ML20084Q778

Ao:On 730922,30 & 1001,iodine & Particulate Release Rates from Reactor Bldg Vent Stack Exceeded Limits.Several Factors Can Be Identified as Cause of Occurrence.Factors & Lack of Control Over Factors Continue to Frustrate Operation

ML20084Q778
Person / Time
Site:	Quad Cities
Issue date:	10/03/1973
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084Q697	List: ML20084Q724 ML20084Q756 ML20084Q766 ML20084Q770 ML20084Q775 ML20084Q778 ML20084Q784 ML20084Q787 ML20084Q791 ML20084Q794 ML20084Q798 ML20084Q800 ML20084Q809 ML20084Q816
References
NUDOCS 8306140076
Download: ML20084Q778 (4)

Text

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October 3, 1973 NG Tjs,

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{i J. F. O' Leary, Director

. Directorate of Licensing R e gulation U.S. Atomic Energy Commission Washington, D. C. 20545

Subject:

Quad-Cities Nuclear Power Station Docket Nos. 50-254 & 50-265 DPR 29 & 30, Appendix A Sections 1.0.A.2, 3.8.B.3.a, and 6.6.b

Dear Mr. O' Leary:

The purpose of this letter is to provide you with additional information concerning recent abnormal occurrences involving iodine and particulate release rates from the reactor building vent etack at Quad-Citics Nuclear Power Station. This sup-plements my letter of September 21, 1973 and in addition reports the releases of September 22, 30, and october 1, 1973 in ac-cordance with paragraph 6.6.B.1 of the Technical Specifications.

The abnromal occur'rence of the 22nd was determined from the -

particulate sample counted on the 25th and the latter two occurrences were detected by the iodine samples counted im-mediately upon removal.

PROBL_EM A_ND_ I_NV_ESTI_ CATION The following table summarizes the release rates from the vent stack as a percentage of the limit of Technical Speci-i fication 3.8.B.3.a:

4 Date of  % of LCO 48 Hour Final (7' day)

R lease I-131 only  % of LCo  % of LCo ,

j I-131& Part. I-131&Part. )

l '9 11 - typical 15 24 23 l 9 12 - U-1 scram 35 111 104 9 13 290 1425 1277 9 14 62 136 140 9 15 76 106 103 9 16 - U-2 scram 56 l

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Mr. J. F. O' Leary October 3, 1973 1

(table cont.)

Date of  % of LCO 48 hour5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> Final (7 day)

Release I-131 only  % of LCO  % of LCO I-131& Pa rt_.

I-131&Part.

9 17 70 122 119 9 18 54 76 75 9 19 36 64 50 9 20 33 44 42 9 21 - U-1 chutdown 48 155 122 9 22 57 121 110 9 23 68 71 70 9 24 54 58 58 9 29 59 61 ~

9 30 - U-1 startup 102

10/1 204 10/2 88 [' []

The only steam leaks of any significance which may have con-tributed to the above releases occurred during the Unit 1 startup on September 30, 1973 following a planned one week 3 '

maintenance outage. A sesi ring leak on a main steam line drain valve was detected and stopped on the-evening of the 30th. The vent system was isolated on that day at about 2100 when an increase in the exhaust Continuous Air Monitor. (CAM) was observed. The vent system was restarted on the 1st and operated all day. On the 2nd another leak was detected on the RCIC testable check valve and a shutdown is currently in pro-gress to isolate and repair this leak. The vent system was isolated again at about 1400 on the 2nd. The remainder _of the occurrences noted in the above tabic can only be attri-buted to the plant activities noted in the first column.

Due to its magnitude'an isotopic analysis of the 9/13 parti-4 culate sample was conducted. As expected the results indicated that it was predominantly iodine-131.

The composition vas:17 1 50 uc/ce, I-131; 4.07 X 10-12 uc/ce, Co 60; and 2.01 X10-ue/ce, Cs-137 DETER _MINATION OF__CAUSE AND CORREC_TIVE_ ACTION Several factors can be identified as contributing to.the cause of the abnormal occurrences cited above. These factors and our lack of control over them have continued to frustrate our efforts to operate within the Technical Specifications.

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'Mr. J. F. O' Leary October 3, 1973

1. The conservatism inherent in the Technical Specification limit and the manner in which release rates must be computed on a daily basis is the principle reason that this LCO has been repeatedly exceeded at Quad-Cities. Commonwealth Edison is in the process of reviewing this limit and we intend to propose Technical Specification changes in the near future.

We believe these changes vill result in a more realistic limit without compromising any margin of safety.

2. Our ability to take prompt corrective action on the day of a release in exccas of the rate specified in Section 3.8.B.3.a is very limited. If an increase in the release rate is suspected based on an increasing CAM reading or discovery of a leak, the vent system can be isolated and the Standby Gas Treatment System initiated. Frequently, however, the release is not known to exist until the iodine sample cartridge in counted the next day or until the parti-culate sample is analyzed three days after the high release rate occurred. Even if the release could always be detected immediately the effectiveness of the corrective action is questionable. The relatively lov flow rate of the Standby Gas System cannot " clean out" the-reactor building. If the release is detected quickly enough and the vent system isolated for the remainder of the day, vc might avoid exceeding the LCO on that day. Due to the long lived nature of the isotopes involved, however, it can be seen that we are only using the building as a large hold-up volume prior to eventual release. .

From the above table it is apparent that it takes 3 to 4 days after an occurrence before the release rate approaches what might be considered an equilibrium. During this period any event such as a minor leak or unit scram unavoidably puts the release rate over the limit again for that day.

3 Recent abnormal occurrences of this nature have clearly demonstrated the sensitivity of the vent ctack release rate to the concentration of iodine in the reactor coolant. This is true even though the iodine le vels during transients con-tinue to be a small fraction (less than 10%) of the steady state limit of Technical Specification 3.6.C.1.- This had the effect of increasing the contribution to the release rate of very minor leaks. This problem is also compounded by the relatively low capacity of the Quad-Citics reactor water cleanup systems. We expect that this problem vill be magni-fied in the near futuro by a recent increase in'the off gas activity on Unit 2 from about 5,000 ue/see to 17,000 ue/sec at full load, l

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Mr. J. F. O' Leary 4- October 1, 1973 SAFETY IMPLIC ATIONS_

As stated in previous reports on this subject we do not consider the saf ety implications of these occurrences to be significant. This conclusion is substantiated by the continued negative finding of our environmental monitoring program.

Very truly yours, COMMONWEALTH EDISON COMPANY QUAD CITIES NUCLEAR PCW ER STATION

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B. B. Stephenson Y$fh5 Station Su~perintendent BhlS/lk 4

cc: Regional Director Dir e c t ora te of Regulatory Operatiohs, Region III e

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