ML19323G115
| ML19323G115 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 05/20/1980 |
| From: | Herbein J METROPOLITAN EDISON CO. |
| To: | Reid R Office of Nuclear Reactor Regulation |
| References | |
| TLL-238, NUDOCS 8005300416 | |
| Download: ML19323G115 (10) | |
Text
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c Metropolitan Edison Company Post Office Box 480 Middletown. Pennsylvan,a,17057 i
717 9444041 Writer's Direct Dial Number May 20, 1980 TLL 238 lirector of Nuclear Reactor Regulation Attn:
R. W. Reid, Chief Operating Reactors Branch No. 4 U. S. Nuclear Regulatory Commission Washington, D.C.
20555
Dear Sir:
Three Mile Island Nuclear Station, Unit I (TMI-1)
Operating License No. DPR-50 Docket No. 50-289 HPI/LPI, Tec.hnical Specification Change Request No. 61B This letter and enclosure are in response to questions transmitted to Met-Ed via a telephone conversation between Mr. D. Dilanni of your staff and Mr.
D. G. Mitchell of Met-Ed on April 30, 1980. The questions were to clarify items of our Technical Specification Change Request No. 61B which concerns High Pressure Injection / Low Pressure Inj ection.
Sincerely,-
5 J. G. H rbein Vice President TMI-I l
JGH:DCM: hah Pnclosure cc:
J. T. Collins B. J. Snyder
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Metropohtan Ed; son Company is a Memeer of the General Puche Utdities Sys*ern
Enclosura 1 TLL 238 l
RESPONSE TO DIIANNI'S 6 QUESTIONS ON HPI/LPI i
Q. 1 Justify deleting the need for limit switch settings.
A. 1 The limit switch settings of MU-V16, A, B, C, D noted in specification 4.5.2.1.c, of Change Request 61A, were required to ensure proper flow distribution of the High Pressure Injection System.
The settings specification was deleted in Change Request 61B because of the installation of passive mechanical devices (cavitating venturi).
For additional information see the TMI-I Restart Report Supplement 1, Part 3, response to questions 1, 2, and 3.
Q. 2 Justify not verifying 200 gpm flow per leg.
A. 2 Specification 4.5.2.1.b of Change Request 61A stated a minimum acceptable flow of greater than or equal to 200 gpm of High Pressure Injection per leg was required.
Change Request 61B deleted that verification requirement.
Passive mechanical devices will accomplish the required distribution of flow.
See the above referenced items of the Restart Report for additional information.
Q. 3 Justify the 500 gpm flow when RC pressure is less than or equal to 600 psig.
A. 3 Specification 4.5.2.1.c of Change Request 61A required a minimum flow per HPI pump of 500 gpm.
Change Request 61B modified that requirement to require at least 500 gpm per HPI pump when the RC pressure is less than or equal to 600 psig.
The changes of Change Request 61B reflect that the amount of flow delivered by the HPI pumps is dependent on RC System pressure and that above 600 psig less than 500 gpm will be delivered.
For RC pressures less than 600 psig, the venturi will begin to cavitate and limit the flow, preventing run out of the HPI pumps.
The predicted performance of the system is contained in Supplement 1, Part 3 of the TMI-I Restart Report along with detailed justifi-cation of the predicted system performance.
Additional supporting justification is contained in the attached B&W letter of April 26, 1980.
Q. 4 Answer 3 items in the NRC letter of July 1, 1977:
Maintenance of proper flow resistance and presure drop in the piping Enclosura 1
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TLL 238 system to each injection point is necessary to a) prevent total pump flow from exceeding run out conditions when the system is in its minimum resistance configuration; b) provide a proper flow split between injection points in accordance with the assumptions used in the ECCS-LOCA analysis, and c) provide an acceptable level of total ECCS flow to all injection points equal to or above that assumed in the ECCS-LOCA analysis.
A. 4 Supplement 1, Part 3 of the TMI-I Restart Report contains the information requested.
The subject report demonstrates that the HPI cross-connect design with cavitating venturi; a) prevents pump run out; b) provides proper flow split between injection points and c) provides acceptable levels of total flow to all injection points equal to or above that assumed in the ECCS-LOCA analysis. Valves are not used to throttle flow (See paragraph 3 of NRC letter dated July 1,1977).
