nuclear cogeneration: advantages of the htr safety … · · 2015-09-30• lessons learnt from...

Nuclear cogeneration: advantages of the HTR safety concept

O. Baudrand – [email protected]

C. Pohl – TÜV [email protected]

NC2I-RNuclear Cogeneration Industrial Initiative Research and Development Coordination

1NC2I workshop - September 2015 - Brussels

Content

• Safety studies in the NC2I-R FP7 project• Lessons learnt from feedback on nuclear cogeneration• Advantages of the HTR safety concept for cogeneration• Foreseen cogeneration layouts• Recommendations for safety assessment and licensing• Recall of « generic » licensing steps• Pending options• Outline


Safety studies in the NC2I-R FP7 project

• Main questions: Which are the specific risks associated with nuclear cogeneration? Are the existing licensing procedures adapted? What could be the additional safety requirements induced by

cogeneration

• Main goals Analyse the feedback on nuclear cogeneration Identify the current status of licensing procedures in potentially

candidate countries and propose safety related milestones for the licensing of a prototype

List the specific issues and propose primary guidelines to support the licensing of a prototype cogeneration plant


Lessons learnt from feedback on nuclear cogeneration (1/5)

4

Typical layout for cogeneration with PWR reactor

NC2I workshop - September 2015 - Brussels

Barrier

Barrier

PRIMARYSECONDARY

TERTIARY

Limit of the nuclear site

Lessons learnt from feedback on nuclear cogeneration (2/5)• Review of past and existing

installations Switzerland (Beznau) Norway (Halden) Lithuania (Ignalina) Hungary (Paks) Slovakia (Bohunice) Czech Republic (Temelín) Germany (PNP project, Stade salt

works) China (project HTR-PM)

5NC2I workshop - September 2015 - BrusselsPaks

Beznau

Lessons learnt from feedback on nuclear cogeneration (3/5)• District heating, salt works, paper, pulp => production of hot

water or steam at low temp. (< 250°C) Steam bleeding from turbines + heat exchangers Primary circuit is separated from the heat grid by two « barriers » at

least (NPP steam generators & heat exchangers/boilers) Small amount of NPP thermal power diverted to cogen. (5~ 10%) No impact on NPP control

• Main safety concern: eliminate the risk of contamination of the delivered fluid Physical barriers => 3 at least (including fuel cladding) Pressure “barrier”=> Pheat grid > PNPP circuit

Control of the delivered fluid + isolation devices No specific licensing on existing installations (including recent safety

reassessments)


Lessons learnt from feedback on nuclear cogeneration (4/5)• Past projects with HTRs

Example of PNP-500 project for conversion of coal to syngas


Steam gasification of coalHydrogasification of lignite

Vessel

Powerproduction

Steam reformer inside nuclear island=> Process “integrated”into the plant

Lessons learnt from feedback on nuclear cogeneration (5/5)

• Past projects with HTRs (80’s) Paper projects Plant and process integration (take benefit of high temperature) Specific risks identified and studied:

Chemical reactions close to radiological barriers Risk of explosion Impact on plant standard parameters (pressure, coolant flow, power) Impact on plant control Potential for tritium contamination of the heat carrier fluid and the end

user product (ex. contamination of syngas.) R&D programs showed global feasibility (in the 80’s…) Licensing specificities have been discussed with safety authorities (ex.:

HTR-Modul in Germany)


Advantages of the HTR safety concept for cogeneration• Intrinsic resistance to external hazards

Naturally safe in case of loss of power supply Good mechanical stability of the core structure Confinement primarily ensured by the first barrier Simple heat removal circuit

• Low sensitivity to helium cooling transients High neutronic stability (favorable power feed-back coefficient) High thermal inertia of the core Helium properties limits the severity thermal shocks (compared with

water)

• Objective of limited releases in case of any hypothetic nuclear accident => reduced exclusion zone ( = plant site itself) safety distance imposed by the risks associated to the process


Foreseen cogeneration layouts

Heat (process steam) & electricity production for an industrial cluster

Energy storage (conversion to syngas)

