ML20010C011

Requests Amend to Certificate of Compliance 9044 Reflecting Method for Disposing of Radwastes.Rept Describing Method of Grouting & Testing Conclusions Encl

ML20010C011
Person / Time
Site:	07109044
Issue date:	07/22/1981
From:	Cunningham G GENERAL ELECTRIC CO.
To:	Macdonald C NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS)
References
19437, NUDOCS 8108180656
Download: ML20010C011 (12)

Text

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hhk NUCLEAR ENERGY GEN ER AL @ ELECTRIC PROGR AMS DIVISION Raronn To Mb GENERAL ELECTRIC COMPANY, VALLECITOS NUCLEAR CENTER,

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910-548-8481 July 22, 1981 n

s C. E. MacDonald, Chief Transportation Certification Branch D

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Ref:

Certificate of Compliance No. 904

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Dear Mr. MacDonald:

i if g Doc m q Because of the diverse materials which must 'b'e3p dhf~from General Electric Co., Vallecitos Nuclear Center Hot Cell Complex, it is not possible to package these radioactive wastes as special form. Accordingly, a method of immobilization and contain-ment was developed, using cement grout to penetrate and encapsulate the radioactive waste materials.

General Electric has tested this method using simulated waste materials on full scale and feels that the resulting package complies with appropriate regulatory reouire-ments for normal and accident conditions of transport. A report describing the method of grouting, testing and conclusions is en-closed.

General Electric proposes that the following be added to Section 5 (b) of the Certificate:

" Radioactive waste materials immobilized with cement grout and con-tained in a metal inner container as described in G.E.'s July 22, 1981 submittal.

Decay heat not to exceed 100 watts, SNM not to exceed 500 gm U-?35 equivalent mass.

G. E. anticipates the release of the requested simplified drawings of the model 1600 package in early august, following review by the other model 1600 owners.

A check in the amount of $2800.00 for a minor amendment to Certificate of Compliance No. 9044 is enclosed.

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Sincerely, Applicadt.....

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G. E. Cunningham U

Sr. Licensing Engineer ge:eived By@4 '

DD7 losure 8108180656 610722 PDR ADOCK 07109044 C

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.. !D MARY GE-VNC proposes to use cement grout to imobilize and contain solid radioactive waste in a metal inner container. ' Itis inner container will be loaded in a GE Model 1600 transport package for shipent to a comercial waste burial gt2 h grout converts the solid but loose waste material into a monolithic cylinder which, when loaded in the Model 1600 package, will be resistant to damage from normal and postulated accident conditions of transport. This report describes the methods, materials and procedures developed and tested by G.E. tc imobilize and contain radioactive waste by-products generated during routine operation of the high-level hot cell facilities at the Vallecitos Nmlear Center. The report further delineates the basis for concluding that this packaging process in conjunction with previously certified packaging complies with federal regulations pertaining to the shi pent of radioactive material.

DESCRIPTION OF WASTE MATERIALS The hot cells are used for a wide variety of functions normally involving radioactive materials. Most of the cell work involves the remote examination ancVor processing of these radioactive materials. These materials are frequently dissected into smaller pieces or chmically processed. As a result of these operations, the cell interiors becme contaminated with loose particulates. Because of this, all items that are entered into the cells become contaminated. The greatest bulk of cell waste is made up of non-irradiated materials which have become contaminated while inside the cells. Many years of operating experience indicate that it is economically and physically impractical to attempt to remove this type of contamination. As a result, essantially all maMrials entering the hot cells eventually must be removed as radioactive waste.

The radioactive waste resulting from operation of the GE-VNC hot cel1F is quitG diverse in nature as are the operations conducted in the cells. Sme of the waste materials are a product of the contamination control process such as absolute filters, manipulator boots, absorbent wipes, but most materials result from specific in-cell operations. The waste volume is about equally divided between non-cabustible materials: metal, glass, abrasives, solidified aqueous media, etc., and combustible materials: wood, plastic, adhesive, rubber, dry paint, resins, solidified organic absorbent, paper and other fibrous materials.

