ML19219A149

Neutron Products, Inc.: Supplemental Response to Second RA1 - EPID L-217-LLA-0133

ML19219A149
Person / Time
Site:	07109215
Issue date:	07/26/2019
From:	Ransohoff B Neutron Products
To:	Allen C Division of Spent Fuel Management
References
EPID L-2017-LLA-0333
Download: ML19219A149 (7)

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Document Control Desk Director.

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Division of Spent Fuel Management

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Office of Nuclear ryiaterial Safety and Safeguards US Nuclear Regulatory Commission Washington, D.C. 20555-0001 Mr. Chris Allen Project Manager Spent Fuel Licensing Branch Division of Spent Fuel Management Office of Nuc.lE!ar Material Safety and Safeguards Re:

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s*upple~ental Re.sponse to Se~ond R~1

• Docket No. 71-9215

• EP*m No: 1-2:611~L(A~di33

Dear Mr. Allen,

neuTROn PRODUCTS inc

(

l 22301 Mt. Ephraim Road, P. 0. Box 68 Dickerson, MaryLtnd 20842 USA

. 301-349-5001 FAX* 301-349-2433 e-mail* neutronprod@erols.com 26 July 2019 As we discussed by telephone, I am writing to supplement our reply to your Request for Additional Information dated January 30, 2019, which we received on March 15, 2019, and to which we initially replied on 5 April 2019.

Our initial reply included calculations based upon the source or sources being radially offset within the round cask through hole, Based upon our previous conversation,.such a configur~tion *~ill ~dt~be: ~~'~d 'going forward until after we have submitted additional -

information which wi11;b~ the subject of a separate amendment ~equest. This supplemental reply addre~ses :sotirces whi~h.are fadi~Uy c~ritered in the round through holes, and sources which are offset in the square through holes, where the potential for rotation during transit or in accident conditions is not an issue.

• A'

• The request from your second RAI states:

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Mr. Chris Allen 26 July 2019

• Page 2 "5.1 Provide additional information regarding the methodology and criteria us~d to determine whether source material is suitable to be loaded.

Staff analysis shows that a penci/.source with the maximum activity/imits in the CoC Condition S(b) will not meet the dose rate requirements of Title 10 of the Code of Federal*

Regul~tions (10 CFR) 71.47(a). Although the applicant confirmed this in an RA/ response (ADAMS Accession No.,V,L182184429), the applicant did not provide separate analysis or

. measurements showing that a package which does not meet 71.47(a) will meet the requirements of 71.4T(b). Therefore, the applicant.needs to provide the criteria or the process by which the maximum activity that can be transported in a pencil source configuration is determined.

This information is necessary to determine compliance with 10 SFR *71.47."

1. Shielding Evaluation - Maximum Lengths for: Cobalt-GO Certificate Activity Limits As discussed in our initial response, the evaluation of whether or npt a proposed source can be

• shipped in our package - from a shielding perspective~ i~cludes consideration of how the proposed source compares to sources previously shipped in.the package and, to the extent previous experi~nce is not applicable, a more detailed shielding*evaluatit>n. For that evaluation,.

we generally consider the proposed source to be several smaller point sources. The.

calculations are explained in some detail in_the initial response, which discussion is not.

repeated here.

Before considering the theoretical. maximum length-for a source at the certificate limit for the

.package, i1; is useful to demonstrate that the evaluation method we use gives a reasonable approximation of survey data from actual shipments in the field.

Example In March 2018, we shipped a cobalt-GO source containing 5290 Ci. It was 5.6" long and 0.772" r

in diarneter. The -5 drum assembly from drawing 240122 was utilized.

The results of that evaluation. and the actual survey data are:

I

• Predicted

-Actual.

Cask contact Dose rate (mR/hr) 170 160 OP contact dose rate (mR/hr) 12 8

1.3 0.9 From this data, arid others, we believe the evaluation to be a reasonable approximation of*..

actual results from the field. The fact that the predicted values are_generally a bit higher than neLJT-ROn PRODUCTS. inc.

1 Mr. Chris Allen 26 July 2019 Page 3 the actual measured values suggests that this approach is conservative. Had a source of the

• same dimensions, containing the certificate.limit 15,000 Ci been shipped instead,.we would have expected the dose rates to be higher by nearly a factor of three, or: approximately 21 mR/hr at contact with the OP and a Tl of 3, still well within regulatory limits fora routine shipment.

