ML19220C742
| ML19220C742 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 04/24/1979 |
| From: | NRC COMMISSION (OCM) |
| To: | NRC COMMISSION (OCM) |
| References | |
| PR-790424, NUDOCS 7905140135 | |
| Download: ML19220C742 (2) | |
Text
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Attachment *o PNO-79-67AF FOR IMMEDIATE RELEASE April 24, 1979 The NRC staff today announced a timetable for placing the Three Mile Island Unit 2 reactor on natural circulation cooling.
As stated on previous occasions, it is now possible to cool the reactor by natural convection circulation if difficulties arise with presently operating equipment.
It is, of course, preferable to place the plant on natural circulation in a planned fashion while presently available plant instruments and equipment remain functioning.
However, if instrumentation in the plant does not retain its reliability and the various backup methods presently available do not function adequately, it may be necessary to place the plant on natural circulation at that time.
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 now reached approximately 175*F.
This reduction in temperature is greater than originally anticipated with steaming in the steam generator A.
Asan=ing current instrumentation continues to perform satisfactorily, the following timetable fcr a planned transition to natural circula-tion has been established. The sequences planned to recch this objective are:
1.
The "B" steam generator will be placed in a water solid condition by April 29th.
2.
The "A" steam generator will be placed in a water solid condition by April 30th.
3.
Action needed to upgrade the backup coeling capability of the existing decay heat removal system will be completed by May 1.
4.
With these steps completed, tne primary system recirculation pump will be shut off on May 2nd and the system will then go into natural circulation.
There are a number of other ongoing actions at the plant.
1.
Radioactive effluent filter systems witbin 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 2.
Modifications are currently in progress 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 steam generator B is not easential to establish stable natural circulation coolLng.
3.
The "A" steam generator also will be modified to permit operation in a closed system.
This modification also is not required to 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.
5.
Modifications on the onsite electrical system are currently being made.
Additional diesel generators have been delivered to tne site to provide a hackup paver :rpply, and are curre9tly 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 deca 7 heat removal system with equipment to process and remove the radioactive materials from the primary coolaut system; the installation of additional tanis to provide for storage of contaminated water that may result from decontamination activities; installation of cdditional coctaminated water processing equipment, and genera? decon-tamination activities needed in the auxiliary building.
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rm IMMEDIATE PRELIMINARY NOTIFTCATION Ap ril 25, 1979 PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE -PNO-79-67AF This preliminary notification constitutes sun: mary information of an event of safety or public interest significance.
The information oresented is a s u:::ma ry o f inf o rma tion a s o f 7 : 00 a. m.
on April 25, 1979.
Facility:
Three Mile Island Unit 2 Middletown, Pennsylvania (DN 50-320)
Sub_i ect :
NUCLEAR INCIDENT AT THREE MILE ISLAND Plant Status In the course of transferring feedwater flow to the auxiliary nozzles, a carryover of water into the steam line was experienced, resulting in water impingement in the er in turbine.
An operator-initiated turbine trip at about 3:00 p.m. stopped the impingement.
The feedwater was being diverted to the auxiliary feedwatu sparger in preparation for secondary system modification for addir.g a closed cooling system.
Steam is currently being admitted to the main condenser through the turbine bypass valves.
This change in cooling mode will not affect preparations for natural circulation operations.
The average primary coolant te-raerature 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 iodine discharges have been reduced by approximately 80 percent.
The charcoal filters of Auxiliary Building Ventilation Sy:.em Train B have been replaced.
Thir ry:t== use placed in service at 5:30 a.m.
April 25.
Following a briefing of the Gevernor's Office, a press briefing was held to outline the anticipated schedule far achieving long term caoling status.
A copy of the press release is att>.ched.
Environmental Status Three Aerial Measuring System (APJfS) Surveys were made on April 24, 1979.
No radioactivity above natural background was detected.
CONTINUED IMMEDIATE PRELIMINARY NOTIFICATION 3R
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