Important stressors in nuclear energy systems (Sustainability Assessment)

Appendix I

Important stressors in nuclear energy systems

Introduction

This appendix, including the tables, is based on Ref. [30]. It presents illustrative lists of important stressors for facilities of an NES with a water cooled reactor using UOX or MOX fuel.
Important radionuclides, chemicals and other stressors which are relevant for various facilities of an NES with a water cooled reactor using UOX or MOX fuel are presented in Sections I.2–I.9, based on current experience. However, it is recommended that, especially, in the case of an innovative design of an NES facility, this list should be revised based on the actual radionuclide and chemical inventories in the innovative NES facility, their toxicity and their environmental mobility.
In the case where calculation of the impact of stressors is necessary, it is desirable to maintain a conservative approach, and to use internationally accepted models, such as those presented in Appendix II, or available licensed national models. Model descriptions with appropriate references should be documented in the INPRO assessment report.
The main facilities of an NES with a water cooled reactor using UOX and MOX fuel are as follows: mining and milling of uranium ore, refining and conversion of uranium ore, enrichment of uranium, fabrication of nuclear fuel, power generation, reprocessing of nuclear fuel, and radioactive waste storage and disposal including waste from decommissioning. Some facilities of an NES have greater environmental impacts compared to others; all facilities have specific stressors and impacts, and therefore each facility should be considered separately. Depending on the scope of a specific Nuclear Energy System Assessment, only some of the NES facilities could be considered.
It should be mentioned that there are about 200 radionuclides which are specific to the different stages of the nuclear fuel cycle and the reactor operation and which can cause radiation impacts on the environment. In the following sections, only relatively long lived radionuclides are mentioned for each facility. However, it should be recognized that short lived progenies, which are in equilibrium with some parent radionuclides, can essentially contribute to the doses to public and biota species for many contamination scenarios. Some of these short lived radionuclides are not discussed here explicitly; however, it is implied that their contributions to doses have to be taken into account together with the impacts from their parent radionuclides in radiation impact analyses (e.g. see Appendix II).

Mining of uranium ore

The environmental impacts of mining of uranium ores may involve the disruption of land surface and water bodies, the release of radionuclides to air and water, the release of heavy metals and acids, the emission of particulates, etc. In 2011, for example, conventional uranium mining produced 47% of the world’s uranium — 18% from open pits and 29% from underground mines [55]. Non-conventional methods have also been used for uranium production, such as in situ leaching (ISL), which produced 42% of the world’s uranium in 2011. The environmental impacts of a uranium mine are potentially numerous and diverse, depending on the mining technologies used [56].
The environmental impacts of mining activities are measured using several criteria14. Individual dose is normally used as the criterion for the radiological impact on humans and non-human species. Several other criteria are used for the non-radiological environmental impact and for the radiological impact on the environment other than humans.
Usually, baseline studies are conducted before any mining activities are undertaken; these studies are to be used when establishing environmental quality objectives needed for the construction, operation, decommissioning and postdecommissioning phases. In other cases, there are pre-established air, sediment, water and groundwater quality objectives that need to be met. Social, aesthetic, economic and recreational values are met by establishing requirements to preserve parts of the affected ecosystem, e.g. fish spawning areas and the habitats of endangered species may need to be preserved for economic or social and ecological reasons.

Radionuclides of concern

Uranium ore contains natural occurring radioactive material (NORM), which includes uranium isotopes (mainly ²³⁸U) and uranium progenies (see Fig. 4) such as ²³⁰Th and ²²⁶Ra. The radioactive decay of the latter nuclides produces ²²²Rn (an inert gas), which is normally responsible for the biggest part of exposure to workers in the mines and often to the public.

FIG. 4. Chain of decay of ²³⁸U (gamma emitters not marked)[1].

The important radionuclides which have to be considered in the environmental assessment are: ²¹⁰Pb, ²¹⁰Po, ²²⁶Ra, ²²²Rn, ²²⁸Th, ²³⁰Th, ²³²Th, ²³⁴Th, ²³⁴U, ²³⁵U and ²³⁸U. The environmental impact from ²²⁷Ac (a decay product of ²³⁵U) is also recommended to be studied. As mentioned above, short lived progenies such as ²¹⁴Bi and ²¹⁴Pb (both progenies of ²²²Rn, see Fig. 4) are responsible for a large portion of the radiation impact, but are not listed here because they are always in equilibrium with ²²²Rn.
For the majority of these radionuclides (except for ²²²Rn), contamination of water with radionuclides is the most important exposure pathway. The radioactivity of water is generally stipulated by the dissolved uranium, thorium, radium and lead ions. However, an aerial pathway can be also important for several radionuclides, e.g. ²²⁶Ra, ²³⁰Th and ²³⁸U.
Some natural radionuclides, e.g. uranium, provide both radiation and chemical environmental impacts, which also have to be taken into account in the assessment.

