Bob, interesting question, for which I don’t believe there is a clear answer.
Besides what has already been posted, here’s some other related information …
not sure it provides much clarity!!
NRC Q&A (Question 375) addresses this question, in part.
Question 375: In supporting a conclusion that individual monitoring of
internal occupational dose is not required [10 CFR 20.1502 (b)] and, therefore,
that summing of internal and external dose is not required [10 CFR 20.1202
(a)], what is considered to be acceptable for bioassay frequency, DAC-hour
administrative limit, and whole-body counting minimum testing level?
Answer: Under 10 CFR 20.1502 (b), there is no required frequency for bioassay,
DAC-hour administrative limit, or minimum testing level for whole-body counting
either for individuals for whom monitoring is required or to support a
conclusion that individual monitoring is not required. However, the answer to
Question 54 provided a number of examples of measures that could be used at
nuclear power plants to verify that the expected degree of respiratory
protection will be achieved so that the concentrations of radionuclides in air
after credit is taken for respiratory protection may be used in making the
prospective assessment that individual monitoring for internal dose is not
required. These measures "include, (but are not limited to) measurements of
nasal smears from workers who have used respirators and whole body counting,
relatively soon after a job, of one or more workers among a group of workers
who wore respiratory protective equipment while working on the job and periodic
whole-body counting (e.g., annually) of all workers who wear respiratory
protective equipment."
It should be recognized that in addition to the bioassay requirements of 10 CFR
20.1502 (b), there is the bioassay requirement of 10 CFR 20.1703 (a) (3) (ii),
which is related to the use of individual respiratory protection equipment. If
whole body counting is to be used to verify the effectiveness of the
respiratory protection program, it must be able to demonstrate that estimates
of intake based on exposure calculations (i.e., on air concentrations and on
taking credit for protection factors) are consistent with estimates of intake
based on bioassay. The licensee should take into account the fact that
demonstrating effectiveness of the respiratory protection program may have to
be based on exposures over durations much shorter than a year, particularly for
materials that are expected to be cleared rapidly from the body. Some general
guidance on air sampling is provided in Regulatory Guide 8.25, Rev. 1, (which
states that this guide does not apply to reactor facilities), and general
guidance on bioassay will be provided in Regulatory Guide 8.9, Rev. 1.
(References: 10 CFR 20.1502, 10 CFR 20.1202, 10 CFR 20.1703, Regulatory Guide
8.9)
Also, Q&A 372 also has some relevant information:
Question 372: When monitoring of internal exposure is required by 10 CFR
20.1502, 10 CFR 20.1204 (a) requires the licensee to take "suitable and timely"
measurements. Will NRC define what is suitable and timely to avoid differences
of opinion among inspectors?
Answer: No. Some general guidance on what is suitable and timely will be
included in Regulatory Guide 8.9, Rev. l, "Acceptable Concepts, Models,
Equations, and Assumptions for a Bioassay Program." Other than this general
guidance, the NRC staff has no plans to provide a definition of what is
"suitable and timely." That definition depends on the circumstances of the
particular exposure. What is "suitable and timely" under revised Part 20 is (as
before, under old Part 20) a matter of professional judgment in a good
radiation protection program. NRC management will resolve any "differences of
opinion among inspectors" that are called to its attention. (References: 10 CFR
20.1204, 10 CFR 20.1502)
As you know, performing bioassays (at some threshold) also supports the
requirement in §20.1703.(c)(2) … and 1 DAC was a definable limit (and
reasonable considering it is one of the airborne radioactivity posting
thresholds and the basis for relating ALI to chronic occupational exposure,
i.e., a DAC = ALI (in μCi)/(2000 hours per working year x 60 minutes/hour x 2E4
ml per minute).
