x -" Assess, •

SREACTOR PHYSICS':

Shtdown M rgins.-, •,):i :•

Reacti~t Feedback' •.- - :ii / ,••:••f : Inherent SaAfetysmeii-..

Powe Denity Distribuin

.,•! ~(Design and Control) . .: _:.,.•• .••• Modu.la. . .. ".a.to "y i

"... . . . . . .... . . . ...... . . . . .

* Shutown.Magins, . ." .

_ eatviyFed ac ,, .,•:-,

•: Modular HTR-2 NPP, Reactor Physics

TOV NORD GRUPPE

TUV Hannover/Sachsen-Anhalt e.V. Division Energy and Systems Technology

El

- 3

I (�) � -4t�.. I

Eli FW� . -� �

�

-o:2� �

0. Cu =0

-�7E > . -�E'

o o 4

Cu..'

IIo C 0 0)

0 UIcI,

(if 0

(3�

U)

Co .1-I

0 Co

Cu I

I-

� - �p 1 � 7k

q-�

-�

I. k �*

ma a. a. = U

a U 0 =

2= I

U,

Co

-c I.. 0

'I-.

Cu C)

CL CL z

ChJ

0

CO

0

I

E

-2

0)

-c

E CD

U)

0) Z...

5)

- - - - - - - - - - - - --- - -

-------------------- 4---

4 .7 .. ... ..

0 #. 0 0, 0~

0cc CD . 4' .RU (

UIF X-C 4a- Rol

miI>

7-7 -7779ýý ý ý Y-.; A-Z, ZY:.7

IN

'V

Modular HTR-2 NPP, Reactor Physics

TUV Hannover/Sachsen-Anhalt e.V. Division Energy and Systems Technology UEJkOMLp

TUV NORD GRUPPE

�.Lbnh1LE��E� *'�

Scheme of Reco PhsisCafculatiorF' V. S.O. P ý(Very. Suvperior ld rogram4s7'7

Nameof the Application" .Result. Program Vf, th: ..

GAM/THERMOS Spectral Cros Section of, Z L/T.,,, Calculation Core-Caland eflecaf

tor Regions~

CITATION Diffus ion M cationn..---ul. CaIculation . Factor, Power •

Density Map

FEVER Burnup- Nuclide-Densities,:;: "Calculation

THERMIX Temperature- Temperatures of:

Calculation Fuel (U02)

- Core-Graphite

- ReflectorGraphite in all Regions

Modular HTR-2 NPP, Reactor Physics

TUV HannoverlSachsen-An halt e.V. Division Energy and Systems Technology TUV NORD GRUPPE Eskoffi94*

iI I

<0 M ill II -- --

Cow -4-70

(nU Cn DC

(D C

o)- -7 - - -

CDCID

0 b ,o: '

-' �,. �

i] • : ,

-- -- -- -- ---- ---------------

C16

•'•;• . :.•0.. ,.: .'

o~c ca C ~>

*. ?' ,-..,: . ..'A. : . -

:a.m

W W

o Of C ,<,,

<U'n C

V

i--arual rower kAeIII I, I [lip I I iLUIC)

Accidental Reactiviy Increase

Partial Power - Zero Power

Efficiency of 5 of 6 Rods

+0,5

+0,1

- 2,6

-0,4%

Modular HTR-2 NPP, Reactor Physics

TUV NORD GRUPPE

Calculationre of Shu(:Dowg•. Rins 1.i

Starting Core (BOOC) ReactivityBalane Ho hut- Down

Control Reserve 100 -90-100% +2

Reactivity Compensation forý, Partial Power (Xenon, ,Temperature)+ 0,6%

Accidental Reactivity Increase -+:•0,5 %

Partial Power- Zero Power -0,11.%

Efficiency of 5 of 6 Rods-." - -3:,3;4%

Steady State Core Reactivity Balance Hot Shot Down

Control Reserve 100-50-100 % + 1,2 %

Reactivity Compensation for n, A 0/J ,

TUV Hannover/Sachsen-Anhalt e.V. Division Energy and Systems Technology

Filter for and" Adiinal"Aspects o HTR.D.sgn(Sutd Safety)

"Event, Effect PWR .. R'ý

Rod ejection yes no0

Uncontrolled rod withdraw .yes yes,

Boron dilution ..- ,; ysno

Water ingress s (no)

Uncontrolled fuel addition "no. no yes "" C cr

Collapsing of holes in the core no . yes

Loss of Collant Accident .yesy yes>

Loss of Flow Event yes (no),

Rod drop with reactivity gain no. yes

Core densification (o yes,:

Boron-loss by earthquake yes no

Burn out of poison in structural materials no yes

Uncontrolled cooling of the core yes yes

Temperature increase of the reflector no es)

Error in excess reactivity (no) yes

ATWS yes yes

Changes of reflector geometry no yes

Burn out of reacitivity control devices yes yes

Modular HTR-2 NPP, Reactor Physics

TUV Hannover/Sachsen-Anfhalt e.V. Division Energy and Systems Technology TUV NORD GRUPPE

,7t5

•"Rules 7 neetSft

Rules HTR D sign Filter-, ac 'Addi

BMVI-Kriterium 3.2 * Negative Temnperatufr

RSK LL, 3.2 - Coefficient.,

DIN 25405 . * Negative Power -Cefficient

KTA 3101.2 . Accidental ReactivityI:ncrease limited sto that 'thereator ican

IAEA Safety Standards' beshut down and tp be sht.on emd~ pera w...

