ML20086H929

Environ RO 75-9:on 750508,radioactivity in Critical Pathway Exceeded Design Objective.Caused by Wind Blowing at Lower Elevation in Direction of Facility.No Corrective Actions Required

ML20086H929
Person / Time
Site:	Peach Bottom
Issue date:	05/18/1975
From:	Meyer R PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	Giambusso A Office of Nuclear Reactor Regulation
References
RO-75-9, NUDOCS 8401200353
Download: ML20086H929 (3)

Text

o (sj

. , . +r (~

nj s u . !-- -, Q, N

PHitADELPHIA ELECTRIC-' COMPANY [ ' > g 2301 M ARKET STREET J

M- no.atvdg ,VD k y -

PHILADELPHIA. PA.19101 ivW$sd56

(- g.g. gg; ggy i

w N . ;u 77 (21518414000 C.,

gy'Q 7 .

p May 18, 1975 4 .g ,

Mr. A. Giambusso Director Division of Reactor Licensing Office of Nuclear Reactor Regulations United States Nuclear Regulatory Commission Washington, D.C. 20555

Subject:

Envi ronmental Deviation i

The following deviation was reported to Mr. Phil Stohr, NRC, Regional Office of Inspection and Enforcement, on liay 9,1975.

Reference:

License Numbers DPR-44/56 .

Environmental Technical Speci fications: 4.3 I oepert Me.- 50-277/279-75-9 Report Date: May 13, 1975 Deviation Date: May 8, 1975 Faci li ty: Peach Bottom Atomic Power Station Units 2 & 3

- R.D. #1, Delta, Pennsylvania 17314 Identifica tion of Deviation: .

,Radioactivi ty in Critical Pathway.

Conditions Prior to Deviation:

Both units operating at approximately full load.

Description of Deviation:

Technical Specifications state that if a measured Icvel of radioactivity in cri tical pathway sampics indicates that the resultant annual dose to an individual from those levels could equal or exceed four times the design objective, the event should be reported. Thi s is equivalent to a continuout concentration of I-131 of 9.6 pCi/1 of milk for the entire year based on a design objective of 15 mrem per ,

year per si te via the grass-cow-milk chain. f Of the eight samples of milk from eight different locations [#

Q7 'Y ;

in the Peach Bottom area taken on May 5,1975, one indicated a level j e> c+"g of I-131 of about 11pCi/1at the time of sampling. The remaining seven samples indicated no measurable I-131 radioactivi ty (less than about 0.06 pCi/1) . No measurable I-131 attributable to the Peach Bottom uni ts had ever been measured in milk samples prior to this time.

8401200353 750518 PDR ADOCK 05000277 .

3g 823 S PDR COPY SENT ltEGION 1

, .e - - _ - _

- ' ./ 5.'tr. A.' Gi mbusso _50-277/278-75-9 May 18, 1975 .

Page 2

. ~u-Of 11 samples of milk taken May 12, 1975, only one indicated measurable I-131. This one sample indicated a radioactivity level of

'abcut 1.8 pCi/l at the time of sampling, which is well be!ow the re- -

portable level. This sample was .taken from the same location tha t had l 11 pCi/1 the previous week.

Desianation of Apparent Cause of Deviation:

As part of the investigation of this occurrence, the recent operating history of the Peach Bottom units was reviewed. Uni t No. 2 scrammed at 6:38 p.m. on April 28, 1975. As a result of this upset and the subsequent return of the unit to service, the levels of gaseous radioactivity increased in the off-gas stack by about an order of mag-t nitude, then decreased gradually, and returned to normal at about 5:00 a.m. on April 29. A slight increase in the levels -of gaseous radio-activi ty was also observed in the Unit 2 vent following scram. Thi s de-creased to normal levels in about three hours. No increase in released radioactivity was observed from the Unit 3 vent. The increase in g gaseous release rates was not higher than expected following a scram.

l Release rates of I-131 from the off-gas stack, averaged over i 20.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br /> beginning on the-afternoon of April 28, and based on iodine

-monitor measurements, increased over the previous week. A correspond-ing increase in - the ref er.se of I-131 was also measured on the Unit 2 l

vent iodine moni tor. The Unit 3 vent iodine moni tor showed no increase.

At no time did any of the above release rates exceed report-able levels.

l= ' An analysis of the meteorology from several of Philadelphia

. Electric Company's meteorological ' facilities .n the area indicated that

~

the wind blew at lower elevations in the direction of the location ex-

[ hibiting I-131 in n.!!k for only one hour beginning about 7:20 p.m. on

! April 28. Higher levei wind data indicated that transport toward this l sample location was extremely unlikely at any time after the scram.

It is concluded, from this meteorological data that the re--

lease of:I-131 from' the Unit 2 vent was most probably responsible for the' increased I-131-level found in the milk. TheestimatedX/qatthe sample locatign for this period from the Unit 2 vent was about 4 x 10-7 seconds / meter. Using this value, the, release rate from the vent would have to be about 5 x 10-2 uci/second of I-131 over the one hour. This

. is in good agreement with the total amount measured by the Unit 2 vent

~

todine monitor, if it'is assumed that the total release occurred during

, that one hour. The fact that no detectable I-131 was found in milk samples from locations toward which the wind was blowing at later times

• confirms .that the I-131 release was of short duration.

Both the levels of I-131 found in the milk samples collected j  : on May -12, and the levels of I-131 observed in the iodine effluent mon-

'itors on May 12 (representing the previous seven days) indicate that the ' levels of released I-131 were again the same as had been routinely measured prior to April 28.

- r Hr. A. Gitmbusso 50-277/278-75-9 ilay 18, 1975 s Paga 3 Analysis of the Deviation:

- The average annual X/q for the location where I-131 was observed -in the milk is 9.6 x 10-o seconds / meter 3 from the roof vents.

Short-term X/Q values as high as 75 times larger can be expected due to normal fluctuations in meteorological conditions. Therefore, psing the NRC staff value of 0.7 curie per year of I-131 assumed to be con-tinucusly released from the vents, the concentration of I-131 in milk could be expected -to be about 1.2 pCi/1 averaged over' the year, or as high as about 90 pCi/1 for short periods due to normal fluctuations in meteorology.

A similar calculation for the off-gas stack, based on con-tinuous release of 1.29 curies / year of I-131, results in an average an-nual concentration in the milk from this location of about 0.1 pCi/1.

Normal fluctuations in meteorology could result in short-term concen-trations of I-131 in milk as high as about 11 pCi/1 or as low as 1.4 x 10-3 pCi/1 with the wind blowing toward this sample location.

Therefore, the concentration of I-131 in a sinq1e sample of milk can be expected. to vary over a much wider range than those observed in the May 5 samples just due to' normal variations in meteorology. The 11' pCi/1 observed does not- really represent an unusually high value but -

is well wi thin . the range of expected short-term values.

No safety consideration is involved since the dose for the worst case hypothetical child, as a result of this event, is only 0.1%

of 10 CFR 20 limits.

Very truly yours, s

0 Y Rankin D. Meyeq/

General Superintendent Generation Division cc: ' Mr. James P. O'Reilly, Director Office of Inspection and Enforcement, Region 1 United States Nucicar Regulatory Commission 631 Park Avenue King of Prussia, PA 194D6 O

a