Chemicals of concern

Water contaminated with chemicals (including NORM) is produced by dewatering of underground and open pit mines, surface water runoff from and seepage through the waste rock piles and ore stockpiles, and ISL restoration activities. In situations when the ore includes pyrites, the generation of acid requires neutralization as part of the water treatment process, if this water is planned to be discharged to the environment. Acid generation is a concern of all types of mining because the acid solubilizes and increases the mobility of heavy metals, and for uranium mining, it also mobilizes radionuclides. Utilization of explosives in mining may add some nitrites, nitrates and ammonia to the mine wastewater.

Other stressors

Examples of other stressors are:

• Temporarily committed land, e.g. for a current NES (using an open fuel cycle with light water reactors (LWRs)), this value is estimated to be about 25 ha/GW(e) for open pit mining [30];
• Permanently committed land;
• Dust, originating at exposed ore stockpiles, ore haul roads, etc.

Illustrative list of stressors

An illustrative list of stressors for evaluation of the environmental impact from uranium ore mining is presented in Table 3.

Table 3. Illustrative list of stressors for evaluation of environmental impact from uranium ore mining

Stressor	Media type	Normalized release units	Average release units
Radionuclides
Pb-210	Water*	MBq/tU or MBq/GW·a	MBq/a or MBq/d
Po-210	Water
Ra-226	Air, water
Ra-228	Air, water
Th-228	Air, water
Th-230	Air, water
Th-232	Air, water
Th-234	Air, water
U-234	Air, water
U-235	Air, water
U-238	Air, water
Rn-222	Air
Ac-227	Air, water
Chemicals
As	Water	kg/tU or kg/GW·a	kg/a or kg/d
Se	Water
Ni	Water
Nirites	Water
Nitrates	Water
Ammonia	Water
Sulphates	Water
Others
Land temporarily committed	Soil	m2/tU or m2/GW	m2 (total area)
Land permanently committed	Soil
Dust	Air	kg/tU	kg/a
Solids dissolved	Water	kg/tU	kg/a
Solids suspended	Water	kg/tU	kg/a

* Water comprises surface water as well as groundwater

Milling of uranium ore

Usually, uranium ore is processed close to the mine to limit transportation costs. The typical process for the extraction of uranium consists of crushing and grinding of the ore, followed by chemical leaching with sulphuric acid or an alkali carbonate solution. Acid leaching is the more common method; however, some mills use alkaline leaching when the ore body contains limestone or similar basic constituents, which would consume uneconomic quantities of acid. The uranium solution is purified and concentrated by ion exchange and/or solvent extraction technology. The uranium is then precipitated from solution, filtered and dried to produce a concentrate, known as yellowcake, which contains between 60% and 90% uranium by weight.
Potential sources of impacts on the environment from mill tailings comprise the following types of release: (i) escape of gaseous radon; (ii) transport of radioactive particulates by the wind; (iii) contamination of surface water and groundwater through runoff or seepage of radionuclides, heavy metals or other toxic materials; and (iv) dispersion of tailings over a wide area caused by erosion or flooding.

Radionuclides of concern

At the stage of milling, radionuclides of concern are similar to those which are considered for mining. The tailing slurry is the most significant source of radionuclides. Mill sites in dry areas give rise to effectively no liquid effluents. However, the runoff water from mills in wet climates will contain radionuclides and may need treatment before release into watercourses. The tailings are characterized by their relatively large volumes and relatively low activity concentrations of long lived natural occurring radionuclides. About 15% of the total radioactivity which was originally contained in the ore is retained in the yellowcake produced by the mill. Once shorter lived radioactive nuclides have decayed, some 70% of the radioactivity originally present in the ore is left in the tailings. The tailings contain nearly all of the naturally occurring radioactive progenies from the decay of uranium, notably ²²⁶Ra and ²³⁰Th. The presence of ²³⁰Th provides a long term source of radon emission. Radioactive airborne effluents from milling may include dusts and radon gas released into the air from ore stockpiles, crushing and grinding of ore, drying and packing of yellowcake, and the tailings retention system. The releases of dusts produced in the processing operations are reduced by ventilation extract scrubbers. Tailings may be a continuing source of radon and radioactive dust after milling operations have ceased. Thus, the list of radionuclides that have to be evaluated for milling is similar to the one for mining.

