ML20247R594
| ML20247R594 | |
| Person / Time | |
|---|---|
| Issue date: | 05/22/1989 |
| From: | Advisory Committee on Reactor Safeguards |
| To: | Advisory Committee on Reactor Safeguards |
| References | |
| ACRS-2640, NUDOCS 8908080063 | |
| Download: ML20247R594 (10) | |
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CERTIFIED COPY MEWL DATE ISSUED:May 22,1989
SUMMARY
/ MINUTES OF THE ACRS SUBCOMMITTEE MEETING l
ON OCCUPATIONAL AND ENVIRONMENTAL PROTECTION SYSTEMS APRIL 20, 1989 BETHESDA, MARYLAND The ACRS Subcommittee on Occupational and Environmental Protection Systems met on April 20, 1989 to review and discuss the NRC staff's.
" interim Standard for Occupational Exposure of the Skin to Radiation from Small Radioactive Particles (hot particles)." The meeting was held at the request of the Conrnittee.
Notice of the meeting was published in the Federal Register on March 28, 1989. The schedule of items covered in the meeting and a list of handouts are kept with the office copy. There were no written or oral statements received or presented from members of the public at the meeting.
E. G. Igne was W t ACRS staff member fw the meeting.
Principal Attendees ACRS NRC J. C. Carroll, Chairman J. Buchanan C. Wylie, Member T. Essig N. Wald, ACRS Consultant L. Cunningham M. Carter, ACRS Consultant A. Rocklein j
D. Moeller, Invited Expert J. Bell 1
M. Shanbaky j
i Others J. Baum, BNL j
T. Tipton, NUMARC i
J. Fairobent, NUMARC l
W. Reece, PNL W. Beckner, NCRP
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E. Medling, So. Cal. Edison 1
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R. War.1ock, So. Cal. Edison f
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M. Williams, Union Electric E. Rollins, So. Cal. Edison dy#7
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Minutes /0 occupational & Environmental 2~
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' Highlights
- 1. 'J. Cunningham, NRR, presented.an overview of the concern for-occupational ~ exposure of the skin from hot particles.
He stated that
" overexposure" from hot particles were first reported in June of 1985, and that many reported overexposure incidents' occurred since then.
It was-stated that hot particles are innate to nuclear power plant operation and that sooner or later hot particles would be found as
. sensitivity.of survey instrument increased. The current NRC dose limit for. skin is delineated in 10 CFR 20, although its basis did not include the consideration of hot particles. The limits are 7.5-rem / quarter to'the skin of whole-body and 18.75 rem / quarter of the skin of hands and forearms, feet and ankles. The NRC position on dose calculation for the purpose of showing compliance with 10 CFR 20.101 dose limits for skin is determined by calculating a skin dose averaged 2
2 over an area of Icm at a depth of 7 mg/cm,
At the present time when hot particle exposures exceed regulatory limits the Regions apply enforcement discretion...in the citing of severity level and civil penalty. This problem should be eliminated with the promulgation of the interim standard.
In reply to a l
question, J. Cunningham stated that prior to the 1986-86 time frame j
J the control of hot particles was not yet well known and procedures not yet formulated because hot particles were difficult to detect. With better equipment and training of health physics personnel, the detection of hot particles in the work place is feasible although it is time consuming, costly and may at times not be beneficial from the j
<l Minutes / Occupational & Environmental
'3 Protection Systems Mtg. April 20,1989
" additional whole body dose" increase standpoint of monitoring ipersonnel.-
.The NRC requested NRCP in March 1987, to provide-guidance on limits of'
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exposure to hot particles on the skin. NCRP major recommendations are as followsi
.o Limit should be based on preventing ulceration, o.
Limit should be expressed in terms of beta particle emission for a particle less than 1-mm diameter in contact with the-skin.
o Emission limits should be 10E10 beta particles emitted, or 75 microcurie-hours.
The NRC staff has discussed staff questions and concerns with the NCRP SC80-1 representatives and is awaiting resolution of comments and issuance of final NCRP report.
In the_meantime, the NRC has proceeded with-the release of its interim standards but will consider NCRP recommendations during rulemaking, which generally takes about two I.
years. The interim standard excludes fragments, internal and BRC L
(below regulatory concerns) quantities.
J. Cunningham emphasized that enforcement actions are based on failure of control, and not necessarily the magnitude of exposure.
