ML20084N654

AO 50-249/75-44:on 751125,offgas Increase Exhibited Which May Have Represented Abnormal Degradation of Fuel Cladding.Cause Unknown.Investigation Underway

ML20084N654
Person / Time
Site:	Dresden
Issue date:	12/11/1975
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20084N649	List: ML20084N646 ML20084N651 ML20084N654 ML20084N664
References
817-75, NUDOCS 8306080412
Download: ML20084N654 (3)

Text

,t ,. Q Commo alth Edison One First vt Plua, Chicago, Illinois [ )

• Address flply to: Post Offica Box 767 Chicago, Illinois 60690 BBS Ltr. #817-75 Dresden Nuclear Power Station R. R. #1 Morris, Illinois 69450;~~l. i - ' i C'

December 11, 1975 S ' '

, - f$ -  !

gf

t..- t ..

3 Mr. James G. Keppler, Regional Director h! Li[.'.l',9N 2" [

Directorate of Regulatory Operation-Region III i  :>>. b/ j/

3, ..uio U. S. Nuclear Regulatory Co:nnission N/

799 Roosevelt Road 9'fU '

Glen Ellyn, Illinois 60137 "D f f , . .. . g 1 .

N oe s :.. ';-

SUBJECT:

REFCRT OF AE!?OR"AL OCCURREICE PER SECTICM 6.6.A 0F TE TECH;ICAL SPECIFICATICO:S OFF-GAS INCREASE CN UNIT-3

References:

1) Regulator / Guide 1.16 Rev. 1 Appendix A

2) Notification of Resdon III of U. S. Nuclear Regulatory Cornnission-Telephone: P. Johnson, 1515 hours0.0175 days <br />0.421 hours <br />0.0025 weeks <br />5.764575e-4 months <br /> on December 1, 1975 Telegram: J. Keppler, 1349 hourc on December 1, 1975 Report Number: 50-249/75 44 Report Date: December 11, 1975 Occurrence Date: November 25, 1975 Facility: Dresden Nuclear Power Station, Morris, Illinois 6c450 IDENTIFICATION OF OCCURRE!CE On November 25,1975, Unit-3 exhibited an off-cas increase which may have Fuel cladding is represented an abnormal decra.dation of the fuel cladding.

one of several boundaries designed to contain radioactive materials, as stated l in definition A.5 of the Technical Specifications.

CONDITIONS PRIOR TO OCCURR9!CE There had Unit-3 was in the Run mode at a power level of 2355A57t and 795 DTo.

routine off-cas sar'ple been no power chances in the preceding 32 hours3.703704e-4 days <br />0.00889 hours <br />5.291005e-5 weeks <br />1.2176e-5 months <br />.

l taken earlier in the day indicated a stack release of .694 curies /second.

Some dificulty had been experienced in maintaining a constant suction pressure l

on the "A" cican-up recirculation pump; however, all major plant parcneters were consistent with reactor power IcVel.

050hhd9 140M PDR 1

A ro Mr. Jam 2s G. Kepplir - O DIcemb3r 11, 1975 l'

b_

DESCRIPTION OF CCCURRE!CE At 1745 hours0.0202 days <br />0.485 hours <br />0.00289 weeks <br />6.639725e-4 months <br /> on November 25, 1975, the "A". clean-up recirculation pump tripped due to high system pressure, and the "B" pump was put into service. };

At approximately 2245 hours0.026 days <br />0.624 hours <br />0.00371 weeks <br />8.542225e-4 months <br />, the uriit operator noticed that the linear off-gas monitor was increasing, and at 2300 honrs the off-gas Ei Rad alarm rctuated.

The shift engineer and shift foreman were i= mediately notified.

.0ff-gas temperature and pressure showed no changes (indicating that the system was still functioning properly), and the off-gas increase appeared to be stabilizing.

Inspection of the linear and logarithmic off-g?.s monitors revealed two distinct

' off-gas increases-one at approximately 2240 hours0.0259 days <br />0.622 hours <br />0.0037 weeks <br />8.5232e-4 months <br />, and another at about 0030 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br /> the following morning. The daily stack release sample of November 26 was found to be 2.180 millicuries /second, well within Technical Specification limits. Station stack releases were due predominantly to Unit-3; Unit-1 was in the shutdown mode, and Unit-2 releases were negligible ( =10 microcuries/

second).

DESIGNATION OF APPARE!? CAUSE OF OCC'JFItENCE Thecauseof$heoccurrencecannotbedefinitivelyestablishedatthistime; however, limited degradation of the fuel cladding is considered probable.

ANALYSIS OF 00CURRECE Several isotopic analyces were performed on steam jet air ejector samples c'ollected after the occurrence. Since the beginning of current reactor cycle, total isotope activity at the air ejectors approximated .21 curiec/second.

Samples taken on the 26th and 28th of November-indicated .50 and .n3 curies /

second, respectively. Isotopic ane. lyses were performed in order to break down the air ejector effluent into percentages of equilibrium, diffusion, and recoil, which denote the origin of fission products observed in the analysis.

Average recoil composition changed from approximately 40% to 8($; diffusion from 55% to 9%; and equilibrium from about 5% to 11%. Most of the off-gas increase, therefore,-appeared to be recoil.

The highest stack release of 2.18 millicuries /second occurred on November 26 at a power level of 2380 I4?t. During the remainder of the week, stack releases stabilized to the following values:

November 27, 1.105 millicuries /second (2056 rat);

No" ember 28, 1.185 millicuries /second (2379 Ist); and November 29, 1.144 millicuries /second (2362 rat).

Stack samples taken since November 29 have indicated lower activity consistent with reductions in reactor power. Stack gas. composition remained relatively e

e O

.- ,. 4 Decemb r 11, 1975

- Mr. Jamts G. Kepp c6nstant before and after the increased off-gas was observed. Since station off-gas releases never remotely approached Technical Specification limits, public health and safety were not adversely affected by this occu rence.

CORRECTIVE ACTION Actions taken to prevent recurrence will be contingent upon the results of the investigation now undenray. The findings of that investigation will be submitted i

in a follow-up letter' i I

j

o. E. Stephenson Superintendent BES:TJR:sep File /NRC i

e 1

=

t E