Special Report is Vere Joseph,' who may be contacted at

(203) 447-1791, extension 5571.

Very truly yours,

- NORTHEAST NUCLEAR ENERGY COMPANY ik CW L Steph n E. Scace Station Superintendent l

Millstone Nuclear Power Station SESNRJ:mo ec: W. T. Russell, Region I Administrator D. H. Jaffe, NRC Project Manager, Millstone Unit No. 3 W. J. Raymond, Senior Resident Inspector, Millstone Units No.1, 2 and 3

~~- ' ~ - - - - - = _ . . . _ , _ , _ _ , _ . _ _ _ . _ _ _ , . _ _ _ _ , , _ _ _ _ _ _ __