Je veux savoir à propos de…

45924

Federal Register / Vol. 86, No. 156 / Tuesday, August 17, 2021 / Proposed Rules
All NRC licensees are subject to the NRCs radiation protection requirements set forth in 10 CFR part 20. These requirements are designed to protect both members of the public and occupational workers from harm that could be caused by a licensees use of radioactive materials. In accordance with 20.1101, Radiation protection programs, each licensee shall develop, document, and implement a radiation protection program commensurate with the scope and extent of licensed activities. 4
The LNT model has been the underlying premise of much of the NRCs radiation protection regulations since the late 1950s.5 The LNT model provides that ionizing radiation 6 is always considered harmful and that there is no threshold below which an amount of radiation exposure to the human body is not harmful. The LNT
model further holds that biological damage caused by ionizing radiation the cancer risk and adverse hereditary effects is directly proportional to the amount of radiation exposure to the human body response linearity. Thus, the higher the amount of radiation exposure, or dose,7 the higher the likelihood that the human receptor will suffer biological damage. The validity of the LNT model has been the subject of dispute within the scientific community for decades.8 The NRCs standards for protection against radiation, which are contained in 10 CFR part 20, are underpinned by the LNT model. These radiation protection standards provide requirements for Dose limits for radiation workers and members of the public, Monitoring and labeling radioactive materials, Posting signs in and around radiation areas, and Reporting the theft or loss of radioactive material.

khammond on DSKJM1Z7X2PROD with PROPOSALS

4 10

CFR 20.1101a.
5 The Atomic Energy Act of 1954 assigned the Atomic Energy Commission AEC the functions of both encouraging the use of nuclear power and regulating its safety. The AEC was the predecessor agency to the NRC.
6 The terms ionizing radiation and radiation are used interchangeably in this document.
7 The biological dose or dose equivalent, given in rems or sieverts Sv, is a measure of the biological damage to living tissue as a result of radiation exposure. NRC Glossary, Definition of Dose, https www.nrc.gov/reading-rm/basic-ref/
glossary/dose.html.
8 For example, in the October 2015 ACMUI
teleconference, Dr. Zanzonico noted that we all recognize that the issue of the linear no-threshold model of radiation carcinogenesis versus a hormetic model versus an alternative model remains highly controversial and really engenders very strong emotions from folks on different sides of the question. ACMUI, Official Transcript of Proceedings October 28, 2015, at 1819.

VerDate Sep<11>2014

16:34 Aug 16, 2021

Jkt 253001

The petitioners do not dispute that high doses of radiation exposure are harmful to the human body. Instead, their argument centers on low doses of radiation exposure, generally doses below 10 rem 100 mSv, the effects of which are difficult to quantify. In this regard, the petitioners contend that there is a threshold below which radiation exposure to the human body is not harmful. As described by the International Commission on Radiological Protection ICRP in its Publication No. 99, Low-dose extrapolation of radiation-related cancer risk, the threshold theory posits that there is some threshold dose below which there is either no radiationrelated health detriment or a radiationrelated health benefit that outweighs any detriment. If the threshold was a universal value for all individuals and all tissues, a consequence of the theory is that, at some point, a very low dose to any number of people would have no associated risk and could be ignored. 9
The petitioners also advance a companion concept to the existence of a threshold, the radiation hormesis concept hormesis, which provides that exposure of the human body to low and very low levels of ionizing radiation is beneficial to the human body.
III. Petitioners Assertions The petitioners request to amend NRC
dose limits dose limit for occupational workers; dose limit for embryos, fetuses, and pregnant workers; and the dose limits for the public as well as to remove the ALARA principle for the NRCs regulations. The requested amendments to the regulations were supported by several assertions made by the petitioners. The NRC reviewed each assertion separately, as outlined in this section and followed by the NRCs response.
Petitioners Assertion That LNT Is Not Justified by Current Science The petitioners assert that current science does not justify the use of the LNT model and that there is a threshold below which radiation exposure to the human body is not harmful.
NRCs Response The NRC does not agree with the petitioners assertion. Exposure to ionizing radiation is a known cancer risk factor for humans. The LNT model assumes that, in the long term, biological damage caused by ionizing radiation i.e., cancer risk and adverse hereditary effects is directly 9 ICRP, Low-dose extrapolation of radiationrelated cancer risk, Pub. No. 99 2005, at 38.

PO 00000

Frm 00002

Fmt 4702

Sfmt 4702

proportional to the dose. The NRC
acknowledges the difficulties inherent in determining the amount of damage to the human body caused by low doses of radiation. The NRC, however, does not use the LNT model to assess the actual risk of low dose radiation. Instead, the NRC uses the LNT model as the basis for a regulatory framework that meets the adequate protection standard of the Atomic Energy Act of 1954, as amended AEA. Furthermore, the LNT model is applied so that the framework can be effectively implemented by an agency that regulates diverse categories of licensees, from commercial nuclear power plants to individual industrial radiographers and nuclear medical practices. The NRCs use of the LNT
model as the basis for its radiation protection regulations is premised upon the findings and recommendations of national and international authoritative scientific bodies, such as the ICRP, that have expertise in the science of radiation protection.
The NRC issued the framework for its current 10 CFR part 20 radiation protection regulations in 1991.10 The NRC acknowledged the role of the national and international authoritative scientific bodies in the 1991 final rule, stating that the U.S. Atomic Energy Commission and the NRC have generally followed the basic radiation protection recommendations of the ICRP and its U.S. counterpart, the National Council on Radiation Protection and Measurements NCRP, in formulating basic radiation protection standards. The 1991 final rule explained that the NRC based its radiation protection regulations upon three assumptions. The first assumption concerned the use of the LNT model, which was described as follows:
The first assumption, the linear nonthreshold dose-effect relationship, implies that the potential health risk is proportional to the dose received and that there is an incremental health risk associated with even very small doses, even radiation doses much smaller than doses received from naturally occurring radiation sources. These health risks, such as cancer, are termed stochastic because they are statistical in nature; i.e., for a given level of dose, not every person exposed would exhibit the effect.11

The other two assumptions supporting the NRCs radiation 10 56 FR 23360; May 21, 1991. Under current NRC
regulations, each NRC licensee must ensure that its operations do not exceed, for each member of the public, a total effective dose limit of 0.1 rem 1
mSv in a calendar year. 20.1301a1. For occupational workers, the primary annual dose limit, per licensee, is a total effective dose equivalent of 5 rems 50 mSv. 20.1201a1i.
11 Id.

E:FRFM17AUP1.SGM

17AUP1