ML092740436

Amendment of License SNM-928, Docket 70-925

ML092740436
Person / Time
Site:	07000925
Issue date:	07/22/1971
From:	Pittman F Kerr-McGee Corp
To:	Nussbaumer D US Atomic Energy Commission (AEC)
References
Download: ML092740436 (6)

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KERR-McGEE BUILDING OKLAHOMA CITY, OKLAHOMA 73102 July 22, 1971 Mr. Donald A. Nussbaumer Fuel Fabrication and Transportation Branch 6

JU4 Division of Materials Licensing U.s.

United States Atomic Energy Commission Washington, D.

C.

20545 Aa, Dear Mr.

Nussbaumer:

V A, k Cy.

Subject:

Amendment of License SNM-928, Docket 70-925 Kerr-McGee Corporation hereby files application for an amendment to the subject license to cover the additional operation of blending low-enriched U02 powder using moderation control for nuclear safety.

The attached Amendment Application No.

26 to License SNM-928 includes the details of the proposed activity for the Cimarron Uranium Plant and the relevant nuclear safety analysis.

Your early review and approval of this amendment request is appreciated as we are anxious to commence the new blending operation as soon as feasible.

Frank K.

Pittman

Director, Technical Services Nuclear Division FKP : rc Attachment (REHM

,)

KERR-MCGEE VROM KERR-McGEE BUILDING

• OKLAHOMA CITY, OKLAHOMA 73102 July 22, 1971 Amendment Application No.

26 to License SNM-928 (Docket 70-925)

INTRODUCTION This application for an amendment to License SNM-928 covers a new process for blending low-enriched U02 powder (with maximum enrichment not to exceed 4.72% U-235) using mod-eration control (H/U

< 0.45) for nuclear criticality safety.-

No other plant activities are changed by this amendment request.

The enrichment limit of 4.72% U-235 is proposed since it is the maximum enrichment currently authorized for Process Area A equipment in the production of ceramic U02 powder, and it is demonstrated to be nuclearly safe for the credible conditions.

This new method for the blending of U02 powder is provided

• to give a larger size lot of uniform U0 2 product by a single blending operation than is attainable by the present method which depends on safe geometry.

PROCESS DESCRIPTION The U02 powder is blended in a double-cone shaped hopper or blending vessel.

The blender hoppers have a capacity of about 77 cubic feet with approximate dimensions of 5'-6" central diameter by 7 '-8" in height.

The maximum quantity of U02 in a blender at any one time will not exceed 2000 kilograms of uranium (94.4 kg U-235 at the maximum enrichment of 4.72% U-235).

The U02 powder is sampled and analyzed for moisture con-tent and checked for hydrogen moderation level prior to transferring from safe geometry interim storage containers to the blender.

The U02 powder to be blended is vacuum transferred from the interim storage containers to the blender just prior to blending.

After a batch of U02 is

blended, it is stored in the sealed double-cone blender container until it is vacuum transferred to a pellet press feed hopper for further processing.

A sequence of the U02 production steps and pertinent features are given to substantiate the numerous controls in the process which provide reasonable assurance of safety by moderation control in the blending operation.

1.

Ammonium diuranate is fed to the calciner where, at high temperature and in an atmosphere of steam, ammonia and nitrogen, it is converted to U02 powder.

The exit end of the calciner is baffled from the feed end and all gases flow counter-current to the flow of material to prevent steam from collecting in the exit end.

2.

The U02 powder is discharged from the calciner and collected in nuclearly safe geometry storage con-tainers which are kept under nitrogen purge during filling.

3.

Prior to being placed in

storage, the U02 powder is tumble-blended in the safe geometry storage container and checked with a neutron gauge which is similar in principle to gauges described in Reference

1.

If this measurement indicates a

H/U > 0.45, the U02 powder is unacceptable for the blending operation and is recycled through the calciner.

Tests on the neutron gauge indi-cate that it will reliably distinguish hydrogen moderation equivalent to moisture levels between 0% and 1.5%.

4.

The storage containers are sealed with a leak-tight cover while in interim, controlled storage awaiting blending.