Q. 5 Verify 500 gpm HPI flow value.
A. 5 500 gpm HPI psmp flow at 600 psig RCS pressure assures that the delivered flow will be greater than that assumed in the ECCS analysis.
Q. 6 Discuss justification section having to do with positive stops.
A. 6 Change Request 61B requests, in the justification, an exception to the suggested surveillance of the position stops of the decay heat t.hrottle valves.
The LPI throttle valves, DH-Vl9 A/B do not have electrical or mechanical position stops in that these valves are manually operated, and are set according to flow indications received in the control room. However, the intent of the suggested surveillance would be met by verifying that the valves be locked in the correct position by observation of the position irc.icators.
=C
Enclo:ura 2 TLL 238 Babcock &Wilcox eo.e, ceneration ct=up P.O. Box 1260. Lynencurg. Va.24505 Telephone: (804) 384-5111 April 16, 1980 TMI-80-076 Mr. D. G. Slear (3)
Tril-I Project Engineering Manager GPU Service Corporation.
100 Interpace Parkway Parsippany, NJ 07054
Subject:
HPI Flows During Small Break Transients
Dear Mr. Slear:
Attached for your information and use is the information requested by your Mr. J. F. Fritzen and the NRC during a telecon on March 4, 1980. Attachment ~ A documents the HPI flows used by B&W in performing the core flood line break analysis. Attachment B provides a writeup concerning the applicability of the HPI flows used by B&W in the small break cnalysis relative to the TMI Unit I HPI flows.
Attachment C provides suggested corrections to Table 1, Column B of System Design Description for High Pressure Injection Cross-Connect, 500 211A,,
Rev. 1.
If you have any questions or require additional information, please advise.
Very truly yours, 4
. j) l'. ;. wAw G. T. Fairburn Service Manager GTF/cw cc:
J. G. Heibein L. L. Lawyer J. J. Colitz J. F. Fritzen T. J. Toole R. W. Keaton - GPUSC F. R. Faist J. C. Lewis - Phila. Sales The Batr:ock & Wil:ox Company I Estabbshed 18G7
i ATTACIDENT A IIPI Flows During CFI Line Break Flow, gpm Pressure, psia 454.5 0.0 440.
615.
365.
1315.
340.
1515.
325.
1615.
325.
3000.
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ATTACID!ENT B Applicability of the Small Break B&W Model to the IMI-l Plant Characteristics On >bech 6,1980, a joint telephone conversation took place with GPU, NRC, and B&W, concerning the TMI-1 HPI system.
The NRC raised the question of the applicability of the
..( small break model (references 1, 2, and 3)'to IMI-1, since the flows delivered.by the TMI-l HPI systcm are lower than those assumed in the B&W analyses for pressures below 600 spig (reference 2).
The HPI flows used by B&W are listed in the attached Table A.
Flows in Column I are used for the first 10 minutes of the transient.
Following manual cross-connecting of the HPI valves at this time, the flows in Column II are assumed for the remainder of the transient.
The difference arises because, for a pressure of 0 psig, the TMI-1 system delivers 500 gym instead of deliver-ing a flow equal to or greater than the 548 gpm analysis value.
This is shown in Table A.
It should be pointed out that the spectrum analyses documented in references 2 and 3 were performed at 2772 Myt, while the rated power of the T1E-1 plant is 2535'1 Hit.
Table B lists the HPI flows which should be used following operator action at 600 seconds, if the THI-1 initial core power were modeled in order to calculate the same system responses presented in reference 2.
It can be seen that at 0 psig, the HPI flow should be 501 gpm.
Therefore, there is a discrepancy of only 1 gpm, between the injection flow needed at 0 psig, and the TIE-1 HPI flows delivered at that pressure.
In order to assess the impact of the smaller HPI flous in the analyses de-scribed in reference 2, two of the cases presented there have been re-evalu-2 ated using hand calculations.
Specifically, the 0.15 ft break at pump dis-charge has been considered since this break depressurizes the system to 600 2
psig more quickly.
