ML20244A588

PNO-79-67AF:summary of Info Re Nuclear Incident as of 790425.Describes Plant Status & Environ Status.Highest Thermocouple reading:312 F

ML20244A588
Person / Time
Site:	Three Mile Island, Humboldt Bay
Issue date:	04/25/1979
From:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE)
To:
Shared Package
ML19199A450	List: ML20244A588
References
PNO-79-067AF, PNO-79-67AF, NUDOCS 7905020230
Download: ML20244A588 (5)

Text

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,. . IMMEDIATE e' PRELIMINARY NOTIFICATION

, April 25,1979 PREI.IMINARY NOTIFICATION OF EVENT OR UTUSUAI, OCCURRENCE -PNO-79-67AF This preliminary notification constitutes sununary information of an eNnt of safety or public interest significance. The information presented is~

a summary of information as of 7:00 a.m. on April 25, 1979. .

Facility: Three Mile Island Unit 2 Middletown, Pennsylvania (DN 50-320)

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Stibj ecta NUCLEAR INCIDENT AT THREE MILE ISLAND Plant Status In the course of transferring feedwater flow to the auxiliary noz=les, a carryover of water into the steam line was experienced, resulting g in water impingement in the main turbine. An operator-initiated turbine trip at about 3:00 p.m. stopped the impingement. The feedwater was being diverted to the auxiliary feedvater sparger in preparation for I secondary system modification for adding a closed cooling r,yr: tem.  !

Steam is currently being admitted to the main condenser through the  :

turbine bypass valves. This change in cooling mode will not affect '

6 dish preparations for natural cirenlation operations. The average

' M primary coolant temperature has increased to 224 degrees F. The highests incore thermocouple reading.is 312 degrees F.

As a result of changing the charcoal filters in the A Trains of the -

Auxiliary and Fuel Handling Building Ventilation Systems, the iodin'.e discharges have been reduced by approximately 80 percent. The I charcoal filters of Auxiliary Building Ventilation System Train B l have been replaced. This system was placed in service at 5:30 a.m. l April 25. I Following a briefing of the Governor's Office, a press briefing was t held to outline the anticipated schedule for achieving long term ]

cooling status. A copy of the press release is attached.

Environmental Status Three Aerial Measuring System (ARMS) Surveys were made on April 24, 1979. No radioactivity above natural background was detected, y [ _ CONTINUED ~

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. i j Continued April 25, 1979 (

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i t c Iodine concentration at Unit 2 ventilation stack (Analyzed by NRC Mobile Laboratory). ,, {

Date/ Time Activity (uCi/ce) .

~0 4/24 (0408) - 4/24 (0637) 3.0 x 10 4/24 (0642) - 4/24 (0813) 4.2 x 10",8 4/24 (0815) - 4/24 (1215) 3.1 x 10 -

4/24 (1217) - 4/24 (1600) 1.6 x 10,83

, , , . _, 4/24 (1602) - 4/24 (1955) 2.4 x 10 -8 4/24 (1958) - 4/25 (0001) 2.6 x 10 Offsite Measurements j

Radiation Levelt Offsite radiation levels identified by NRC survey teams continue to be consistent with natural background levels (0.02 mR/hr maximum).

These results were obtained from routine daily surveys performed downwind on the east. side of the Susquehanna River at distances up i i gg to five miles north and south of the site. gy Dose rates (47 locations) as measured by NRC thermoluminescent '

dosimeters (TLDs) for the past 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> period continue to be consis- ,

tent with natural background levels.

NRC Environmental Samples (Samples tak,en offsite within 3 miles of site analyzed in mobile laboratory)

Nunber of I Sample Type Date of Sample Samples Results air 4/24-25 6 Less than MDA*

milk 4/23 3 Less than MDA daily air 4/23-24 1 Less than MDA

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EPA Environmental Samples (Analyzed at Remote Laboratory) ,

Number of >

Sample Type Date of Sample Samples Results air 4/23 28 Less than MDA ,33 air 4/23 '

3 Range from 2.3 to 7.1 x 10 1 microcuires per cubic centi-

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meter (0.23 to 0.71 picoeuries )

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.. per cubic meter) air #,,

4/20 2 One sample was less 'than MDA. One sample indicated 168 picoeuries per cubic meter of Xe-133.**

Both samples indicated approximate background levels of Kr-85.

CONTINUED

• IMMEDIATE PRELIMINARY NOTIFICATION l

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Continued Page 3 April 25, 1979 PNO-79-67AP All EPA samples were taken at distances greater than 2 miles from this site. '

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• MDA - minimum detectable activity.

