United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 85-46: Clarification of Several Aspects of Removable Radioactive Surface

                                                 SSINS No : 6835           
                                                 IN 85-46

                                 UNITED STATES
                         NUCLEAR REGULATORY COMMISSION
                     OFFICE OF INSPECTION AND ENFORCEMENT
                            WASHINGTON, D.C. 20555

                                 June 10, 1985

Information Notice No. 85-46: CLARIFICATION OF SEVERAL ASPECTS OF       
                                 REMOVABLE RADIOACTIVE SURFACE 
                                                                                       CONTAMINATION LIMITS FOR TRANSPORT
                                                                                           PACKAGES

Addressees:

All nuclear power reactor facilities holding an operating license (OL).

Purpose:

This Information notice is provided to clarify the application of the 
U. S. Department of Transportation (DOT) requirements pertaining to the
control and  monitoring of removable radioactive surface contamination on
packages and  transport vehicles. It is expected that recipients will
review this  information for applicability to their transportation
activities, and consider  actions, if appropriate, to preclude any
problems from arising due to  inappropriate applications of the DOT
requirements. However, suggestions  contained in this notice do not
constitute NRC requirements; therefore, no  specific action or written
response is required. Specific clarification and  guidance is provided in
the Attachments on:

1. Averaging of Wipe Samples
2. Use of Higher Efficiency Wipe Sampling Methods
3. "Wrapping" of Packages
4. Exclusive-use Vehicle Surveys for Surface Contamination

Background:

The recent resumption of transportation of commercial power reactor spent
fuel  in the U.S. has focused renewed attention on the chronic problem of
cask  "weeping." This is a phenomena whereby certain casks, after their
removal from  underwater storage basins (pools) and decontamination,
subsequently exhibit an  increase in the level of removable radioactive
surface contamination during  and after transport. This increase is
believed to be the result of a "weeping"  or "sweating" of previously
entrapped activity within surface pores, fissures,  etc. Its occurrence
and magnitude appear to be dependent on such variables as  cleanup
methods, surface porosity, types of detergents used, surface treatment 
history, duration of and temperature during transport, and the period of
time  between completion of transportation and performance of a
contamination  survey. Although the levels of contamination which have
been observed in cask  "Weeping" episodes do not present a significant
health and safety problem, the  levels have been



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                                                 IN 85-46
                                                 June 10, 1985
                                                 Page 2 of 3

technically above the regulatory limits, particularly when no further 
consideration is given to determining the wiping efficiency more precisely 
than the ten percent efficiency that is assumed within the regulatory
limit.  Recent changes to DOT regulations as promulgated in Docket HM-169
(48 FR  10218, March 10, 1983, and 48 FR 31214, July 7, 1983) have also
raised a  question because of an apparent unintended revision in the
regulatory language  relating to averaging of wipe samples.
Notwithstanding the guidance in this  notice, shippers of radioactive
packages, particularly spent fuel casks, are  reminded of the continuing
need for improving cask decontamination methods and  spent fuel pool
techniques, so as to maintain removable radioactive surface  contamination
levels as low as practicable.

Current Regulatory Requirements:

The DOT regulations in 49 CFR 173.443 prescribe limits for control of 
removable (nonfixed) radioactive contamination. The level of such
contamination on the external surfaces of each transport package offered
for  shipment must be kept as low as practicable. Determination of the
nonfixed  contamination may be made by wiping (e.g., "smears") an area of
300 cm2 of the  surface concerned with an absorbent material, using
moderate pressure, and  measuring the activity on the wiping material. 
Sufficient wipe samples should  be taken in the most appropriate locations
so as to yield a representative  assessment of the nonfixed contamination
levels. The limits of 173.443, Table  10, are restated below:

                        TABLE- 10 - REMOVABLE EXTERNAL
                    RADIOACTIVE CONTAMINATION - WIPE LIMITS

                                                 Maximum
Contaminant                                      Permissible limits

                                                 uCi /cm2    dpm/cm2

Beta-gamma emitting radionuclides;
all radionuclides with half-lives
less than ten days; natural uranium; 
natural thorium, uranium-235; uranium-238; 
thorium-232; thorium-228
and thorium-230 when contained in
ores or physical concentrates                    10-5          22 
All other alpha emitting radionuclides           10-6          2. 2

The above limits apply to packages transported as nonexclusive use, e.g., 
mixed freight. For packages shipped as exclusive-use by rail or public 
highway, the provisions of 173.443(b) provide that the removable
(nonfixed)  radioactive surface contamination at any lime during transport
may not exceed  10 times the limits stated above. At the beginning of
transport, however, the  levels may not exceed those stated above.
Further, pursuant to 173.443(c), any  transport


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                                                 June 10, 1985
                                                 Page 3 of 3

vehicle in which packages are transported within the "factor of 10" higher 
values, e.g., above the Table 10 limits, must be surveyed with appropriate 
radiation detection instruments after each use and shall not be returned
to  service until the radiation dose rate is below 0 5 mrem/hr and the
removable  contamination is below the limits stated in the above table.
(An exception to  this vehicle survey requirement is provided by
173.443(d) for closed transport  vehicles (highway) which are dedicated
solely to the transport of radioactive  materials packages and are
appropriately marked on the exterior of the  vehicle. Also, in such cases
the removable surface contamination on packages  within such vehicles may
be at the "factor of 10" limits at the start of  transport).