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Many of these materials are packaged in-cell into containers for ease of handling. One gallon tin cans are frequently used to hold tubing, wire, floor i

sweepings, absorbent solidification, melted plastic, and other miscellaneous small items. These and other bulky itans are then loaded into a sheet metal bucket or slip liner which is sized to slip-fit into a 55-gallon drum or similar metal inner container.

l PROPOsm PACKAGING METHODS Since all of the materials in a waste shipnent have high levels of smearable surface contamination, a method of assuring containment and inmobilization during transport adds to the overall package integrity. The method described in this report utilizes cement grout to accomplish this result, m v.~~yy

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Slip Liners and Extended DOT Metal Inner Container In this application, the slip liners are fabricated frca perforated sheet metal to allow a cement grout mix to be pumped in to thoroughly permeate and penetrate all opn spaces around the waste. Figure 1 shows a pair of the perforated slip liners in front of an extended DOT 17H Drum inner container. The six vertical tubes on the outside effectively center the liners in the inner container, and the grout forms a solid, inpervious layer between the slip liner and the inner container. Figure 2 shows a simulated typical load of hot cell waste spread out in front of the slip liners and inner container, and Figure 3, the two slip

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liners loaded and ready to be installed in the inner container for grouting.

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CEMENT GIG 7f he formulation of cement grout for waste imobilization was selected after a l

thorough review of literature published on this subject. Cement grcut is comonly used in the industry as a solidification media for aqueous waste but no meaningful details of other application for solid material int >edment were found. Information extracted from this literature was used to prepare six proposed grout formulations which were then tested to determine optinum conformance with performance requirments.

The following parameters were used as a guide in establishing optinum formulation for the grout mix.

1.

High penetrability - to result in a monolithic encapsulization of the waste.

2.

Resistance to a:400 F anbient temperature as soon as possible after initial setting.

('Ihis is the maximum cavity tmperature of the Model 1600 package during accident conditions.)

3.

Lack of bleeding or water standing on top of the grout after initial setting.

'4.

High early strength.

5.

Readily pumpable with standard comercial equipnent.

The six formulatior.3 included three based on portland cment (Type II) and three based on calcium aluminate cement. This calcium aluminate cement is comonly used for applications requiring very high early strengths and/or refractory applications up to 2550 F.

Strength terts were run on these batches as follows:

Cnanressive Strenarbs:

ASIM C109 procedures were used as applicable with 2"x2"x2" test cubes.

IJ. G. Moore, H. W. Godbee, A. H. Kibbey, " Leach Behavior of Hydrofracture Grout Incorporating Radioactive Wastes", Nuclear 'Ibchnology, Vol. 32, American Nuclear Society, Jan.1977.

. 'blitti. o Tensile Strenoths ASIM C496 procedures were followed with 3" dia. x 6" long test cylinders.

hrmal Resistance The 2" cubes were cured 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> and then subjected to a thermal exposure test by heating to'400 F (20 min) and holding this temperature for 30 minutes. The oven was then turned off and allowed to reach anbient temperature. The cubes were then removed and tested in cmpression.

GROUP TEST RESULTS The three portland and three calcium aluminate formulations are compared generically as material vs. material, without reference to exact formulations.

As expected, the three calcium aluminate batches showed very high early strength compared to the portland cuent formulations. C m pressive testing indicated portland formulations only '40% as strong as calcitn aluminate in 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> and 60% in 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />. Splitting tests again indicated portland formulations lagging (60%) at 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> but about equal ati48 hours. The thermal exposure test resulted in a considerable loss of compressive strength by the calcium aluminate sample (38%) and a small increase by the portland sanple (6%). The portland cement sample was, however, only 75% as strong as the calcium aluminate after this exposure. Despite the reduction and increase of these materials' strength values, the calcium aluminate sample was 25% stronger than the portland sample.

GROUT TEST CONCLUSIONS Both types of cement grout demonstrated adequate strength (greater than 3000 psi) at 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> even after exposure to a thermal environment of 400 F.

(Calculations for the Model 1600 package indicate this temperature is not exceeded in the cask cavity during postulated accident conditions.) Grout formulations using either type of cement will retain adaquate strength to assure that the imobilization medium is not degraded by normal or accidtnt thermal environments during transport.

