Opinion for the court filed by Circuit Judge J. SKELLY WRIGHT.
Petitioners seek review of a final decision of the Atomic Energy Commission1 to grant a license to the Philadelphia Electric Company, intervenor here, for operation of a light-water-cooled nuclear reactor to be used for generating electricity.2 The licensed reactor, which is now in operation, has a rated capacity of 1065 megawatts of electrical power 3 and is one of two such reactors4 built by *814intervenor at its Peach Bottom Atomic Power Station located in York County, Pennsylvania, along the west shore of the Susquehanna River. Peach Bottom is approximately 38 miles northwest of Baltimore and 63 miles southwest of Philadelphia.
Petitioners have raised a host of objections to the Commission’s procedures, interpretations of its own regulations, and findings of fact. We have considered each of these objections, and we find no flaws in most aspects of the Commission proceedings. We agree with petitioners, however, that the Commission appears to have followed a course inconsistent with its governing regulations which require licensees to keep the level of radioactive material, including radioactive iodine, in effluents released to unrestricted areas “as low as practicable.” 10 C.F.R. §§ 20.1, 50.34a, 50.36a (1975). The regulations offer the following definition:
The term “as low as practicable” as used in this part means as low as is practicably achievable taking into account the state of technology, and the economics of improvements in relation to benefits to the public health and safety and in relation to the utilization of atomic energy in the public interest.
10 C.F.R. § 50.34a.
At the time of the licensing proceeding for Peach Bottom, the regulations did not further specify the meaning of the qualitative standards set forth above. The Commission had, however, issued an interim Regulatory Guide to “provideQ interim licensing guidelines to aid applicants in implementing §§ 20.1(c), 50.34a, and 50.36a of the Commission’s regulations with respect to keeping radioiodine releases from light-water-cooled nuclear power reactors as low as practicable.” U.S. Atomic Energy Commission Regulatory Guide 1.42 at 1.42-2, JA Vol. 9 Item 1. That Guide, which did not have the legally binding effect of a regulation and therefore could not modify the “as low as practicable” standard, stated, in essence, that the Commission’s regulations were satisfied if the release of radioiodine from a reactor site5 would result in a thyroid dose6 of 15 or fewer millirems per year.7 See id. at 1.42-4, 1.42-6, 1.42-9. Relying on this guidance, the Commission held that the expected radiation releases from the Peach Bottom site would be “as low as practicable.” 8
Petitioners contend that the Commission’s regulations do not allow establishment of a numerical guideline whose satisfaction can be considered the equivalent of meeting the “as low as practicable” standard. Solely as a matter of interpreting the plain language of the Commission’s definition of that standard, we agree. The Commission’s definition, quoted above, requires consideration of health and safety effects, costs, the state of technology, and utilization of atomic energy in the public interest. While the *815last two factors may be constant for any reactor built or operating during a particular time period, the first two will presumably vary depending on the circumstances of each reactor. Since two of the four factors which determine whether radioactive emissions are “as low as practicable” are not constants, the Commission is precluded from determining that any particular positive level of emissions satisfies its requirement in all cases.
Our conclusion that the Commission’s regulations do not permit establishment of a single numerical criterion under the “as low as practicable” standard is supported by the similar conclusion of a rule-making proceeding which was ongoing at the time of the Peach Bottom licensing proceeding and which has since been completed. That rule-making replaced Regulatory Guide 1.42 with an Appendix I to 10 C.F.R. Part 50. Appendix I establishes “Numerical Guides for Design Objectives and Limiting Conditions for Operation to Meet the Criterion ‘As Low as Practicable’ for Radioactive Material in Light-Water-Cooled Nuclear Power Reactor Effluents.” 40 Fed. Reg. 19442 (1975). The numerical guide for radioiodine exposure is set at 15 millirems per reactor.9 Appendix I also specifies, however, that in addition to satisfying the numerical guides,
the applicant shall include in the rad-waste system all items of reasonably demonstrated technology that, when added to the system sequentially and in order of diminishing cost-benefit return, can for a favorable cost-benefit ratio effect reductions in dose to the population reasonably expected to be within 50 miles of the reactor. As an interim measure and until establishment and adoption of better values (or other appropriate criteria), the values $1000 per total body man-rem[10] and $1000 per man-thyroid-rem (or such lesser values as may be demonstrated to be suitable in a particular case) shall be used in this cost-benefit analysis.
Id. Thus the Commission recognizes in Appendix I that its “as low as practicable” standard requires individualized consideration of the costs and benefits of reducing radioactive emissions from any particular reactor below the numerical guidelines.
In this case it does not appear that such an individualized analysis was ever performed, and the Commission’s decision did not rest on a finding that no further reduction in radioactive emissions would produce a favorable cost-benefit ratio. We therefore reman'd this case to the Commission in order to allow such an analysis to be performed.11 Following the analysis, the Commission can determine in an appropriate proceeding12 *816whether to modify the operating license for the Peach Bottom reactors to require additional emission control equipment. See 10 C.F.R. § 50.109 (1975). Since the current level of emissions is low, the public interest does not require the operating license to be suspended during the pendency of the remand proceedings.13
So ordered.