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Hot Resin Supercompaction - the development through the years Henning Fehrmann, Mannheim/ Germany

Address of the Author:Dipl.-Ing. Henning Fehrmann

Westinghouse Electric Germany GmbHDudenstr. 6

68167 Mannheim

1. Introduction

Ion exchange resins are widely used in op-erational systems of NPPs or other nuclear applications for water make up. Ion ex-change is an effective treatment method for radioactive aqueous liquids. Spent ion exchange resins are considered to be a challenging waste stream that requires spe-cial attention before and during the condi-tioning to meet the waste acceptance crite-ria. Several countries have different con-cepts concerning nuclear waste disposal which are technically as well as politically driven. These concepts have a strong im-pact on the waste acceptance criteria and defining waste form properties like free liq-uids, leaching resistance, form stability etc.

In those countries where these accept-ance criteria exist appropriate treatment options can be identified. But in some cas-es the requirements change over time which puts the waste generator in a diffi-cult situation.

When choosing the waste treatment method the waste acceptance criteria, the site boundary conditions as well as the spent resins technical parameters like physical, chemical and radiological char-acteristics must be taken into account. Ad-ditionally the waste treatment method should be flexible covering regulatory un-certainties.

Basically, 3 main methods for the treat-ment of spent organic ion exchange resins are available:•Direct immobilization with cement, bi-

tumen, polymer or High Integrity Con-tainer (HIC)

•Oxidation of resins by incineration, plasma or wet oxidation

•Removal of all structural water in the resins by thermal treatment

The waste volume is increased by immobi-lization with cement, bitumen, polymer in-

side a HIC, which is a disadvantage in re-gards to the limited space of interim stor-ages and repositories. Oxidation of resins by incineration, plasma or wet oxidation provide a high volume reduction, but also require special off gas treatment, high in-vestment costs and are not licensed in all countries for spent ion exchange resins treatment. The residuals of the oxidation treatment can show very high specific ac-tivities and dose rates.

A thermal treatment process like Hot Resin Supercompaction (HRSC) combines the advantages:•Volume reduction of spent resins•Generation of waste forms which meet

acceptance criteria•Generation of waste forms which are

flexible in handling •Simple off gas treatment and less sec-

ondary wasteThe nuclear industry is interested in reduc-ing the waste volume because in an envi-ronment without final disposal options and limited interim storage capacity, vol-ume reduction is an essential criterion to control the overall costs.

Beside the treatment of spent ion ex-change resins during the power operation of a NPP, there is a need of spent resin treat-ment in the post operation phase in order to remove all nuclear inventories including waste and fuel. Thus the volume reduction criterion applies for the power operation as well as during the post operation phase.

2. Hot Resin Supercompaction process and its development through the years

The HRSC is a thermal spent resin treat-ment process which has been developed by Hansa Project Anlagentechnik (now West-inghouse) in the late 1980’s as a conclusion of the so called TN-Scandal” (1).

The first commercial nuclear applica-tion for powder resin treatment was at NPP Philippsburg (Germany) in the mid 1990’s.

In 2009 a new HRSC system was in-stalled at NPP Tihange (PWR – Belgium) to treat spent bead resins.

In 2013 another system was installed at the SRTF (Site radwaste treatment facility) of the AP1000 NPPs in Sanmen (PWR – China) for treating spent bead resins.

In March 2014 HRSC NextGen develop-ment program was finalized to improve the overall volume reduction of bead resin treatment.

All plants and systems mentioned repre-sent a milestone in the HRSC development. The above mentioned plants differ from each other in details and are optimized re-garding spent resin treatment, volume re-duction and meeting waste acceptance cri-teria.

With the experience gained in these projects, the HRSC process and equipment can be tailored to customer needs.

In the following the different systems are described.

2.1 General process description of Hot Resin Supercompaction

The HRSC process itself is simple, it com-bines drying with a robust mechanical compaction. It does not require any chemi-cal adjustments to overcome negative effects (e.g. cementation) or any sophisti-cated process control to meet certain re-quirements (e.g. pH adjustment, specific incineration temperature, or dosing oxida-tion agents for wet oxidation).In general the process flow is:•Dosing dewatered resins into the dryer

vessel (or dosing resin suspension and dewatering inside the dryer vessel)

•Drying of resins (under atmospheric pressure or vacuum)

•Dosing into compactable drum •Supercompaction

The dosing of resins is conducted by vol-ume into the dryer vessel directly or by predosed volumes (e.g. 200 l drums or a separate dosing tank). The dewatering is conducted by means of draining the wa-ter by gravity, a pump or a centrifugal sys-tem. Normally the dryer vessel is filled with one batch resulting in 2 compacted pellets.

