ML20084J174

Ao:On 730406,while Returning 1-A Cleanup Demineralizer to Svc,Offgas high-high Alarm Actuated & Offgas 15 Minute Isolation Timer Initiated.Caused by Air Injected Into Reactor While Valving 1-A Cleanup Demineralizer

ML20084J174
Person / Time
Site:	Quad Cities
Issue date:	04/18/1973
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	Giambusso A US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084J178	List: ML20084J174 ML20084J184
References
BBS-73-72, NUDOCS 8305120221
Download: ML20084J174 (2)

Text

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Common Ith Edison O V

• Ouad Cities)Eclear Power Station 3Md Post Office Box 216 j l - Cordova, Illinois 61242 Telephone 309/654-2241

, G- N April 18, 1973 - i^ ? .

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Mr. Angelo Giambusso d d, y/

Deputy Director for Reactor Projects gf rg /

4 Directorate of Licensing > _

U. S. Atomic Energy Commission --

Washington, D. C. 20545

REFERENCE:

Quad-Cities Nuclear Power Station Docket Number 50-254 p DPR 29, Appendix A, Sections 1.0.A.2.,

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3.6.C.4.

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Dear Mr. Giambusso:

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The purpose of this letter is to provide you with the de-T/(i

taile of exceeding the limiting condition of operation fcr Unit I-reactor coolant conductivity.

This abnormal occurrence took place on April 6, 1973 as

_h (J reported to you by telegram on the same day. This occur-rence was caused by air being injected into the reactor b[D while valving in 1-A clean-up demineralizer. As a result

') of this injection the reactor water conductivity and the off-gas activity increased. According to Section 3.6.C.5 of the Technical Specifications an orderly shutdown was immediately commenced and the clean-up system was used to bring the conductivity below the Technical Specifica-tions limit.

, DESCRIPTION OF INCIDENT At about 2:30 p.rn. on April 6, 1973 while returning 1-A clean-up demineralizer to service, subsequent to mainten-ance, the off-gas high-high alarm actuated and the off-gas fif teen minute isolation timer initi.ated. The unit operator decreased load from 780 FMe to 500 FMe. The off-gas monitors remained above their isolation signal set point for less than six minutes and were near normal when the operator reset the off-gas isolation timer seven min-utes after timer actuation. The analysis of a reactor water samp,le indicated a conductivity of 23 umhos/cm.

There was no detectable increase in the chimney monitors.

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. Mr. A. Giambusso April 18, 1973 The. clean-up' system was used to decrease the reactor water

- conductivity below the Technical Specifications limit.

I Additiona11y, an orderly shutdown of unit one at a rate of 10 MWe/hr was initiated. At 12:50 a.m. on April 7, 1973 the reactor coolant conductivity had decreased to 9.35 umhos/cm and, therefore, the shutdown was terminated at 400 MWe. The reactor power was held constant until the coolant conductivity had dropped to 5 umhos/cm.

ANALYSIS OF THE INCIDENT _

While maintenance was being performed on the clean-up system the demineralizers were in a holding cycle for over twenty-four hours prior to being put back into the system.

Due to lack of make-up water and slow leakage of water from valve packings, because of low pressure in a high pressure system, an air pocket was formed in the domin-eralizers. When the 1-A domineralizer was valved back into the system, the air was injected to the reactor causing high conductivity and high off-gas activity.

Reactor water samples showed high concentration of Mn-56 indicating release of corrosion products from the vessel walls and internals due to the lowering Ph of the reactor water. Activation products were mostly composed of N-13, N-16, 0-19 and Ar-41 while the equivalent I-131 concentra-tion remained unchanged. However, chlorine concentration did not change from its initial value of(.03 PPM.

CONCLUSION AND CORRECTIVE ACTION l l

The result of the reactor water sample indicated no fuel failure and the formation of the short lived activation gases resulted in no notable release through the chimney.

This incident is not attributable to operator error or equipment failure and is due to incorrect procedures. -Our procedures will be modified to prohibit a . future recurrence.

. Sincerely yours, gy!)l*[kk h/f5

[F2B . B . Stephenson '

Station Superintendent BBS:KS/dp

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