Re: Nuclear Reactor Fuel Rods are Radioactive Sealed Source

["Wesley M. Dunn" <WDUNN@brc1.tdh.state.tx.us>]

David,

Let's start with the caveat, I'm not claiming to be an NRC or fuel 
cycle expert.  So have this comment is based on generic knowledge 
of sealed sources (and licensing) and distant memories from my Nuc E 
days.  So it might be totally wrong from how the NRC actually does 
interpret the issue.

First, I believe the NRC does treat fuel elements as sealed sources.  
"Sealed Source" doesn't really connote a lot of meaning (unlike 
"Special Form", which requires stringent engineering analysis and 
testing).  You may be reading more info the "sealed source" 
definition than is actually there.

What it does mean is that you don't have to take all the additional 
precautions necessary for handling loose material (e.g., unsealed 
sources).  From a practical standpoint, the NRC would have a greater 
problem authorizing reactors to operate if the core inventory to be 
dumped into a pool of water instead of being contained in the fuel 
element.  So treating it like a sealed source has tremendous 
advantages all around -- especially for used fuel.

The other advantage of sealed sources is the limited contamination 
survey requirements (e.g., routine leak tests instead of continual 
contamination surveys).  This advantage is somewhat limited in a 
power reactor, since neutron activation products show up all over -- 
especially in BWRs.  So you have to do contamination surveys and 
bioassays anyway -- but NOT because of the fuel.  Leak testing is 
done similarly to pool irradiator irradiator sources -- you monitor 
the pool water. 

Wes

> Date sent:      Mon, 25 Nov 96 13:50:13 -0600
> Send reply to:  radsafe@romulus.ehs.uiuc.edu
> From:           David W Lee <lee_david_w@lanl.gov>
> To:             Multiple recipients of list <radsafe@romulus.ehs.uiuc.edu>
> Subject:        Nuclear Reactor Fuel Rods are Radioactive Sealed Sources,

> Dear Radsafers:
> 
>         Hopefully some of the NRC experts on the Radsafe net will respond to
> the questions below.
> 
>         The NRC has specified in two parts of federal law (10 CFR 30.4 and
> 70.4) its official definitions of a "sealed source."  The wording of these
> definitions, if combined, would be as follows:
> 
>                 Sealed Source means any byproduct or special nuclear
> material (SNM) that is encased in a capsule designed to prevent leakage or
> escape of the byproduct or special nuclear material.
> 
>         The NRC does not provide in either of these federal law parts any
> special NRC definition of a "capsule"; therefore, one must presume the
> generic or 'common' meaning of the word 'capsule' by default.
> 
>         Based on the above NRC definition of a sealed source, does any
> Radsafer disagree with the semantic conclusion that nuclear reactor fuel
> rods are "sealed sources" as far as the NRC is concerned?
> 
>         Assuming then that the NRC actually intended power reactor fuel rods
> to be construed as "sealed sources," can any Radsafer provide any background
> or elaboration as to why or how the NRC originally felt that it was useful,
> from a regulatory viewpoint, to include reactor fuel rods under a broad
> general 'sealed source' definition?  If it is logical to conclude that the
> NRC views nuclear reactor fuel rods as 'sealed sources,' then how does the
> NRC regulate such rods as 'sealed sources'?
> 
>         Most licensed radioactive sealed sources (RSS) are "regulated" in
> the sense that periodic physical inventories are required (make sure you
> still have the sources firmly under your control) and wipe tests of some
> sort at some periodicity are required, generally at a minimum semiannual
> frequency, unless in long-term storage.  Given this reality, what is the
> advantage that redounds to the NRC of semantically defining nuclear reactor
> fuel rods as 'sealed sources' and presumably "regulating" them as RSSs?
> 
>         Would this also mean that the NRC semantically regards a 'fission
> chamber' as a 'sealed source' and presumably would regulate it as an RSS?
> How about a Pu-238 radioisotope thermoelectric generator (RTG) whose thermal
> temperature on the exterior of the total RTG module can easily exceed 150
> degrees centigrade (not very amenable to traditional leak test methods).
> Does the NRC regard RTGs also as 'sealed sources' and regulate them as such?
> 
>         I have previously asked some of these questions of Radsafer Keith
> Brown of the NRC, but have received no reply; therefore, I am soliciting the
> thoughts/opinions of all those on the Radsafe net.
> 
>         Thank-you in advance for your consideration of these questions.
> 
> REGARDS
> 
> 
> 
>         
> David W. Lee
> Radiation Protection Policy
> & Programs Analysis Group (ESH-12)
> Los Alamos National Laboratory
> PO Box 1663, MS K483
> Los Alamos, NM  87545
> Ph:  (505) 667-8085
> FAX: (505) 667-9726
> 
> 
*********************************************************************
Wesley M. Dunn, CHP                        512-834-6688
Deputy Director, Licensing                 512-834-6690 (fax)
(Texas) Bureau of Radiation Control        wdunn@brc1.tdh.state.tx.us
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