ML19308B651
| ML19308B651 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 12/26/1979 |
| From: | Jay Collins NRC - TMI-2 OPERATIONS/SUPPORT TASK FORCE |
| To: | Vollmer R NRC - TMI-2 OPERATIONS/SUPPORT TASK FORCE |
| References | |
| NUDOCS 8001160526 | |
| Download: ML19308B651 (3) | |
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DEC 2 61979 i
l MEMORNiCUM FOR:
Richard H. Vollmer, Director, Three Mile Island Support FROM:
John T. Collins, Deputy Director, Three Mile Island Support SUDJECT:
RE-EVALUATION Ai4D REC 0r+1EfiDATI0HS FOLLOUING LOSS OF C0ilTIHU00S liATURAL CIRCULATI0t1 AT D11-2 The following connents are in response to your letter of Hover.ter 28, 1979, "ttatural Circulation at TsI-2".
We have re-evaluated the need for the nDHR (mini-decay neat removal) system to be operational prior to the loss of continuous natural circulation in light of tne last two months of socewhat cyclic circulation. Our conclusion as previously stated (letter prepared by S. i;cwberry, J. Wemiel, and H. Greenberg, dated Septe:aber 20, 1979) remains uncnangeo.
It is not necessary to have the MDHR systea operaticnal as soon as possible. The licensee's current work schedule shows that this systea i.ill ce ready for use by Feoruary 8, 1980, which is acceptable. Start-up of this systea can be further delayed for the following reasons:
1.
The MDHR systeu interfaces with the installed decay heat removel (DHR) systeu. The suction and discharge paths are comen to both systeus.
Tnus prior to the M0HR system operation, certain valves in the LHR systeu will have to be opened and closed. The concern is of potential intersystea leakage across the valves that isolate the two systeas.
Even tnough several DH3 system nydro tests have been perfomed to identify and fix leaks, there is still some apprehension by the utility and our staff to activate the MCHR system. The unprecessed high radioactive reactor coolant may migrate to the DHR systea, thereby increasing radiatica uctivity in the equiprant area. Tne radiation activity levels would also increase witnin the area wnere tne MDHR system is lccated.
Tnus accessibility for component maintenance of coth systems located-in the Auxiliary Building would be reduced. And, potential leaks in either systua would worsen the situation.
2.
Should natural circulation be lost, the expected reactor coolant system pressure and temperature increase following heatup would be considerably less than that reported back in mid-September because of lower decay heat generation. Based on current decay heat generation rate, the expected pressure increase following a reactor coolant heatup event would be less than 100 psi. This asswaes that letdown would be available. The increased pressure would be within the Technical Specification limits.
Tha. c.axiaum reactor coolant tecperature following heatup would be less ~
tnan 300 F.
Taus, intermittent loss of natural circulation followed by 0
heatup should not create, any foreseen short-tem problems.
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R. H. Vollmer 2
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The cyclic RCS loop flow'that the plant has been experienceing for the past two montns is not expected to cause any detrimental consequences.
This would not alter conclusions specified in item 2.
ine cyclic / flow behavior is most likely due to very low flow rates which have a tendency to cause changes in fluid inertia and result in unstable flow. The e
current flow rata is estimated to be less than 150 gpu as compared to approximately 400 gpa toported back in mid-Septammer.
4.
The HD!iR system as desig ed and installed has a removabic filter that should collect the debris generated during fabriatir,a and possicly some of the crud tnat will be stirred up by the flow. But because of the difficulty in replacing this filter, i.e. physical location, tne licensee is not planning on replacing it more than a few times.
If the filter clogs up too fast, they will consider abandoning the MGliR system and switching to another mode of decay heat removal.
5.
A study is underway to'cieanup the reactor ecolant water using the EPICOR II system. Although the ilDHR system will be proviced with piping connections for reactor coolant cleanup, the design for the tie-in to the future cleanup systm (if there will be one) does not exist. Therefore, it would be simpler to consider the use of the existing feed and bleed i
systec (e.g., letdown line and cake up pump or Standby Pressure Control System) in conjunction witn the reactor coolant cleanup systea(s).
If 4
t.he EPICOR II system were to be used for reactor coolant cleanup, it may take two to four months to process all the water due to slow flow rate (10 to 12 gpm) and more frequent liner changes. By that time the F.DHR system can be put into operation.
In conclusion, should conti5uous natural circulation be lost within the next six montns, we recourend u:ing the OTSG "B" modified long-tem cooling systea as the preferred mode of ref.oving the remaining cecay heat. This syste.a has been installed, hydro tested, the operating procedure has been reviewed and approved. However, it should be noted that the tie-in to the demineralizer sys te:.4 nas not been completed. We recccraend that priority be given to completa this system. Also, before tnis system can be completed we need infomation on wtimum pernissible radiation levels and to deteraine waat action wuld nave to oc taken if fluid Icakage were to occur. Further mre, please note that when 1he decay heat generation approaches tne heat loss of the RCS to the reactor building enviroimlent, this system will lose its effectiveness because RCS loop flow will stop. The esti.aated RCS_ heat losses through the piping and insulation range from 200,000 to 500,000.BYU/hr. Based on the decay heat load curve, we anticipate that equilibrium will be reached some time in the latter half of 1980.
John T. Collins D"*D
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