Gas Turbine - Modular Helium Reactor Design & Safety Approach

Presented to Nuclear Regulatory Commission Staff

24 September 2002

Laurence L Parme Manager, Reactor Safety & Licensing

General Atomics

1 of 20 24 Sept 02 4.GENERAL ATOMICS

Attachment 3

U.S. AND EUROPEAN TECHNOLOGY BASES FOR MODULAR HIGH TEMPERATURE REACTORS

BROAD FOUNDATION OF HELIUM REACTOR TECHNOLOGY

2 of 20 24 Sept 02

Steam Cycle Gas Turbine Cycle

+ GENERAL ATOMICS

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3D Arrangement of Plant

Reactor equipment Positioner Refueling Reactor maintenance and machine auxiliary repair building building

Crane central room * 600 MW(t)- 285 MW(e)

Electrical-technical buildin 3 vessels primary

coolant system

Power conversion system integrated in single vessel

OREN* Below grade housing

• Continuously conversion cavity operating, natural syte cooling

msystem circulating, air cooled reactor cavity cooling

Reactor

Reactor building + GENERAL ATOMICS

GT -MHR COMB INE S ADVANCED REACTOR

WITH SINGLE SHAFT

GAS TURBINE BASED POWER

CON VERS ION SYSTEM

+ GENERAL ATOMICS

5 of 20 24 Sept 02 I

I

11Z

Annular Core Limits Maximum Accident Fuel Temperature

REPLACEABLE CENTRAL &SIDE REFLECT OR•.

36 X OPERATING CONT ROL RODS

CORE BARRE LE

ACTIVE CORE -.

102 COLUMNS 10OBLOCKS HIGH

PERMANENT S IDE REFLECTOýd

BORATED PINS (1YP)

REFUELING PENETRATIONS

S ART-UP L)OLRODS

Fuel Elements

.ANNULAR CORE USES EXISTING TECHNOLOGY

L-199(10) 6 of 20 24 Sept 02

6-9-95+ GENERAL ATOMICS

I

I

GT-MHR Power Conversion Uses High Efficiency Brayton Cycle

LOW PRESSURE COMPRESSOR

7 of 20 24 Sept 02L-271 (12a) 8-14-94 A-36

+ GENERAL ATOMICS

:

HEM ]

Modular Gas-Reactor Safety Approach Differs From Earlier Reactor Designs

* GT-MHR safety emphasizes

- Keeping radionuclides at source during all accidents - Minimizing reliance on active/complex engineered systems

• Passive safety design is based on reoptimized application of established HTGR technology - High temperature fuel and core - Single phase, chemically & neutronically inert coolant - Specially tailored core power and geometry

Conservative, robust design with defense-in

depth remain foundations of safety

8 of 20 24 Sept 02 +.GENERAL ATOMICS

Key to GT-MHR Safety Multiple Ceramic Fuel Coatings

Pyrolytic Carbon Silicon Carbide

-- Porous Carbon Buffer

- Uranium Oxycarbide

TRISO Coated fuel particles (left) are formed into fuel compacts (center) and inserted into graphite fuel elements (right).

PARTICLES COMPACTS FUEL ELEMENTS

+ GENERAL ATOMICSL-029(5) 9 of 20 24 Sept 02

4-14-94

III II III II III

III 'I III II III

Coated ParticlesEven at Very High

Remain Intact Temperatures

� 4 � -- '-'�r :---.- - -

2600FUEL TEMPERATURE (°C)

10 of 20 24 Sept 02 + GENERAL ATOMICS

1.0

0.8z 0

LU LL uJ -I

IUL

0.6

0.4

0.2

0L1 1000

L-266(1) 7-28-94 W-9

Safety Focused on Assured Fuel Particle Integrity

* Fission (heat generation) shut down assured by - Large negative temperature coefficient 1 Passive - Large temperature margins JShutdown

• Heat removal assured by - Low power density & module thermal - Annular core and high LID ratio

Passive Cooling

* Chemical attack limited by - Absence of high pressure water sources - Nuclear graphite, core geometry, and limited air availability

11 of 20 24 Sept 02 4.GENERAL ATOMICS

Multiple Means Available to Control Heat Generation

* Control rods capable of terminating fission

* Reserve shutdown system provides independent and diverse means of terminating fission

• Large negative temperature coefficient and large core temperature margins can provide passive shutdown for anticipated transient without scram

12 of 20 24 Sept 02 GENERAL A TOMICS

Heat Generation Stops During Loss of Cooling Without Rod Motion

TIME (DAYS) 2

49

TIME (HOURS)

+ GENERAL ATOMICS13 of 20 24 Sept 02

0 I 3I I I I

NO REACTOR SCRAM Pressurized Loss of Forced Cooling 350 MW(t) MHTGR

450

r~n i-,

S40

30 CD

20 C30

10 CL

0' -1

Power controlled by negative temperature coefficient

REACTOR RECRITICAL

6 0 16 32 64 s0 96 112

I

I

'4ýý

Core Temperatures Maintained at Safe Levels With and Without Reactor Trip

50 100

TIME (HOURS)

