ML19343B985
| ML19343B985 | |
| Person / Time | |
|---|---|
| Issue date: | 02/11/1981 |
| From: | Mark J Advisory Committee on Reactor Safeguards |
| To: | Ahearne J NRC COMMISSION (OCM) |
| References | |
| ACRS-R-0917, ACRS-R-917, NUDOCS 8102180458 | |
| Download: ML19343B985 (2) | |
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UNITED STATES NUCLEAR REGULATORY COMMISSION
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February 11, 1981
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Honorable John F. Ahearne Chairman U.S. Nuclear Regulatory Commission Washington, D.C. 20555
SUBJECT:
STATE OF TECHNOLOGY REPORT ON FISSION PRODUCT IODINE
Dear Dr. Ahearne:
In response to your request of January 14, 1981, the Advisory Committee on Reactor Safeguards met with the NRC Staff on February 6,1981 to review progress in the preparation of the State of Technology Report on Fission Product Iodine.
This.was also the subject of a meeting of our Subcommittee on Reactor Radiological Effects on February 5,' 1981.
Although the NRC Staff did not provide us with a draft of the Report, we did review ;he proposed report outline as well as some of the details on the subjeccs to be covered.
We also heard a report from a representative of the Electric Power Research Institute.
On the basis of our review, we offer the following comments.
1.
The experience in the TMI-2 accident again demonstrated the desira-bility of a better understanding of the behavior of radioiodine, as well as other fission products, in an accident environment.
Prepa-ration of the Technology Report should provide a basis for better assessment of accident source terms and we support this effort.
2.
The Committee recommends, however, that care be taken to sprify l
clearly what the Report it intend 2d to accomplish. While its pri-mary goal is to su.nmarize the current state of knowledge on radio-iodine transport during accidents, it will not provide answers to One of many pertinent questions concerning accident source terms.
its principal benefits will be to clarify areas needing research.
3.
The ;uthors should define clearly the physical and chemical environ-ments that have accompanied past reactor accidents being evaluated in the Report.
Also, the physical and chemical environments of the various experiments which have been conducted on the behavior of l
fission products should be defined in orde.r to relate the resulting i
l data to accident situations.
4.
It should be realized that the physical t.nd chemical environment may change over short periods of time during the course of an accident.
Before potential source tera can be defined, there is a need for a much better understanding of this subject.
There is also a need for a clearer definition of the range and types of accidents to be considered 81esisoter/
Honorable John F. Ahearne February 11, 1981 5.
In assessing the behavior of radiciodine, we note that, although most of the iodine-131 inventory would be present at the time of an acci-dent, a small amount (about 2.75%) would be formed subsequently by decay of the iodine-131 precursors, antimony and tellurium.
This is unimportant with the present conservative regulatory position, but it could become important if the assumed iodine releases were reduced by an order of magnitude or more.
The behavior of antimony and tellurium in the accident environment, as well as the behavior of the delayed iodine-131, may be important in assessing the radiciodine release.
6.
Although computer codes exist for the assessment ~ of the behavior of.
radioactive materials released in an accident, these codes appear to lack real means of accounting for the behavior of radioactive aerosols in certain physical and chemical environments.
Further improvements of these codes may be necessary before details of the behavior of the various components of-the source term can be confirmed.-
7.
The efforts of the EPRI staff in reviewing previous fission eroduct behavior tests and their possible application to a better definition of accident source terms have been useful.
We would encourage studier un De general issue by other groups and organizations.
8.
We were encouraged to note the review planned for the final draft of the Report, and the planned use of foreign data, information, and reviewers in its preparation.
The schedule for this review, however, does not appear to be realistic. More time is needed.
j The Committee agrees with the need for improving the understandir.g of nuclear reactor accident source terms since changes in the quantities of radiciodine l
available could lead to significant alterations in certain of the concepts related to site selection, nuclear facility design, and emergency planning.
However, we do not yet have information that would justify major changes in the regulatory approach.
We recommend that care be taken to specify clearly the limitations on the use of the Report that results from the current efforts.
This might involve drawing attention to radionuclides, other than radioiodine and its precur-sors, that might influence regulatory requirements for radionuclide releases.
l Also in need of clarification are plans for subsequent work on accident l
source terms.
The Committee will review the final draft of the Report when copies are available.
Sincerely, 1
J. Carson Mark Chairman l
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