ML20055C476
| ML20055C476 | |
| Person / Time | |
|---|---|
| Issue date: | 05/11/1990 |
| From: | Taylor J NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| To: | |
| References | |
| TASK-PINC, TASK-SE SECY-90-169, NUDOCS 9005160055 | |
| Download: ML20055C476 (17) | |
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RELEASED TO THE PDR
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SEW-90-169 F_ol:
The CommissionMGATIVE CONSENT) e o
From:
James M. Taylor Executive Director for Operations
Subject:
MODIFIED ENFORCEMENT POLICY FOR HOT PARTICLE EXPOSURES - REVISION TO INCORPORATE RECOMMENDATIONS MADE IN NCRP REPORT NO.106
Purpose:
To respond to the Commission's request to revise a proposed modification of the enforcement policy for hot particle expo-sures to use the recommendations in the National Counct) on Radiation Protection and Measurements (NCRP) Report No.106 as the basis for the modified policy.
Discussion:
In SECY-89-370, dated December 11, 1989, the staff proposed a modification to the NRC enforcement policy that addressed the use of enforcement discretion in cases involving an occupational dose to the skin f rom exposure to radia+. ion frora radioactive particles called " hot particles."
In a staff requirements memorandum. "SECY 89-370 - Modified Policy for Hot Particle Exposures," f rom S. J. Chilk to J. M. Taylor, dated March 8, 1990, the staff was informed that the Commission had disap-proved the modification of the policy proposed in SECY-89-370..
The Commission requested that the staff revise the policy to use the recommendations in NCRP Report No. 106 as the basis for the policy or provide a basis for an alternative approach.
The recommendations of NCRP Report No. 106 are provided in to this paper. provides the revision of the modified enforcement policy based on the recommendations in NCRP Report No. 106.
}70 CONTACTS: Frank J. Congel, NRR 492-1088 James Lieberman, OE 492-0741 NOTE:
TO BE MADE PUBLICLY AVAILABLE WHEN THE FINAL SRM IS MADE AVAILABLE.
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A The Commissioners
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Consistent with the use of the recommendations of NCRP Report No. 106 as the basis for the policy, the following changes have been made to the policy proposed previously as Enclosure 1 to SECY-89-370:
(1) The definition of the term " hot particle" has been changed to the NCRP definition, which sets an upper limit on par-ticle size.
(The policy proposed in SECY-89-370 did not limitparticlesize.)
(2) The terms " beta emission " " beta emission crit 6rion," and
" skin dose criterion" have been defined and used in the policy.
(3) Exposures from a hot particle in contact with the skin will be evalueted against the 75 microcurie-hour beta-emission criterion while exposures from a hot particle in the hair or on clothing will be evaluated against the skin dose criterion of 50 rads.
(4) Conforming changes have been made in the " Enforcement Examples."
The recommendations section of NCRP tteport No.106 includes thefollowingparagraph(p.26):
When hot perticles are found on e person, they are not always in contact with the skin. They may, for example, be on clothing or in the hair. Regardless of where tney are iound, due to their considerable mobility, their past positions and movements are not known and cannot be determined.
in general, therefore, to be conservative, it is recommended that a hot par-ticle be assumed to have been in contact with the skin throughout the possible irradiation period, in cases where it can be determined that the hot particle was never in contact with the skin (for example, if it were betweentwolayersofclothing)doselimitsforexpo-sure of large areas of the skin should be applied.
The circui.istance in which skin is irradiated by hot particles not directly on the skin requires further study.
Thisrecommendation(toassumethatahotparticlewasin contact with the skin throughout the possible irradiation period, unless it can be determined that.the particle was never in contact with the skin) has been incorporated into the enclosed policy.
It is noted, however, that neither current staff practice nor the policy proposed in SECY-89-370-incluots such a con traint.
