ML19289C376

Responds to NRC 781121 Request for Aid W/Licensing Review Re Postulated Dbda & Loss of Forced Circulation Accidents. Concludes Each of the New Postulated Cases Results in Max Temp No Greater than FSAR-assumed Worst Case

ML19289C376
Person / Time
Site:	Fort Saint Vrain
Issue date:	12/21/1978
From:	Ball S OAK RIDGE NATIONAL LABORATORY
To:	Schamberger R NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES)
Shared Package
ML19289C364	List: ML19289C363 ML19289C374 ML19289C376
References
NUDOCS 7901120107
Download: ML19289C376 (5)

Text

OAK RfDGE NATIONAL LABORATORY CEEPATCO SV UNION CARBIDE CORPORATici1 NUCLEAR HV1510N e

Po1T OFFICE sox Y cAE RioGE. TENNE 15EE 3700 Dece=ber 21, 1978 Dr. R. ' Schamberger, Chief Experimental Gas Cotied Reactor Safety Research Branch Division of Reactor Safety Research U.S. Nuclear Regulatory Commission Wasnington, D. C.

20555

Subject:

Response to DSS Request of November 21, 1978 for Assistance with Fort St. Vrain Reactor Licensing Review This letter responds to a request by DSS for CRNL to provide additional i

calculations of postulated D3DA and LCFC accidents for Fort St. Vrain (FSV).

is to determine if initial conditions other than those The intent of ths request specified in the FSAR could lead to worse conditions during a DBDA or LOFC Specific conditions chosen are points along the power-to-flow ratio accident.

vs core thermal power curve (Fig. 3.1-2 from the FSV Technical Specifications),

The 5 points marked on the curve were chosen as initial shown in Attachment 1.

conditions for the nalyses. A sixth point, with an initial power of 102 and an initial flow of ',3.5%, is also included to represent compounded worst-case measurement uncertainties.

Since detailed calculated core input parameters and functions are not available for these analyses, the following assumptions are made based on the GA data supplied for the FSV analyses done by ORNL last May:

z Equilibrium core (EQSB3) peaking factors and associated refueling 1.

In order to obtain a heat balan<s for region curlet temperatures.

the inf rial cenditions, the assumed core inlet temperature has to be adjusted (Table 1);

Post DBDA and LOFC energency cooling flows and core helium inlet 2.

temperatures and pressures are the same as those given in Ref. 2; and Af terheat equations used are based on the updated estimates approved 3.

by NRC for LETCR safety studies, which include substantial uncertainty factors.3

~

I

R. D. Scha=berger December 21, 1978 Page Two The results of the study are su=marized in Table 2, which shows peak predicted temperatures of interest for both the DBDA and the LOFC + FWCD accident. It should be noted that the predicted values of maximum cover plate temperatures are based on poorly-understood models of the plume heat transfer phenomena. Even so, the data shows clearly that eAch of the new postulated cases results in maximum temperatures that are no greater than the

" FSAR-assumed worst case.

Please let me know if there are any questions about the analysis, or if more detail about any of the runs is needed.

Have a nice Holiday, 6 % MR w S. J. Ball SJ3:rev Attachments cc:

J. C. Cleveland J. C. Conklin R. Ireland DSS /NRC P. R. Kasten G. Kuzmyc:, DFM/NRC F. R. Mynatt L. Phillips, DSS /NRC Z. Rosztec:y, DSS /NRC J. P. Sanders B. Sheron, DSS /NRC T. Spies DPM/NRC R. S. Stene P. M. Williams, DPM/SRC

/

3 Letter from 2. R. Ros:toczy to R. D. Schamberger, "CRNL Cn-call Assistance for Fort St. Vrain," Nov. 21, 1978.

2Letter frem G. A. 3ramblett (CA) to S. J. Ball on FSV accident cases submitted to ::RC, Y.ay 1,1978.

3R. E. Sund, "Afterheat Calculations for the HTCR," Gulf CA-Al2499A (CA-LTR-4, Amend. A), July 1974.

Table 1.

Initial Conditions for DBDA and LOFC Analyses.

Equilibrium core (EQSB?) parameters.

Power to Flow T core inlet Power Flow Case ratio

'F We lb/ min Ref.

1.043 773.0 104.3 878.3 100 56,500 1

1.05 768.3 100 842.0 95.2 54,760 2

1.095 737.6 80 673.6 73.1 41,871 3

1.14 706.9 60 505.2 52.6 30,084 4

1.17 686.4 40 336.8 34.2 19,511 5

1.1 734.2 20 168.4 18.2 10,418 6

1.091 740.4 102 858.8 93.5 53,601

Table 2.

Maximum Temperature Estimates for FSV DBDA and FWCD Accidents for Various Initial Conditions. Equilibrium (EQSB3) Core, LTR-4-A + 20/10 Afterh'est.

Ref Case Case 1 Case 2 Case 3 Case 4 Case 5 Case 6 Inftial Power, 2 104.3 100 80 60 40 20 102 DBDA Max. Fuel Temp., 'F 2676 2617 2335 2094 1923 1826 2627 Max. Avg gas out, 'F 1768 1751 1664 1580 1512 1476 1758 Max. Region gas out,

• F 2351 2313 2106 1928 1923 1736 2322 2-hr LOFC + WCD Max. Fuel Temp.

@ t=2 hrs, 'F 2858 2808 2555 2317 2072 1840 2826 Max. Reverse Flow temp @ t=2 hrs, 'F 1950 1923 1762 1586 1417 1232 1929 Max. Cover Plate temp. @ t=2 hrs, "F 1619 1598 1474 1338 1209 1078 1599 Max. Forward Flow temp. af ter WCD,

'F 2269 2235 2065 1926 1305 1757 2241 T-streak at time of max. Forward flow temp., *F 1924 1903 1829 1736 1646 1605 1913

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