05000316/LER-2076-052, Re Iodine Spike Following Power Transient

Re Iodine Spike Following Power Transient

ML18219C276
Person / Time
Site:	Cook
Issue date:	12/06/1976
From:	Jurgensen R Indiana Michigan Power Co
To:	James Keppler NRC/RGN-III
References
LER 1976-052-00
Download: ML18219C276 (30)

LER-2076-052, Re Iodine Spike Following Power Transient

Event date:
Report date:
3162076052R00 - NRC Website

text

U.S. NUCLEAR REGULATOR MMISSION NRC FORM 195 I2.76)

NRC DISTRIBUTION FDR PART 50 DOCKET IVIATERIAL DOCKET NUMBER

+0- g/Q FILE NUMBER INCIDENT REPORT Mr Keppfer E9LETTER OORIGINAL SCOPV

DESCRIPTION

ONOTORI2ED QUNCLASSIFIED PROP Indiana

& Michigan Pwr Co Bridgamn, Mi

~ R W Jurgensen INPUT FORM ENCLOSURE DATE OF DOCUIlIENQ 6

DATE RECEIVED NUMBER OF COPIES RECEIVED 1

CC Ltr trans the following:

Licensee Event Report (ROID 76-52) on 11-20-76 concerning excessive iodine spike......

PLANT NAME'

'C Cook yl ACKNOWLEBGEO 80 NOT RglQOyg NOTE:

IF PERSONNEL EXPOSURE IS INVOLVED SEND DIRECTLY TO KREGER/J, COLLINS BRANCH CHIEP:

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INDIANA & It/IICHIGAN PDNE8 CO I/IPA NY DONALD C. COOK NUCLEAR PLANT P.O. Box 458, Bridgman, Michigan 49106 December 6, 1976 Mr. J.

G. Keppler, Regional Director Office of Inspection and Enforcement United States Nuclear Regulatory -Commission Region III 799 Roosevelt Road Glen Ellyn, IL 60137

Dear Mr. Keppler:

Operating License DPR-58 Docket No. 50-315 Pursuant to the requirements of Appendix A Technical Specifications and the United States Nuclear Regulatory Commission Regulatory Guide 1.16, Revision 4, Section 2.a, the following report is submitted:

RO-50-315/76-52 During preliminary reviews, this occurrence was classified as a 30 day report and no followup report was submitted.

Subsequent reviews indicated that this should be a

14 day report.

The RO III Resident Inspector was on site on the day of the occurrence.

Sine ly, r

. Jur s

Plant Ma ge RWJ/mj cc:

R. S. Hunter J.

E. Dolan G.

E. Lien R. Kilburn R. J. Vollen BPI R.

C. Callen MPSC K. R. Baker RO: III P.

W. Steketee, Esq.

Walsh, Esq.

G. Charnoff, Esq.

G. Olson J.

M. Hennigan R. S. Keith PNSRC Dir., IE (40 copies)

Dir., MIPC (4 copies)

OEC 91976

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INDIANA 5 MICHIGAN POWER COMPANY DONALD C.

COOK NUCLEAR PLANT IODINE SPIKE FOLLOWING POWER TRANSIENT NOVEMBER 20, 1976 This report is submitted persuant to the requirements of Appendix A Technical Specifications 3.4.8 and 6.9. 1.

Specification 3.4.8 indicates that, "The specific activity of the primary coolant shall be limited to ~1.0 pCi/gm dose equivalent I-131...."

On November 20, 1976, at 0510 hours0.0059 days <br />0.142 hours <br />8.43254e-4 weeks <br />1.94055e-4 months <br />, DOSE EQUIVALENT I-131 was found to be 3.33 pCi/gm in violation of Specification 3.4.8.

This spike resulted from a unit trip at 0055 hours6.365741e-4 days <br />0.0153 hours <br />9.093915e-5 weeks <br />2.09275e-5 months <br /> on November 20, 1976.

