Trends in Domestic Regulations
Relating to Radioactive Waste
Disposal I
Satoru Tanaka
The University of Tokyo
Department of Nuclear Engineeringand Management1

Recent discussions and future issues at the Nuclear Safety
Commission, Radioactive Waste and Decommissioning SpecialDivision(1)Clearance Level Study"Clearance level at major nuclear reactor facilities" (March 17, 1999, Nuclear SafetyCommission)"Clearance level at heavy water reactors and fast reactors" (July 16, 2001, Nuclear
Safety Commission)"Clearance level at nuclear fuel using facilities (handling facilities of irradiated fuels andmaterials)“ (April 24, 2003, Nuclear Safety Commission)“Concentration of radioactivity not required to be handled as radioactive materials
among those generated along with demolition of nuclear reactor facilities and nuclear
fuel using facilities" (December 16, 2004, March 17, 2005 partial correction andamendment, Nuclear Safety Commission)“Clearance level at uranium handling facilities" (October 5, 2009, Nuclear SafetyCommission"
Other clearance levels will be studied as needed.

2(2) Safety Review Guides Related to Low Level
Radioactive Waste Burial Facilities (Study to EstablishSafety Review Guide on Sub-surface Disposal)"Fundamental concept on safety regulation of land disposal for low level
radioactive solid waste" (October 24, 1985, Nuclear Safety Commission)"Fundamental concept of safety review for radioactive waste burial facilities"(March 17, 1988, Nuclear Safety Commission decision, January 7, 1993 (partialrevision), March 29, 2001 (partial revision), October 5,2009 (partial revison))"Common important matters at safety regulation for radioactive waste disposal"(June 10, 2004, Nuclear Safety Commission)"Upper limit of radioactivity concentration on burial disposal of low level
radioactive solid waste" (May 21, 2007, Nuclear Safety Commission)"Fundamental concept of safety review on low level radioactive waste burial(interim report)" (July 12, 2007, Nuclear Safety Commission)"Concept on safety review after control period finishing of sub-surface disposal 3(draft)" under receiving public comments (January 25 to February 25, 2010)

(3) Study of Fundamental Concept of Safety Regulation of ResearchInstitute Waste"Fundamental concept on safety regulation of near-surface disposal of radioactive solid wastegenerated at radioactive isotope using facilities" (January, 2004, Nuclear Safety Commission)"Fundamental concept on safety regulation of near-surface disposal of radioactive solid waste
generated at research institutes" (April 20, 2006, Nuclear Safety Commission)(4) Study of Whole Concept for Security on Decommissioning of
Nuclear Facilities"Fundamental concept of ensuring safety on demolition of nuclear reactor facilities"(December 19, 1985, August 6, 2001, partial revision, Nuclear Safety Commission)"Radioactivity concentration not required to be handled as radioactive materials among thosegenerated at the demolition of nuclear reactor facilities and nuclear fuel using facilities"(December 16, 2004, March 17, 2005, partial correction and amendment, Nuclear SafetyCommission)"Whole concept of safety regulation system after finishing operation of nuclear facilities"(January 28, 2005, Radioactive Waste, Decommissioning Special Divisions)4(5) Specific Regulation on Treatment and Disposal of Radioactive
Waste Including Transuranic Elements (TRU)
The Nuclear Safety Commission report has already reported that radioactivewaste, including transuranic elements with low TRU concentration, are suitablefor pit and sub-surface disposal and the upper limit of alpha nuclide
concentrations, including TRU, in the inventory studying upper concentration limit.

(6) Facilities Site Relieving Criteria(7) Fundamental Concept of Safety Regulation on Uranium Waste
Disposal and Upper Concentration Limit(8) Ensuring Safety and Safety Regulation of High Level Radioactive
Waste Disposal

These items will be studied and reviewed in future.

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"Concept on Safety Review After Control Period Finishing ofSub-surface Disposal (Draft)"（Open to public feedback: January 25 to February 25, 2010)