The dryer vessel is a conical vessel (in the following called conical dryer) which is heated by thermal oil. Thus the resins are contact dried. The drying process can be conducted under normal pressure as well as under vacuum.

The dosing of the dried resin into the compactable drum is carried out by vol-ume.

The compactable drum with the hot res-ins is capped and transferred to the Super-compactor where the drum is compacted in the hot state. The compaction force is adjusted according to the type of resins. The final pellet is put into an overpack of suitable size meeting the country specific requirements.

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Westinghouse provides comprehensive integrated services and

solutions to the decommissioning and dismantling (D&D) and

waste management industries. We have extensive experience in

the dismantling of nuclear installations from uranium mill plants

to nuclear power plants. We provide state-of-the-art solutions for

spent fuel services and for the treatment and handling of radioactive

waste. Westinghouse offers proven solutions for the interim storage

and final disposal of low-, intermediate- and high-level waste.

Our dedication to a cleaner environment extends to servicing

existing nuclear power plants and managing by-products in an

environmentally responsible manner.

For more information, visit us at www.westinghousenuclear.com

WESTINGHOUSE DECOMMISSIONINGAND REMEDIATION SERVICES

GLOBAL PROJECT EXPERIENCEADVANCED TECHNOLOGY

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2.2 Hot Resin Supercompaction – first application in NPP Philippsburg (Germany)

The HRSC process with its first application at NPP Philippsburg (KKP) gives a good in-sight on the general principle how the pro-cess works (see Figure 1). The process is described in general in chapter 2.1, more details can be found in (1). The following generations of HRSC stick to this general process, but do have some adaptions.

NPP Philippsburg has a special situation as 2 different types of reactors are located on the site, which generate 2 different types of spent resins:•KKP 1 (Boiling water reactor) – mainly

powdered resins (from condensate pol-ishing)

•KKP 2 (Pressurized water reactor) – mainly bead resins.

Approx. 23 m3/a of powdered resins and approx. 3 m3/a of bead resins were gener-ated during the normal operation phase (1). The HRSC process as realized in NPP Philippsburg is shown on Figure 1. The spent resins are dewatered with centrifuge (separator and decanter) system and are filled into 200 l drums. These 200 l drums contain a specific volume of resins and are used to dose the needed amount of dewa-tered powdered and bead resins into the conical dryer. NPP Philippsburg uses a spe-cific mixture of powder and bead resins to achieve an optimal volume reduction. The conical dryer operates under atmospheric pressure. The end of the drying process is determined by product temperature. The compaction force applied is 1,000 t (2) which is more than 30 MPa. This means that the product produced meets the re-quirements for the repository Konrad for waste product group 04 (3).

The final pellets after compaction are placed into 200 l drums, but so far no grouting is done. This offers flexibility for possible changing requirements on the fi-nal waste form. The HRSC process produc-es repository qualified waste forms, reduc-es interim storage volume, but still leaves the option for repacking if future require-ments change. Either the pellets can be re-moved from the 200 l drum or the 200 l drum itself can be placed into a final dis-posal container.

For measuring the volume reduction of the process 2 different scenarios have to be taken into account. The volume reduction factor (VRF) of the HRSC process itself and the VRF (final) – the pellets incl. the final package. The VRF of the HRSC process is reported with up to 4 (1).Various authors use different approaches to calculate the volume of the final package. In the case of NPP Philippsburg the effective storage vol-ume of a 200 l overpack drum is given with 270 l (1). The effective volume reduction

for the interim storage is given with ap-prox. 25 to 30 %, which results in a VRF (final) ≈ 1.33 to 1.43.

Other authors (2) use the filling volume of the overpack drum itself to calculate the VRF (final). Applying this calculation meth-od for NPP Philippsburg the VRF (final) would be approx. 1.8 to 1.9. In the following the method described in (2) is used to calcu-late the VRF (final) because drum dimen-sions and storage concepts can vary.

