ML022960332

Response to TAC No. MB3761, License No. R-37 Dated 10/15/2002

ML022960332
Person / Time
Site:	MIT Nuclear Research Reactor
Issue date:	10/15/2002
From:	Bernard J, Newton T Massachusetts Institute of Technology (MIT)
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
TAC MB3761
Download: ML022960332 (6)

Text

NUCLEAR REACTOR LABORATORY AN INTERDEPARTMENTAL CENTER OF MASSACHUSETTS INSTITUTE OF TECHNOLOGY JOHN A. BERNARD 138 Albany Street, Cambndge, MA 02139-4296 Activation Analysis Director Telefax No (617) 253-7300 Coolant Chemistry Director of Reactor Operations Tel. No. (617) 253-4211 Nuclear Medicine Principal Research Engineer Reactor Engineenng October 15, 2002 U.S. Nuclear Regulatory Commission Washington, D.C. 20555 Attn: Document Control Desk

Subject:

Response to TAC No. MB3761, License No. R-37, Docket No. 50-20.

Gentlemen:

On 11/21/01, the Massachusetts Institute of Technology submitted a request to amend its operating license (R-37) to modify Fission Converter surveillance requirements and eliminate unnecessary procedures, in accordance with ALARA considerations. On 09/05/02, the U.S. Nuclear Regulatory Commission sent a request for additional information. Enclosed is our response to that request.

Please contact either of the undersigned should further information be required. This request has been reviewed and approved by the MIT Committee on Reactor Safeguards.

Thomas New on, P.E. Aohn A. Bemard, Ph.D.

Reactor Engineer Director MIT Nuclear Reactor Laboratory MIT Nuclear Reactor Laboratory I declare under penalty of perjury that the foregoing is true and correct.

Executed on Date JAB/gw cc: USNRC - Senior Project Manager, NRR/ONDD USNRC - Region I - Project Scientist, Effluents Radiation Protection Section (ERPS)+

FRSSB/DRSS A- b2-D

Response to NRC reauest for additional information 9/5/02

1. Installation or repair of a level probe will result in the probe being placed in a non-adjustable position that will result in actuation at or above 2.1 m above the top of the fuel. Because of the probe's fixed position, a calibration requirement is not needed. All that is necessary to ensure proper operation is a functional check.

The proposed TS has been modified (new provision 5) to make this explicit.

2. The float switch is bolted to the FC tank at 2.2 m above the top of the FC fuel.

This determines the actuation position. Testing to date has shown no change in probe function. The functional test consists of insertion of pressurized helium into the annular space surrounding the float. This forces the coolant around the float to drop, thus activating the switch. When the helium supply is stopped, the helium is vented to the helium cover gas space of the tank, allowing the coolant around the float to rise to its normal level.

3. A loss of coolant in the FC tank during FC operation would result in loss of coolant to the intake of the coolant pumps, resulting in a low flow indication, as well as a reactor scram and CCS closure from loss of flow. A loss of coolant would also be indicated on a digital coolant level indicator. Also, it would result in increased radiation levels above the FC.

4. Removal of the tank ,trp is very difficult and is done only when maintenance is required inside the tank. This has not happened in the two years that the tank has been in place. Functional testing of the probe with the tank lid removed is possible, but has no added advantage beyond the monthly functional check that is currently preformed.

5. Units in TS 6.6.2.6 have been changed to jIS/cm.

6. Attached is a graph of H2 0 and D2 0 conductivity vs. pH from D. Barber and J.P.

Van Berlo, "An Introduction to CANDU Chemistry," AECL CANDU, March 1994. It shows both H20 and D20 have similar shapes, with the D 20 conductivity slightly lower. Measurements of pH are made monthly. The data are close (i.e.,

within measurement error) to the calculated pH-conductivity curve for D20.

7. Conductivity of pure D2 0 at pH 7 is about 0.013 [tS/cm (0.0013 mS/cm). A measurement of 0.04 #iS/cm would be a normal indication. Indications of conductivity below 0.013 pS/cm constitute the lower limit of sensitivity of the conductivity probe.

10 I

0001*!

,.0 5.0 6.0 7.0 B.0 P.0 10.0 MEASURED pH OR pHA Figure 9-2 Thcorefical Relationships for pH and PHiA to Spccific Conductivity

I pH - CONDUCTIVITY WITH MIT MEASUREMENTS 19 0.01 4.0 4.001 5.0 6.0 7.0 JIG 9.0 MEASURED PH OR PHA FigRp 9-2 Theoretical Relationships for pH and PHA tO Specific Condletiit'hy

a. Neutron flux level channel,

b. Primary coolant flow channel, and

c. Primary coolant outlet temperature channel.

3. The neutron flux level channel and a fission converter primary system heat balance shall be checked against each other at least annually and when design changes in the reactor and/or the fission converter are made that may affect the existing calibration result.

4. The gross P-7 activity of the fission converter primary coolant shall be determined at least monthly. The conductivity of the fission converter primary coolant shall be determined either by a continuous on-line instrument or a monthly sample.

The pH of the fission converter primary coolant shall be measured monthly if the average conductivity exceeds 0.10 #S/cm. The tritium content of the coolant shall be determined quarterly if D20 is used as the fission converter primary coolant.

5. The following instruments used in the fission converter shall be subject to a functional test when initially installed, any time that the instrument has been repaired, and at least annually:

Fission Converter tank coolant level channel Basis The specification for functional tests, calibrations, and primary coolant sampling adhere to current MITR practice.

The annual frequency for performance of the calorimetric was chosen because the fission converter's power is a function of the MITR's power and the burnup of the fission converter fuel. The latter will occur very slowly. Hence, the annual performance of a calorimetric is sufficient to detect any change in fission converter power production.

Experience with the MITR primary and D2 0 systems has shown that an out-of specification chemistry condition is extremely rare. Heat fluxes present in the fission converter are too low to contribute to fuel cladding degradation in the event of out-of specification chemistry. Continued operation of the fission converter is thus permitted.

6-59

6.6.2.6 Fission Converter Primary Coolant Quality Requirements Applicability This specification applies to the pH, conductivity, and activity of the fission converter primary coolant.

Obiective To control corrosion of the fission converter fuel and primary coolant loop structure, and activation of impurities and leakage of fission products in the fission converter primary coolant.

Specification

1. The pH of the fission converter primary coolant shall be kept between 5.5 and 7.5, except as noted in provision (4) below.

2. The conductivity of the fission converter primary coolant shall be kept less than 5 pS/cm at 20'C, except as noted in provision (4) below.

3. Any gross B-y sample activity that exceeds the average of the previous monthly values (normalized by power) by a factor of three or more shall be investigated to determine the cause.

4. Operation of the fission converter with the pH or conductivity outside the limits given in (1) and (2) above is permitted provided:

a. The pH is between 5.0 and 8.0,

b. Any increase in conductivity is not the result of a chloride ion concentration in excess of 5 ppm,

c. Sampling of the fission converter coolant is done at least once every eight hours, and

d. The pH band specified in provision (1) is re-established with 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />, Otherwise, the fission converter shall not be operated.

6-56 Amendment No. 31 December 21, 1999