1.1 Review history
Some low level radioactive waste, when containing radioactive
materials with significantly long half-lives, requires a safety assessment after
the control period has elapsed. After burial, control for several centuries
should be required to monitor the leakage of radioactive materials fromburial facilities and limit land utilization. In addition, after the control period
has elapsed, complete measures should be applied to avoid exposurerelated safety problems, even assuming contact between human andradioactive waste, and an appropriate disposal system should beconstructed to sufficiently constrain the transfer of radioactive materials.
The Nuclear Safety Commission began a survey and study in 2001.
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"Common important matters at safety regulation for radioactive waste
disposal" (June 10, 2004, Nuclear Safety Commission)("Commonimportant matters")
Ensuring safety was studied on burial of radioactive wastes
requiring safety assessment after finishing control period. The study
revealed that risk-based concept appropriately handling uncertainty withlong-term prediction after finishing control period should be applied to thesafety regulation.
"Fundamental concept of safety review on low level radioactive waste
burial (interim report)" (July 12, 2007, Nuclear Safety Commission)(“interim report")
For low level radioactive wastes burial including disposal below thegenerally used depth for radioactive wastes ("sub-surface disposal"), afundamental concept was developed for safety regulation on the basis of
the risk-based concept.
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"Safety regulation on the basis of risk-based concept" involves
classifying the safety assessment scenario by properly considering thepotential occurrence by reflecting on the uncertainty of long-term
predictions in the post-control period safety assessment and comparing itwith the corresponding "target". It is, therefore, particularly important in
the risk-based concept to specify the scenario for the safety assessment.
In the interim report, referring to the dose rate/probability
resolving approach, the scenario was divided into three groups of afundamental scenario, a variation scenario, and an artificial rare
phenomenon scenario, to which a "target" dose was attached forindividual judgment. The fundamental scenario is defined as one that canbe “easily generated as a normal scenario", while the variation scenario is“rarely possible to generate but takes variable factors significant for safetyassessments into account", and the artificial rare phenomenon scenario is"a natural or incidental artificial phenomenon extremely unlikely to occur."
The resultant dose "target" values from the assessment result for eachscenario were determined as 10μSv/y, 300 μSv/y, 10 mSv/y to
100mSv/y, respectively.
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In October 2007, the radioactive waste and decommissioning
special division established the second class waste burial subcommittee topromote a survey and review on the revision of the present safety review
guide based on the interim report. The division also surveyed and reviewed
a scenario establishing the concept of the long-term safety assessment
among requirements to be included in the present safety review guide forlow level radioactive solid waste as specified in the interim report andsummarized as a draft report delivered for public feedback.

“Present safety review guide”:"Fundamental concept of safety review for radioactive waste burialfacilities" (March 17, 1988, Nuclear Safety Commission decision, January 7,
1993 (partial revision), March 29, 2001 (partial revision), October 5, 2009
(partial revision))91.2 Studying Scope* Waste appropriate for sub-surface disposal among radioactive waste
generated from nuclear facilities* The main focus will be the concept of a safety assessment after thecontrol period has elapsed.
* It is important to consider uncertainty on properties when specifying
disposal system conditions in future.
* The scenario should be specified considering phenomena responsible forplate movement and climate change, changes in living zone conditions, thefacility environment and artificial barriers. The formalization concept wasemployed for the human lifestyle mode in the living zone.
* The artificial rare phenomenon in the interim report was divided into theartificial phenomenon scenario and the rare phenomenon to study basedon four division scenarios.

10Fundamental scenario:
This scenario is defined as very frequently generated as a normal
scenario and should involve consideration, based on past and present
conditions, of the disposal system, property of an exposure path and thepredicted sequence of changes which are credibly considered likely tooccur in future. This scenario is to be applied in the basic design and policyof the disposal system to ensure resultant doses can be reasonably
minimized as far as possible.
Variation scenario:
The scenario is far less likely to be generated but takes variable factors
significant to safety assessments into consideration, as well as the area ofintegral variation subject to various changes other than those specified in
the fundamental scenario as well as the disposal system and exposure
path. This scenario is applied to ensure that the disposal system design
can respond to various uncertainties. This means that the scenario is also
used to confirm sufficient reasonability not exceeding a dose rate recently
internationally agreed as a "target" for judgment on the long-term safety ofradioactive waste disposal, even when considering such variation factors.
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Rare phenomenon scenario:
The scenario is extremely unlikely to occur naturally and is applied toconfirm whether the design of the disposal system can effectively alleviate
the expected phenomenon from a radiation protection perspective. Thismeans the scenario is applied to confirm that no special radiation
protection measures are required for uncertainty, even taking very
unlikely scenarios into account.
Artificial phenomenon scenario:
The scenario assumes damage to burial facilities due to human activity
not taking the existence of radioactive waste disposal facilities into
consideration. Similar to the rare phenomenon scenario, this one isapplied to confirm whether the design of the disposal system caneffectively alleviate the expected phenomenon from a radiation protection
perspective. For this reason, the scenario is applied to confirm that nospecial measures for radiation protection are required, considering
persistent uncertainty regarding disposal system design and approaches
such as report conservation.