Chemicals of concern

Contaminated water is discharged from uranium mills to tailing management facilities. The contaminants include heavy metals, sulphates, chlorides, organics and ammonia. The exact mixture will depend on such factors as type of process used and ore grade, and should be evaluated separately for each case.
Airborne chemical contaminants released to the environment include combustion products (oxides of carbon, nitrogen and sulphur) from the process steam boilers and power generation, sulphuric acid fumes in small concentrations from the leach tanks and vaporized organic reagents from the solvent extraction ventilation system. In addition, from some plants where sulphuric acid is made on-site, sulphur dioxide is released to the atmosphere.

Other stressors

It is estimated that currently an average of about 4 ha of land area is required for milling of uranium ore sufficient to produce 1 GW(e) of energy in a once through fuel cycle. About 75% of this land is devoted to impoundment for the permanent disposal of mill tailings. The amount of land required is highly dependent on the grade of ore being processed. Lower grade ore milling operations normally use more land per GW(e) compared with facilities processing higher grade ore.

Illustrative list of stressors

An illustrative list of stressors for evaluation of the environmental impact from uranium ore milling is presented in Table 4.

Table 4. Illustrative list of stressors for evaluation of environmental impact from uranium ore milling

Stressor	Media type	Normalized release units	Average release units
Radionuclides
Pb-210	Water	MBq/tU or MBq/GW·a	MBq/a or MBq/d
Po-210	Water
Ra-226	Air, water
Th-228	Water
Th-230	Air, water
Th-232	Water
Th-234	Water
U-234	Water
U-235	Water
U-238	Water
Rn-222	Air
Ac-227	Water
Dust (total alpha activity)	Air
Chemicals
Heavy metals	Water	kg/tU or kg/GW·a	kg/a or kg/d
Organic	Water
Chlorides	Water
Ammonia	Water
Sulphates	Air, water
Others
Land temporarily committed	Soil	m2/tU	m2 (total area)
Land permanently committed	Soil
Dust	Air	kg/tU	kg/a
Solids dissolved	Water	kg/tU	kg/a
Solids suspended	Water	kg/tU	kg/a

Refining and conversion of uranium ore to uranium hexafluoride

Uranium ore concentrate (UOC) may consist of any of several different uranium compounds. It still contains elements other than uranium and some uranium radioactive decay products. UOC is refined to obtain higher purity uranium compounds. Two different processes — wet and dry — are used to purify UOC and convert it into a usable form. The more commonly used process, the wet process, consists of dissolving UOC in nitric acid and refining it by solvent extraction. The pure uranyl nitrate formed is then converted to uranium trioxide, which can be converted to uranium dioxide (UO₂) for natural uranium fuel, or converted progressively to uranium tetrafluoride and uranium hexafluoride (UF₆) for enrichment to produce LWR fuel

Radionuclides of concern

Emissions from uranium refining and conversion facilities are relatively minor. The only radioactive emission of significance is natural uranium, which may be emitted as dust or as a volatile reaction product of UF₆ [30]. The plants are equipped with dust collectors and scrubbers to mitigate the impacts of these emissions.
The effluents from the wet and dry processes of UF₆ production differ substantially. In the wet process, most of the impurities entering with UOC are rejected in the raffinate solution from solvent extraction, whereas in the dry process, most of the UOC impurities are contained in solid wastes from the fluorination and distillation stages. In the case when raffinate from the wet process is recycled through the uranium mill where residual uranium is recovered and the remaining waste is disposed of with the tailings, the radiological impact of the raffinate is included in the radiological impact of the milling facility. Where the raffinate is not recycled, the radiological impact is due to residual thorium and, to a lesser extent, radium.

Chemicals of concern

Atmospheric emissions from the refining and conversion processes contain greenhouse gases such as NOX. Aqueous release may contain residual tributylphosphate and heavy metals that could have a potential impact on benthic fauna. Other contaminants with potential for environmental impacts are nitrates, and, under accident conditions, ammonia and fluorides may also be released.