HPS N13.39-2001 contains the following …
B.2.4 Screening Level
The committee believed that to be useful a derived screening level had to be
set based on the results for
a single measurement or sample. Therefore, the value had to be small enough
that multiple results
applicable for a single person over a year that were each just below the
derived screening level, and
therefore not converted to dose, would not result in the loss of significant
total dose for the year. Also,
the screening level should be reasonably compatible with the need to record
dose, and the rationale for
establishing a “recording level” of 10 mrem (0.1 mSv) committed effective dose
applies equally well to
establishing a screening level of 0.002 SALI. The value is also approximately
equal to the detectability of
intakes for many industrial radionuclides through routine bioassay programs.
The committee understood
and considered appropriate that for harder-to-detect radionuclides this
screening level is equivalent to
“anything detected.” However, because the screening level is much less than the
investigation levels
recommended by the ICRP and the DOE, and set by regulation by the NRC, the
screening level was
established as guidance only. Use of the screening level of 0.002 SALI was
considered reasonable and
practical for most radiation protection programs, but may not be necessary for
some short-term or smallscale
applications.
[cid:[email protected]]
Brent L. Robinson
TECHNICAL RP SUPERINTENDENT
Florida Power & Light
St. Lucie Plant
6501 S. Ocean Drive
Jensen Beach, Florida 34957
(772) 467-7308
[email protected]<mailto:[email protected]>
From: McCarthy, John:(GenCo-Nuc) [mailto:[email protected]]
Sent: Friday, April 28, 2017 6:59 AM
To: Mathiasen, Glenn D.; Cady, Jeffrey James:(GenCo-Nuc); Sorber, Bob;
[email protected]
Subject: [powernet] RE: Basis for WBC after exposure to 1 DAC?
CAUTION - EXTERNAL EMAIL
Regulatory Guide 8.9 has periodic measurements (2.1.2) at >0.02 ALI
Jack McCarthy, CHP
DTO - Decommissioning Health Physics
Oyster Creek / Exelon Corporation
609-971-4764
From: Mathiasen, Glenn D. [mailto:[email protected]]
Sent: Thursday, April 27, 2017 6:04 PM
To: Cady, Jeffrey James:(GenCo-Nuc); Sorber, Bob;
[email protected]<mailto:[email protected]>
Subject: [powernet] RE: Basis for WBC after exposure to 1 DAC?
The Area Action Level Matrix in the previous revision of the EPRI Alpha
Monitoring Guidelines (Dec 2009) included a recommendation for WBC after
exposure to >1 DAC alpha or >4 DAC-Hr alpha. (after applying APF).
From: Cady, Jeffrey James:(GenCo-Nuc) [mailto:[email protected]]
Sent: Thursday, April 27, 2017 2:54 PM
To: Sorber, Bob; [email protected]<mailto:[email protected]>
Subject: [powernet] RE: Basis for WBC after exposure to 1 DAC?
The closest requirement I am aware of is ANI which states a whole body count
should be performed if an individual is exposed to airborne concentrations
>1DAC alpha or an intake of >4 DAC-hours (alpha-beta-gamma) per seven
consecutive days.
Jeffrey J. Cady, CHP
Radiation Protection Manager
Exelon Generation - Braidwood Generating Station
35100 South Route 53
Braceville, IL 60407-9619
Office: 815-417-2700│Cell: 208-360-9480
Email: [email protected]<mailto:[email protected]>
From: Sorber, Bob [mailto:[email protected]]
Sent: Thursday, April 27, 2017 2:33 PM
To: [email protected]<mailto:[email protected]>
Subject: [EXTERNAL] [powernet] Basis for WBC after exposure to 1 DAC?
RPs,
I’m trying to track down the basis of a requirement in our procedures that we
perform a whole body count (WBC) following work in an airborne area greater
than 1 DAC (after taking account of any respiratory protection factor). This
is regardless of the time spent at that concentration. Does anyone know of the
basis for this requirement?
Thanks in advance.
Bob Sorber
Corporate Radiation Protection 704-382-7259
[email protected]<mailto:[email protected]>
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