1.1 Theoretical 15,000 C[ Pencil Source for -5 Drum Assembly Using the same eva.luation technique, and conti'nuing with the -5 drum assembly frnm the drawing, we can.evaluate a theoretical 15,000 Ci cobalt-60 source of different lengths.to

• establish a maximum length for this activity. A source. measuring 11.625" in length would allow for 5" shield plugs on eac;:h side. For the purposes of this evaluation, materials of construction of the shield plugsto be used will be tungsten alloy, with a specific gravity of 17. Such an arrangement would give the following dose rates:

Cask contact OP contact Tl Dose rate (mR/hr) dose rate (mR/hr).

. Predicted 28,000

• 1AOO 130

• Ignoring for a *moment the occupational exposure issues presented by preparing such a shipment, this *source could not be shipped in our package in accordance with the requirements of 10 CFR 71.47(b) because the 1 R/hr limit at contact with the package (OP) is exceeded.

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Shortening the source by two inches, thereby adding an additional one inch of shielding on

• each side of the source reduces the predicted dose rates as follows:

Cask contact.

OP contact

n.

Dose. rate (mR/hr)..

dos.e rate (mR/hr)

Predicted

. 6,200 330 31 There are other dose'rc1te requirements i.nclude~ in 10 CFR 71.47(b}. Those are evaluated in the following example which has higher dose rates than those* in this example. Accordingly, we submit that the 15,000 Ci limit forthe*-5 drum a'ssembly should apply to lengths !ess than.or equal to 9.625".

1.2 Theoretical 9,500 Ci Pencil Source for -4 Drum Assembly The-4.drum assemblyJrom drawing 240122 is authorized for actlvities.up to 9,500 Ci of cobalt-

60. p-erforming a similar series of calculations on an 11.625" source in that drum assembly yields the follo.wfr1g results:

1 neuTROn PRODUCTS inc

Mr. Chris Allen 26 July 2019 Page4

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Predicted Cask contact Dose rate (mR/hr) 16,000 OP contact

. Tl dose rate (mR/hr)

.730 65 This shows thatthis source could be shipped in the 9215 package in accordance with the**

requirements of 10 CFR 71.47(b).

In order to evaluate compliance with 10 CFR 71.47(b)(4), it should be understood that the only regions of significant dose rate are those around the flanges of the end caps. As a result, when loaded onto the transport vehicle, the package would be oriented such that the endcaps were pointing towarc;I the front and rear of the vehicle, not toward the sides. Using the inverse square law from the center of the source (which is 2 feet from the surface of the OP):

(730 mR/hr)

• 22 / x2 = 2 mR/hr

solving for x gives approximately 38 feet. Assuming.8 feet between the batk of the tractor and the front of the trailer means that the package would have to be secured approximately 30 feet back in the trailer. For a typical 48 foot trailer, and t1:1kin_g into consideration the 4 feet occupied by the package itself, the 0th.er side of the package would be 14 feet from the end of

. the trailer: Using the inverse square law again:

(730 mR/hr)

• 22 / 142 = 15 mR/hr at the back.doors of the trailer, which is well b~low the 200 mR/hr limit in 10CFR 71.47(b)(2).

Regar~ing the 2 m from the vehicle limit of 10 mR/hr in 10 CFR 71.47(b}(3), the highest point would be behind the back doors ofthe trailer:

(730 mR/hr)

• 22 /-(14+.6.6)2 = 7 mR/hr Based upon the foregoing evaluation, we submit that the 9500 Ci limit. shoul<!_ apply to *a cobalt-.

60 *source less than or equal to 11.625 11 in length for the -4 drum assembly. One could argue whether or not.it would be atjvisable to,ship such a source in this configuration and, to'b-e frank, we woujd have to have a very compelling reason to even consider such* a shipment as* it would.

require considerable effort and investment to manage the occupational exposures.entailed in doing the work.. That said, we believe that the foregoing demonstrates that such a source could*

• be shipped in a compliant manne*r and that, as such, it should _be authorized by the certificate.

1.3. Theo,:-etical 6,000 Ci Pencil Source for -2 Drum Assembly*

The.-:-2:drum :assembly from drawing 240122,is authorized for activities up to 6,000 Ciof cobalt-

. 60. Performing a similar series of calculations ~n. an 11.625" source centered in that drum

• assembly yields the following results:

. neuT*ROn PRODUCTS inc

I Mr. Chris Allen 26 July 2019 Page 5 Predicted Cask contact Dose rate (mR/hr) 11,000 OP contact Tl dose rate (mR/hr) 500 45

• These results are comparable to those discussed abov~, so that we may conclude that the -2 drum assembly is suitable for shipping cobalt-60 sources up to 11.625" in length at tbe maximum activity of 6,000 Ci.

-2. Shielding Evaluation - Maximum Lengths for Cesium 137 Activity Limits

• In practice, the longest source~ we have shipped in the 9215 have been cesium source assemblies. For our pc:Jckage, the best way to shield these sources is to use the square drawer drum (the -2 drum assembly).and offset the so.urce toward the center of the package.

