ML20148F134

Final Deficiency Rept CP-88-16 Re Containment Spray Sys Chemical Additive Tank.Initially Reported on 880115. Inservice Insp Program Will Be Developed to Monitor Tank/ Piping Corrosion Rates.Completion Anticipated by 881115

ML20148F134
Person / Time
Site:	Comanche Peak
Issue date:	01/19/1988
From:	Counsil W, Woodlan D TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC)
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
CP-88-16, TXX-88116, NUDOCS 8801260185
Download: ML20148F134 (2)

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$',7,'",$d%,"$,,, January 19, 1988 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555

SUBJECT:

COMANCHE PEAK STEAM ELECTRIC STATION DOCKET NOS. 50-445 AND 50-446 CONTAINMENT SPRAY CHEMICAL ADDITIVE SYSTEM SDAR: CP-88-16 (FINAL REPORT)

Gentlemen:

On January 15, 1988, we verbally notified your Mr. R. F. Warnick of a potentially reportable deficiency involving the Containment Spray System chemical additive tank and associated piping which has been identified as being designed and fabricated from material that does not provide the specified design life. We have concluded that this issue is reportable under the provisions of 10CFR50.55(e). The required information follows.

DESCRIPTION The Containment Spray System chemical additive tank, piping and valves have been designed and fabricated from ASTM TP-304 stainless steel. The wall thickness of the chemical additive tank is .250 inch for the shell and .320 inch for the head of the tank. The wall thickness for 3/4 inch, 2 inch and 3 inch diameter schedule 40 TP-304 piping is .113 inch, .154 inch and .216 inch, respectively. The chemical additive tank contains a 30'4 sodium hydroxide solution (Na0H). The ambient temperature in the chemical additive tank room is 104 degrees conditions. F during Based normal on National conditions Association and 122 Engineers of Corrosion degrees FNACE) during(emergency publication "Corrosion Data Survey", 5th Edition 1974, a corrosion rate of approximately .020 inch / year may be develo)ed which would provide a life expectancy of about 10 years maximum for t1e tank. The life expectancy of the piping exposed to the NaOH solution is shorter than that of the tank because of the thinner minimum wall and higher stress requirements.

The cause of this deficiency is a failure of the design organization to properly consider the corrosion rate of ASTM TP-304 stainless steel when exposed to a highly caustic solution. The chemical additive system is the only safety system exposed to these service conditions. Materials of the Containment Spray System components which are normally exposed to less concentrated caustic fluid have been reviewed and no other discrepancies were found.

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TXX-88116 January 19, 1988 Page 2 of 2 SAFETY IMPLICATIONS Undetected thinning of this tank and piping over the life of the plant could

.have resulted in tank or pi3e failure. Had this occurred during a LOCA, insufficient Na0H may have ]een added to containment spray water.

Although failure of this system during a LOCA is unlikely, it is the conservative basis for concluding the issue is reportable under 10CFR50.55(e).

CORRECTIVE ACTION An inservice inspection program will be developed to monitor tank / piping corrosion rates by periodically measuring component wall thicknesses and reviewing the results against minimum wall and stress requirements.

The appropriate materials criteria for the Containment Spray System chemical additive piping and components have been specified in the Containment Spray System Design Basis Document (DBD-ME-232). Future system modifications and pipe / component replacement will utilize the DBD criteria to ensure material compatibility.

Development of the inspection program will be completed by November 15, 1988.

The program will remain in effect until an actuai in tervice corrosion rate can be determined and acceptable tank life confirmed, or required replacement date established.

very truly yours, '

(,J.c>. L a 0 W. G. Counsil By:

D. R. Woodlan Supervisor, Docket Licensing BSD/grr c-Mr. R. D. Martin, Region IV Resident inspectors, CPSES (3) -

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