ML19221A295
| ML19221A295 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 05/18/1979 |
| From: | Office of Nuclear Reactor Regulation |
| To: | Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML19221A296 | List: |
| References | |
| NUDOCS 7905210227 | |
| Download: ML19221A295 (5) | |
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MISCELLANEOUS INFO RE NATURAL C.
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Today, the NRC announced the t ime table that is to be followed for preparing to olace the Three Mile Island Unit 2 teactor on natural circulation cooiing.
As stated on previous occasions, it is possible now to cool the reactor by natural convection circulation if difficulties arcse with presently operating equipment.
It is, of course, p re f e rabl e 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 adequatelv, it may be necessary to peace the plant on naturai circulation at that time.
The excessive nn, condensable gases in the system have been removed and are now at an acceptable level.
The phased reduction in pr ima ry sys tem tempe rature has now reached aoproximately 175 This reduction in temperature is greater than originally anticipated with steaming in the steam generator A.
s-e Assuming current instrumentation continues to perform satisfactori;s,
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the following time table for a planned transition to natural circulation ;2 +> c has been established.
The sequences planned to reach this objective are:
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The "B" steam generator will be placed in a water solid condition
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The "A" steam generator will be placed in a water solid condition
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by April 30th.
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3 Action needed to upgrade the backup cooling capability of the existing decay heat removal system will be completed by May 1.
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With these steps complete,d, the primary system recirculation pump
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~~2 circulation.
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//c There are a number of other ongoing actions at the plant.
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Radioactive effluent filter systems within the plant have been upgraded.
An independent redundant charcoal filter system which a
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for some time.
The new sys tem is expected to be operational by c
May 2nd.
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Modificat ions are cu rrently in progress that will permit the jp,/
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secondary side of the "B" steam generator to be operated in a closed system, i.e.,
without the need ror the availability of the
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This activity is scheduled for completion for May 7th.
Closed sys tem cooli~g of steam generator 8 is not essential to establish stable natural circulation cooling.
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The "A" steam generator will also be modified to permit operation in a closed system.
This modification is also not required to establish natural circulation.
Its schedule for completion is currently estimated to be the middle of May.
4.
A passive level and pressure control system that will augment existing plant systems is expected to be completed by mid M.y.
Th i s s ys t em is not needed to achieve natural circulation, but it is prudent to add this redundancy to the existing plant equipment for long term monitoring of natural circulation cooling.
5.
Modifications to the onsite electrical syst em are currently being made.
Additional diesel generators have been delivered to the sitt 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 which are related to the long term recovery from the accident.
Such modifications include:
adding an additional decay heat removal system with equipmeet to process and remove the radioact ivi ty ma te rials from the primary coolant system; the insta':ation of additienal tanks to provide for storage of contaminated water which may result from decontaminatior activities; installation of additional contaminated water processing equipment and general decontamination activities needed in the auxiliary building.
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