Other stressors

Of the temporary land commitment for a UF₆ production plant (~1.3 ha/GW(e)), approximately 10% is needed for roads, fills and plant structures [30]. Approximately 1% of land needed for a plant is permanently committed for waste burial.

Illustrative list of stressors

An illustrative list of stressors for evaluation of the environmental impact from refining and conversion is presented in Table 5.

Table 5. Illustrative list of stressors for evaluation of environmental impact from refining and conversion to uranium hexafluoride

Stressor	Media type	Normalized release units	Average release units
Radionuclides
Pb-210	Water	MBq/tU or MBq/GW·a	MBq/a or MBq/d
Po-210	Water
Ra-226	Air, water
Th-228	Air, water
Th-230	Air
Th-232	Air
Th-234	Air, water
U-234	Water
U-235	Air, water
U-238	Air, water
Chemicals
Heavy metals (have to be specified within the assessment)	Water	kg/tU or kg/GW·a	kg/a or kg/d
Fluorides	Air, water
Nitrogen oxides	Air
Sulphur oxides	Air
Carbon monoxide	Air
Volatile organic compounds	Air
Tributylphosphate	Water
Others
Land temporarily committed	Soil	m2/tU or m2/GW	m2 (total area)
Land permanently committed	Soil
Heat rejected	Air	MW(th)/tU	MW(th)/a
Solids dissolved	Water	kg/tU	kg/a
Solids suspended	Water	kg/tU	kg/a

Enrichment of uranium

LWRs normally use uranium enriched to about 4–5% in 235U. Current commercial enrichment technologies are based on gaseous diffusion or centrifugation of uranium isotopes in the form of UF₆. Reference [57] briefly explains the gas diffusion process as follows:

“In the gaseous diffusion process, gaseous UF₆ is compressed and passed over a porous membrane. Molecules of UF₆ containing the lighter isotope, uranium-235, diffuse through the membrane more rapidly than those with the heavier uranium-238 isotope; consequently, the UF6 passing the membrane has a slightly greater proportion of molecules containing uranium-235. The degree of enrichment for one membrane is minute and over a thousand successive diffusion stages are necessary to raise the proportion of uranium-235 from the naturally occurring level of 0.71 per cent to the 2–4 per cent required in the product stream, with about 0.25 per cent in a reject ‘tails’ stream.
“Each stage requires recompression of the gaseous hexafluoride. Uranium enrichment by gaseous diffusion requires large quantities of electrical energy. About 36.5 MWe-y of electricity would be needed by a gaseous diffusion plant to enrich the uranium for the generation of 1 GWe of electricity in a LWR”.

For the the uranium enrichment by centrifugation process, Ref. [57] provides the following simplified description:

“During enrichment by gas centrifugation, molecules of UF₆ containing the heavier isotope uranium-238 migrate preferentially to the wall of a rapidly rotating cylinder. There is a consequent enrichment in the lighter uranium-235 isotope in the gas near the tube axis. The separation factor is greater than in the diffusion process, and the two streams removed from the tube axis and wall require only tens of stages arranged in a cascade to produce the required percentages of uranium-235 in the product and the reject tails. High centrifugal stresses limit the size of the equipment, and many parallel cascades involving hundreds of thousands of centrifuges are required to achieve the separative capacity of a commercial enrichment plant.”

Radionuclides of concern

Emissions of radionuclides from the enrichment process are generally small and consist essentially of long lived uranium isotopes, such as ²³⁴U, ²³⁵U and ²³⁸U, together with ^234mPa and ²³⁰Th, which are the short lived decay products of ²³⁸U. The long half-life of ²³⁰Th prevents activity buildup of any other radionuclide of the ²³⁸U series. For current facilities, the radiological impacts on the public and non-human species are negligible. At the Capenhurst enrichment site in the United Kingdom, doses to the critical group members of the public are estimated to be less than 0.01 mSv per year.

Chemicals of concern

The enrichment plant itself generates small quantities of airborne fluorides and oxides of nitrogen and sulphur from the process cooling systems, process cleanup operations, on-site steam plant and auxiliary production facilities. Uranium losses in the effluents are very low. Some sludge from container cleanup operations is usually retained on-site. The depleted uranium residue from enrichment plants is normally stockpiled for possible future recovery of the remaining fissile material. The depleted uranium can be used in the future as a resource, and is therefore not considered as a release (or waste). It is noted that near current enrichment facilities, the concentrations of gaseous and liquid effluents are below the ranges for which deleterious effects have been observed.

