ML20136J421

Forwards Answers to Questions Raised in Re Defueling Procedure for License L-77.Approval Requested as Registered User of Fuel Shipping Packages.Final Procedure Will Be Submitted Following Rev & Review

ML20136J421
Person / Time
Site:	05000433
Issue date:	12/11/1985
From:	Profio E CALIFORNIA, UNIV. OF, SANTA BARBARA, CA
To:	Wenslawski F NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
References
NUDOCS 8601130360
Download: ML20136J421 (5)

Text

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UNIVERSITY OF CALIFORNIA, SANTA HARBARA DE.RKELEY

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• SANTA CRUZ DEPARTMENT OF CHEMICAL AND SANTA BARBARA, CALIFORNIA 93106 NUCLEAR ENGINEERING A Y December 11, 1985 's - 2S

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Frank A* Wenslawski, Chief i; Emergency Preparedness and Radiological

" N Protection Branch U.S. Nuclear Regulatory Commission, Region V 5

1450 ilaria Lane, Suite 210 Walnut Creek, CA 94596

Dear iir. Wenslawski:

Enclosed are the answers to the questions you raised in your letter of November 22,19d5, regarding the Defueling Procedure for the UCSB L-77 reactor.

We are applying for approval as a registered user of the fuel shipping packages.

We will send your office a copy of the final procedure for defueling under our license, when it has been revised and reviewed by the appropriate committees, t Sincerely, 6f', det h A. Edward Profio Reactor Director

Enclosure:

Reply to Questions on Defueling Procedure cc; Frank Gallagher, Radiation Protection Officer

~ l I 8601130360 851211 PDR P

ADOCM 05000433 1[O ( I \

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1 December 11, 1985 Reply to Questions from NRC Region V on Defueling Plan for i UCSB L-77 Reactor, License R-124, Docket 50-433.

Question on Step 1. If the fuel line leaked or the bottle overflowed, where would the fuel be contained?

Answer:

A plywood catch pan, 36 in. x 36 in. x 6 in., lined wi th polyethylene sheet, will be positioned in the defueling area and will contain a single 10-liter fuel bottle. The catch pan is sized to contain the entire L-77 fuel inventory in the event of a major spl11, in a noncritical ge ome t r y .

The entire area is covered with polyethylene sheeting, as outilned in the procedure, which would catch any small leaks from the fuel line. The floor drains have been sealed so that no liquid may drain into the drainage piping.

Question on Step 2. Is the gas inlet nozzle on the line controlled by valve V7?

Answer: '

The gas inlet to the reactor core is c'ontrolled by two valves in series, V2 and V6 or V7. Valve V2 is built into the reactor tank. Valve V6, external to the reactor, directs gas flow to vacuum tank T1, and valve V7, also external to the reactor, directs gas flow from the air vent filter.

. Question on Step 3. Is the fuel outlet nozzle on the line controlled by valve V1? -

Answer:

The fuel outlet from the reactor core is controlled by two valves in series, V1 and V3. Valve V1 is built into the reactor tank. Valve V3 is external to the reactor.

Question on Step 8. What is the identification number of the valves that are fuel transfer valves?

i Answer:

In the context of Step 8, it is intended that all valves be closed (V1, V2, V3, V4, V5, V6, V7, and V8) to start. The fuel flow will- be controlled by valves V1 and V3.

Question on Step 10. Is valve V1 considered to be a gas valve or is valve U2 intended to be opened here?

Answers I

l

2 Valve V2 is the gas valve. This is an error in the writeup of the procedure, and will be corrected.

Question on Step 13. Is it intended that valve V2 be opened before the fuel transfer?

Answer Valve V2 (gas valve) is opened in step 10.

Question on Step 15. Can the fuel in the line run out during the fuel bot tle change?

Answer:

After filling one fuel bottle to the desired 10-liter level, the fuel transfer valves V1 and V3 are closed, and the fuel bottle cap is removed by unscrewing the fuel bottle from the cap. During this operation, the fuel solution which remains in the transfer line is contained by capillary action. Added precautions are taken to catch any fuel drops in absorbent tissues as the full fuel bottle is exchanged for an empty bottle. The absorbent tissue is then placed in the radioactive waste.

Question on Step 17. This vacuum cannot be established in the core with valve V2 still closed (see Step 10 and Step 13 questions). The vacuum in the reactor core cannot be read at tank T1 with valve V2 closed.

Answer:

Valve V2 (gas valve) is not closed after Step 10.