G. Brinkmann –NED 1231 (1990)

Processsteam

Electricity


Condenser

Multipurpose installation: heat (steam, hot water) & electricity for an urban and industrial zone

NGNP - D. Petti

Clearly separated process => may ease the licensing

Recommendations for safety assessment and licensing (1/4)


• Principle: risks induced by the vicinity of industrial facilities shall not lessen significantly the nuclear plant safety

• Limitation of the extension of exclusion and low population zones ex.: no protection measures needed for the industry operators in the

vicinity of the plant <=> if needed, operators of industrial sites could continue to monitor processes in case of accident on the NPP

• Mastering of the impact of heat demand variations on the core and reactor structures loading


• Risks induced by cogeneration and specific industrial environment should clearly appear in the safety documents List of man induced hazards to be completed

Standard licensing procedures already provide a good frame to cope with cogeneration specific risks

Specific aspects of the standard licensing procedure need extended evaluation/documentation




• Assessment of the minimum distance between nuclear island and industrial site Consideration of generic hazards induced by the chemicals on the NPP

(plume effects, explosion, fire, toxic and corrosive effects, etc.) For hydrogen production:

consideration of chemical hazards of end products (oxygen) and intermediate products (HI, H2SO4)

Use of existing knowledge base to define standard criteria for safety distance

Consideration of potential domino effects for determining scenarios (potential for accident worsening)



• Elimination of the risk of noticeable contamination of the delivered fluid (water, steam or helium) Demonstration of the performance of the barriers Demonstration of the performance of the protection based on fluid

quality monitoring and isolation devices between nuclear circuits and circuits crossing the fence of the nuclear site

• Residual risk to be evaluated in the environmental impact study to take into account potential doses incurred by the public through the use or ingestion of process end products

Definition of contamination limits (approach depending on domestic regulations)

Recall of « generic » licensing steps (1/2)

1) Set up of the safety objectives Working groups with Safety Authorities / Commissions

of experts First review by TSO

2) PSAR Risk analysis Definitions of design options Design criteria

ValidationSafety approachFeasibility

PreliminarySafetydemonstration

Interface withindustrial risks

Cogen. 15NC2I workshop - September 2015 - Brussels

Main parameters impacted by the

cogen. applications

Recall of « generic » licensing steps (2/2)

1) Site selection2) Public inquiry: Environmental impact study, risk

analysis (extract from Preliminary Safety Report), summary of advantages for the local region Review by local Authorities / security authorities Review by independent associations, etc.

3) SAR4) Construction and operation license: Safety

Report + Emergency Planning Safety analysis of the SAR, EP report Feedback of commissioning tests

SafetydemonstrationSecurity

Definition of specific external

hazards

Specific safetystudies

Interface withindustry EPs

Cogen. 16NC2I workshop - September 2015 - Brussels

Legal aspectsPublic acceptanceSite validation

Pending safety options

• Mastering of tritium permeation to secondary circuit => foreseen technical solutions to be validated

Note : objective would be that the tritium concentration in process steam remains below an “approval free” limit.

• Definition of an envelope safety case involving radioactive releases (ex.: depressurisation accident) Already covered as part of the standard licensing procedures Depends on confinement strategy and design


Outline

• HTR safety concept would certainly ease the licensing of an HTR based cogeneration plant

• Depending on its design options, HTR has a potential for very low radioactive releases in case of accident no interference with safety distance (determined against external

hazards)

No significant increase of the risk in the industrial site area or local public (district heating)

• Current licensing procedures are convenient for nuclear cogeneration with HTR provided some adaptations: consistency of nuclear and conventional emergency planning Regulatory basis for assessment of delivered fluid safety


Acknowledgement

• Special thanks to Christoph Pohl (TÜV Rheinland) Attila Kiss (BME) Raimondas Pabarcius (LEI) Gerd Brinkmann (AREVA-D) Karl Verfondern (FZJ) Lukasz Koszuk (NCBJ) Karin Stehlik (Čez)


nuclear cogeneration: advantages of the htr safety … · · 2015-09-30• lessons learnt from...

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