2.3 Hot Resin Supercompaction for PWR application – NPP Tihange (Belgium)

The system of HRSC installed at NPP Tihan-ge (PWR) has been modified for treating bead resins exclusively. This required some adaption especially in terms of integration of the system into the plant. The filling of the conical dryer in Tihange is carried out by means of direct transfer from reservoirs into the conical dryer. The dewatering is done simultaneously to the filling by a sieve and a pump. The drying is carried out in the conical dryer under vacuum instead of atmospheric pressure. But in general the process principal is the same as described in chapter 2.1.

The compaction of bead resins only is the major difference compared to the pro-cess in NPP Philippsburg. The elastic be-havior of the bead resins and the ball-shaped particle form restrain the resins forming a stable block. As a result the bead resins show a significant spring back effect which can, in the worst case, damage the compactable drum. It was found that an additive can be applied to minimize the spring back effect. Therefore various tests were conducted to find an optimal additive and its concentration. Nevertheless an al-

ternative method by applying reduced compaction force without an additive was tested successfully. As an additional safety factor to ensure a contamination free pel-let a “double drum” system was developed. The double drum works with placing the compactable drum into a slightly larger outer drum. With the double drum, the ad-ditive solution as well as the additive free, low compression force solution is fea-sible. At the end the additive free solu-tion was selected due to slightly better vol-ume reduction of the final pellet. In Figure 2 and Figure 3: the double drum before and after compaction is shown.

Compared to NPP Philippsburg the com-pacted final pellets are directly put into a 400 l drum with internal shielding. After the pellet has cooled down, the 400 l drum is filled with cement.

The resulting VRF (final) is calculated in (2) with 0.95 using the filling volume of a 400 l drum.

2.4 Hot Resin Supercompaction for the AP1000® Sanmen (China)

Compared to the HRSC system as de-scribed for NPP Philippsburg and Tihange, Westinghouse engineered a fully integrated handling and treatment system for the SRTF Sanmen. The HRSC system in the SRTF of AP1000 is fully integrated into the overall treatment concept and waste flow. The HRSC is part of the so called Spent Resin Processing System (RES).

The RES consists of reception systems like tanks and fill heads, a conical dryer, the Supercompactor, Grouting and Cementa-tion Station as well as automatic Transport Units and finally the Radiation Monitoring Station for data tracking of the 200 l drum before entering the local storage.

Fig. 1. HRSC at NPP Philippsburg.

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Spent ion exchange resins (bead resins) from the AP1000 are transported by a transport tank to the SRTF. The transport tank is coupled automatically without manual operator interaction and spent res-ins are sluiced to a buffering tank. From the buffering tank the resins are flushed into a dosing tank and dewatered. The pre-cise amount of dewatered resins is trans-ferred directly from the dosing tank into the conical dryer (see Figure 4).

The resins are dried in the conical dryer under vacuum until all moisture has es-caped. The end of the drying process is de-termined by vapor pressure and material temperature. During the drying process the resins shrink up to 60 %. To be in compli-ance with the contractual and repository requirements an additive is used to apply a compaction force of ≥30 MPa. The experi-ences gained from the Tihange equipment in regard to the additive are used. The ad-ditive minimizes the elastic properties of the bead resins and forms a solid block. With additive dosing and the minimum compaction force of 30 MPa a volume re-duction of approx. 2 is achievable.

Similar to the Tihange process the re-sulting resin pellet is grouted/immobilized with cement, but instead of using a 400 l drum a 200 l drum is used. This optimizes the overall VRF(final) compared to the ap-plication at Tihange site from approx. 0.95 to approx. 1.6. This optimization is possible due to the missing requirement of using a shielded 400 l drum as described in (2).

3. Discussion of volume reduction factor

When comparing the 3 different HRSC in-stallations it becomes obvious that there are differences in VRF. The volume reduction is affected by several boundary conditions:•Repository requirements •Type of resins, bead or powder resins •Pretreatment of resins

•Process conditionsFirst of all the repository requirements have a significant impact on the volume re-duction factor. Comparing the VRF (final) of Tihange and SRTF where the VRF (HR-SC) is nearly the same (approx. 2) the VRF (final) shows significant difference of 0.95 (Tihange) to approx. 1.6 for the SRTF. This difference is caused by the different used overpack designs. The VRF(final) at NPP Philipsburg is superior compared to Tihan-ge and SRTF due to the different physical properties of the spent resins.

