ML20029D997

Follow Up on Telcon on Dec 15th Re Repair of Emrc Reactor Heat Exchanger & Resumption of Reactor Operations

ML20029D997
Person / Time
Site:	University of Buffalo
Issue date:	01/05/1994
From:	Landi D NEW YORK, STATE UNIV. OF, BUFFALO, NY
To:	Joyner J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML20029D996	List: ML20029D995 ML20029D997 ML20029D998
References
NUDOCS 9405130281
Download: ML20029D997 (7)

Text

[,.-

UNIVERSITY AT BUFFALO office of the Provos; Vice i, resident for Research STATE UNIVERSITY OF NEW YORK 516 cyen nati ihm 6016n fluffalo, Mw iork 142tAIM i pl6) t45 3321 FAX F16)64V2M3 January 5, 1994 James H.

Joyner, Chief Facilities Radiological Safety and Safeguards Nuclear Regulatory Commission Region 1 475 Allendale Road King of Prussia, PA 19406-1415 Re: Docket 50-57 License R-77

Dear Mr. Joyner:

The purpose of this letter is to follow up on our phone conversation on December 15th, regarding the repair of the BMRC reactor heat exchanger and the resumption of reactor operations.

We have completed repair of the heat exchanger by plugging two additional tubes (for a total of three) and performed a successful pressure test at 35 PSI.

The status of the heat exchanger was addressed at a special meeting of the University's Nuclear Safety Committee on Friday, December 10th.

Operation of

'he reactor was resumed on the morning of December c

16th.

The University is evaluating options to expedite the acquisition and installation of a new heat exchanger system.

In the interim, additional surveillance tests are being performed to moniter the secondary cooling water for radioactivity.

Samples will be drawn twice per day.

The first will be analyzed by ganma spectroscopy, while the second will be analyzed for gross beta activity using a low background (phoswhich) detector system.

The reactor will be operated at lower power, commensurate with the requirements of current research and service programs.

Enclosed you will find an analysis of the potential consequences of catastrophic failure of the Heat Exchanger tubes.

This w' 1 not lead to uncovering of the reactor core because of the difference in elevation between the tower basin and the core.

In order to provide an additional margin of safety, the isolation valves on the secondary side of the Heat Exchanger will be closed over weekends or when the reactor is otherwise unattended.

The primary loop isolation valves will be left open to operate the clean-up domineralizer system.

9405130281 940504 PDR ADOCK 05000057 V

PDR

p-Mr. James 11. Joyner January.5, 1994 Page 2 These measures will allow reactor programs to continue without placing the staff or the public at risk.

We will stay in close communication with the Commission staff and will advise you if there are any further problems.

Your consideration in this matter is appreciated.

Please contact me if you have any questions.

i Sincerely, Dale M.

Landi Vice President for Research DML 760 Encl.

cc:

President William R.

Greiner Provost Aaron N.

Bloch Sr. Vice President Robert J.

Wagner i-.

1 l-

.)

I e

Enclosure James H.

Joyner January 5,

1994 Analysis Catastrophic Failure of the BMRC Heat Exchanger Tubes

==

Introduction:==

The BMRC reactor uses an aluminum shell and tube heat exchanger to transfer heat from the primary coolant loop to the secondary J

coolant loop. The secondary coolant loop in turn rejects the reactor heat to the atmosphere using an evaporative cooling tower.

During reactor operation, when the primary and secondary circulating pumps are running, there are regions within the heat exchanger where the pressure in the secondary loop is lower than ~in the primary loop, and thus there_ exists a potential leak path _from the primary system into the-secondary.

When the circulating pumps are not operated,-

the same leak potential exists since the hydrostatic pressure on the primary side of the heat exchanger is higher than the secondary.

The purpose of this analysis is to evaluate the reactor safety issues resulting from significant (multiple tube) failure of the lleat Exchanger, which would lead to significant loss of primary coolant from the reactor tank. This analysis demonstrates that there is no potential to uncover the reactor core, because of the difference in elevation between the cooling tower and the core. A minimum of seven (7) feet of water will remain over the top of the fuel elements.

This analysis will also identify potential protective actions to mitigate the consequences of significant failure of the Heat Exchanger tubes.

Background:

The BMRC reactor operates at a steady state power of two megawatts, using "Pulstar" fuel. The Pulstar fuel is composed of 6% enriched Uranium Dioxide Pellets, clad with Zircalloy II. The reactor core is located in a nominally 30 foot deep tank, and the depth of water above the reactor core is typically 21 to 21.5 feet. Figures I, and II show the primary and secondary cooling water systems.

Catastrophic loss of water from the reactor tank (LOCA) was analyzed in support of the reactor re-licensing in the early O

- - _ ~.