Attempts;to count the sample taken at 0510 on November 20, 1976, were initially unsuccessful with geometry configurations available at that

time, as the total activity caused significant instrument dead time.

For this reason, the sample was held for decay to be counted as, soon as instrument dead time permitted.

Since the sample still could not be counted 16 hours1.851852e-4 days <br />0.00444 hours <br />2.645503e-5 weeks <br />6.088e-6 months <br /> later, the sample was diluted and counted at 2200 hours0.0255 days <br />0.611 hours <br />0.00364 weeks <br />8.371e-4 months <br /> on November 20, 1976.

Sample results indicated 2.77 pCi/cc I-131; however, the" technician on duty at that time felt that the four hour surveillance requirement of Table 4.4-1, Item 4a~

was no longer required with the unit out of service at the time.

Sampling continued at the normal eight hour frequency.

During data review.

at 1115 hours0.0129 days <br />0.31 hours <br />0.00184 weeks <br />4.242575e-4 months <br /> on November 21, 1976, the Chemical Supervisor found the out-of-specification condition.

All samples taken since the November 20,

1976, 0510 hours0.0059 days <br />0.142 hours <br />8.43254e-4 weeks <br />1.94055e-4 months <br /> time period were counted immediately, with data indicating that DOSE EQUIVALENT I-131 was below 1.0 pCi/gm at the 2100 hour0.0243 days <br />0.583 hours <br />0.00347 weeks <br />7.9905e-4 months <br /> sample on

0 November 20, 1976.

Sampling frequency at this point was kept at once/8 hours

1 as I-.131:was <1.0 pCi/cc', however, during the period from 0510 to 2100 hours0.0243 days <br />0.583 hours <br />0.00347 weeks <br />7.9905e-4 months <br /> on November 20,

1976, samples were taken each 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />, rather than each four hours, resulting in a violation of the monitoring requirements of Table 4.4-4, Item 4a.

The unit had been operating at 1005 power since November 10,

1976, with a slow decrease in power to 70/ on November 19, 1976.

I-131 values had increased from 2.0x10 pCi/cc at equilibrium to =4.0x10 pCi/cc following the reduction to 70Ã power.

This small spike was similar.to those seen during 'earlier power transients, i.e.

power reductions to 705 from November 5

to 12, 1976.

(Figure 1)

Prior to return to full power, the unit was tripped at 0055 hours6.365741e-4 days <br />0.0153 hours <br />9.093915e-5 weeks <br />2.09275e-5 months <br /> on November 20, 1976, resulting in the larger I-131 spike to 2.77 pCi/cc with resultant DOSE EQUIVALENT I-131 dropping below 1.0 pCi/gm within 16 hours1.851852e-4 days <br />0.00444 hours <br />2.645503e-5 weeks <br />6.088e-6 months <br /> after the spike.

DOSE E(UIVALENT I-131 values were in the "Acceptable Operation" portion of Technical Specification Figure 3.4-1 at all times during the transient.

Data from WCAP-8637 -- "Iodine Behavior under Transient Conditions in the Pressurized Water Reactor",

indicates that for power transients, the iodine release rate peaks at 3.5 - 5.25 hours2.893519e-4 days <br />0.00694 hours <br />4.133598e-5 weeks <br />9.5125e-6 months <br /> following the initiating event (Table 1).

As the 0510 sample was taken 4.25 hours2.893519e-4 days <br />0.00694 hours <br />4.133598e-5 weeks <br />9.5125e-6 months <br /> following the unit trip, recorded values are assumed to be quite close to the actual I-131 peak value.

The plot of I-131 activity prior to and following the unit trip (Figure 2) also indicates that the 0510 data is quite close to the Coolant samples are brought to ambient conditions before counting, therefore, units of pCi/cc are essentially inter changeable.

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peak value, taking into account peak release times and the slope of the I-131 activity decrease.

This curve can also be utilized to indicate I-131 values during the four hour periods when samples were not obtained as per requirements of Table 4.4-4, Item 4a.

The plot of I-133 and k

)(~

I-135 activities during this period (Figure 3) also validates this assumption.