Other stressors

Essentially, none of the land required for enrichment facilities is committed permanently. The temporary land requirement is estimated to be 0.3 ha/GW(e). Water is required for the operation of cooling towers associated with the gaseous diffusion process and also for the large amounts of electricity that need to be generated. For enrichment by gaseous diffusion, 92% of all the electricity required in a nuclear fuel cycle up to fuel fabrication is consumed in enrichment. Other enrichment techniques such as centrifuges require less than one tenth of the electricity needed for a gaseous diffusion plant.

Illustrative list of stressors

An illustrative list of stressors for evaluation of the environmental impact from an enrichment plant is presented in Table 6.

Table 6. Illustrative list of stressors for evaluation of environmental impact from an enrichment plant

Stressor	Media type	Normalized release units	Average release units
Radionuclides
Ra-226	Water	MBq/tU or MBq/GW·a	MBq/a or MBq/d
Rn-222	Air
Tc-99	Air, water
Th-234	Air
U-234	Air, water
U-235	Air, water
U-238	Air, water
Chemicals
Fluorides	Air, water	kg/tU or kg/GW·a	kg/a or kg/d
Nitrogen oxides	Air
Sulphur oxides	Air
Carbon monoxide	Air
Volatile organic compounds	Air
Tributylphosphate	Water
Others
Land temporarily committed	Soil	m2/tU or m2/GW	m2 (total area)
Land permanently committed	Soil
Dust	Air	kg/tU	kg/a
Dust (radioactive)	Air	MBq/tU	MBq/a
Solids dissolved	Water	kg/tU	kg/a
Solids suspended	Water	kg/tU	kg/a

Conversion to uranium dioxide and fuel fabrication

The required material for the fabrication of fuel for an LWR is UO₂. The UF₆ (enriched to about 4–5% in ²³⁵U) is converted to UO₂ powder, which is formed into pellets, sintered to achieve the desired density and ground to the required dimensions. Fuel pellets are loaded into tubes of zirconium alloy (zirconium–tin or zirconium–niobium), which are sealed at both ends. These fuel rods are spaced in fixed parallel arrays to form reactor fuel assemblies.

Radionuclides of concern

The radionuclides of concern are about the same as those described in Section I.5 for enrichment. The most important pathway of the population and non-human species exposure is inhalation. The doses due to liquid discharges are much less than those from airborne discharges.

Chemicals of concern

The effluent from fuel fabrication with the greatest potential environmental impact is chemical in nature. Hydrogen fluoride (HF) is potentially the most significant airborne chemical effluent from fuel fabrication. Liquid effluent from fuel manufacture contains nitrogen compounds formed from ammonia in the production of UO₂ powder and by nitric acid in the scrap recovery operations. Very small quantities of uranium are released with the effluent gases and liquids. Ammonia and nitrates are found in liquids released from the waste holding ponds.
In a dry fuel production process, the emissions of HF to the environment are very small. Nearly all of the HF produced will be removed from the off-gas by the condensing and cleaning system. The end products, liquid HF and CaCO₃/CaF₂, are suitable for industrial use. Thus, the non-radiological impacts are mitigated by the recovery and recycling of potential contaminants.

Other stressors

The temporary land requirement is estimated to be 0.1 ha/GW(e) for an NES with an LWR reactor. All of the land required for fuel fabrication can be reclaimed by conventional techniques. Care would have to be taken when decommissioning the holding ponds or lagoons. The facility requires water, most of which is used for cooling of plant processes. The water does not come into contact with uranium or process chemicals during operation. In the dry process, there is no cooling water discharge.

Illustrative list of stressors

An illustrative list of stressors for evaluation of the environmental impact from UO2 fuel fabrication is presented in Table 7.

Table 7. Illustrative list of stressors for evaluation of environmental impact from uranium dioxide fuel fabrication

Stressor	Media type	Normalized release units	Average release units
Radionuclides
Ra-226	Air	MBq/tU or MBq/GW·a	MBq/a or MBq/d
Th-234	Air
U-234	Air, water
U-235	Air, water
U-238	Air, water
Chemicals
Fluorides	Air, water	kg/tU or kg/GW·a	kg/a or kg/d
Nitrogen oxides	Air
Ammonia	Water
Others
Land temporarily committed	Soil	m2/tU or m2/GW	m2 (total area)
Land permanently committed	Soil

Mixed oxide fuel fabrication

Two processes are currently used to produce MOX fuel; these processes differ mainly at the beginning, owing to the nature of their feed materials. For the dry process, the feed materials are UO₂ (ammonium uranyl carbonate, ammonium diuranate and integrated dry route) and PuO₂ powders. The alternative wet process starts with plutonium and uranium nitrate solutions. MOX powder is prepared by co-milling or co-conversion, depending on the type of feed material.
Following the main fabrication, the steps (pelletizing, sintering, rod fabrication and assembling) are comparable with those of uranium fuel fabrication. The main difference to UO2 fuel fabrication is related to a strict alpha activity containment of the processed material in tight gloveboxes and shielding against gamma and neutron radiation.