5.

The U02 is further checked for moisture content prior to blending by the following methods:

a)

Each container is checked for moisture content using a dew point analyzer (type Foxboro Dewcel element or equivalent).

Any container which indicates a water saturated atmosphere by the dew point analysis is rejected for blending and the U02 is recycled to the calciner.

Test measurements have shown that a water saturated atmosphere will be indi-cated if the UO'2 powder has a moisture content in excess of 0.85 w/o.

b)

Each container of U02 is thief sampled.-

A composite sample of the blending lot is pre-pared and analyzed by the laboratory for moisture content.

c)

Each container is rechecked with the neu-tron gauge just prior to transferring the U02 from interim storage containers to the blender.

If the moderation level is H/U > 0.45, the container of U02 will be rejected for blending and recycled to the calciner.

6.

The blending operation is conducted under direct supervisory control.

7.

After blending, the blender hopper is sealed and placed in storage to await further processing of the U02 powder to the pellet presses.

NUCLEAR SAFETY ANALYSIS The actual blending operation and the storage of the blended U02 in large double-cone blender hoppers is based on moder-ation control for nuclear criticality safety.

With ad-herence to the double contingency principle, control against accidental criticality is assured, based on the two factors:

process control with administrative procedures and measure-ments of moisture content.

Moderation is controlled to an H/U of < 0.45.

No blending batch shall exceed 2000 Kg U with enrichment limited to maximum 4.72% U-235.

The basis for safety of handling such large quantities of dry powder is moderation control as shown in Figure 1 of Refer-ence

2.

By controlling the atomic ratio, H/U to be < 0.45, the infinite medium multiplication factor is less than one (k-<l) for enrichments up to and including 5% U-235 and criticality is not possible for the undermoderated system.

The fact that the referenced Figure 1 is for a U03-H20 system rather than a U02-H20 system is considered insignifi-cant because the neutron absorption cross section for oxygen is negligible.

Controls to assure nuclear safety for the undermoderated U02 in the blending operation and in blender storage include:

1.

Process Control -

Under normal process conditions, U02 powder from the calciner usually has a low moisture content of between 10 and 1000 parts per million.

Adherence to procedures on operating temperature and the direction of gas flow assures that the powder from the calciner is low in moisture.

The operating procedures also require that each container of U0 2 be purged with dry nitrogen gas during filling of a storage can and the filled container be sealed with a leak-tight lid to as-sure the the U0 2 powder is stored under a dry atmosphere.

2.

Administrative Controls -

Operating procedures pro-vide additional control features as follows:

a.

Calcined U02 powder is segregated from other uranium materials while in storage to provide improved storage control for material to be blended.

b.

Storage containers (milk cans and blender hoppers) are of leak-tight design and are sealed with a leak-tight closure while in storage.

c.

The results of the moisture and moderation measurement methods shall be recorded and cans of U02 powder will be released for blend-ing by supervisory personnel only after checking that the moisture and moderation level is acceptable for the blending opera-tion.

3.

Measurement Techniques for Moderator Control Several measurements are made to assure that a mod-eration level in the U02 powder does not exceed H/U = 0.45 (approx.

1.5 w/o H20).

a.

Each can of U02 powder from the calciner is checked with a neutron gauge at the time of loading.

b.

Each can of U0 2 in interim storage is checked with a dew point analyzer to determine the relative humidity in the container at least 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> after the can has been sealed and just prior to blending.

9 9

--5--

c.

Each can of U0 2 in interim storage is thief sampled and a moisture analysis is made by the laboratory of a composite sample of the blending lot.

d.

Each storage container is rechecked with the neutron gauge just prior to transferring the U02 into the blender.

REFERENCES

1.

Neutron Moisture Gauges, Technical Reports Series No.

112, IAEA,

Vienna, 1970.

2.

C.

E.

Newlon and A.

J.

Mallett, Hydrogen Moderation A Primary Nuclear Safety Control for Handling and Transporting Low-Enrichment UF6, K-1663, Oak Ridge Gaseous Diffusion Plant, Union Carbide Corporation, May 31, 1966.