Utilizing the above data, the specific activity of the primary coolant exceeded 1.0 pCi/gm DOSE EQUIVALENT I-131 conservatively.

for a period of eighteen (18) hours.

(Figure 4 )

Power transients have been identified as one of three distinct':

causes

of iodine spiking.

Data from operating plants has indicated iodine spiking of similar (Haddam Neck, April 16, 1971 I-131 - 3.0 pCi/gm) or greater (R. E. Ginna, February 26,

1971, I-131 - 6.8 pCi/gm; April 14,

1971, I-131 - 18.3 pCi/gm) magnitude (Figures 5, 6, 7) than the one reported following reactor trip on November 20, 1976.z Primary coolant I-131 activity had been stable at 100'A power at 2.0 x 10-z pCi/cc since October 7, 1976, following an increase in I-131 during steady-state operation indicating development of a fuel clad failure.

DOSE EQUIVALENT I-131 during this time period was also stable at 0.02 - 0.03 uCi/gm.

For this reason, the iodine spike on November 20, 1976, is attributed to the normal spiking phenomena during power transients rather than additional fuel clad failures.

Mon-itoring of iodine data following return:to equilibrium at 100Ã power had validated this assumption as the I-131 activity has stabilized at 1.5 x 10 vCi/cc with DOSE EQUIVALENT I-131 at 0.03 pCi/gm (Figure 8 and 9).

Westinghouse

Electric, WCAP-8637,

November, 1975.

As mentioned'reviously, reactor power had been stable at 100%

since November 10, 1976, with a scheduled slow decrease to 70K power occurring on November 19; 1976.

Purification flow was reasonably stable at 75 gpm through the CVCS Mixed Bed Demineralizer following start-up in September 1976, until 1130 hours0.0131 days <br />0.314 hours <br />0.00187 weeks <br />4.29965e-4 months <br /> on November 21,

1976, when the flow was increased to 120 gpm.

(Figure 4)

There were no de-gassing operations performed during this time period.

Fuel burn-up by core region is indicated in Table 2.

To ensure the four hour sampling requirements are met in the future, the incident has been 'discussed with all chemical technicians and supervision with instructions to perform DOSE E(UIVALENT, I-131 cal-f*

V culations whenever I-131 activity approaches 0.75 pCi/cc. In 'addition, new geometries have been added to the counting room Ge(Li) systems to

,enable counting of samples with higher total activities,.:as well as instructions to dilute samples if necessary to ensure that samples are counted as soon as possible following system transients.

INDIANA 5 MICHIGAN POWER'.COMPANY DONALD C.

COOK NUCLEAR PLANT TABLE 1 SUMMARY OF RELEASE'RATES DURING POWER TRANSIENT CONDITIONS 0.5 1.0 3.5 5.0 5.25 7.5 10.0 14.0 TIME 0.5 hr 1.0 hr 3.5 hr 5.0 hr 5.25 hr 7.5 hr 10 hr 14 hr R/Ro 13 19 40.5 56 65 39 25 14 0.0

Reference:

Westinghouse Electric Corp.,

WCAP-8637, "Iodine Behavior Under Transient Conditions In The Pressurized Water Reactor",

November, 1975.

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INDIANA 5 MICHIGAN POWER COMPANY DONALD C.

COOK NUCLEAR PLANT TABLE 2

FUEL BURNUP BY CORE REGION REGION NO.

BURNUP FOR CUMULATIVE PERIOD BURNUP ENERGY FOR PERIOD CUMULATIVE ENERGY MWD MTU MWD/MTU BTU BTU 2.

3.

0. 4661E+13

0. 4993E+13

0. 1797E+05 0.2094E+04

0. 1520E+04

0. 1264E+05

0. 3606E+13

0. 1934E+04

0. 1785E+05 0.4303E+14

0. 4285E+14

0. 2998E+14 Core Total

0. 1850E+04

0. 1617E+05

0. 1326E+14 Period:

October 1,

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