TXX-4409, Interim Significant Deficiency Rept SDAR-152 Re Ventilation Exhaust Dampers Failing to Close Possibly Causing Radioactive Releases.Ventilation Sys Will Be Modified to Provide Adequate Heat Removal

Interim Significant Deficiency Rept SDAR-152 Re Ventilation Exhaust Dampers Failing to Close Possibly Causing Radioactive Releases.Ventilation Sys Will Be Modified to Provide Adequate Heat Removal

ML20111A393
Person / Time
Site:	Comanche Peak
Issue date:	03/06/1985
From:	Clements B TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC)
To:	Hunter D NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
References
SDAR-152, TXX-4409, NUDOCS 8503120483
Download: ML20111A393 (3)

Text

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7 .y 30!@ 20W s v NAR -81985 TEXAS UTILITIES GENERATING COMPANY -y MMYWAY TOWER . 400 NORTH OLIVE MTHEET, L.B. Mt . DA LLAM.TEXAM 73201 i

..c. .e..u.. v. n.m . cta..=..n.t.s. March 6, 1985 TXX-4409 Mr. D.R. Hunter, Chief Reactor Project Branch 2 U.S. Nuclear Regulatory Commission Office of Inspection & Enforcement 611 Ryan Plaza Drive, Suite 1000 Docket Nos.: 50-445 Arlington, TX 76012 50-446 .

COMANCHE PEAK STEAM ELECTRIC STATION VENTILATION EXHAUST DAMPERS QA FILE: CP-84-27, SDAR-152 FILE NO.: 10110

Dear Mr. Hunter:

In accordance with 10CFR50.55(e), we are submitting the enclosed report of actions taken to correct a deficiency regarding ventilation exhaust dampers that have been observed to be designed / installed to fail closed which would divert radioactive releases to rooms in which operator action is required. We have submitted interim reports logged TXX-4333, TXX-4365 and TXX-4379, dated October 12, 1984, November 20, 1984 and December 17, 1984, respectively.

Supporting documentation is available at the CPSES site for your inspector's review.

Very truly yours, i ly R. Clements BRC:tig cc: NRC Region IV - (0 + 1 copy)

Director, Inspection & Enforcement (15 copies)

U.S. Nuclear Regulatory Commission Washington, DC 20555 850312O g $5dh 45 - .

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TXX-4409 3/6/85 Page 2 ATTACHMENT VENTILATION EXHAUST DAMPERS Description During disposition of a design deficiency report by site engineering, the designed failure mode for several ventilation dampers was observed to be fail-closed. Also, it was determined that when in the post-accident mode of operation, airborne radioactive releases could be diverted from normal exhaust paths to rooms required for access for operator actions.

Evaluation of this issue involved an assessment of the primary plant ventila-tion scheme. Initial concerns regarding the effects of radiation were dispelled without affecting offsite releases or operator action. Compromise of the class lE power supply, also an initial issue, was resolved without adverse affects; however, the review concluded the effects of increased temperature and hydrogen releases within the ventilation system were ,

unacceptable. Specifically, increased temperatures during an accident could exceed qualification parameters and result in indeterminate operability of the electrical equipment in the affected areas. In addition, radioactive, hydrogen-rich gases could result in an explosive mixture of hydrogen in the event of an inadvertent leak from the boron recycle holdup tanks.

Safety Implications In the event the deficiency had remained undetected, the ability of the operator to safely perform essential functions could be impaired or pro-hibited. In addition, the operability of this equipment required under accident conditions could not be assured.

Corrective Actions In order to assure operability of the affected electrical equipment, the ventilation system will be modified to provide adequate heat removal.

Eighty-eight (88) dampers will be removed or modified to accomplish the system rework. An additional thirty-three (33) dampers will be involved in the effort in order to minimize the impact to scheduling and engineering.

Further activities, such as insulating additional piping, have been implemented to reduce heat generation.

Equipment qualification reports of the affected electrical equipment are being reviewed and updated to incorporate a 72-hour loss of ventilation.

The relocation of components and instruments is also underway to minimize the impact of the qualification program.

.':TXX-4409 3/6/85

.Page~3

'For Unit 1,-design, construction, and inspection activities for the damper

-effort are scheduled for completion in July 1985. ' Equipment qualification .

report, FSAR, and specification updates will be complete in September 1985. Unit 2 activities will be completed prior to startup testing.

In order to mitigate the effect of potential hydrogen releases, explosion-proof lighting will be installed where applicable. A special HVAC test to ensure. gas removal will also be performed.

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