Radionuclides of concern

Atmospheric discharges result from ventilation — for dynamic containment purposes — of production buildings and gloveboxes wherein the manufacturing process is performed. The discharges consist of aerosols of uranium/plutonium.
Very low alpha active liquids, principally from cleaning of non-contaminated or very low contaminated areas (operators, floors, etc.), are discharged into the environment after nuclear control measurements (range of activity: 1–5 kBq/m³). The balance of discharged activity is exactly maintained.
Liquid discharges increase with the throughput of a plant (these discharges mainly depend on the number of workers and the surface of the buildings); typical discharged activities are in the range 0.5–3 MBq/a.

Chemicals of concern

The chemical emissions from this process are negligible (for the dry process, there are no chemical emissions).

Other stressors

Basically, MOX fuel fabrication is a recycling activity. Plutonium is a valuable fissile material originating from the reprocessing of UO₂ spent fuel. The replacing of ²³⁵U by plutonium in LWR fuel contributes to a more efficient use of uranium resources. In most cases, for the fuel matrix, natural uranium, depleted uranium and reprocessed uranium can be used. Utilization of other resources (e.g. energy, fluids and land) is comparable with those used in UO₂ fuel fabrication. The land requirement is estimated to be 3 ha/GW(e). The dry process does not use water, and its energy requirement is estimated to be 0.3 MW/a per GW(e).

Illustrative list of stressors

An illustrative list of stressors for evaluation of the environmental impact from MOX fuel fabrication is presented in Table 8.

Table 8. Illustrative list of stressors for evaluation of environmental impact from mixed oxide fuel fabrication

Stressor	Media type	Normalized release units	Average release units
Radionuclides
Pu	Air	MBq/tU or MBq/GW·a	MBq/a or MBq/d
U-234	Air, water
U-235	Air, water
U-238	Air, water
Others
Land temporarily committed	Soil	m2/tU or m2/GW	m2 (total area)
Land permanently committed	Soil

Power generation

Radionuclides of concern

Discharges from nuclear reactors (LWRs and heavy water reactors) to the atmosphere consist mainly of the noble (inert) gases: ⁴¹Ar, ⁸⁵Kr, ^85mKr, ⁸⁸Kr, ¹³¹Xe, ¹³³Xe, ^133mXe, ¹³⁵Xe and ¹³⁸Xe. Most of these radionuclides, except for 85Kr with a half-life of 10.8 years, are short lived, and their environmental impacts are essentially limited. Other radioactive gases include ¹⁴C, ³H and ¹³¹I.
Radionuclides in liquid discharges with potential environmental impacts consist of ¹³⁴Cs, ¹³⁷Cs, ⁵¹Cr, ⁵⁸Co, ³H, ⁵⁵Fe, ⁵⁴Mn, ^110mAg and ⁶⁵Zn.
Examples of the most important radionuclides that can be discharged from nuclear power plants are briefly discussed in Ref. [29]. A UK study [58] provides detailed information on discharges of radionuclides from two water cooled reactors of latest design, namely the European pressurized reactor (EPR) (AREVA) and the AP1000 (Westinghouse) reactor. Data on estimation of releases of radionuclides from the AP1000 reactor, the EPR, the economic simplified boiling water reactor (ESBWR) (GE Hitachi) and the ACR-1000 reactor (Atomic Energy of Canada Limited), and operational data for their predecessor designs, are summarized in Ref. [59].

Chemicals of concern

Atmospheric emissions of chemicals from this process are negligible. Aqueous releases may contain sewage with organic compounds and heavy metals originating from auxiliary facilities, such as radioactive waste facilities, the condensate polishing plant, the steam generator blowdown system, the laundry, laboratories, etc. The Environment Agency provides comprehensive information on discharges of chemicals from the EPR and the AP1000 reactor in Ref. [60].