.i l

Analysis': lleat Exchanger Tube Failure 1980's. Specif ically the complete uncovering of the reactor core was analyzed, and the SAR demonstrated that the reactor core will not be compromiced in the event of complete LOCA. The principal hazard associated with LOCA is the direct shine of radiation from the cor.e inventory, and not the release of fission products to the environment. Rapid loss of coolant was identified as a credible event by several mechanisms including a non-isolable guillotine break of the primary piping, or the shearing of a 6" beam tube.

l Nevertheless, it is recognized that LOCA is a serious event and all reasonable steps should be taken to protect the integrity of the reactor coolant boundary.

The reactor is equipped with a 3"

" Emergency Pool Flood" (EPF) system which may be manually actuated by the reactor operators.

This system was initially installed to protect the MTR reactor core which was operated from 1961 co 1963. It is not required to protect the Pulstar core. Initially the system was operated through eight 1.5" spray heads which penetrated Une reactor tank at about mid elevation. During the react.or liner replacement project, the EPF system was re-routed using a single header which projects over the top of the tank. This was done to reduce the possibility' of primary system Joakage.

Failure of the Heat Exchanger While the Reactor is Operating Simultaneous failure of several tubes could lead to rapid' loss of primary coolant from the reactor tank.

'A low water level 3

annunciator will trip at 20.5 feet of water above the reactor core.

If the situation is not corrected the reactor will scram when the water level reaches 20 feet above the core. The annunciator and scram systems are tested during the reactor pre-operational checks (nominally each week).

Assuming that the reactor tank is freshly filled to the top of the operational range, a maximum of 720 gallons of coolant will leak into the secondary before the reactor trips. The operators will then close the pool isolation valves and secure the leak. The

)

isolation valve actuators are located on the control deck adjacent to the reactor control room. In addition the remaining primary loop and secondary loop isolation valves may be closed to redundantly coal off the leak.

The LOCA Emergency Procedure requires the operator to secure all cooling systems and close the isolation valves.

Failure of the Het' Exchanger While the Reactor is Unattended.

In the event of a failure of the tubes while the reactor is unattended, additional water will leak into the secondary (while the cooling tower is not operating). The secondary circulating loop 2

J

l Analysis : Heat Exchanger Tube Failure

- is equipped with a check valve to prevent back-flow. If this check l-valve functions properly, only about three (3) feet of water will-be lost from the pool

( approximately 2160 gallons )

leaving eighteen (18) feet of water above the reactor core. If the check valve fails, additional water will be -lost until the elevation heads equalize. At this point approximately seven feet of water would cover the reactor core.

The reactor bridge is equipped with an Area Radiation Monitor, which will trip if the reactor tank water level drops a few feet.

This monitor includes a remote visual alarm (red light) outside of each containment personnel air lock. This would alert personnel to the existence of the potential radiation hazard before entry to the j

containmer.t building.

J Recommendation for Protective Action Significant loss of primary coolant can be prevented by closing the Secondary loop Heat Exchanger isolation valves when the reactor is unattended. This could also be accomplished by closing the primary isolation valves. However closing the primary valves will prevent operation of the clean-up domineralizer system which for ALARA purposes is operated over the weekend. Also this would increase the probability that through operator. error, the interlock could be challenged, which prevents starting the primary purnp while the primary isolation valves are closed. (This interlock was installed to preclude the application of excessive suction on the N-16 delay tank.)

==

Conclusions:==

The simultaneous failure of several Heat Exchanger tubes will not result in compromise of the reactor core, and will not create an unmanageable radiation hazard. The consequences of such a failure may be adequately mitigated using the existing protective systems.

The' reactor post-operational checks should be amended to include closure of the secondary heat exchanger isolation valves.

j 3

1 a

s e-

,y y

y,.,,s

...3.,.,im.

p,,...,-,,rI

F i

O

. _ ~ -. _ _ ~ - - -

. ~ _ _ -.. _ _.

!a8

.. l 7j 3

l ->

l l lc<

sW8 4

.We s *z o 8::ln M

'g: <

SKQ$

c o-Ni=I m

s

~

s

2. l ~

3-

~.

Wfg E !

"s c

^

9 N

a

2. -

dl i

9 io c.

[ y Xp

! g I

?!I as "b

i en lo!.lm

- i, n

S

s 8

- -** I 3

4 l.

u m

n s:b v: lQ w

't l

gj

/

B:

• +h

){

J ms c

uu >

i e/

gr 8!

e n.

m c:

s

i. Ih

-d h

W fi n.

$!l l

t

,y v

c--

J l

ga [

Ej

->g"-

^

i e

f b

2 c

o E

l s

e I!.

3., d l

[ t

[

in J

E e

m 7

a e

l S:

t3 m

m n,..