IAEA Safety Guides, ture.f the fuel elemen•ts•,,. remaining beloW.a'- specified Value:

Temperature Coefficient of the fuel: Negative

Temperature Coefficient of the fuel-graphite: Slightly

negative, a small positive value at Xenon-maximum

Temperature Coefficient of the reflector: Slightly positive

• Inherent Safety confirmed

Modular HTR-2 NPP, Reactor Physics

TUV Hannover/Sachsen-Anhalt e.V. Division Energy and Systems Technology TOV NORD GRUPPEE*-10-wp~f

e a

sibilitieso accen increase o reactivity • Core densification, by erhqu'ke

y ar qU

" Water ingress into the core

* Uncontrolled withdraw of reflector rods

P

Earthquake §

STime'

S•'•-: -'.. " ,.......

Water ingress_

""- Water density

',• p

Uncontrolled withdraw

or reflector rods

-' Time/depth

Modular HTR-2 NPP, Reactor Physics

TUV HannoverlSachsen-Anhalt e.V.Division Energy and Systems Technology TUV HORD GRUPPE

'I

4,

I

I4-

PRoi

No- Time

d drop

".-- Time

Modular HTR-2 NPP, Reactor Physics

TOV NORD GRUPPE

TUV Hannover/Sachsen-Anhalt e.V. Division Energy and Systems Technology

Inh. nt aft

Search for possibilities of accidental increase pf -, reactivity : . . . . . ". . , -.

Change of reflectorgeometrie.,

"* Uncontrolled cooling of the c'ore'

"" Rod drop .

Change of reflector geometry .

.. 'Time

Uncontrolled cooling..

- 22

r 27

14-

- - -- - -- - U -

-U CU Co

~---~ca

o 'a

*~ .j-- .JT .7 ... ..

ens.~ ~" ditiu' is*6b

During opration the power de nity dio

in a proper shapc-e by:'

Reactor Physics calculation,

Measuring the depth of the reflector rods and: by

adjusting the rods to the same depth,'

Measuring the height of the columns of th'' ma

sphere shutdown system. and by: adjusting the'm to.. the same height.

The power density distribution is controlled by the 3 x 4

neutron flux instrumentation outside the RPV.

An indirect control of the axial shape is given by

measuring the helium-inlet and -outlet temperatures.

Under safety aspects the power density distribution is

important as start condition for accident analysis.

Modular HTR-2 NPP, Reactor Physics

TUV HannoverlSachsen-Anhalt e.V. Division Energy and Systems Technology TUV HORD GRUPPE

II

I wCD CO)

0

m CD

C', (I)

CD

CD 0

(0

(DH C', 7;m

C,) G)

0

0)

(0

0

0*"*

- - ----- -- - - - - - - - - - '

(D,,

(D

CL

'Mi

0 14

-o

-I

= 0

.3

I

1'�

I.

U120

-200

,Scram-, (Power)Scram (C ooa nt.Temperati

<10

Decay Heat

Decay Heat

•ire )...........- ...:

S. .. :/D 5 0 ::o ........ .

5. .

-1050 .Ct-'

-1240. C

Conditions:

"* Conservative integral power, only area cooler system

"* Skipping of first reactor protection limit -- R',; cs-k-•4

Result:

Fuel temperature well below limit: 1620 °C, also for different starting conditions like zero power, partial power.

Modular HTR-2 NPP, Reactor Physics

TOV NORD GRUPPE

ddhtldent .. I..Acid enAn a lysi .

Reactivity Accident .... , 2:.

Uncontrolled withdraw of reflector rods

Time Power-' , Action Max: Fue [sec] [%. .. <Tempeiratu r&;

0 105 -- 80C

(12

90

120

3700

- some hours

TUV Hannover/Sachsen-Anhalt e.V. Division Energy and Systems Technology

"Acd ,ien.t Analysis

LUS5 UI V_,UUtdI L /PWAAUHI L

Starting conditions:-~n4-

- Reactor power: 105 % (limitation system limit)

- Inlet temperature 280 0C (near protection system limit)

_ Outlet temperature: 750 ,C 6i(near protection system limit)

2. Scram limit -.

Leak of 65 mm"C(

Calculation

Programs TAC 2D (TOV) and THERMIX

Detailed 2-dim model with evaluation: of the main tolerances

(1 a-value):

- Decay heat 2,8 /0 - Local power density ± 5 %

- Fuel heat conductivity+ 1,15 W/moK

- Effective core heat conductivity ± 5 %

Results for maximum fuel temperature (incl. 2 a-tolerance)

THERMIX TAC 2D limit

1608 0C 1625 0C 1620 0C

(- 1% of the core > 1500 °C)

Modular HTR-2 NPP, Reactor Physics

TUV Hannover/Sachsen-Anhalt e.V. Division Energy and Systems Technology Eskom_8.pp4

TUV NORD GRUPPE

A.

I .=-:• •';f"•

a

Accident Analysis

Loss of Coolant Accident

Additional temperature results (THERMIX)

Position

Reflector rods

Core container wall

Core container bottom

RPV wall

RPV bottom

Outlet temperature

Maximum temperature

880.

500

380

360

350

750

0c

0C

0C

0C

0C

0C

Design limits

650

500

500

500.

500 900

0C

6C 0C

00 00

I

Modular HTR-2 NPP, Reactor Physics

TOV Hannover/Sachsen-Anhalt e.V. Division Energy and Systems Technology EBkoM_8.Wp

TUV NORD GRUPPE

The high temperatures of the reflector rods do not affect the

conceptual design, because:

- The mechanical integrity of the rods can perhaps be approved by additional experiments,

- The shutdown safety is not affected by a loss of the rods during temperature increase,

- The rods can be changed.