ML20009A891
| ML20009A891 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 07/07/1981 |
| From: | Mills L TENNESSEE VALLEY AUTHORITY |
| To: | Adensam E Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8107140422 | |
| Download: ML20009A891 (4) | |
Text
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TENNESSEE VALLEY AUTHORITY CHATTANOOGA. TENNESSEE 37401 400 Chestnut Street Tower II July 7, 1981 ne,\\\\
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[1 y j Director of Nuclear Reactor Regulation 34 Attention: Ms. E. Adensam, Chief Licensing Branch No. 4 4~
ve' Division of Licensing
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U.S. Nuclear Regulatory Commission 4
Washington, DC 20555 W
Dear Ms. Adensam:
In the Matter of
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Docket Nos. 50-327 Tennessee Valley Authority
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50-328' My letter to A. Schwencer dated March 4, 1981 committed TVA to provide additional information related to the Sequoyah Nuclear Plant Ice Condenser Containments. The information is enclosed.
Very truly yours, TENNESSEE VALLEY AUTHOR 1IY n
,b L. M. Mills, Manager Nuclear Regulation and Safety Sworn dsubscr{bedbeforeme
- this, day ork /f V'1981 L JCL Notarf Public
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g My Constission Expires
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'b Enclosure 0107140422 810707 hI
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PDR ADOCK 05000327 PDR An Equr1 Opportunity Employer j
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ENCLOSURE SEQUOYAH NUCLEAR PLANT ICE CONDENSER INFORMATION I.
Ice Condenser Maintenance Program A.
Current Program at Sequoyah Nuclear Plant 1.
Perform weighing every six months in accordance with Surveillance Instruction SI-106, 2.
If required, perform ice addition in accordance with procedure SMI-1-61-1.
a.
Break up existing accessible ice, remove by vacuuming, replace, and compact.
b.
Blow in new ice using permanent ice making equipment.
c.
Reweigh according to SI-106 and evaluate weights.
3 If ice addition fails to provide sufficient weight, proceed with water addition according to the special maintenance instructions.
B.
Proposed Improvement Studies 1.
Investigation and development of mechanical devices to provide rapid removal of ice from individual baskets when ice addition method is used:
a.
Extendable tube with positive displacement auger.
b.
Extendable tube incorporating high-efficiency vacuum 4
device.
2.
Development of instructions for maximizing quality of ice delivered by permanent ice mPahines, i
(
3 Investigation of improved water addition methods and equipment (based primarily on D. C. Cook's experience) if ice addition method proves inadequate.
4.
Evaluation of methods to minimize heat gains in ice condenser area during maintenance activities:
a.
Addition of air locks at end-wall access doors.
b.
. Prechil'ing of air locks.
c.
Improved administrative control over personnel entry into upper and lower inlet doors during normal operation and maintenance periods.
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C.
Maintenance Concepts Previously Rejected 1.
Partial or complete melting of individual ice baskets with heat strips, laser cevices, etc.
2.
Ice addition through bottom of baskets.
3 Settling of ice in Lnderweight baskets by vibration or shock.
II.
Projection of Ice Mass as Function of Time We are not including a graph projecting the ice mass as a function of time because of insufficient supporting data to establish reliable sublimation rates.
We can, however, show soae early data taken on Sequoyah unit 1 as follows:
Average Wt. (lbs.)
Sublimation Date Status at 955 C.L.
% per yr.
Jan. 1979 Initial loading 1528.2 N/A June 1980 Reweight 1455.7 33 Feb. 1981 Reweight 1439.8
- 1.6 "The percentage of annual ice loss for the period ending in February 1981 is significantly lower than the rate experienced during the initial period ending in June 1980. This improvement is primarily a result of increased operational experience, correction of associated equipment deficiencies, and improved administrative controls. We expect that this trend toward improved sublimation rates will continue with additional operating time and implementation of future study program recommendations.
III. Heat Balances Heat balances, including calculations for hydrogen, were submitted in letters from L. M. Mills to A. Schwencer dated April 1, 1981 and June 2, 1981.
IV.
Minimizing Ice Loss Rate A.
Ice condenser modifications or methods already implemented to minimize equipment failure, maintenance time, and subsequently the rate or ice loss, are as follows:
1.
Changed differential pressure type coil defrost to timer type defrost.
2.
Changed air handling unit (AHU) glycol valves from 3-way to 2-way type.
3 Installed viewing windows on face of AHU's as a maintenance /
inspection expedient to identify fan and related malfunctions.
4.
Changed insulation on coil drain lines from fiberglass to foam rubber. Improved vapor barrier, "K" factor, and thickness.
5.
Installed water soluble paper covers over floor drains to eliminate back drafts.
B.
Proposed Modifications
'1.
Change AHU glycol valves from existing normally closed (energize to open) to normally open (energize to close). This will minimize glycol shutoff to cooling coils in case of electrical power failure. These valves are in open mode 94 percent of the time.
2.
For each AHU, add local indication fdr electrical power continuity to defrost heaters and heat tapes for early warning detection of faulty electrical equipment before AHU's ice up and damage cooling equipment.
C.
Areas of Study 1.
Improved insulation for ice condenser envelope.
2.
Improved flow paths for chilled air and/or exterior ventilation systems.
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