. There is a vacuum gage (P1), not shown into the figure, l built into the reactor tank and connecting on the core vessel side of the builtin gas valve. Thus the core pressure (vacuum or atmospheric) can be monitored at all times.

Question on Step 19. Water will not enter the core without the vacuum sought but not achieved in Step 17 (see Step 17 question).

Answer:

Transfer of 1-11 ter of distilled water is by vacuum.

With the core at 10 to 15 inches of Hg vacuum, and values V1 and V3 open, water is transfered from the water bottle to  ;

the core'.

Question on Step 20. Subsequent rinse steps are also not valid for the reasons addressed in Steps 10, 13, 17, and 19.

Answer:

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When the transfer of rinse water to the core is completed, the fuel valves V1 and V3 are fully opened, allowing the core pressure to increase to atmospheric. The operation assures that the small amount of fuel retained in the horizontal section of the fuel line is transfered to the core and is mixed with the rinse water, and that the inner surfaces of the core are wet by the bubbling action. The core pressure is observed, either on the re9etor vacuum gage (P1) or on tank T1 vacuum gage (P2) with valves V2 and V6 open.

Question on Step 25. Are the bott1-5 containing fuel mixed in their individual drums for sampling, or are they sampled before being put into their drums? Will adequate separation be maintained to preclude interaction? Sample measurements to be made when and by whom?

Answer:

The reactor fuel inventory is to be transfered into three fuel bottles. The rinse water is to be transfered and contained only in the fourth bottle. When bottle no. 4 contains all of the rinse water, the solution will be thoroughly mixed by agitation before a sample is removed for chemical analysis. No mixing of fuel in bottles no. 1 through 3 will be required. A noncritical geometry is maintained during the defueling procedure by placing the filled fuel bottle in its respective shipping cask prior to filling a subsequent bottle. Sample measurements are to be made by the subcontractor for the UCSB L-77 decommissioning, the Rocketdyne Division of Rockwell International

. Corporation.

Question A. Are the vacuum tank, filters, water reservoir and fuel bottles all favorable geometry containers?

Answer:

All are safe geometry containers except the vacuum tank. Admi ni strat ive con trol wil l be used to assure the fuel bot tle .does not overfl ow and f uel does not enter the vacuum tank. Also, with one bottle full, the maximum remaining fuel inventory that could enter the vacuum tank is less than '2:0 li ters, containing less than the critical mass in the spherical, reflected core vessel (1172 grams U-235).

Question *B. What redundancy precludes a minimum critical mass (MCM) of this fuel from entering a nonfavorable geometry container?

Answer See answer to Question A.

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(. Question C. Does UCSB have authorization to be a user of the shipping container?

Answer:

An application to become an authorized user is being prepared.

Question D. During reactor oiperation, hydrogen and oxygen

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gases were generated as a resul t of hydrolytic decomposi tion of water. Address steps taken to preclude an explosive recombination of any residual gases during defueling.

Answer:

The core vessel contains a catalytic recombiner in the gas space. The presence of any hydrogen and oxygen which may not have been recombined would have been indicated by an increase in core pressure, when corrected for changes i n' baroa-tric pressure. Such an increase has never been observed. Furthermore, most of the gases are removed semiannually during the core-recombiner pressure scram test.

The UCSB L-77 reactor was last operated on October 21, 1985, and the core-recombiner test is scheduled and will be performed before the defueling. The core will be reevacuated ,

to about 29.5 inches of Hg vacuum as part of the test. Thus no hydrogen-oxygen explosion can occur during defueling.

Question E. Determine the TRU content of the fuel.

Answer:

The TRU content of the (HEU) fuel is calculated to be less

. than 0.01 pCi/gm. The reactor has been operated for only some 350 watt-hours since install ation at UCSB.

Question F. Address the method by which the reactor vessel will be dried, and the technique to be used to verify that the vessel is dry.

Answer Drying involves flowing room air through the reactor core, fuel line to gas line, and exhausting the moist gas i through a Drierite filter. An inlet air drying tube (filled ,

i with Drierite dessicant) is attached to the gas inlet nozzle. An exhaust air drying tube (filled with indicating Drierite dessicant) is attached to the reactor fuel line. An absolute

• fil ter and posi tive displacement air pump are attached to the exhaust drying tube. The reactor core I vessel is purged with dry air at room temperature until the l I

exhaust Drierite gives no further indication of moisture being removed. Then the drying tubes are removed from the gas and fuel lines, and the lines are sealed. 1

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