Powdered resins or a mixture of bead and powder have better volume reduction properties as bead resins itself. This is due to the fact that bead resins have a round shape so they do not adhere after compac-

tion so the void space between the beads does not change significantly. The void ratio for bead resins ranges between 0.2 for “hexagonal close packing”, 0.48 for “simple cubic packing” and 0.35 for “random close packing” (4). When the resins dry, they shrink and lose weight but their shape does not change. This results in nearly un-changed void ratio. In the case of Tihange this void space remains unfilled whereas in the case of SRTF the void space is filled with an additive. In the case of HRSC in NPP Philippsburg where powdered and bead res-ins are used, the void ratio in the compact-ed pellet is reduced as the powder particles can adhere together and voids of the bead resins are filled. The addition of an addi-tive, as done for the SRTF HRSC process,

Fig. 2. Double drum before compaction. Fig. 3. Double drum after compaction.

Fig. 4. Model of conical dryer (left), temporary installation during factory acceptance test.

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follows the same idea as the Philippsburg process. But adding inactive additive results in less waste loading, increases the volume and therefore reduces the overall VRF.

Reducing the void space in the com-pacted resins was the simplest solution to improve the volume reduction of the HRSC process for bead resins. But to maximize the volume reduction it was necessary to develop a suitable pretreatment of resins and optimize the overall process.

4. Hot Resin Supercompaction NextGen

It was obvious that the VRF of the HRSC can be optimized for bead resins by removing the voids between the beads. A HRSC NextGen development program was initiated where the VRF of the HRSC is improved by grinding bead resins to powder, optimizing the com-paction process as well as the drum design.

4.1 Grinding bead resins to powder and optimize VRF

For grinding the resin beads to powder sev-eral grinding technologies have been as-sessed and tested. Dry grinding was exclud-ed due to cleaning issues. A wet grinding system was chosen which is designed as add-on equipment for the HRSC. The sys-tem is installed on a skid as shown in Fig-ure 5. The design itself is compact and fits in 2 20 ft. containers. The grinding process works as follows:•Dosing and adjustment of water/resin

ratio•Pre-crushing•Grinding and transferring to the drying

equipmentThis process is designed as a single pas-sage, means resins/resin slurry is not cir-culated but directly transferred to the dry-ing equipment after grinding.

Intensive research was conducted to find the optimal settings for the grinding process as well as for the later compaction process. With the single passage design it is possible to dose resins of different particle sizes into the dryer to produce different particle sizes distribution in the mixture to improve com-paction properties. In Figure 6 the graph shows the test results of various powder compositions, compaction forces and the re-sulting VRF’s. It demonstrates that the com-pression force has a significant impact on the VRF, but additionally the powder composi-tion can be optimized to get the best result. These results were derived from testing the resin material itself. In order to take advan-tage from these improved VRF’s results at 2,000 t compaction force, it was mandatory that the compactable drum can resist high force without damage. This validation and verification was done as described in chapter

4.2 by means of simulation and real tests. Various compaction runs at approx. 2,000 t using the improved compactable drum de-sign (filled with a mixture of powdered res-ins) have been conducted successfully. Nei-ther the compactable drum showed resin powder contamination on the outside nor damages were visible.

With the optimized setting it was possible to achieve a VRF (HRSC) of up to 3. This would result in a VRF (final) ≈ 2.3 using a 200 l drum as overpack and VRF (final) ≈ 1.6 using a 400 l overpack.

4.2 Improvement of compactable drum design

The solution of a double drum system as used at NPP Tihange works well retaining the resins in the pellet. From the handling and cost perspective 2 drums are more complex as well as more expensive. For

that reason intensive research and testing was conducted to develop a single drum design which ensures a contamination free pellet after compaction. At first, various simulation runs were conducted to find the optimal solution. In Figure 7 and Figure 8 the simulation results are compared to the actual results. The results revealed that the risk of a drum failure is raised when com-pacting bead resins with high pressure. This has been proven by real test situation when using to high compaction force. As a conclusion the simulation works reliable to predict the drum behavior and allows us-ing it for optimization.