Presumably, the " dose limits for exposure of large arest,f the skin," in the paragraph quoted above, are the limiy i
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The Comissioners,
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i provided in NCRP Report No. 91, "Recomendations on Limits for Exposure to lonizing Radiationt" a limit of 50 rem (rad) por year. Although the 50-rem (rad) limit is an annual limit in NCKP Report No. 91, it is treated in the enclosed policy as a.
i separate criterion for each hot particle exposure in order to avoid inconsistency with other aspects of-the policy. Although the annual skin dose limit of 50 rem (rad) in NCRP Report No. 91 i
is different (larger) than the skin dose limits in 10 CFR 20.101, the staff will continue to use the same calculational methods and parameters (1 cet skin area and 7 mg/cm8 depth) as l
betore in determining compliance with the limits of 10 CFR 20.101 and in comparisons with the dose criterion of the policy.
l The recommendatiuns of hCRP Report No. 106 include a recommen-dation for medical evaluation following an exposure in excess of the NCRP limit; however, this recommendation is not rele-vant to enf orcement policy.
l Although it is not based on the recommendations in NCRP Report No. 106, an example of a Severity Level V violation has been added to enforcement examples in the policy. This example provides the severity level f or violations involving f ailures to make notifications or reports of hot particle exposures that result in skin doses that exceed the limits of 10 CFR E0.101 but that do not exceed the relevant beta-omission or skin-dose criterion of the policy. These notifications and reports are needed for the rulemaking process as a basis f or juoging the extent to which licensees are continuing to pro-vide controls for protection of workers from hot particle exposures.
Further, the staff will exercise enforcement discretion and will not issue notices of violation for failures to siake the immediate notifications required by 10 CFR 20.403(a) for skin l
doses that are a result of hot particle exposures.
SECY-89-370 briefly discussed differences between the NCRP recomendations and draf t recomunendations 'of a task group of the International Comission on Radiological Protection KICRP).
The ICRP task group draf t recommendations included a limit, for hot particle exposures, of 100 rad averaged over an area of I cm8 and a depth range of 10-15 mg/cmt. SECY-89-370 noted that NCRP and ICRP subgroups were continuing to discuss their
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differences, but had not resolved them. Additional meetings and discussions have taken place since the date of SECY-89-370;.
however, the differences remain unresolved. _The NRC staff has been following and will continue to follow the technical delib-erations of the NCRP and ICRP.
However, because of differing interpretations of complex biological data and differing philosophies concerning the severity of the biological effect-2 -.,,
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considered acce) table, it appears, at this time, that the ICRP will publish a lot particle skin dose limit that is significantly lower than the NRCP limit.. The staff will consider both NCRP and ICRP recommendations as well as all other relevant technical information and public coments during the forthcoming rulemaking action on an occupational radiation protection limit for hot i
particle exposures of the skin.
Recomendation: That the Comission:
1.
Ncte that the staff plans to implement the enclosed modi.
T Ration of the enforcement policy. The staff intends to implement this policy within 10 working days unless other-wise instructed by the Comission.
2.
Note that the following aspects of the enclosed policy which are based on NCRP recomendations, are more restric-tive than the policy proposed in SECY-89-370:
(a) Requirements of the assumption that a hot ) article has been in contact with the skin throughout tie possible irradiation period unless it can be determined that the particle was never in contact with the skin.
(b) Use of a 50-rad rather than a 100-rad skin dose cri-terion when it can be determined that a particle was never in contact with the skin.
(c)Provisionofanumericalupperlimitonthesizeofa hot particle, j
3.
Note that the enclosed policy incorporates a radiation i
protection standard at which some visible nonstochastic effects (acuteulceration)couldoccur. This standard departs from existing and proposed radiation protection standards of the NRC and other Federal agencies without l
benefit of public coment.
4.
Note that the Office of Nuclear Regulatory Research has provided additional comments in Enclosure 3.
The Office of the General Counsel has no legal objection.
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1E 5
aties N. Tay r xecutive D rector for Operations
Enclosures:
See next page SECY NOTE:
In the absence of instructions to the contrary, SECY will notify the staff w.
Friday, May 25, 1990, that the Commission, by negative consent, assents to the action proposed in this paper.
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The Commissioners l l
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Enclosures:
1.
" Recommendations on Radiation Exposure Limits for the Special j
Case of a Hot Particle on the i
Skin," NRCP Report No. 106, pp 25-26 2.
" Modified Enforcement Policy for Cases of Occupations 1 Doses to the Skin f rom Radiation Emitted f rom Hot Particles" 3.
