ML20210G626

Forwards App I,Inadvertently Omitted from 990624 Response to TAC M99844

ML20210G626
Person / Time
Site:	MIT Nuclear Research Reactor
Issue date:	07/29/1999
From:	Bernard J, Linwen H MASSACHUSETTS INSTITUTE OF TECHNOLOGY, CAMBRIDGE
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
TAC-M99844, NUDOCS 9908030160
Download: ML20210G626 (4)

Text

s

,he ** v yp NUCLEAR REACTOR LABORATORY j AN INTERDEPARTMENTAL CENTER OF '?S ,g,f MASSACHUSETTS INSTITUTE OF TECHNOLOGY JOHN A BERNARD 138 AJbany Street. Carnbodge. MA 02139-4296 Activate Analysts Director Telefax No (617)253-7300 Coolant Cherrhstry Director of Reactor operates Nuclear Me$one Tel. No. (617) 2534202 Pnnopal Research Engineer Reactor Engmeenng July 29,1999 Nuclear Regulatory Commission Attn: Document Control Desk l Washington, D.C. 20555 l

Subject:

hiassachusetts institute of Technology Research Reactor, Docket No. 50-20, l License No. R-37 l Gentlemen: l On June 24,1999, a response to TAC NO. h199844 was submitted. That response l references information contained in an Appendix 1. That appendix was iriadvertently omitted from the submission. It is forwarded herein. We apologize for any inconvenience that resulted.

l Sincerely, I l

Lin-Wen Hu, Ph.D.

Reactor Relicensing Engineer L 6L J hn A. Bernard, Ph.D. ,

Director  !

JAB /lwh t cc: USNRC -

Senior Project hianager,

/b3D ,

NRR/ONDD USNRC -

Region I - Project Scientist Efiluents Radiation Protection Section (ERPS) 030033 FRSSB/DRSS 9908030160 990729 PDR ADOCK 05000020-P PDR

4 M g h

e L

h i

A 4 APPENDIX I

O NUCLEAR REACTOR LABORATORY +

AN LVrERDEPARTMENTAL CENTER OF '1 MASSACHUSETTS INSTirUTE OF TECHNOLOGY 3pgp LIN4VEN HU 138 Albany Street, Cambridge, MA 021394296 Activation Analysis Reactor Relicensing Engineer Telefax No. (617)253-7300 Coolant Chemistry Telephone No. (617)258-5860 Nuclear Medicine Email: twhu@mit.edu Reactor Engineering May 24,1999 MEMORANDUM

~

From: Lin-Wen Hu h?--

To: Fission Converter Files

Subject:

Margin Between SL and LSSS

1. The margins between the safety limits (SL) and the limiting safety system settings (LSSS) for fission converter operation using both forced convection and natural convection for overpower, loss of primary flow, loss of primary coolant, and high coolant temperature transients are outlined below. For all cases, it is assumed that instrument response time is one second and blade insertion time 6 ane second.

Forced Convection

a. Overpower The LSSS power is 300 kW. Assume that the reactor power increases at a 10 second period (the MITR period scram setpoint). The fission converter would reach 366 kW after two seconds before the reactor and the fission converter shut down. The SL power is 396 kW (at 45 gpm, 60 C, and 2.1 m). Therefore, the SL will not be exceeded during an overpower transient.

b. Low coolant level The LSSS coolant level is 2.1 m. Assume a loss of coolant accident is caused by a crack (6" long and 0.5" wide) at the bottom of the fission converter tank. After two seconds ofinstrument and scram delay time, the coolant level will be 2.03 m. The 1.6 m curve on the SL figure (using 45 gpm and 60 C) is applicable. The corresponding SL power is 387 kW which is well above the 300 kW LSSS power. Therefore, the reactor is protected from exceeding the SL during a loss of coolant transient.

c. High coolant temperature The LSSS coolant temperature is 60 C. Assume that the heat sink is lost instantaneously and all the energy is deposited in the upper coolant region in the fission converter tank. Note that the heat sink is the reactor's secondary coolant. An automatic reactor scram would be activated by low secondary flow. The upper coolant temperature will reach 61.8 C after a two second instrument and scram delay time. The SL temperature is 72 C (at 300 kW,45 gpm and 2.1 m). Therefore, the

1 reactor is protected from exceeding the SL during a high coolant temperature transient.

d. Low primary flow The LSSS flow is 45 gpm. The reactor automatic scram would be activated when the i

fission converter primary flow is less than 45 gpm. The SL will not be exceeded I because the reactor power (and fission converter power) will be decreasing to zero with the low flow scram activated. Calculation shows that the maximum fuel tempera:ure is about 112 C during this transient.

Natural Convection

a. Overpower The LSSS power is 20 kW. Assume that the reactor power increases at a 10 second period. The fission converter would reach 24.4 kW after two seconds before the reactor and the fission converter shut down. SL power is 27 kW (at 60 C, and 2.4 m).

Therefore, the SL will not be exceeded during an overpower transient

b. Low coolant level The LSSS coolant level is 2.5 m. Assume a loss of coolant accident is caused by a crack (6"long and 0.5" wide) at the bottom of the fission converter tank. Atler two seconds ofinstrument and scram delay time, the coolant level will be 2.48 m. The SL coolant level is 2.4 m. Therefore, the reactor is protected from exceeding the SL during a loss of coolant transient.

c. High coolant temperature The LSSS coolant temperature is 60 C. Assume that all the energy is deposited in the upper coolant region in the fission converter tank without convection to the atmosphere. The upper coolant temperature will reach 63.5 C afler a 60 second delay time due to the CCS automatic closure. The SL temperature is 68 C (at 20 kW and 2.4 m). Therefore, the reactor is protected from exceeding the SL during high coolant temperature transient.