The second break to be studied was the 0.07 ft at pump discharge, which turned out to be the worst case.
d
a Results of the 0.15 ft at pump discharge small break analysis show that the 2
primary system pressure reaches 600 psig at about 500 seconds, i.e.,
before the operator action (Figure 3, reference 2).
At this time the HPI pump is delivering 450 gpd (Table A, Column I), of which 50% en.'.ers the' system, and the other 50% is lost through the break.
This pressure also coincides with the actuation of 2 core flood tanks, which, for this case, inject an average of,about 55 lbm/s of additional flow to the reactor vessel.
Core boil-off is matched in the analysis at about 550 seconds.
The mixture height in the reactor vessel at this time is about 1 ft above the top of the core.
Following operator action at 600 seconds, which results in an increase of the flow delivered to the reactor vessel, the mixture level in the vessel starts to ine mse.
Assuming, for conservatism, the small break' model power of 2772 MUt, as opposed to 2535 MRt, the mixture level in the vessel is estimated to increase at a slightly slower rate than calculated 'in the analysis, due to the difference in HPI flows between the model and the
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TMI-1 plant.- The core never uncovers, thus preventing any cladding tempera-ture excursion, assuring conformance with 10 CFR 50.46.
The 0.07 ft2 break at PD, which, in reference 2 was found to be the worst small break, resulted in a minor core uncovery and a peak cladding tempera-ture of 1095F, which is well below the 2200F criteria of 10 CFR 50.46.
Figure 3 of reference 2 shows that the system reaches 600 psig at about 1500 seconds, which also corresponds to the minimum core mixture level (reference, Figure 4).
The top of the core is re-covered at about 1800 seconds.
Using TMI-l flows, and the model core initial power of 2772 MRt, a deficiency of about 350 pounds of liquid water exicts in the vessel at this time, as co= pared to liquid in-ventory calculated in the analysis.
Because of this difference, the vessel refills to the top of the core with a 15 seconds delay.
Thus the peak temperature i
remains in the neighborhood of 1100F, as calculated in reference 2, ensuring cocpliance to the 10 CFR 50.46 criteria.
2 Reference 3, Appendix C, documents a core flood tank line break (0.44 ft )
analysis, performed for a typical 177 low-loop plant, having an initial power
.of 2772 MWt.
The HPI flows assumed in that analysis are lower than the HPI flows used in reference 2 (see Attachnenc A).
A'ain, the calculated cystem
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responses following the initiation of the transient comply wholly with the 10 CFR 50.46 criteria.
In summary, the TMI-l IIPI system, when used in a single failure mode in an hypothisized small break LCCA, can safely mitigate the transient within the limitations of Appendix K.
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Table A.
HPI Flous Assumed in the HPI Small 3reak Model Assumed HPI flows
, Assumed HPI flows the first 10 min af ter 10 min (50%'is lost (30% is lost Pressure, osig throuch the break) throuch the hreak)_
0 515 548 600 450 500
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1200 380 438.
1500 342 404
.1600 328 3 91.7 1800 300 3 64.3 2400 210 260.0 Table B Assumed HPI fiou for TMI-l
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after 10 min (30% is lost Pressure, p'sig through the break) 0 501 600 457 l
1000 400
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1300 369 2000 358" 2400 333 l
l REFERENCES 1.
Topical Report BAU-10104, Rev. 3, "B5hs ECCS Evaluation Model," August
-c 1977.
2.
Letter from J.H. Taylor (B&W).co S. A. Varga (NRC), July 18, 1978.
l 3.
Topical Report EAU-iO103A, Rev. 3, "ECCS Analysis of BSU's 177-EA
. Lovered-Loop NSS," July 1977..
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ATTACHMENT C
. Table 1.
EPI Flow Rcoutrements(
Column A Column B Pump flow Pump flow RC pressure, psig undegraded, gpm degraded, gpm 0
550 515 600 500 450 1200 437.1
~
380
' 42.
1500 404.3 3
1600 391,4 328 1800 364.3 300 2400 260 210 2500 216,0 191.7 G)Only for small break conditions other than a HPI line break.
See reference (0) for flow assumed under HPI line break conditions.
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