ML19221A627
| ML19221A627 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 04/11/1979 |
| From: | Campbell B, Muench R, Solbrig C INDUSTRY ADVISORY GROUP |
| To: | |
| References | |
| OSP-790411-1, NUDOCS 7905230469 | |
| Download: ML19221A627 (6) | |
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DESIRED LONG-TERM
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CONTAI.'CET CONFIGURATION INDUSTRY ADVISORY GROUP THREE MILE ISI.AND #2 4/11/79 Agreed to and understood by
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C.iuck Solbrig Rick Muench Jim Thiesing Bob Campbell 166 081
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RECOMMENDATION FOR TiiE LONG TERM STATE 0' CONTAIN51ENT.
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The desired long term containment status is -recommended to be maintained at a pressure of approximately -1.0 psig (thi s implies tracking local barometric pressure by starting and stopping cooling water to fan ecolers), and an appropriate temperature less than 120 F to maincain the above desired pressure.
The pressure requirement maintains the containment pressure less than atmospheric
(, inflow is better than outflow), it is close to current conditions (so that it should be an easily achievable condition), it is close to normal operating conditions of the containment (so that it is easy to modify procedures to operate at this condition), the reccabiner operates at low pressure (and it may possibly be required), and the pressure difference between containment and surroundings will remain less than the containment operating limit of
-2.5 psi, "and avoid future potential degradation of liner plate integrity (inward bubbling). Pressure control should be accomplished with fan coolers l
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and no non-condensibles should be added to the system.
0 The temperature is specified as less than 120 F co minimize equipment degredation and it is consistent with the desired pressure and the amount of non-condensible gas now in the containment.
The desired pressure may not be achievable for one of the three possible long term cooling states of the primary system.
In this case, the pressure should be kept as low as possible to minimize outleakage.
Analyses with a containment code is recuired to determine the expected containment pressure and operating heat removal equipment required for this mode of operation.
The reasons for these recommendations as well as the requirements for other systems to support this mode are discussed in this report.
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INTRODUCTION The primary objective of the inve'stigation was to determine the desired final pressure and temperature of the. containment required for the long tem (that is, during the next year).
Subsidiary objectives consisted of specifying the desired status of all containment systems, the current state of each system, the mode of change from the current system to the final state, and a d'etermination of any factors which could adversely change the desired final state to an undesirable one-The final state of the coatainment depends upon the final configuration of reactor cooling. The modes of cooling which allow the heat to be removed from the primary system with the stean generators will allow operation of the contain-ment at a. negative gauge pressure.
However, the perculation mode of long term cooling exhausts the heat generated in the core as steam to the containment and this steam must be condensed. The heat removal capability of the containment will probably require the containment pressure to be above atmospheric to allow enough heat loss to condense the steam. A plot of the expected decay heat is shown in Figure 1.
This is the maximum amount of heat which must be removed by the containment.
Preliminary estimates indicate that this mode of core cooling can ce accomplished with containment pressures of perhaps slightly negative to +5 psig, depending on decay heat and time of year.
Computer predictions of this state is recommended to estimate the pressure expect 4 Leak rate information obtained previous to the accident can be used to estimate the leak rate from the containment.
CONTAINMENT STRUCTURE The primary objective in considering the long term state is maintaining
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the integrity of the containment.
The release rate from the containment must be as low as practically achievable.
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The design pressure is 2.5 psig. negative and 60 psig positive.
A low pressure can cause the metal liner to buckle inward.
(In fact, some inward buckling may already have occurred).
The inward buckle could introduce air between the liner and the concrete.
The pressure in the containment should be kept high enough so that the liner plate / anchor integrety will nct be compromised.
The pressure in the containment should be kept low enough so that only inleakage occurs.
An operating procedure should be initiated or reviewed to ensure that the containment pressure control room recorder is monitored and instructions provided for operator actions when containment pressure increases or decreases.
Considerat, ion should be given to providing adjusting set points for control room audible and visual alarms on high or low containment pressure.
Consideration should be given to weather forecasts to allow lead time prior to atmsspheric barometric changes in anticipation of cnanging fan cooler duty.
Consideration should be given to the feasibility of measuring the pressure between the liner and the concrete wall in an atte=pt to evaluate the integrety of the metal liner.
FEAT FEMOVAL SYSTEM The fan coolers in the containment should be selectively shut off in order to reduce duty time.
At least two of the coolers should be shut off as long as the pressure remains within ine limits.
When the service water temperature rises, it is recogni:ed that more fan coolers will be needed. The fans also are beneficial in avoiding H2 pockets.
The fans can also be used to circulate the containment atmosphere pf H7 appears.
i66 ORB 5
It is desireable to leave the sp. ray system off because of the large Y
decrease in pressure which these systems can create.
If the sprays are being
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used to assist in decontamination, the. pressure should be raised to near a atmospheric before the sprays are turned on.
The pressure can be increased by turning off the fan coolers or by running hot water through them.
COMBUSTIBLE GAS CONTROL When the reccebiner is used, the pressdre of the containment is limited by the recombiner design pressure.
The recombiner will not be needed if no hydrogen comes from the RCS. The recombiner adds non-condensibles from fuel and can also reduce them if it combines the hydrogen and oxygen.
Purge,should not be used because of the addition of non-condensibles to the system. The percent of hydrogen should be continuously monitored.
CONTAINMENT ISCLATION VALVES The valves necessary for the long term core cooling should be aligned correctly to allow the cooling to occur. Other valves may be aligned as needed to perform other desired functions as long as they do not affect the long term cooling functicn of the core.
An accelerated preventive maintenance program should be instituted or containment isolation valves, particularly those that may later be used in highly radioactive service which would make maintenance impossible.
CO.NCLUSIONS The most desirable containment condition approximately a pressure of -1.0 psig and a temperature less than 1200F.
Allsystemsbhichmight affect this condition should be reviewed if they have not been reviewed here.
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