United States Nuclear Regulatory Commission - Protecting People and the Environment

U.S. Nuclear Regulatory Commission

Boeing Company Request Concerning Depleted Uranium Counterweights

HPPOS-206 PDR-9111210356

Title: Boeing Company Request Concerning Depleted Uranium

Counterweights

See the letter from G. H. Cunningham to W. E. Morgan dated

April 14, 1983, and the incoming requests from W. E. Morgan

(Boeing Company) dated March 18, 1983 and January 6, 1983.

The Boeing Company's proposal to apply a corrosive

preventive compound to depleted uranium (DU) counterweights

was not considered "... chemical, physical, or

metallurgical treatment or process ..." and was appropriate

for exemption under 10 CFR 40.13 (c) (5).

The 747 airplane program utilized DU weights for mass

balance of outboard elevator and upper rudder assemblies on

the first 550 aircraft built. This equates to

approximately 12,000 cast parts and a total mass of DU in

excess of 200 tons. Depending upon the model, each

aircraft had either 21 or 31 weights. At each major

aircraft overhaul (about 4 to 5 years), it was anticipated

that over 20% of these weights would be corroded to where

they required reprocessing. This condition was considered

to present an unnecessary maintenance burden on the 747

operators. Aside from the high corrosion rate, the weights

were extremely difficult to transport with only one

recognized reprocessing source in the world.

In a letter dated January 6, 1983, the Boeing Company

proposed originally to apply an additional protective

coating of Cosmoline (MIL-C-11796) over the protective

coating of undamaged DU weights. They intended to require

that the weights be (1) corrosion free, (2) properly nickel

and cadmium plated and painted, (3) heated to 150-160F,

(4) dipped in MIL-C-11796 at the same temperature, and (5)

cooled to ambient temperature. The weights in question

were exempt items manufactured by NL Industries of Albany,

New York. When the weights were reinstalled on the

airplane, they intended to fill the attachment holes with

MIL-G-23827 grease. Cautionary marking on the weights

would be kept free of corrosion preventative compounds.

They asked if these additional processes in any way

violated the conditions of 10 CFR 40 of the NRC rules and

regulations.

It was NRC staff's view that the above processing falls

within the prohibition of 10 CFR 40.13 (c) (5) (iv). That

provision states clearly that the exemption from licensing

in 10 CFR 40.13 (c) (5) for DU weights does not authorize

any treatment or processing of the counterweights except

for repair or restoration of any existing plating or

covering. This has been the regulatory position for over

20 years [see 25 FR 6427]. The above proposal involved the

processing of the DU weights to add a new coating of a

different material. If the work was performed at the

Washington plant, Boeing would need (1) a license from the

State of Washington authorizing the procedure for coating

the DU weights in its possession, and (2) a license from

the NRC to distribute the weights to exempt persons (i.e.,

the operators of the aircraft) after being coated [see 10

CFR 40.13 (c) (5) (i) and 150.15 (a) (6)].

In a second letter dated March 18, 1983, the Boeing Company

proposed the application of corrosion preventative compound

MIL-C-16173 to DU weights in service. This procedure would

be accomplished during operators scheduled maintenance

programs. It would be required that the weights be

corrosion free and finished per drawing (nickel and cadmium

plus primer) prior to brush application of MIL-C-16173.

Both MIL-C-16173 and weights would be at ambient

temperatures during application. Attachment holes would be

filled with grease (MIL-G-23827) to eliminate water traps

and cautionary markings on the weights would be kept

legible. No chemical interactions would occur between the

corrosive preventative compound (MIL-C-16173) or the grease

(MIL-G-23827) and the plating or paint because these

compounds do not contain solvents or other agents which

might soften paint. The Boeing Company believed that this

process, while not as effective in preventing corrosion as

their previous proposal, would be a significant improvement

and did not violate the intentions of 10 CFR Part 40 of the

NRC rules and regulations.

It was NRC staff view that the second proposal was not

considered as "... chemical, physical, or metallurgical

treatment or process ..." and was appropriate for exemption

under 10 CFR 40.13 (c) (5).

Regulatory references: 10 CFR 40.13

Subject codes: 11.1, 11.6

Applicability: Source Material

Page Last Reviewed/Updated Thursday, March 29, 2012