ML20148B519

Comments on Encl ACRS Re Xenon Emissions. Integrity of Vent Header Sys Should Be Upgraded by Requiring More Rigid Preoperational Testing Criteria & Routine Surveillance

ML20148B519
Person / Time
Site:	Three Mile Island
Issue date:	11/26/1979
From:	Jay Collins NRC - TMI-2 OPERATIONS/SUPPORT TASK FORCE
To:	Vollmer R NRC - TMI-2 OPERATIONS/SUPPORT TASK FORCE
Shared Package
ML20148B524	List: ML20148B519
References
NUDOCS 8001220288
Download: ML20148B519 (2)

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[ T' t. CENTRAL FILE T "W;X

• November 26, 1979 NRC PDR l

LOCAL PDR JTCollins ,

l MRANDUM FOR: R. B. Vollmer, Director, TMI Support \f i'

FROM: J. T. Collins, Deputy Director, TMI Support

SUBJECT:

COHKENTS RELATIVE TO THE EMISSION OF NOBLE GASES FROM THI-2

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I have reviewed the letter from M. Carbon, Chairman, AERS, to V. Gilinsky dated October 9,1979, (copy attached) relative to the emissions of xenon from TXI-2 nucicar plant, and the possibility of reducing such releases in similar accidents, which may occur in the future. I have the following counnents on the ideas set forth in this letter.

t Dr. Carbon suggested that consideration be given to tihe use of chilled or cryogenic charcoal adsorption beds of adequate capacity to control noble gases released during accident conditions. It isn't clear from Dr. Carbon's ictter whether he is suggesting that these systans be installed to handle gases released into containment or to the Auxiliary / Fuel Handling Buildings.

In either case, the volume of air to be treated is considerably larger than the 30 cfm nominally handled by the low temperature or ambient charcoal delay systems used to treat off-gases from the main condenser / steam jet air ej ectors. Normally, these systems will use in the range of 18-24 tons of charcoal to provide a delay time of 45-60 days decay for xenon and several hours for krypton. It should also be recognized that these delay systems are always used in combination with H2 recombiners to reduce the

volume of air prior to processing through the charcoal beds.

A typical 3,500 MWg FWR Containment Building will have a free volume of about 2 x 106 ft3 The Auxiliary Building will have a volume in the range i of 5 x 105 to 1 x 106 gg3 and the Fuel Handling Building vill have an equal voluma. These buildings will normally have exhaust air flows in the range of 50,000 to 100,000 cfm. Unless provisions are made to chill the air to reduce the volume of air to be treated, the amount of charcoal necessary to effect a delay of 45-60 days would be so large as to make

the system impractical and certainly not cost effective. For example,

! Met-Ed points out in their submittal of November 13, 1979, that 11.5 con-tai = =nt volumes would need to be processed using a " bleed and feed" operation to reduce the contaf=*nt activity to 1 MPC. This amounts to l 23 x 106 cf of processed volume. The charcoal required to process this air would be about 24,000 tons or about 40% of the total US production.

In addition, as Dr. Carbon points out, there is a problem of moisture content which would result from the accident. Equipment capable of handling

, this problan would further complicate the systen and make it even less cost offective. .

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• In addition to the above, it would be necessary to design the Auxiliary j Buildings and Fuel Handling Buildings as leak tight buildings to minimize i leakage of noble gases to the environment. This would add to the cost 8

of the buildings with little or no added benefit.

In my opinion, there are other ways of coping with the probism some of which were discussed in the various investigation reports, but none in my opinion, have received the attention they should have.

For example, shortly after the accident TMI-2 had a pressure transient

, caused either by a hydrogen burn or an explosion. Following that transient the Containment Building went negative and has been at a negative pressure ever since. As you know, the B&W Conta4= ant Buildings are designed to operate at a slight positive pressure not negative pressure. This current mode of operation at TMI-2 should have told us something because sinsembhe accident, all noble gases have been contained and allowed to decay with the exception of Kr - 85. Perhaps we should re-evaluate our containment design criteria and require all PWR's to operate at a slight negative pressure.

At TMI, the principle source of noble ga.ses released into the Auxiliary Building originated from the " letdown / makeup system" (volume control system in a West PWR). In addition, gases were also released from the vent header system. At one time, this was thought to be the main source, but subsequent leak tests have shown this to be a secondary source. Since the " letdown" systess is outside the pressure boundary, it is not required to have the integrity required of pressure boundary systems. From what I have been able to determine, the system is not even designed to the criteria required of radwaste systems as called for in R. G. 1.143. I believe we should give serious consideration to putting these systems inside the Containment Building.

If this is not possible, and I am not convinced that it isn't, then we should upgrade the system integrity to that required of the pressure boundary systems.

In addition, we should upgrade the integrity of the vent header system by requiring more rigid pre-operational testing criteria and routine surveil-lance of this and the letdown systems. All pressure relief valves from tanks in auxiliary building should be hard piped to the vent header. Routine surveillance requirements should be placed on the vaste gas compressors.

, All PWR's should be required to install a hard piped system for transferring

, gases from the waste gas storage tanks and the makeup tank back to the contain-l ment. All of these.;1tema:could be done with minimum expense to the utility

and would go along way in reducing releases to the environment. It certainly I could be shown to be more cost effective than trying to design and install

! systems to handle the entire free volume of these buildings.

J. T. Collins 96024095 1 Deputy Director "I hype-t

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