The drum shapes and the material have been modified to improve the compactable drum performance. The simulation results for the optimized shape and material in Fig-ure 9 demonstrate good correlation to the real test results shown in Figure 10. The new drum design has been simulated and tested successfully with resins for 1,000 t as well as for 2,000 t compaction force. This new drum design is used for the SRTF Sanmen.

This new drum design is a real step for-ward because before that development, powder resin compaction was limited to 1,000 t compaction force. Now it is possi-ble to use the full power of the supercom-pactor reaching maximum volume reduc-tion as well as eliminating the need for a double drum.

5. Areas of application of HRSC into post operation

All NPP’s have spent resins on site once they enter the post operation phase and start preparation for decommissioning. These spent resins came from the power operation phase and very often from full system decontamination which is usually carried out before starting decommission-ing. In order to remove all nuclear invento-ry incl. waste and fuel, these wastes have to

Fig. 5. Modular grinding equipment.

Fig. 6. VRF vs. powder composition.

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be treated on or offsite. Some plants have waste treatment equipment available, some do not.

In each case it is worth to reconsider the existing waste treatment system if it is suit-able to support actual waste treatment tasks as well as future tasks during decom-missioning. An integrated waste treatment approach for post operation as well as the decommissioning and dismantling phase can offer cost benefits.

Waste treatment tasks in the post oper-ation phase could already be different to the tasks performed in the normal power operation. Especially spent resins coming from full system decontamination can con-tain chemicals and dissolved metals which are different from the usual waste coming from the power operation. In case of ce-mentation, as the preferred waste treat-ment method, changing waste composi-tion could lead to significant challenges due to the fact that the resins can interact with the cement. To be sure cementation works for this new spent resin waste stream testing and qualification is recom-mended.

The HRSC process is robust towards changing chemical composition of spent resins and does not require additional qualification. Furthermore the waste prod-uct is minimized in volume, flexible in handling and packing. Looking into the German requirement, the waste product from HRSC is qualified according to (3) when applying at least 30 MPa compaction force, but still flexible for repacking if re-quired. Grouting/Immobilization with ce-ment can be done without cost intensive cement recipe development efforts. If nec-essary the HRSC waste product can be ad-justed to be packed in MOSAIK contain-ers. With that, the VRF (final) could be sig-nificantly enhanced so more treated spent resins would fit into the MOSAIK container.

The HRSC waste product can be re-trieved from every container, repacked ac-cording to future requirements or reclassi-fied in regards to activity. Especially in countries where no final repository site is  available or regulatory requirements can change a flexible waste product with minimized volume can offer benefits in the

post operational and decommissioning phase.

In addition to the flexible handling of waste product itself the Supercompactor (needed for the HRSC) can be used for oth-er waste streams during post operation and decommissioning phase. This multipur-pose property and flexibility of the HRSC process and the Supercompactor fits well into the Westinghouse adapted products for the decommissioning market.

6. Summary

The HRSC process looks back into a history of nearly twenty years. The process was first used successfully for powdered and minor amount of bead resins at NPP Philippsburg. In NPP Philippsburg more than 3,800 pellets have been produced since 1995.

The adaption of the HRSC to the bead resins coming from a PWR was successful-ly. Currently the HRSC in Tihange is await-ing the demonstration test with the Bel-gian authorities.

Fig. 7. Simulation results old drum design. Fig. 8. Actual test results old drum design.

Fig. 9. Simulation results new drum design. Fig. 10. Actual test results new drum design.

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The installation of the HRSC in SRTF Sanmen is under commissioning and the first run is expected for 2014. In SRTF San-men the new improved drum design will be used. The development of HRSC Next-Gen including the Resin Grinding and the improved drum design has proved its per-formance in full scale testing successful-ly. With the HRSC NextGen the achieva-ble VRF is improved up to 40 %. Each in-stalled HRSC system can be upgraded to HRSC NextGen. This provides a great flex-ibility so each user can chose the configu-ration of the HRSC process according to his targets and requirements. The HRSC

process represents an effective waste treatment technology which can deal with the challenges of volume constraints, po-litical uncertainties and changing requi-rements. The HRSC process is also a good choice in the post operation and de-com-missioning phase as it consists of multi-purpose components like the Supercom-pactor.