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2 Condition setting of long-term variation phenomenon on geologicalenvironment
2.1 Fundamental concept at setting
2.2 Setting of phenomenon caused by plate movement
2.3 Setting of phenomenon caused by climate change
2.4 Setting of phenomenon caused by both plate movement and climatechange3. Environmental changes in human living zones in future
3.1 Fundamental concept at setting
3.2 Major constituting element in the living zone and modeling
3.3 Formation of the exposure path by natural and artificial processes
3.4 Necessary data for living zone assessment
4. Condition setting of burial facilities
4.1 Basic formation of burial facilities
4.2 Fundamental concept at setting
4.3 Artificial barrier function and characteristics
4.4 Studying items at condition setting
4.5 Condition setting method
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5. Fundamental scenario setting, 6. Variation scenario setting
5(6).1 Safety assessment concept for fundamental (variation) scenarios
5(6).2 Setting of fundamental (variation) groundwater scenarios
Setting concept, transient period, period expecting multiple barrier function,
period mainly expecting natural barrier function, period expecting burial
facilities nearing the land surface
5(6).3 Expectation of fundamental (variation) gas transfer scenario
Setting concept, transient period, period expecting multiple barrier function,
period mainly expecting natural barrier function, period expecting burial
facilities nearing the land surface
5(6).4 Setting of fundamental (variation) land utilization system
5(6).4.1 Setting concept5(6).4.2 Present land utilization
5(6).4.3 Land utilization available alongside sea level variation
5(6).4.4 Land utilization from re-deposition at a site downstream of burial
facilities
5(6).4.5 Land utilization for shallow burial facilities

147. Setting of rare phenomenon scenario
7.1 Safety assessment concept of the rare phenomenon scenario
7.2 Setting of rare phenomenon scenario
1) Influence assessment of mechanical destruction due to earthquake
and fault activity2) Influence assessment of mechanical destruction and thermal,
chemical deterioration due to volcanic igneous activity
8. Setting of artificial phenomenon scenario
8.1 Safety assessment concept of the artificial phenomenon scenario
8.2 Setting of boring scenario
Direct boring core observation scenario, transfer path short-circuit
scenario, ground water intake scenario at boring hole around burial
facilities
8.3 Setting of tunnel excavation scenario
Excavation scenario near burial facilities, excavation scenario of burial
facilities penetrating tunnel
8.4 Setting of a land utilization scenario for full-scale development
159. Concept on finishing control period
Based on the contents in the "common important matters report" and“interim report", the control period is to be studied reflecting
recommendations by international organizations and the resultant review
trend by the Japan radiation review committee.
1) For the long-term safety assessment of radioactive waste disposal, therecent international concept whereby judging criteria should be based on
ensuring dose restraint values less than 300μSv/y or risk restraint valuesof 10-5/y. The Japan radiation review committee also accepts a similarconcept.
2) Each country refers to such international concept to define its individual
criteria. In Japan, the long-term scenario should be assessed for several
tens to several hundred millennia for the safety assessment referring to thecountry-specific concepts. With the considerable resultant uncertainty inmind, it is reasonable to define the risk less than 10-6/year after the control
period has elapsed.
3) Employing the criterion of 10-6/y is important from the perspective ofclarification that significant concentrations of radioactive materials, if left,
can be controlled to a level not requiring any regulation.
164) It is basically difficult to quantify the potential occurrence of long-term
scenarios. Therefore, a safety judgment in comparison with acorresponding "target" value is reasonable when an objective value isused. Consequently, the dose/probability decomposition approach should
be applied.
5) Artificial phenomena are typically handled separately to naturalprocess phenomena in international organizations and overseas. Unlikein the “interim report", this scenario has been discussed as opposed to
the rare phenomenon scenario.
6) The “goal" in the interim report should be referred to, but after issuing
the interim report, the ICRP recommendation 2007 is referenced to study
the "goal" for artificial phenomenon and rare phenomenon scenarios.

177) Substantial reasons not to require any regulations after the control
period has elapsed, or explanation based on division assessments ineach scenario to reduce the risk concerned to less than 10-6/y can besummarized as follows:a) Applicants should clarify the scientific probability for the basic designand its policy toward the disposal system, in a safety assessment basedon the fundamental scenario, whereby the risk can be reduced to lessthan 10-6/y or where the resultant impact can be lowered under 10μSv/y.
b) Applicants should demonstrate that influence can be reduced to lessthan 300μSv/y through a safety assessment for variation scenario,
considering the uncertainty involved in setting the latter.
c) Applicants should have the courage to conduct safety assessments
for rare phenomenon scenario to be considered, in order to clarify that
their influence does not exceed basically 10mSv/y and remains less thana maximum of 100mSv/y, eliminating the need for special measures onradiation protection on such occasions.

18d) Applicants should formalize the scenario for artificial phenomena anddemonstrate that the influence on peripheral individuals does not exceed
the range 1 to 10mSv/y, and the particular personal impact on those
approached does not basically exceed 10mSv/y, with 100mSv/y themaximum.
(The lower limit of 1mSv/y for the influence on peripheral people
represents a level used to judge whether a reducing measure tominimize the influence of artificial phenomenon as far as possible ispreviously applied. The upper limit of 10mSv/y is a level to judge theadequacy of the applied burial project plan, even considering theuncertainty on formalization.)e) Summarizing the above classification assessment results, theplanned burial project can be judged on the basis of the scientific scopeto transfer the duration of the control period without any regulation.

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