+ GENERAL ATOMICS14 of 20 24 Sept 02

2000

0 LuJ

R 1500

LUJ I-L

1000

5000

Multiple Means Available to Remove Core Heat

Power conversion loop provides normal heat rejection - Normal operation

- Preferred mode of shutdown cooling - Operates with pressurized or depressurized coolant

* Shutdown cooling system offers alternative means of forced circulation heat removal

* Passive heat rejection to Reactor Cavity Cooling assures safety for all events

• Passive heat rejection to the surroundings limits maximum consequences

2GENERAL ATOMICS 15 of 20 24 Sept 02+

Passive Heat Removal Changes Reactor Design Philosophy

LARGE HTGRs r3000 MW(tUl

.O FSV [842 MW(T)]

PEACH BOTTOM [115 MW(T)]

1967 1973 1980

RADIONUCLIDE RETENTION IN

FIIEL PARTICLES

0 C.

w

UJ CL 2

I-w

0 I

z 0 Z5

C.) M

1985

CHRONOLOGY

SIZED AND CONFIGURED TO WITHSTAND EVEN A SEVERE ACCIDENT

1-222(1) 161of 20 24 Sept 02 1-12-96

+ GENERAL ATOMICS

4000

MHR

3000

2000

1000

4000

3000

1000

I

jw.At3'VP II'Viiii ,

.L. I P%" I i%06-L-17I

,///////2000

II I I

Temperature Gradient Provides Driving Force for Residual Heat Removal

600 MW/102 Column- I -I I

-------Central

Central Reflector

I I I I I

"--- Mm''

Core Barrel I

RSR RSR IPSR

0 10 20 30 40 50 60 70 80 90 100 110120130

Radius (inches)

3500

3000

2500 0 4-J

2000 CL

1500 E

1000

140 150

+ GENERAL ATOMICS17 of 20 24 Sept 02

2000

1800

1600

1400

1200

1000

800

600

0

a) 3

4-'

3

a) E a) F-

400

200

mr-

5 ff 2 -JI _I. 91500

a am

I Vessel

FUEL TEMPERATURES REMAIN BELOW DESIGN LIMITS DURING LOSS OF COOLING EVENTS

2

Time After Initiation (Days)

passive design ensures fuel remains below 1600 0C

18 of 20 24 Sept 02L-340(3) 11-16-94

+GENERAL ATOMICS

1800

1600

1400

1200

1000

E-4 0)

o~ a)

800

6000

Risk From Water Ingress Significantly Reduced in GT-MHR

* No steam generators therefore no high pressure steam source

• Precooler and intercooler water pressure below primary coolant operating pressure

* Low water pressure in heat exchangers greatly reduces potential for water ingress during normal operation

* Liquid water transport to core under depressurized conditions limited by geometry

19 of 20 24 Sept 02 4.GENERAL ATOMICS

Inherent and Passive Features Control Air Attack

"* Non-reacting coolant (helium)

"* Embedded ceramic coated particles

"* Air ingress limited (requires failure of Class 1 vessels)

"• Below grade, closed reactor silo (isolation)

"* Air flow rate limited by core flow area (LID > 700)

"* Slow oxidation rate (nuclear grade graphite)

2 4GENERAL ATOMICS 20 of 20 24 Sept 02+

Low Potential for Graphite Fires

"• Test results successfully compared favorably to computer code (AlP) predictions

"• Extremely low probability of burning graphite - requires temperatures above those during

operation or accidents, and - requires large quantities of air

"• MHTGR analyses show introduction of air results in limited, decay heat driven oxidation

21 of 20 24 Sept 02 +,GENERAL ATOMICS

Graphite Oxidation Limited by Available Air

CROSS DUCT VESSEL FAILURE-

- INGRESS OF ONE SILO VOLUME

- OXIDATION MINIMAL

- OXIDATION SMALL

,OPENING AT TOP - INGRESS OF ONE VESSEL VOLUME

- NEGLIGIBLE OXIDATION

OPENING AT BOTTOM

- NO INGRESS

- NO OXIDATION

+ GENERAL ATOMICS22 of 20 24 Sept 02

Mass Transfer, Core Temperature, & Graphite Purity Limit Oxidation Rate

20 25

LU

C)

C/3

8

LS

0.05 <

30

TIME PAST INITIATING EVENT (DAYS)

+GENERAL ATOMICS23 of 20 24 Sept 02

1 0I

10-1

10-2

10-3

10-4

LU

LU

LU

CL

LU

LL.

z

LL.