2.T. Essig, NRR, discussed the interim standard for occupational exposure of skin from hot particles. Characteristically hot particle ranges in size from about one micrometer up to about 0.2cm and its
Minutes / Occupational & Environmental'L4' f
Protection Systems'Mtg. April 20,1989 activity ranges from manocurie to millicurie. Maximum dose rate from hot particles on skin to date is about 360' rad / hour, of which beta dose is predominant.
It was stated that if. gamma dose dominates the j
interim, standard dnes not apply. There is no indication to date of significant inhalation or ingestion problems of hot particles.
'Regarding stochastic effects, he stated that there is a probability of l;
occurrence, but not severity, and increases with increasing dose without threshold, i.e., cancers and genetic defects. On non-stochastic affect the severity varies with dose and a threshold may exist, i.e., cataracts, blood changes, and visible changes on l:
skin.
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Referring to ICRP publication 26, NCRP 91 and the pending mejor revision of 10 CFR Part 20, T. Essig stated that in each document the annual-skin dose limit is 50 rem (rad), based to prevent cosmetically unacceptable changes in the skin or to prevent clinically significant and health-impairing diseases. In each document, nothing specific is mentioned on hot particles. He stated that changes in standards are necessary because current limits are inappropriate and that possible savings in whole-body dose may be obtained by relaxing some current limits. The interim standard for enforcement discretion was decided on by the NRC staff because it takes effect upon its release without public comments until rulemaking is comp?ete. The staff recognizing the limitation of current technical data base aimed the rule to be conservative until rulemaking with better technical data base becomes available. The NP.C staff rejects recommendation from NCRP in its L_-
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.Minut'es/ Occupational & Environmental
. Protection Systems.Mtg. April 20;1989 l,
report 101 based on skin ulceration that is taken as the biological.
endpoint of' concern.
' A' generic' letter.on' interim standard for occupational exposure of skin
.to radiation is an interim standard for exercise of enforcement discretion, tht applies to occupational. exposure of skin from hot particles'on body.or clothing to a single exposure of individual in a calendar quarter. NRC will enforce limit of 50 rad averaged over 1 2
2
-cm at a' depth of 7mg/cm and that no notice of violation will be issued for..a single or multiple exposure sure each below 50 rad, although failure.to survey may bring a possible notice of violation.
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-Enforcement %11cy for hot particle on skin are 2500 reds, Severity level 1; 500 rads, Severity Level II; 100 rads, Severity Level III; and 50 rad, Severity Level IV.
3.
J. Bell, RES, discussed technical assistance contracts on hot particles. He stated that PNL has a contract to develop computer codes for calculating dose to skin from hot particle contamination.
VARSKIN code was the result of PNL efforts. A grant was issued to NCRP to rake recommendations for new limit for special case of dose to skin from hot particle in contact with skin. A draft report was
. issued in June 1988 recommending 75 microcurie-hour limit.
NRC staff questioned NCRP on its recommendation. Final report is due from NCRP in September 1989. BNL was provided a Technical Assistance Ce tract to provide technical information to NRC staff as basis for rulemaking.
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4.
J. Baum, BNL, discussed basis-of NRC proposed criteria. He
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stated that the. threshold for tissue breakdown may be closer to 2E 9 betas-than to 1E 10 betas, and that the limit of 50 rad averaged over 2
Icm at 70 m depth is below-both'Forbes and Hopewell' test results.
Skin cancer studies in pigs are needed at doses about 2000 rad to test rat / mouse / human / pig correlations. Non-stochastic effects studies are needed using 100 u and smaller particles if possible.
5.
M. Shanbaky, Region I, discussed the NRC regions concern on the hot particle concern.
He discussed the experiences at Yankee Rowe, Nine Mile Point.-Salem, and Haddam Neck. He stated that confusion over the interpretation of 10 CFR 20 exists at the regions and that the interim standard will provide relief to the utilities and uniform enforcement actions by region inspectors.
6.
W. Beckner, NCRP, discussed its activities.on hot particles requested by NRC on March 1987. As a result of NRC's request NCRP established a subgroup of its committee on " beta-ray dosimetry of the skin" to address this problem. A number of problems were evident to the committee early on. Some of these problems are as follows:
o There is very little relevant human data on the biological effects of hot particles.