" Response to the Staff Requirements nwncrandum on SECY-89-370 - Modif ied Policy for Hot Particle Exposures,"
t memorandum f rom Eric S. Beckjord, RES, to Thomas E. Murley, NRR, April 20, 1990.
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DISTRIBUTION:
GPA IUCGIONS ED0 ACRS ACNW ASLBP ASLAP SECY k
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E!4 CLOSURE 1 s
8.
Recommendations on Radiation Exposure Limits for the Special Case of A.
Hot Particle on the Skin t
it is recommended ht:
t1> A limit for enposurs to het panieles be board on ensurin that acute deep ulceration of the skin be preursted end that this be attemplished by e limit based on the time integral of the beta particles emitted due to the eesivity of the peniele in tentact with the skin, (2) Esposure to the skin f>om a
- point"porticle or a ponicle of s.nknown sine but less then ! mm in diameter be limited to 20'*
beta particles emined f>om the radionueliales conseined in the partselt. For the eau where 1 beta poniele is emitted per dis.
integration, this limit may be espmeed as 10 GBq s or to sci s
- h. Tor a paniele for which the utf absorption een br meuured or coleulated, the limit een be inerwesed by the ratio of the beta panieles emitwd by the radionuelidu divided by the base par.
tseles emitted />om the surface of the porticle. Alternetisely, the limit een be espmud as 20* beta penieles emitted from the surface of the poniele, (3) Esposurs in anceu e{the limit should requirs persedse medical esoluotion of the exposed site for e period of oppranimately four uneks in order to eletermine what offeet, if any, occurs. lf an.
ulost occurs, & decision on allowing b esposed individual to work should be based on the name criteria one would apply to any open wound, h affected individual abould be aware that h risk of skin enneer from such eventa is estremely emall.
N basis for this recommendation is data obtained primarily from beta particle emissions from irradiated fuel particles.N probability for serious tissue damage f>om particles sontaining "Co is no greater than that for particles sentaining irradiated fool and is likely to be much less due to the ahorter range of the "Ce beta particle.
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- s. AtconottNDAttoNs ON RADtATl0N EXPO 5t'RE LDCTS l
The twommendations in this upon are intended for application to hot particles in contact with the skin. When a given hot particle is not in contact,it produeos lower doses in h skin: also A radiation 6 eld changes less rapidly with distance, both laterally and with depth. Under thew circumstantes, a given het particle is orpeeled to produce less harm.
When hot panicles are found on a person, they are not always in contact with tM skin. They may, fw example, be on clothing or in the hair, Regardless of where by are found, due to their consider.
i able mobility, their past positions and movements are not known t
and cannot be determined. In general, hrefore, to be conservative, it is twommended that a hot particle be assumed to have been in contact with the skin throughout h possible irradiation period. In d
cases where it can be determined that the het panicle was never in contact with Ae skin (for eatmple, if it were betwwn two layers of clothing) dow limits for uposure of large areas of h skin should be applied. The circumstance in which skin is irradiated by hot particles not directly on h skin requires funher study, There are wide variations in the data on which twommendations for limits of exposure of the skin to hot panicles must be based.
j Additional research is occurring preuntly and abould be continued on both the biological effeos of hot panicles and the dosimetry of hot particles. Resulta from this ongoing work may well eventually provide sufficient new information to further support these recom.
mendations or to require their review at a later time.
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ENCLOSURE 2 Modified Enforcenent Policy for l
Cases of Occupational Doses to the Skin f rom Radiation i
Emitted from Hot Particles t
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purpose f
l This policy modifies the NRC enforcement policy in 10 CFR Part 2.
Appendix C, to provide for the use of enforcement discretic. In cases that involyr, an weepational dose to the skin r6 citing from I
exposure to radi6 tion emitted f rom a hot particle on or near the skin.
I The provisions of this rolicy will be followed by the NRC staff until a new limit applicable to such cases is established by revision of l
10 CFR Part 20.
2.
Scoge' This policy applies only to occupational doses to the skin that
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exceed the limits of 10 CFR 20.101 for.the " hands and forearms, feet and ankles" or the " skin of the whole body" and that are the result of radiation emitted from a hot particle on the body or clothing of the exposed individual. This policy does not change criteria for
.i whole-body doses.
3.