• • Maximum Permissible Concentration for Xe-133 is 300,000 picoeuries' per cubic meter.

The' Commonwealth of Pennsylvania has been informed of these results.

Attachment:

Press Release Dated 4/24/79 Contaett Distribution: Transmitted H St ~2' I v-Chairman FIEdrie Commissioner Bradford S. J. Chilk, SECY I Coassissioner Kennedy Commissioner Ahearne- C. C. Kassnerer, CA Conseissioner Gilinsky (For Distribution)

Transmitted: MNBD ~ P. Bldg L. V. Gossick, EDO H. R. Denton, NRR J. G. Davis, Region I IE )

H. L. Ornstein, EDO g.

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m R, C. DeYoung, NRR Reg, ion'II _

i J. J. Fouchard,.PA R. J. Mattson, NRR Region III l

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! N. M. Haller MPA V. Stello, NRR Region IV L IN R. C. Ryan, OSP R. S. boyd, NRR Region V H. K. Shapar, ELD J SS Bldg . (MAIL)

W. J. Dircks, NMSS J. J. Cummings, OIA i

S. Levine, RES R. Minogue, SD M ) IE (THI) Site (Provide copy to STATE)

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White House Situation Room j FDAA' (Provide copies to the Administrator and the Operations. Center)

EPA DOE /EOC PEMA BRP (State of PA)

DCPA BEW (Pickup)

Handcarry (FAA)

IMMEDIAIE '

I PRELIMINARY NOTI.F-ICATION j

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Attachment to PNO-79-67AF FOR IMMEDIATE RELEASE i

i ._+ April 24, 1979 .

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The NRC staff today announced a tbnetable for placing the Three .

Mile Island Unit 2 reactor on natural circulation cooling. As i stated on previous occasions, it is now possible to cool the reactor by natural convection circulation if difficulties arise l

with presently operating equipment. It is, of course, preferable L

to place the plant on natural circulation in a planned fashion

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• while presently available plant instruments and equipment remain

[ functioning; However, if instrumentation in the plant does not  ;

l retain its reliability and the various backup methods presently available do not function adequately, it may be necessary to place f the plant on natural circulation at that time, j The excessive non-condensable gases in the system have been  !

removed and are now at an acceptable level.

The phased reduction in primary system temperature has nov reached

' approximately 175*F. ' This reduction in temperature is greater g

.";;.; _ than originally anticipated with steaming in the steam generator ha3 A. ~

l Assuming current instrumentation continues to perform satisfactorily,

! the following timetable for a planned transition to natural circula-l tion has been established. The sequences planned to reach this

• objective are:

l 1. The "B" steam generator will be placed in a water solid condition by April 29th. ,

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2. The "A" steam generator will be placed in a water solid condition by April 30th.

3. Action needed to upgrade the backup cooling capability of the existing decay heat removal system will be completed by May 1. l

4. With these steps completed, the primary system recirculation pump will be shut off on May 2nd and the system will then go into natural circulation. --

There areca~ number of 'o'ther ongoing actions at the plant. - - '

1. Radioactive ef fluent filter systems within the plant have been upgraded. An independent redundant charcoal filter system, which will serve as a second stage of removal, has been under construction for some time. The new system is

. expected to be operational by May 2nd.

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.2. Modifications are currently in progres's that will permit the

secondary side of the "B" steam generator to be operated in a closed system, i.e., without the need for the availability of the main condenser. This activity is scheduled for comple-tion for May 7th. Closed system cooling of stcan generator B is not essential to establish stable natural circulation cooling.

3. The "A" steam generator also will be modified to permit operation in a closed system. This modification also is not required t.o establish natural circulation. Its schedule for completion is currently estimated to be the middle of May.

4. The passive level and pressure control system that will augment existing plant systems is expected to be completed by mid-May. This system is not needed to achieve natural circula-tion, but it is prudent to add this redundancy to the existing plant equipment for long term monitoring of natural circula-tion cooling. ,

f@$$~ 5. Modifications on the onsite electrical system are currently  %

being made. Additional diesel, generators have been delivered to the site to provide a backup power supply, and are currently being placed on their foundations. Electrical instrumentation and other necessary connections will be completed by April 27th.

6. There are a number of additional modifications being made within the facility that are related to the long term recovery from the accident. Such modifications include adding an additional decay beat removal system with equipment to process and remove the radioactive materials from the primary coolant system; the installation of additional tanks to provide for storage of contaminated water that may result

! from decontamination activities; installation of additional i

contaminated water processing equipment, and general decon-tamination activities needed in the auxiliary building.

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