Other stressors

Other stressors are: temporary land requirement estimated to be about 50 ha for a 1.2 GW(e) nuclear power plant [61]; use and depletion of water resources and disturbance of the hydrological state of surface water and groundwater; heat discharge; and changes in the biodiversity of non-human species in the terrestrial and aquatic ecosystems in the vicinity of a facility.

Illustrative list of stressors

An illustrative list of stressors for evaluation of the environmental impact from power generation is presented in Table 9.

Table 9. Illustrative list of stressors for evaluation of environmental impact from power generation [58,60]

Stressor	Media type	Normalized release units	Average release units
Radionuclides
H-3	Air, water	MBq/tU or MBq/GW·a	MBq/a or MBq/d
C-14	Air, water
Na-24	Water
Ar-41	Air
Cr-51	Air, water
Mn-54	Water
Fe-55	Water
Co-58	Air, water
Fe-59	Water
Co-60	Air, water
Ni-63	Water
Zn-65	Water
Kr-85	Air
Kr-85m	Air
Kr-87	Air
Kr-88	Air
Sr-89	Air, water
Sr-90	Air, water
Y-91	Water
Zr-95	Air, water
Nb-95	Air, water
Tc-99m	Water
Ru-103	Air, water
Ag-110m	Air, water
Te-123	Water
Sb-124	Water
Sb-125	Water
Xe-131m	Air
I-131	Air
I-133	Air, water
Xe-133	Air
Xe-133m	Air
Cs-134	Air, water
Xe-135	Air
Xe-135m	Air
Cs-136	Water
Cs-137	Air, water
Xe-137	Air
Xe-138	Air
Ba-140	Air, water
La-140	Water
Ce-144	Air, water
Pr-144	Water
Pu-241	Water
Chemicals
Organic compound	Water	kg/tU or kg/GW·a	kg/a or kg/d
Heavy metals	Air, water
Other chemicals[60]	Air, water
Others
Land temporarily committed	Soil	m2/tU or m2/GW	m2 (total area)
Land permanently committed	Soil
Heat rejected	Air, water	MW(th)/tU or MW(th)/GW·a	MW(th)/a
Water quality solids dissolved	Water	kg/tU or kg/GW·a	kg/a
Direct damage solids suspended	Water

Reprocessing

The principal objectives of reprocessing are: (i) to recover uranium and plutonium for reuse as nuclear fuels; (ii) to separate radioactive and neutron absorbing fission products; and (iii) to convert the radioactive wastes of spent fuel reprocessing into forms that are suitable for safe storage and disposal. The difference between a once through fuel cycle of an NES and a reprocessing cycle (also called a partly closed fuel cycle) is that the reprocessing cycle makes more efficient use of the fuel through extraction of plutonium and recycling of the residual ²³⁵U.
The spent fuel is first stored to allow its thermal power and its radioactivity to decrease to the design levels of the reprocessing plant. Generally, for spent LWR fuels, the total cooling time is at least three years. The fuel cooling pond water can become slightly contaminated, primarily with ¹³⁷Cs, ⁶⁰Co, ⁵⁴Mn and ⁹⁰Sr, and needs to be decontaminated by filtration, to remove particulates, and by ion exchange, to absorb the activity present in a soluble form.
In the following, the currently used industrial (wet) process for reprocessing of spent uranium fuel (plutonium uranium redox extraction — PUREX) is described. The spent fuel is mechanically chopped into small pieces, which are dipped into a dissolver solution. The fuel is leached from the chopped cladding by boiling nitric acid. After leaching, the fuel hulls (chopped cladding) are washed and transferred to a storage. The liquid in the dissolver will contain some insoluble material, including fission product compounds from the spent fuel and both coarse and fine particulates from the cladding material, together with debris from the structural components of the fuel elements. These insoluble residues are separated by centrifugation or filtration. Both these wastes will need to be stored prior to disposal. The clear solution is analysed to determine its nuclear fuel content and is eventually adjusted for uranium–plutonium concentration and acidity prior to extraction.
The liquid from the dissolver, after the removal of solids, is passed to successive extraction systems to separate the fission product wastes from the uranium and plutonium. The products from the solvent extraction cycles are uranium and plutonium nitrates, while the bulk of the fission products are removed as high level wastes for storage prior to conditioning and ultimate disposal. The solvent of the washing process is reused. The two products of the solvent extraction process are first concentrated by evaporation. The uranyl nitrate solution can then be converted to UOX form. Subsequently, this product can be sent to another site for conversion to UF₆ and used in a re-enrichment cycle. The plutonium nitrate is converted first to plutonium oxalate by a precipitation process and subsequently to the oxide by thermal decomposition and calcination.