One example was a source shipped in January 2018, which was 2454 Ci of cesium-137. The source was 15.94" long, and was attached to a tungsten rod which brought the total length of

• the assembly to 20", including a short length (3/8") bf threaded rod attached to the en*d of the tungsten. The rod was typically used to handle and control the source. Because the sourcewas being shipped for disposal, the short rod was no longer required for the use of the source. The certificate for the 9215 requires that at least 2" of shielding be used. Because the available

• length is only 21.625", w.e would not be able to ship the cesium source as it was configured.

However, by grinding the short, small diameter threaded rod off of the end of the tungsten, the overall length of.the sour~e assembly was reduced to 19.625 11

, which allowed us tp use the required 2 11 shield plug on the end of the source that did not alre;:1dy have the tungsten attached.

In order that this type of activity not be confused with the.recent events in Seattle, there was mor~_ than 3 11 of solid tungsten rod between the source and the short handling rod to be.*

removed. In addition, the modification was performed by the manufacturer of the source assembly. As a result, there was no credible scenario in which this 'operation could jeopardize the integrity of the sgurce.

• The calculated dose rates were quite close to the actual results from the surveys:.

Calculated Actual*

Cask contact

• Dose rate {mR/hr}

300 350 OP contact

• dose rate (mR/hr) 9.1 11 Tl 0.75 1

neuTRQn PRODUCTS inc

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Mr. Chris Allen 26 July 2019 Page 6 This example is instructive for two reasons. First, had a source of the same geometry containing the certificate maximum of 20,600 Ci of Cs-137 been shipped, the data_ above can be used to show that the Tl for such a loading would have been:

(1 mR/hr) * (20,600)/(2454) = 8.4 In addition,the OP contact dose rate would'have been approximately 92 mR/hr. Thus, the source could have been shipped in the package in ac_cordance with 10 CFR 71.47(a).

Second, we have requested thatthe requirement to use at least 2" of axial shielding be removed from the* certificate for sources such as this. This sour~e, had it not been modified, would have used a 1.625" source plug instead of_the full 2 11 plug currently required. Using an even shorter plug (1 "), calculations show that the dose rates would be expected to be:

Cask contact

• OP contact Tl Dose rate (mR/hr}

dose rate (mR/hr)

Predi.cted 4,300

99.

.8 Thus, a shipment.in-this configuration with an activity of 2454 Ci of Cs-137, with at least 1" of axial shielding would be in compliance with 10 CFR 71.47(a). For a 4,000 Ci source, the OP contact dose rate would be expected to be 160 m_R/hr with a Tl of 13. Such.a shjpment would.

meet the requirements of 10 CFR: 71.47(b) by a comfortable margin. As a result, we request that the r-e_quirement to use* at least 2" of axial shielding be reduced to 1" for shipments involving less than 4,000 Ci of Cs-137.

Additional Considerations As you know, I have had a *difficult time,with this response primarily because I am ccincerned that !he ultimate result is that the certificate is going to be made more restrictive. The fact of the matter is, however, that we do not ship 9.5" long 15,000 Ci sources in this package. Nor do we load the package such that the contact dose rate with the cask. is on the order of 16 R/hr, or so that the contact dpse rate_ with the overpack is on the order of 750 mR/hr. Nor do we make

. shipments with a Tl of 65. All of these conditions are presented in the foregoing as if we do these things in the normal course of conducting our business. One point I would like to make in this response is that, even though we don't generally do any of those things, we currently have authorization to do them and that authorization gives us a wide margin of compliance when compared to the activities which we do routinely conduct. That wide margin is important to us

• and we would prefer that it remain intact.

Furthermore, as discussed in our initial response, the package has been used t9 ship a wide range of sources, both in commerce and in the removal of sources under the OSRP and IAEA

• programs. Some of thes~ sources are standard, but many pf them are not and there are neuTROn PRODUCTS 1n:c *

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I Mr. ChrisAllen.

26 July 2019 Page 7 undoubtedJy sources out there to be shipped that we do not even know about. To the extent a proposed shipment.presents unusual challenges, those details - including shielding considerations - a.re evaluated on the merits prior to performing the work. I hope that these two responses*have clarified how we evaluate the adequacy of the shielding provided by our package.. we greatly appreciate the operational flexibility we have been afforded to date and

. believe that an approc;1ch can be devised which will enable you to satisfy your regulatory responsibilities and will at the same time allow us to maintain the operational flexibility we r

• require..

Thank you for your patience. If I have missed the mark in this response, or if you require additional information, please let me know.

Thank you for your consid~ration.

wur Bill R~nsohoff *f

' Neutron Products, Inc.

President