Definitions As used in this policy --
" Beta emission" means either (1) the number of beta particles emitted fromtheradionuclide(s)inthehotparticleduringthetimeperiodof
-l the occupational exposure of the skin or (2) the number of beta par-ticles emitted from the surface of the particle during that time period.
" Hot particle" means a discrete radioactive fragment that is insoluble
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in water and is less than 1 mm in any dimension.
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" Hot particle exposure" means en occupational dose to the skin resulting from exposure to radiation emitted from the radionuclides p
in a hot p rticle on the body or on the clothing of the exposed individual.
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" Occupational dose" includes exposure of an individual to radiation (1) in a restricted area or (2) in the course of. employment in which-the individual's' duties involve exposure to radiation, provided,~ that j
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" occupational dose" shall not be deemed to include-any expoare of an individual to radiation for the purpose of medical diagnosis or' medical l
therapy of such individual.
(Note:
Thib is the definition of this term i
giver in 10 CFP Part 20.)
h; 4.
,0ccupational Exposure Criteria The limits on occupational dose specified in the table in paragraph (a) of 10 CFR 20.101 for the hands and forearms, feet and ankles, and l
the skin of the whole body apply to all ex.posures, including hot q
particle exposures. However, because of the nature of the principal radiation involved (beta), the. extremely localized effects, and the 1
lower biological risk, the NRC believes a different limit for hot particle exposures-should be established through rulemaking action anc that enforcement discretion should be applied until a new limit for hot particle expo;ures is established by rule. Consequently, the staff will use a new bete emission criterion and a,new skin dose cri-terion for determining appropriate discretionary enforcement actions.
and appropriate severity levels for hot particle exposures; however,=
the staff will continue'to evaluate hot particle exposures to terms of. absorbed dose for comparison with'the limits of 10 CFR 20.101.
For a hot particle-exposure of an individuni above the limits of 10 CFR.
20.101 that results trom a hot particle in contact with the skin, the NRC will issue a notice of violation if the beta emission from thc-' particle is greater than the beta emission criterion.
For purposes of this policy.
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the beta emission criterion is established as a beta emission value of-0 10 beta particles (75 microcurie-hours). A notice of violation will not be issued when an individual rcceives a-hot particb exposure that" l
is equal to or less than the beta emission criterion.
For each hot particle exposure, the hot particle will b? assuned to have been in contact with the skin throughout the possible -irradiation period, even if the particle was found on the hair or' clothing of the exposed individual, unless it can be determined that the particle was never in I
contact with the skin-(for erample, if the ' particle was between two layt:rs of clothing).
if it can be determined that the particle was never-in contact with the
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skin, the. skin dose criterion, rather than the beta dmission criterion -
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1 applies. That is,-in this.ctse. the NRC will issue a notice of viola-l tion if the dose to the skin exceeds-the skin dose criterion.- For pur-poses of this policy, the skin dose ' criterion if s established as an:occu-r averaged over pational dose to the skin of 50 rad at.a. depth of 7 mg/cm L
an area of I cm2 in the region of.the highest dose. A notice of viola-tion will not be issued when an individual receives'a hot particle expo-sure that is equal to or less than tha' skin dose criterion.
The beta emission criterion or the skin dose criterion will be used for o
each hot particle exposure. There are no quarterly.or annual limitations.
1 In any case.
notice of violation may be issued for violations of
.other regulatory requireu nts associated with an event involving hot-particle expcsures (e.g., violation of 10 CFR 20.201, " Surveys"). regard-less of the magnitude of the hot particle. exposure;-
L In determining whether a hot particle exposure has exceeded the limits j'
of 10 CFR 20.101, the beta emission criterion, or the skin dose criterion, hot particle exposures will not be added to skin doses from sources other than hot particles, nor will hot particle exposures from different par-ti les be summed unless the dif ferent particles result in doses to thc' t
L same area.(location) of skin.
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. 5.
Records, Notifications, and Reports Nothing in this policy should be construed as changing, or in'effect' 1
changing, other requirements of_10 CFR Parts 19 and 20.