6 eo 7

?

l

. o u

l I

' a L:

e

'-l 9

rp a

()

y W l 6

6 g:

l 0:

/

4 o

U i

z

)

8, ShD 9

hI W

l g

Xm w

2 w

w i r

e m

f b

h h8 O l M

)~

I o 5

E 2

e e

gj

• 5 l E

o 9

8 o

m i e l

43 s

o e

o 8

m a

2 9

E b h b

8 1 0

^

Z e

i j a w

7

=

a m

a y'

I LJ j

(-

l a

I

~-}

,e

'w

' 7-JA

-]

l s-e o

,ao a

O I

a t

O W t' l

._ k b

M S

v '.:

Es[

I l

2aw Q

i e a 3. M + 2

"?_" n d,

2

=

3 i

m.

z e

p I

-1

__J o%e 2

r---

F C

4 b__ H_. _ _ _ _ _...-. _. _ _.. _ _ _ _ _ _ _ _ ] l l

l ri

'l l

2 c

- - - - - - - - - - - - - - - - - u

• ?

i g jj g

I M~

Li i

_._.___.--.-- _,kI,!1 f CE 4

?

x;

.a 111 z g h.

g 1 o

a.

I a

e I

s 11 s

x a l C g z

<(

l y g N!:

II e

> l i

2 K

$lj

+ F-b Y I o

g 9 i!

( I u

I c.

4 6

Il j Ss

=.b"--:'mngl5 F j I

H lI E3 S

f.

l O

l.c==.2 s'

4 J

'4 z

w ll y

O l l V z

15 2

11 s

3' b

l s

r z oj, o

IE i ;L7 @

RO i i l 8

p a m

ll c:

zj l 0 0

, G Ep. 8 z o 8:

b 2

Ihk b

l h

9

!I

- X. -] l Ie Q

w L

Il d

l I

$:.,!N O d'u,g

_J j

- c A

.<:o )

l

-O l

u J

~

hl l

l ym r~-~n r m...,.r

- 33 r,

t_._____________________i<___....__.________;

I

SECONDARY COOUNG SYSTEM

[

OP : 21: 22:

r-'------------------------------------

I smAv stria l

FENCED AREA

"""M0 'N"'"

'W*"N'""""2**

' istisy;iss '"k.{jjjg:i:

sijjij ll Ss.i :-i8iij:isSM^l'gjs:k.M:gp'.y

" yjj@@iil j!:ssi-!:gjig[ss OUTSiDe

p.

gig:9wx p:g!bs.g!R:g,. " id..jij:gx!!!3ip.! py.a&> g.8MiO}g::

D

! -d.ch

^

i c

ow m Ent s

.. y, gg:.3 g

7_________.______________________sy

,. sy ; g7

3

!I CHILLER ROOM NI l

f \\jl I

• \\

I n cwi vun COdlNG TOWER d

(

g p...

.. _ Y, ?.w:-

- w :m m:m:m :m:+ n, ~mn :m:< -

m.

i g

w_

str i

I

• @f k,

f I

S32 g

f g 1l

j CHILLER COND.

'I I

\\

5 33 l

Q(

L.

sm [ sis l-L i

- Pr ucecvt t simo mre (o'.s nrtow na resaw)

--g 1

[-

I su s,.

s----------------------

lc*=>-

i (, CHILLER COND. fl

M-l l

"^" " " " " " '*

• 1

-c==\\

/

S35 y _ _ _ __ _ _ _._ _ _.___ __ _ i rp i

- =ir mm -

,1 l

l 5 _. =

1

! l i

I SECOt0NW COfCUCTMTY F------------I M il { f

)

2 l

1, I

g r-g, i

i,p m

sa ss

g jq j

1 g.j s-nf sti sto m

t

, n%

i

p. _

i 0

t HEAT)

I,

.A

/

.LJ i;

b 'N 1

f s.e4 e

r,

I i r _ _.._ _

llE%v COOL NG W ATER FL OW K

r\\ I II.

i EXCH.

1 J

c csuta ccurme i i

i 1 \\

srcoso^av g

I i

\\

i t.

3

}

i; costr<x vsw s m ss vaw I

l m

N 1

i Il g

secoE'N g; '.(

S27 i

q 3

,4 I;

h ^ TREAWENT l

+ 25 i

l COUPON PUMP s.7 l

1 Hot. DER Q) N il I

l i

3:,

k YS25

.M-f{

S5 T

MACHINEFtY ROOM I

XS2i lj ss s2 I

i S'

%N PUMP l1 s42 ROOM iI l

I i

BIOCIDE g[

CHILLER CONDENSER PUMP l

MEAT 7EJ4T s

--_-._____________J

[

f~" TANK I

I I

_ L(ccric.uu i

1 SECONDARY PUMP l

' ~(____

___._____._______._._._J i

w:f?/

Date : 02/27/9.

.