22 FT2 CROSSDUCT VESSEL FAILURE WITH UNLIMITED AIR SUPPLY (APP. G.4)

22 FT2 CROSSAUCT VESSEL FAILURE (APRP.4)A

13 IN.2 RELIEF VALVE FAILURE (DBE-IO)

n0.05 IN.2 INSTRUMENT LINE LEAK (DDE-l)

10-50 5 10 15

I I

With Fuel Damage Precluded, Accident Releases Limited to Lesser Sources

"• Fission products within particles with initially defective coatings (as-manufactured defect fraction)

"* Fission products within particles experiencing inservice particle failure

"* Fission products associated with Uranium contamination of graphite

* Activity in primary coolant

* Activity "plated-out" on coolant boundary surfaces during normal operation

240of 20 24Sept02 + GENERAL ATOMICS

Below-Grade Siting Augments Enhanced Safety

Reactor equipment Positioner Refueling Reactor maintenance and machine auxiliary repair building building ° Reduced seismic

Crane central room response

Electrical-technical n Effective heat sink using

.. , surrounding earth

p. Robust structure - Additional containment

of accident releases 7,-Limited vulnerability of

core and key safety features to surface Po-wer Reactor

conversion fcavity events system -cooling

system Limits oxidant ingress

Ratbuln+ GN ALTMReactor

Reactor building + GENERAL ArTOMICS

GT-MHR Optimization of Established Gas Reactor Features Provides

* Enhanced, easily understood safety

• Assured accomplishment of safety functions with simple, passive features

• Limited consequences, even for beyond design basis accidents

Cost of passive features offset by

design simplicity and modularity

260of120 24 Sept 02 + GENERAL ATOMICS

G T-MHR Project Update

and Pre-Application Objectives

Presented to NRC Staff 24 September 2002

Walter Simon Senior Vice President, Power Reactor Division

General Atomics

+ GENERAL ArTOMICS

:Attachment 4

GT-MHR Design Development An International Program

S....___________.. ..... ' - • •• • • •. , • -- .. •L• .. .. . -. . ...... • ,,•, •....

o Engineering in Russia under joint US/RF agreement for destruction of surplus weapons Plutonium

• Sponsored jointly by US (DOE) and RF (Minatom) with support from provided

V by Japan and EU

Ky~aae~au ýOKBMv

+uGcmuEym ALATOIC

+GENERAL ATOMIfCS

Preliminary Design Completed

"* System design requirements and component specifications established

"* System configurations and component layouts developed

"• Nuclear, thermal, and structural analyses prepared

"• Technology development plans in-place

"* Test articles, test facilities and rigs are being developed

"• Bench-Scale fuel facility construction initiated

"• Subcontractors selected in key areas and assisting with hardware development

+ GENERAL ATOMICS

Design Effort is 40% Complete

• More than 1800 work products (10,000 pages) completed.

• Includes more than 300 drawings, 80 development test plans & 100 analysis reports.

• More than 30 meetings of US and Russian engineers to discuss design details held

• Detailed schedule with more than 6000 activities prepared.

+ GENERAL ATOMICS

Final Design Begun Major Items in Next Phase Planning

"• Continue final design of systems and components

"• Initiate reactor and Power Conversion Unit (PCU) development tests

"• Continue structural material development for vessel, reactor, and Power Conversion Unit components

"* Perform validation of computer codes

"* Start physics validation tests

"* Complete Bench-Scale Fuel Facility & test fuel

"* Complete initial plot plan, plant layout, building arrangements and auxiliary system designs

"• Initiate reactor irradiation tests of fuel, graphite, and carbon-carbon composites

O'GENERAL ATOMICS

U.S. Effort Aimed at Commercializing Russian Developed Design

• GT-MHR industrial consortium for US deployment being pursued

* Potential users of GT-MHR - Providing input on design

- Supporting very long lead activities (e.g., licensing)

GT-MHR Utility Advisory Board (UAB) includes 35% ofUS nuclear cap

Enteigy

)acity

PDominion- a Prog

ConstollaUon NWx~ar

ress Energy

* DOE/I National Labs supporting generic gas cooledreactor technologies

+ GENERAL ArTOMICS

4 m

PSEG

Objective & Expectations for GT-MHR Pre-Application Interaction

* Familiarize staff with GT-MHR technology

• Identify and resolve key, GT-MHR specific, licensing issues as early as possible

* Leverage ongoing DOE and NEI activities for GTMHR applicability

• Candid dialogue between NRC staff and design team

• Receive NRC feedback on GT-MHR approach to safety assurance

Prepare way for commercialization of GT-MHR

+ GENERAL ATOMICS

Key Areas Seen As...

"• GT-MHR Source Term - Coated particle fuel

- Use of mechanistic release model

- GT-MHR containment system including reactor building

"* Import of non-US technology including use of test data from outside US

"• Licensing approach and unique aspects of modular reactor licensing

Ideally, pre-application aimed at GT-MHR specific subtopics not covered by DOE & NEI efforts

+ GENERAL ATOMICS

.. ,.X.-