In particular, therequirementsof10~CFR20.401(records),10CFR.20.403(notifica-tions of incidents), 10 CFR 20.405 (reports of overexposures),
10 CFR 20.408 (reports of personnel monitoring on' termination), and 10 CFR 20.409 and 10 CFR 19.13 (notifications and reports to individ-ua'Isi remain in effect and concern the current dose limits in 10 '.,FR 20.101. - For example, a hot' particle exposure resulting in a skin dose of 75 rads to the feet, ankles, hands, or forearms must be reported to the NRC within.24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.: However3 no notice of violation will be issueo f or a f ailure to make an imsdiate notification required by 10 CFR 20,403(a) for a skin oose that 'is a result of a hot particle exposure. A Notice of Violation will be issued for a failure to make a 24-hour notification required by 10 CFR 20.403(b) or to report as required by 10 CFR 20.405 for a-dose that is a result of hot particle.
exposure.-
s 6.
Enforcement Examples:
10 CFR Part 2, Appendix C, Supplement IV-l l
In addition'to the enforcement discretion concerning: issuing lotices of violations, enforcement discretion also will be used concerning the severity levels of violations. For a cose to the ' skin f rom. hot particle:
exposures, the following examples will be used for determining severity levels:
a.
Severity Level 111 - Violations involving, for uample --
(1) Hot particle exposures for which ce dose to the' skin
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exceeds the limits of 10 CFR 20.101 and exceeds'three.
times the relevant criterion (either the beta emission.
criterion or the skin dose criterion).
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(2)- Failure to make a notification required by 10 CFR 20.403(b) or a report (required by 10 CFR 20.405) for_a hot particle exposure that results in a skin dose that exceeds the limits j
of 10 CFR 20.101-.and exceeds three times the relevant cri-i terion (either the beta emission criterion or the skin dose criterion).
b.
Severity Level IV - Violations involving, for example---
(1) Hot particle exposures.for which the dose to the skin exceeds the limits of 10 CFR 20.10' and exceeds the relevant l
criterion but does not exceed three times the relevant cri-
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terion (either the beta emission criterion or the skin dose criterion).
(2) Failure to make a notification required by 10.CFR 20.403(b) or a report (required by 10 CFR 20.405) for a hot' particle.
exposure;that results in.a skin dose tnat exceeds the limits of 10 CFR 20.101 ano exceeds the relevant criterion but does.
notexceedthreetimestherelevantcriterion(eitherthebeta i
emission criterion or the skin dose; criterion).
c.
Severity Level V - Violations Tnvolving, f or example---
(1) Failure to make a notification (required by 10 CFR 20.403) or a report (required by 10 CFR 20.405) for a hot particle -
exposure that results in a skin dose 'that exceeds the limits of 10 CFR 20.101-but that does not exceed the relevant cri-terion (either the beta-emission criterion or the. skin dose.
I criterion).
Note: No numerical criteria (beta emission values'or skin doses) have been established as examples for Severity Levels 1 and~11.
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Effective Date This policy is effective imediately.
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Enclosurs 3-o UNITED STATES g
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g NUCLEAR REGULATORY COMMISSION E
WASHINGTON, D, C. 20666
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APR 2 01990 i
MEMORANDUM FOR: Thomas E. Murley, Director, Office of Nuclear Reactor Regulation FROM:
Eric S. Beckjord, Director, Office of Nuclear Regulatory Research'
SUBJECT:
RESPONSE TO'THE STAFF REQUIREMENTS MEMORANDUM ON SECY-89-370 - MODIFIED ~ POLICY.FOR HOT PARTICLE EXPOSURES-The Office of Nuclear' Regulatory Research concurs'with the subject staff paper as being responsive to the March 8,1990 Chilk to Taylor SRM, and RES concurs in the intent of the paper.. However, RES believes that certain -technical issues related to the paper and the National Council on Radiation Protection and Measurements (NCRP) report should be brought to the Connission's attention.
The significance of hot particle exposures within the overall framework of radiation protection is controversial and likely to remain controverr,ial for some time to come. As-requested by the NRC staff..the NCRP, in.its Report l
Ho. 106, has provided recommendations concerning hot particle exposures that can help establish a basis for setting appropriate regulatory limits for such exposures. The NCRP report acknowledges the need for flirther research in this radiation protection area. The RES staff has initiated research programs to-better define hot particle exposure. effects sources, and control and prevention techniques in order to define needed changes:to 10 CFR Part 20 limits'for such exposures. The early results from these research. efforts indicate significant uncerttinty in relating radiation exposure to effect.