It was decided to use the calcium aluminate cement for the test, not only for its strength, but also to provide experience with this type of cement. This test experience will facilitate the conversion of the test data to the actual operation.

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. SIMJLATED PACK 1CING TEST The proposed internal waste package was assembled using non-radioactive materials to simulate typical waste contents. A stand was used to simulate the support available during in-cell loading.

A grout formulation using calcium eluminate coment the same as that previously tested for strength was prepared and pumped into the drum. The grout was pumped through a metal tube into the annular space between the slip liners and the drum with release near the bottom of the drum. A vibrator shown in Figure'4 was used during the entire filling operation to insure maximum grout penetration.

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. The drum head was then installed and the assembly was lef t in the stand to set up. One of the primary aspect-of this test was to identify the practicality of the grout pumping process. Smie problms were experienced at the beginning of the mixing und pumping operation. To further expedite the flow capability of the grout mix, it is planned to substitute vl5% of the cement with pozzolaa (fly ash). This is a cmmon cementitious additive used to increase the fluidity of the mix.

It will also enhance the ability of the mix to grmeate into cavities in the waste without reducing the final strength of the mix.

RESULTS OF SIMULATED PAGAGING TEST Following the grout filling operation, the simulated waste package was closed and allowed to stand overnight. The next day it was delivered to a concrete sawing contractor. The package was cut in half from two directions, yielding four sections.

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The grotit dmonstrated a high level of penetration to surround and enter most open containers in the package. This is shown in Figure 9.

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Closeup of Sectional Cut Through Drum Figure 9 above shows the complete penetration of the grout throughout the waste and the layer between the slip liner (shiny dotted edge) and the drum. The cut surface indicated no evidence of cracking or separation.

The outside surface of the grout as seen in Figure 9, did show sme minor hairline cracks as expected.

Figure 11 shows a complete cross-section of the bottm half of the drem, with glass, plastic, cans, tubes, etc. solidly embedded in the grout matrix.

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CONCIDSIONS It is apparent frcm the simulation test that cement grout is a good medium in which to imnobilize and contain hot cell waste for disposal. The addition of a pertorated retainer plate just below the top of the metal inner container or drum allow a cmplete and essentially impervious layer of grout, approximat4f 3/4" thick, to cover all radioactive waste contents. Highly soluble isotopic l

forms would tend to get locked up with the water of hydration in the concrete 2

and fly ash and would therefore demonstrate very low loachability. Na significant loss of grout strength was identified for thermal exposures of 400 F which is a reasonable limit for accident conditions in the cavity of the Model 1600 package. The 30-foot free fall could be expected to crack the grout matrix but it is likely that the fractured pieces would be of significant size and not likely to be dispersed from the cask cavity;

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.. Procadnral Outline of the Tn=nhilization of Cell Waste Usiro camant Grout 1.

Waste products shall be placed in a perforated metal slip liner which fits I

into a metal inner container. The metal inner container shall be at least 18 gauge steel, closed and sealed with a gasket and cover retained with bolts or a bolted clang ring. Typically, an extended 55' gallon drum will be used but the method is not limited to this specific inner container.

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2.

The slip liners shall be mechanically centered in the inner container and I

waste shall be retained in the assenbly to prevent flotation of contents during grouting.

3.

The cement grout shall be primarily a mixture of sand, cemer.', pozzolan, and water in the following proportions by weight.

Includ-Without ing H O HO 2

2 (Wt. %)

(Wt. t)_

Cement 33-42 40-50 Pozzolan 0-8.5 0-10 Sand 3 7-46%

44-55 Water 14-20%

4.

The grout shall be punped into the annulus between the metal inner container and the slip : Mer so that the groet fills the package from the bottom up.

The assenbly shall be vibrated continuously during grouting to maximize penetration of the grout into the waste material.

5.

The grouted assenbly shall be allowed to set without moving until the grout is hard and firm on the surface. Any frae standing water shall be removed from the top of the grout. pri.or to installation of the gasket and closure mechanism.

6.

The inner container shall be a single trip container sized to fit easily into the cask cavity but without excessive clearance. It shall be fitted with appropriate lifting devjces to allow removal using installation and removal with normal remote handling tools.

19437

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