ML20150C916

Safety Evaluation Re Employee Concern Element Rept 23508, PVC Liquid-Tight Flex Conduit

ML20150C916
Person / Time
Site:	Sequoyah
Issue date:	03/11/1988
From:	NRC OFFICE OF SPECIAL PROJECTS
To:
Shared Package
ML20127A683	List: ML20127A681 ML20150C791 ML20150C795 ML20150C800 ML20150C805 ML20150C813 ML20150C816 ML20150C822 ML20150C835 ML20150C838 ML20150C849 ML20150C896 ML20150C900 ML20150C902 ML20150C907 ML20150C911 ML20150C916 ML20150C920 ML20150C928 ML20150C933 ML20150C937 ML20150C940 ML20150C947 ML20150C951 ML20150D296 ML20150D303 ML20150D315 ML20150D318 ML20150D322 ML20150D326 ML20150D331 ML20150D334 ML20150D338 ML20150D583 ML20150D592 ML20153A915 ML20153A930 ML20153A934 ML20153A951 ML20153A974 ML20153A977 ML20153A982 ML20153A996 ML20153B005 ML20153B010 ML20153B016 ML20153B022 ML20153B042 ML20153B045 ML20153B052 ... further results
References
NUDOCS 8803220416
Download: ML20150C916 (2)

Text

.

a ceco o

UNITED STATES g

NUCLEAR REGULATORY COMMISSION m

g p,..

1 E WASHING TON, D. C. 20555 t

\\

os...../

SAFETY EVALUATION REPORT BY THE OFFICE OF SPECIAL PROJECTS EMPLOYEE CONCERN ELEMENT REPORT 23508

'PVC LIQUID-TIGHT FLEX CONDUIT" TENNESSEE VALLEY AUTHORITY SEQUOYAH NUCLEAR POWER PLANT, UNITS 1 AND 2 00CXET NOS. 50-327 AND 50-328 1.

SUBJ E_C_T i

Category:

Engineering (20,000)

Subcategory:

Electrical Safety (23.500)

Element:

PVC Liquid-Tight Flex Conduit (23508)

Employee Concern:

IN-85-973-003 Elenent Report 23508 Revision 1, prepared April 21, 1987, involves an employee i

concern which stated, "Plastic type flex conduit installed between instruments and for all floor mounted panels (l' nits 1 and 2) cannot withstand heat l

generated in cont 6f nment and valve rooms."

II.

St;MMARY OF ISSUE A concern was expressed by a TVA employee that the plastic type flex conduit may not be abic to withstand extreme heat generated in areas such as the containment following an accident.

The employee indicated that a friend was aware of this problem in another plant.

The employee therefore did not (and could not) provide specific panels or conduit numbers.

This concern was I

considered to be generic to Sequoyah since PVC jacketed conduit is used in the Sequoyah containment and valve room areas.

TVA analyzed this concern and found that design basis events will not adversely affect the ability of the conduit to perform intended safety functions.

The TVA respcnse was based on environmental qualification testing conducted at Central Laboratories.

This test demonstrated that the PVC jacket wculd remain intact for two hours at 360*F.

This is above the TVA projected conditions for LOCA and the main steam line break.

TVA, therefore, found this concern to be unimportant for the safe operation of the Sequoyah plant.

III. EVALUATION NRC and.its consultant, SAIC, reviewed'the TVA employee concern.

NRC requested a clarification of the Central Laboratory environmental qualification test results.

In particular, NRC asked if the Central Laboratory qualification test included the energy contribution resulting from superheated steam during 8803220416 880311 PDR ADOCK 05000328 P

PDR

7-the steam line break accident.

TVA in their October 7, 1987 response stated that the Central Laboratory test did not include the energy contribution resulting from steam during a main steam line break (tiSLB).

However, test data are available on PVC jacketed cables which envelopes the temperature profile for the fiSLB.

This testing was done for the Browns Ferry plant by Wyle Labcratories.

During this testing the pressure was not recorded.

The Wyle Lab test showed no flaking or n!elting of the PVC jacket.

Nevertheless, fiRC was concerned that the transient differential pressure from outside to inside the PVC conouit might nke the PVC yield and flow and can potentially clog floor sump drains.

TVA has stated that the conduits are generally sealed for a differential pressure of six inches of water (approximately 0.25 PSI) and therefore, the differential pressure of approximately 1? PSI will break the cor.duit seals and equalire the pressure inside and outside of the flexible conduits.

TVA further stated that all inttalled PVC conduits at Sequoyah are PVC over steel and the steel has a minimum differential pressure strength of 12 psi.

Eased on these reasons, TVA believes that the Wyle test data is applicable for the Sequoyah PVC conduit and is therefore acceptable.

)

IV. _ CONCLUSION Based on our review, we have concluded that TVA has adequately justified the use of PVC liquid-tight flexible conduit for their application at Sequoyah.

Hence, this concern is considered to be satisfactorily resolved for Sequoyah.

r r~,-

--m

+. -. -

.__m

.-..y

,.