- Because of this, great caution should be exercised in establishing a limit' on such exposures, whether
" interim" or final.
Information f rom English. research indicates that' acute. (i.e., rapidly.
occurring) ulceration may occur at exposure levels significantly below the limit proposed by the NCRP. The NCRP recognizes this, but apparently i.
believes that such ulcers are " superficial" and unimportant.from a healthi u
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standpoint. The NCRP selected an endpoint of " deep ulceration" as the effect L
to be controlled by a ' limit, but then states that even " deep ulcers" are "not serious." Allowing health effects at or below the~11mit'is a' departure from past. radiation protection philosophy in that all other recoseended limits are set at levels which will prevent observable effects such as ulcers.. Furthermore, i
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. undefined terms such as "not serious" make it difficult to put-the relative risks of whole body exposure and hot particle exposure into perspective.
Establishing a limit that allows health effects is.also inconsistent with cur m t o
ICRP thinking. The ICRP's task group on skin has recommended a limit'of 100 3
L
. rad (compared to the NCRP's recommendation of 75 uC1-hours or about 400 rad)
- based on preventing any) effects that may result-in opening of the skin to i
. infection (i.e., ulcers.
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APR 2 01990 Thomas E. Murley 2
On February 28, 1990, Drs. Monty Charles and Jonn Hopewell, members of an ICRP task group on skin, met with staff members of the Office of Nuclear Reactor Regulation (NRR), Nuclear Regulatory Research (RES), and Brookhaven National Laboratory (BNL) to discuss research on the effects of hot particles on the skin and skin exposure standards. Dr. Charles directs the Radiation Biophysics Group at British National Nuclear Power's Berkeley Nuclear Laboratories and Dr.
Hopewell directs the Radiobiology Research Group at the University of Oxford's Churchill Hospital. These two British researchers and their colleagues have-done virtually all of the recent research on hot particle effects.
Specific topics discussed at that meeting included the status of NCRP Report No.106 and the draft ICRP report.
Both Dr. Charles and Dr. Hopewell expressed serious concern about the NCRP report. They recognized the apparent differences in-philosophy between the NCRP and TCRP as to the degree to which effects such as i
ulcers should be avoided; however, they were of the view that exposure at and just below the NCRP limit would result in a high probability of workers developino medically significant acute ulceration of the skin.
They stated that the experimental data on which the authors of the NCRP report had decided to base their dose limit were too few to make such a judgement and that these were, in any case, contradicted by the results of other investigators.
In their view, the ICRP draft report had taken all available data into account.
In light of this controversy, and the uncertainties associated with relating exposure to effect'(acknowledged in the NCRP report), the RES staff believes that great cautirn and circumspection is required in establishing Commission policy in this area and would recommend an exposure limit consistent with the more conservative recommendaticns based on credible scientific findings. We i
believe that the Commission would, in the future, be in a better position by I
increasing the limit, rather than by later finding it necessary to reduce the limit.
The following is a brief list of some specific areas of controversy based on a preliminary staff review of the NRCP's Report No.106 on " Limits for Exposure to ' Hot Particles' on the Skin," which RES believes should be brought to the Comission's attention.
1.
Although the recommended basic limit of 75 uCi-hours did not change from i
the 1988 draft to the 1990 final report, the basis for the limit did.
change from " acute ulceration" to " deep ulceration." The basis for~the determination of a "thre A old" for " deep ulceration" is not made clear in the report. Likewise, the rationale' for the change in basis is not explained. Also, terms such as " deep ulceration" and "not serious" are not defined, making it very difficult to put the NCRP's " deep' ulcers" into 1
perspective with other effects of radiation.
2.
The NCRP report contains the state m t:
"The cost both in additional whole body radiation exposure d"r to frequent surveillance of workers and P
in money that would be requird te comply with a limit employing a safety factor is not justified in tus casr> This statement implies that there can be no justification for 1ttempi!ng to limit hot particle exposures to a level below the NCRP's receremtion in accordance with the ALARA 1
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Thomas E. Murley 3
APR 2 01990 I
principle. The application of the ALARA )tinciple to the control of hot particle exposures has been discussed wit 1 industry.