7. List of references

1. Schenke, J. and Roth, Andreas: Experiences from over 10 years operation of the Resin Hot High Force Compaction as well as new

applications for PWRs. Dresden : s.n., 2007. KONTEC ‘07 Conference Transcript.

2. Johan Braet, David Charpentier, Baudouin Centner, Serge Vanderperre. Radioactive Spent Ion-Exchange Resins Conditioning by the Hot Supercompaction Process at Tihange NPP – Early Experience. Phoenix, Arizona, USA : s.n., 2012. WM2012 Conference. Co-mapct 12200.

3. Brennecke, Dr. Peter: Anforderungen an end-zulagernde radioaktive Abfälle (Endlage-rungsbedingungen Stand: Oktober 2010) – Endlager Konrad –. s.l.  : Bundesamt für Strahlenschutz – Fachbereich Sicherheit nuk-learer Entsorgung, 2010. SE-IB-29/08-REV-1.

4. A. Alan Moghissi, Herschel W. Godbee, Sue A. Hobart. Radioactive waste technology. [ed.] Amer Society of Mechanical. 1986. p. 705.

Decommissioning and Waste Management

_____________________________________

Enhanced Productivity in Reactor Decommissioning and Waste ManagementKarl Wasinger, Offenbach/Germany

Address of the Author:Karl Wasinger

Areva GmbHKaiserleistraße 2963067 Offenbach

1. Introduction

As for any industrial facility, the service live of nuclear power plants, fuel cycle facili-ties, research and test reactors ends. Deci-sion for decommissioning such facilities may be motivated by technical, economical or political reasons or a combination of it. Front-end and back-end facilities are shut down to be replaced by new, more efficient plants, designed in compliance with up to date safety standards and regulatory re-quirements. As of today, a considerable number of research reactors, fuel cycle fa-cilities and power reactors have been com-pletely decommissioned. Others have al-ready been shut down for decommission-ing either because further operation results economically unreasonable or following a change in the national energy generation

plan such as decided by the German Feder-al Government in 2011 and determined by the 13th Amendment of the German Atomic Energy Act (Atomgesetz – AtG).

However, the end point of such facilities’ lifetime is achieved, when the facility is fi-nally removed from regulatory control and the site becomes available for further eco-nomical utilization. This process is com-monly known as decommissioning and in-volves detailed planning of all related activ-ities, radiological characterization, disman-tling, decontamination, clean-up of the site including treatment and packaging of radi-oactive and/or contaminated material not released for unrestricted recycling or indus-trial disposal. Decommissioning requires adequate funding and suitable measures to ensure safety while addressing stakehold-ers’ requirements on occupational health, environment, economy, human resources management and the socioeconomic effects to the community and the region.

One important aspect in successful management of decommissioning projects and dismantling operation relates to the economical impact of the endeavor, pri-marily depending on the selected strategy

and, as from commencement of disman-tling, on total duration until the end point is achieved. Experience gained by Areva in executing numerous decommissioning projects during past 2 decades shows that time injury free execution and optimum productivity turns out crucial to project cost. Areva develops and implements spe-cific “performance improvement plans” for each of its projects which follow the phi-losophy of operational excellence based on Lean Manufacturing principles. Means and methods applied in implementation of these plans and improvements achieved are described and examples are given on the way Areva offers to support owners to benefit from this experience.

2. Strategic Approach

Determining the right strategic approach to decommissioning is crucial for optimi-zation of works and the resulting econom-ic burden. The variety of constraints and challenges involved with decommissioning requires a systematic approach to define the strategy to be adopted for each individ-ual case for which IAEA (International Atomic Energy Agency) has published relat-ed guidance on Policies and Strategies for the Decommissioning of Nuclear and Radi-ological Facilities [1].

Strategies which may be adopted for de-commissioning disused nuclear facilities typically include immediate dismantling or deferred dismantling1. A third option de-nominated as entombment is described as to enclose the radioactive inventory of a disused facility for long time until it is de-cayed to such level permitting unrestricted

___________1 For more detailed definition see [1]