Radionuclides of concern

Reprocessing is one of the most important sources of radionuclide release to the environment. The radionuclides of particular interest in airborne discharges include ¹³⁷Cs, ¹⁴C, ³H and ¹²⁹I, and in liquid discharges ¹³⁷Cs, ¹⁴C, ³H, ¹²⁹I, ¹⁰⁶Ru and ⁹⁰Sr. Additionally, reprocessing of nuclear fuel results in the discharge of actinides such as ²⁴¹Am, ²³⁷Np, ²³⁹Pu, ²⁴⁰Pu and ²⁴¹Pu.

Chemicals of concern

Releases of chemicals from reprocessing facilities are negligible. For example, Ref. [30] gives an estimation of discharge of non-radiological liquid effluent from the Thorp reprocessing plant in the United Kingdom on the level that produces pollutant concentrations that are less than 1% of the relevant environmental quality standards.

Other stressors

The temporary land requirement is estimated to be 1.5 ha/GW(e). About 95% of this land use is a fenced-in buffer zone and is not disturbed. The La Hague (France) reprocessing site is a 300 ha complex and its reprocessing capacity is 1600 t/a. It also has 14 400 t of spent fuel storage pools capacity.

Illustrative list of stressors

An illustrative list of stressors for evaluation of the environmental impact from wet reprocessing of nuclear fuel is presented in Table 10.

Table 10. Illustrative list of stressors for evaluation of environmental impact from wet reprocessing of nuclear fuel

Stressor	Media type	Normalized release units	Average release units
Radionuclides
H-3	Air, water	MBq/tU or MBq/GW·a	MBq/a or MBq/d
C-14	Air, water
Na-24	Water
P-32	Air, water
Sc-46	Air, water
Si-41	Water
Cr-51	Water
Fe-55	Air, water
Co-58	Air, water
Mn-54, 56, 58	Air, water
Co-60	Air, water
Cu-64	Water
Zn-65	Air, water
As-76	Air
Kr-85	Air
Kr-85m	Air
Kr-87	Air
Zr-95	Air, water
Nb-95	Air, water
Sr-90	Air, water
Ru-106	Air, water
Sb-124	Water
I-129	Air, water
I-131	Air, water
Xe-133	Air
Xe-133m	Air
Xe-135	Air
Xe-138	Air
Cs-134	Air
Cs-137	Air, water
Ba-140	Air, water
La-140	Air, water
Ce-141	Air, water
Ce-144	Air, water
Eu-152	Water
Eu-154	Water
Pu-239	Air, water
Pu-240	Air, water
Pu-241	Air, water
Np-237	Air, water
Am-241	Air, water
Chemicals
Organic compound	Water	kg/tU or kg/GW·a	kg/a or kg/d
Heavy metals	Air, water
Others
Land temporarily committed	Soil	m2/tU or m2/GW	m2 (total area)
Land permanently committed	Soil

Storage of spent nuclear fuel away from the reactor

Compared to other nuclear facilities of an NES, rather minor stressors occur in facilities away from reactors for storage of spent nuclear fuel. No chemicals are expected to be released from such a facility. Spent fuel can be stored in dry casks or in fuel ponds. Environmental stressors from a dry storage and a wet storage essentially differ. A preliminary list of stressors for the evaluation of the environmental impact from a wet storage facility is presented in Table 11.

Table 11. Illustrative list of stressors for evaluation of environmental impact from a wet storage facility

Stressor	Media type	Normalized release units	Average release units
Radionuclides
Co-60	Air	MBq/tU or MBq/GW·a	MBq/a or MBq/d
Cs-137	Air
Others
Land temporarily committed	Soil	m2/tU or m2/GW	m2 (total area)
Land permanently committed	Soil

Disposal of radioactive waste

Releases from radioactive waste disposal facilities including facilities for direct disposal of spent nuclear fuel are discussed in a separate manual of the INPRO methodology covering the NES sustainability assessment in the area of waste management. In this current INPRO Manual on the environmental impact of stressors, the waste disposal facilities are considered in UR2 along with other NES installations contributing to the total radiotoxicity, and in UR3, which is focused on the optimization of measures to reduce environmental impacts.