However, the data necessary to the appropriate application of the ALARA principle has not been made available to the staff. Therefore, the validity of this statement i
t,y the NRCP cannot be established.
3.
It is not clear that the NCRP's recomendations are internally consistent.
j It appears that there'are three hot particle exposure situations to which the NCRP's recommendations apply:
i (A) A pt.rticle on the skin Recomended limit:
75 uti-hours i
(B) A particle off the skin under conditions where it is clear'that' the particle was never on the skin (e.g., a particle between two layers of clothing).
Recomended "large area" limit (see 5, below): 50 rads per year (C) A particle off the skin under conditiors where it is not clear that the particle wes never on the skin (e.g., a particle on hair or the inside of clothing).
Pecomended limit:
75 uCi-hours.
A particle resulting in a 75 uCi-heur, or less, exposure when on the skin (situation A), may deliver a dose greater-than the NCRP's recommended limit of 50 rad when off the skin (situation B). For example, a fuel particle delivering a 75 uti-hour exposure when on the skin (situation A) would deliver a dose in excess of 50 rads (about 80 rads) when located.at 5 m from the skin (situation B). Only at distances from the skin of 7 m or more would the particle c'eliver a dose less than the recommended 50 rad limit. Therefore, the appropriateness of using the 75 uti-hour limit is gestionable for exposure situation C; because such a limit may not be conservative.
It appears that the dose from a particle in exposure situation C.should be determined based on its probable location off of the skin and compared with both the 50 rad limit and the 75 uti-hour limit to determine which is the more limiting in each particular case.
4 The NCPP's emission' unit of exposure has some advantages.
It' avoids the use of dose values that may convey a greater than actual risk to some workers, and it may be easier than dose to measure in the field. However, the dose to skin varies significantly with.the energy of.the' irradiating beta particle, the emission unit is an unfamilar term (most workers vill-probably want to know their " dose *) and the NCRP's use of the emission unit does not seem justified by its argument that dose is difficult to~
determine in a consistent manner. Furthermore,:in recent informal discussions with-licensee health physicists; significant concerns were expressed about changirg to the use of an emission limit-in place of the more familiar dose limit.
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Thomas E. Murley.
4 APR 2 01990 l
i 5.
There is some evidence from English research that late effects such as dermal thinning may occur at doses significantly below those required-to produce acute effects, i.e., ulcers.
Research is proceeding to better define the relationship between radiation dose and these effects.
In addition to those concerns expressed above with res,
'. to the implementation of the NRCP recommendations, we also have some concern that the proposed implementation of the NCRP's recommendations concerning "large area" irradiationi by hot particles may be considered inconsistent with the application of 10 CFR Part 20 limits to skin exposures in other situations. The NCRP explicitly.
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states in its Report No. 106=that "dosa limits for exposure of large areas of the skin should be applied" in those cases w'ere a particle was not, at any
. time, on the skin. The only such limit iecommended by the NCRP is the 50 rem / year limit appearing in NCRP Report No. 91.
Based on this NCRP recomendation, a 50 rad limit is proposed in the enforcement policy for such "large area" exposures.
Then, instead of applying this limit on an annual basis as recommended by the NCRP, the limit is applied to each exposure. The existing skin limits of 7.5 rem (whole body) and 18,75 rem (extremities) per quarter currently in 10 CFR Part 20 apply to "large area" exposures.
Licensees may fail to perceive any difference between irradiation of a "large area" of the ekin by a hot particle-and irradiation of a "large area" of the skih by a source other than a hot particle and question whether any skin exposures should be limited by the l
existing 10 CFR Part 20 limits.
Finally, we believe that theLsignificance of the particle size limit (1 mm).is not adequately specified in the paper.
Since a particle larger than 1 mm will not fall within the definition of a " hot particle," it will not be subject to the 75 uCi-hour limit, but will be subject to the much more restrictive existing limits of 10 CFR Part 20, i.e., 7.5 rem (whole body) and 18.75 rem (extremities) per quarter.
l We would appreciate having these comments brought to the attention of the Commission for its consideration with the paper.
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Eric S. Beckjor, Director Office of Nuclea Regulatory Research
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