No specific action or written response to this information notice is
required.  If you have any questions on this matter, please contact the
appropriate NRC  Regional office or the technical contact listed below.


Edward L. Jordan, Director
Division of Emergency Preparedness 
and Engineering Response
Office of Inspection and Enforcement

Contact: A. W. Grella, IE
         (301) 492-7746

Attachments:
1. Averaging of Wipe Samples
2. Use of Higher Efficiency Wipe Samples
3. "Wrapping" of Packages (Casks)
4. Exclusive-use Vehicle Surveys for Surface Contamination
5. List of Recently Issued IE Information Notices


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                                                 Attachment 1
                                                 IN 85-46
                                                 June 10, 1985

AVERAGING OF WIPE SAMPLES

The DOT regulations currently state in 173.443(a) that "... the amount of 
radioactivity measured on any single wiping material when averaged over
the  surface wiped .. " shall not exceed the Table 10 values. Prior to the 
regulatory amendments by DOT in 1983 (see Docket HM-169, 48 FR 10238,
March  10, 1983), formerly applicable 173.397(a) provided that wipe
samples could be "...averaged over any area of 300 square centimeters of
any part of the package surface."  A February 21, 1984 query was made by
NRC to DOT to clarify  this matter. It read as follows:

The language of 173.443(a) has been modified somewhat from that contained
in  the previous 173 397(a). The new language no longer specifically
addresses  averaging of multiple wipe samples within any given 300 cm2
area of a package  surface. We understand that it was not DOT's intention
to disallow such  averaging and further that DOT will consider processing
a future rule change  to restore such a provision to 173.443. A suggested
text for such a  modification is enclosed. In the interim, until the text
has been formally  modified, we will continue to consider that averaging
of multiple wipe samples  over any 300 cm2 area of a package surface is an
acceptable practice.

In their March 19, 1984, reply to NRC the DOT stated:

It was not our intent to disallow averaging of wipe samplings over a 300
cm2  area. Consequently, we believe this is an acceptable practice and
will take  the necessary action to clarify this in 173.443(a)....


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                                                 Attachment 2
                                                 IN 85-46
                                                 June 10, 1985
                                                 Page 1 of 2

USE OF HIGHER EFFICIENCY WIPE SAMPLES

As is stated in 173.443(a): "Other methods of assessment of equal or
greater  efficiency may be used. When other methods are used, the
detection efficiency  of the method used shall be taken into account and
in no case shall the  nonfixed contamination on the external surfaces of
the package exceed ten  times the limits listed in Table 10." NRC also
queried DOT on this matter, as  follows:

We understand that DOT considers that the reference in 173.443(a) stating
that `other methods of assessment of equal or greater efficiency may be
used,' may  include other wipe sampling methods wherein the efficiency has
actually been  demonstrated to be greater than 10 percent. Therefore, in
effect, the wipe  sample limits stated in 173.443(a) and (b) and Table 10
therein, are limits  "by default," which do not take advantage of
utilizing an efficiency which has  been demonstrated to be greater than 10
percent.  In our evaluations of  licensees' package surveys, we therefore
plan to accept assessments based on  efficiencies which have been
appropriately demonstrated to have a higher than  10 percent efficiency.

The reply by DOT on the usage of higher efficiency wipe samples was as 
follows:

It is our interpretation of this section that wiping methods with a 
demonstrated efficiency greater than 10 percent may take this greater 
efficiency into account. As you point out, the higher efficiency must be 
documented and in no case may the removable levels exceed 10 times the
values  in Table 10.

It should be understood that where the term "detection efficiency" is
used, it  refers to the efficiency of alternate methods for quantifying
the amount of  removable contamination on a package surface. It does not
refer to the  laboratory term relating to instrument effectiveness for
counting analyses.

An additional clarification also was received from DOT relative to use of 
contamination assessment techniques with greater than 10% efficiencies in 
exclusive-use vs nonexclusive-use shipments. It stated that "the provision
for  using higher efficiency techniques, described in 49 CFR 173.443(a)
may also be  used when operations are being performed in accordance with
173.443(b)."