O Most all of the skin irradiation data in non-human systems, primarily in pigs, mice and rats, is not directly applicable because of dissimilarities in source size and
Minutes / Occupational & Environmental 7
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Protection Systems Mtg.: April-'20,1989-dose distributions.
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There doesn't appear to be~ any biological basis'on which to pick any.particular depth in the skin or volume element of skin for assessing the dose from hot particles.
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.The NCRP rs,rt on hot-particles concluded:
o That a' hot particle be defined as a discrete radioactive fragment that is insoluble.in water and is no larger than 1 mm in any dimension.
o The. report also concludes that the potential stochastic risks of hot particles are overweighed by their nonstochastic acute risks. Therefore, acute ulceration was selected as being the risk of concern from hot particles.
Even though acute ulceration, in itself, was considered-ered to be a relatively benign effect, its higher probability of occurence as compared to the other potential effects caused the committee to recommend to the Council that acute ulceration be the effect of concern for radiation prot".ction purposes.
The report recommended:
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o Exposure from hot particles be limited to 75 microcurie-hours.
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Exposure in excess of the limit should require frequent medical evaluation in order to determine if an ulcer
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An application of a safety factor was not' applied in the development of these recommendations.
W. Beckner stated that the final NCRP report that incorporates NRC comments may or may not have to be. resubmitted to Council review.
In any event, it no longer has an NCRP Report No. 101, as its position in the sequence ~of NCRP publications is undetermined.
7.
W. Reece, Battelle PNL, discussed discrete radioactive particles (DRPs) -- regulations and reality. He stated that DRPs are costing the industry millions of dollars and that DRP decontamination efforts are leading to. significantly higher whole-body exposures. Experiments are presently being conducted at PNL in-order to balance DRP risk with risk from whole-body exposure and to protect workers from nonstocha3 tic effects, the following need to be determined:
o Verify and extend knowledge of effects of beta endpoint energies and beta field sizes.
o Measure dose profiles throughout the dermis and epidermis to 1
understand mechanism of damage.
Minutes /0 occupational & Environmental 9 Protection Systems Mtg. April 20,1989 o
Provide definitive dosimetry for the sources, contrary to work by previous investigators.
l Define methods to properly access dose from DRPs based on o
comparable risk from whole-body exposures.
5 8.
P. Robinson, EPRI, discussed DRPs skin ulceration threshold studies performed on pigs. EPRI survey results out of 61 stations indicate that 28% reported no DRPs, 30% reported fuel, 69% reported k
only activation DRPs, and 90+% of all particles reported are Co-60.
After 28 days of testing the results of low energy (Co-60, Ca-45) resting on pig skin produced no ulceration. Mid-high energy (CE-144, Sr-90) testing also produced no ulceration.
(Note:
Redness and dry peeling occurs but not wet desquamation.) Continued testino is in progress.
9.
M. Williams, Union Electric, discussed conservatism in NCRP recommendations. He stated that 75 microcurie-hours is extremely conservative.
He also stated that the NRC recommendation of 50 rad applies to erythema not ulceration. The NRC recommendations will also increase 1) monitoring frequency, 2) whole-body dose, 3) radwaste generation, and 4) operation and maintenance expenses.
M. Williams recommended to use NCRP's 75 microcurie-hours recommendation as interim guidance:
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o expressed as 300 rad over 1 cm at 7mg/cm 4
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o consider separate;(higher) limit for Co-60 t
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allow correction for self-absorption, and o
.all for particles not in contact with the-skin.
l 10.
E. Medling, Southern California Edison Co., discussed hot particle control program man-rem cost at San Onofre. He stated that-it cost San Onofre'from Oct 1985-1987 $2.05 million for hot particle control pr'ogram. During this time period he stated that there was a 50% decrease in productivity for hot particle zone controls, vice presidential intervention in.two concerned employee cases _and two hours added training for all site employees (approximately 5,000 person-hours).
1 Subcommittee Action i
The chairman of the subcommittee suggested that a two hour subcommittee report including NRC~and NUMARC presentation', be provided at the full ACRS meeting in May 1989.
NOTE: A transcript of the meeting is available at the NRC Public Document Room, Gelman Bldg. 2120 "L" Street, NW., Washington, D.C. Telephone -(202) 634-3383 or can be purchased from Heritage Reporting Corporation,1220 L Street, NW., Washington, DC 20005, Telephone (202) 628-48E8.
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