An acceptable method of demonstrating wipe (smear) efficiency is
repetitive  wiping of a portion of the package surface. The demonstrated
wipe efficiency  is the ratio of the initial smear activity to the
summation of activity on all  the wipes of the designated portion of the
package surface. For the purpose of  this calculation, one can assume all
activity is removed when two consecutive  wipes show less than 10% of the
activity of the initial wipe. Because of   variations in package surfaces
and contamination characteristics, care should  be


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                                                 Attachment 2
                                                 IN 85-46
                                                 June 10, 1985
                                                 Page 2 of 2

taken to ensure that the demonstrated wipe efficiency is representative of
the  wipes to which it is applied. This will normally require delaying
package  decontamination until after conduct of wipe efficiency
determinations if an  efficiency greater than 10% is used.  In no case, 
however, may the removable  contamination levels exceed ten times the
Table 10 limits for packages in  exclusive-use shipments when no
consideration is given to a demonstrated  higher wiping efficiency. Upon
such an appropriate demonstration, however,  removable contamination
limits may not exceed 100 times the Table 10 limits,  as would be the case
for a wiping method demonstrated to have been 100%  efficient.

In general, licensees may only utilize demonstrations of high smear
collection  efficiencies which have been determined by smear results taken
on the same  cask for which the initial smears (using the assumed 10%
efficiency) indicated  the regulatory limit was exceeded. Licensees will
not be allowed to use the  generic collection efficiencies obtained on one
specific cask for other future  cask shipments.


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                                                 Attachment 3
                                                 IN 85-46
                                                 June 10, 1985

"WRAPPING" OF PACKAGES (CASKS)

The question of "wrapping" the exterior of transport packages has been
raised  on several occasions, particularly in instances where "weeping" of 
contamination has occurred on casks that have been immersed in spent fuel 
storage pools prior to transport. DOT also was queried on this matter by
NRC  as follows:

The issue of whether exterior "wrapping" of casks can be used to achieve 
compliance with removable contamination limits has been raised on a number
of  occasions. Our position on this, with which I understand you also
concur, is  as follows:

x The addition of "wrapping" to an NRC-certified package would not be 
permissible without_obtaining prior authorization of the modification in
the  applicable NRC certificate. In proposing such a provision, an
applicant's  safety analysis obviously would have to address heat
retention since the  contents are a heat source.

x The "wrapping" of a non-NRC certified package would not relieve the
shipper  from compliance with the removable contamination limits
applicable to the  exterior surface of the unwrapped package unless the
wrapping constituted an  integral part of a DOT Specification 7A, Type A,
package design. In such  cases, the shipper's documented package safety
evaluation would need to  address whether the wrapping would maintain its
closure integrity during the  normal conditions of transport.

The reply to NRC by DOT on this matter read as follows:

For both NRC-certified and non-NRC-certified packages, any wrapping must
be  addressed in the package design evaluation. For NRC certified packages
this  would include specific mention in the certificate of compliance. For
DOT  Specification 7A, Type A, packages, the shipper's package safety
evaluation  would have to document the ability of the wrapping to
successfully pass the  Type A tests.


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                                                 Attachment 4
                                                 IN 85-46
                                                 June 10, 1985

EXCLUSIVE-USE VEHICLE SURVEYS FOR SURFACE CONTAMINATION

The exact requirements of 173.443 are sometimes misunderstood as they
relate  to quantitative limits on the vehicle surface during the survey
required by  173.443(c). For this purpose, the vehicle surface is meant to
be those  surfaces wherein or on which packages are stowed during
transport. That  paragraph does not actually set forth any quantitative
limit on the surface of  the vehicle itself during the survey which is
performed to return the vehicle  to service.  The important subtlety
therein is that the quantified limit of  173.443(b) applies to the
packages in the vehicle. The "bottom line" of  173.443(b) and (c),
considered collectively, is as follows:

x The packages within an exclusive-use vehicle may have up to 22,000
d/m/100  cm2 during and at the completion of transport but must be limited
to 2,200  d/m/100 Cm2 at the start of transport, unless the vehicle is
dedicated to  radioactive materials service only, and so marked, pursuant
to 173.443(d), in  which case the 22,000 d/m/100 cm2 limit applies at the
start of transport.

x 173.443(c) requires a survey of an exclusive-use vehicle (and also, 
presumably the dedicated vehicles) after transport of packages that
indicate  removable contamination above the Table 10 limits, but within
the "factor of  ten" higher limit of 22,000 d/m/100 cm2.

x 173.443(c) does not address quantitative limits on the surface of the 
vehicle during the survey, however, the vehicle may not be released for
other  service until the 2,200 d/m/100 cm2 and 0.5 mrem/hr limits are met.

x Noncompliance with 173.443(c) would therefore exist if the survey to
return  a vehicle to service was not performed, and/or the contamination
or radiation  dose rate on the vehicle exceeded the stated limits upon its
release for other  service.


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