ML19344E766

Forwards Response to Forwarding Rc Gray Questions on Condition of Reactor Core & Vulnerability of Equipment & Instrumentation in Facility Reactor Bldg

ML19344E766
Person / Time
Site:	Crane
Issue date:	08/18/1980
From:	Dircks W NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO)
To:	Walker R HOUSE OF REP.
References
NUDOCS 8009110268
Download: ML19344E766 (8)

Text

'

c PQ

/

'o UNITED STATES "g

E

NUCLEAR REGULATORY COMMISSION o

p WASHINGTON, D. C. 20555 c

\\...../

AUG 181980 The Honorable Robert S. Walker United States House of Representatives Washington, D.C.

20515 Dest Congressman Walker:

Enclosed are the NRC staff responses to your note dated May 28, 1980 to !!r. Carlton Kammerer regarding the letter of !1ay 21,1980 from your constituent Robert C. Gray. Mr. Gray's presented questions express his concerns on the condition of the reactor core and the vulnerability of equipment and instrumentation in the reactor building of the Three Mile Island Unit 2 as the time goes by.

Please note that we were requested to answer the first four of the five questions and trust that the response is adequate to tir, Gray's concerns.

Sincerely,

%~De$ Wi!!iam1Dircks William J. Dircks Acting Executive Director for Operations

Enclosures:

1.

NRC Staff ResN ase to Questions 2.

NUREG-0662

,8009110 pgg

_*,e.

/

1.

Given possible (indeed, probable) damage to instruments and equipment in the reactor building, would there now be warning of an absence of water over the core?

Answer With the loss of instrumentation in the reactor building, there would be warning of an absence of water over the core.

However, it would be indirectly determined.

This condition is based on the detailed discussion provided below.

The presence of reactor coolant water is continually monitored by the resis-tance temperature detectors (RTD's) in the hot and cold legs, the incore thermocouples (temperature detection) located inside the reactor vessel, and by the Standby Pressure Control (SPC) System which provides p0.;itive pressure control and reactor coolant makeup capability.

The incore thermocouples best represent the condition of reactor coolant nearest the core.

Absence of water; whether in the hot and cold legs or inside the reactor vessel in the vicinity of the core, would be indicated by a sig-nificant increase in temperature.

There are 50 incore thermocouples, each located in the upper end fitting of a fuel assembly and distributed in a fairly uniform fashion across the core.

Since the accident, only four of these thermocouples have failed.

They are monitored daily.

The current average temperature is approximately 156 F, and the highest reading is less than 195 F..Thus, there is assurance that the reactor coolant is in a sub-cooled state and is not likely to boil-off in the event of inadvertent

2 depressurization.

With regard to thermocouple reliability, we think that the probability of failure of a large number of these instruments in the near term is very low, due to their past performance.

The reactor coolant pressure is monitored by a Heise gaur-installed in the sampling line located outside the reactor building.

Therefore, this parameter is not likely to be lost.

In conclusion, given the loss of incore thermocouple instrumentation, we will have warning of a loss of coolant event by monitoring the tank levels of the Standby Pressure Control System (SPCS).

Change in water level of these tanks is used for the determination of reactor coolant leak rate.

The reactor coolant system (RCS) is maintained in a water solid condition at an approxi-mate pressure of 100 psig, and the SPCS automatically compensates volumetric decreases in the RCS due to system leakage or thermal contraction.

Also the status of the SPCS is monitored in the control room.

This system is located in the fuel handling building, and is independent of any instrumentation or equipment inside the reactor building.

2.

What is the NRC risk assessment of catastrophic consequences of instrument /

equipment failure as each month passes?

Answer The following equipment and instrumentation inside containment are susceptible to damage and ranked in order of the potential consequences that could occur if left unattended as time goes by. The risk for each assumed failure (s) is described in each response.

t

3 Equipment Failure and Effect (1) Source Level Count Rate Only one of the two installed source level Meter count rate meters is operative.

It is used for monitoring neutron generation rate and the criticality state of the reactor.

Failure of this meter would result in a loss of detecting a criticality condition.

However, even with the loss of this instrument, the licensee is relying on boron injected into the reactor coolant system (RCS) to maintain the core subcritical and RCS water is sampled weekly for boron concentration.

Although the staff considers the potential for recriticality to be of low probability, recriticality would result in the production of additional radioactive material, the possible spread of contamination outside the reactor coolant pressure boundary, and potential increases in exposure to occupa-tional workers required to perform maintenance or decontamination operations in the reactor building.

Assuming that the reactor building integrity is maintained, off-site consequences.

would be negligible.

1

4 Equipment Failure and Effect (2) Reactor Building Air Fans may fail due to lack of yearly maintenance Cooling Fans and/or operating in a high relative humidity environment.

These fans have been qualified for 3 to 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> of continuous operation at 100% relative humidity.

They now have been operating for nearly 14 months.

Since these fans maintain a slight negative pressure ir.

the reactor building, failure of them would result in a positive pressure a: 1 possibly cause uncontrolled leakage of the contaminated air to the outside environment.

However, it should be noted that this is no longer a concern because the reactor building purge of Kr-85 commenced on June 28 and was i

completed on July 11, 1980.

(3) Decay Heat Isolation The motor operators for these valves may be Valves, DH-V171 and DH-V1 submerged in the near future (3 to 6 months).

One or both of these valves will most likely be opened before they become inoperable.

As a result the pressure boundary of the decay heat system separating the highly radioactive water from non-radioactive water will be extended and isolated by one valve instead of two. Thus a small possibility exists for

5 Equipment Failure and Effect increased radiological activity levels in por-tions of auxiliary building piping which may hinder free accessibility for workers to perform inplant modifications.

There would be no off-site consequences.

(4) Reactor building and As the reactor building sump water continues,

RCS instrumentation to rise at its current small rate, certain instrumentation and equipment penetrations will t ecome inoperable.

Direct consequence would be loss of redundant instrumentation used to check plant status.

For example, in the near term, the spare penetration ustJ for determining reactor building water level could become unavailable.

However, a backup source exists wh'ich has been used in the past.

Also, pres-surizer heater power and some RCS hot leg temperature elements will be lost, but the former is no longer needed and the latter is not a significant loss.

In addition, it should be noted that there are other contributors to plant deterioration such as high radiation levels that may degrade the instrumentation and penetration seals with time.

Also, long-term effects on partially submerged RCS piping are not well known.

A 3.

If, as seems likely, the passage of time degrader instruments and equipment, shouldn't the highest priority be attached to entering the reactor building to determine the status of conditions, followed by the swiftest possible action to bring the core to a safe and confidently monitored status? (I recognize this as a loaded question - sorry.)

Answer The staff is in agreement that priority should be given to reactor building entry in order to survey and maintain equipment (e.g., air coolers, neutron monitors), and expedite decontamination work leading to eventual core dis-assembly.

However, the decontamination of the reactor building atmosphere.tus a necessary first step toward extensive work efforts in the reactor building.

. On June 12, 1980, the Commission approved a staff recommendation (see NUREG-0662) to purge the Kr-85 from the reactor building as the safest and most expeditious way of effecting decontamination. The purge commenced on June 28, 1980 and was concluded on July ll, 1980. A manned entry into the reactor building was conducted on July 23, 1980 to perform initial' radiation an.d visual surveys of 305 pool elevation.

~~~~~'

With respect to the condition of the core, the plant is currently maintained in a safe condition and monitored as discussed in response to Question 1.

4.

Did NRC/ Met Ed have a plan if they had opened the door yesterday and been unable to close it? Will it really take months to plan the.next move, as press reports indicate? Should it take this long?

k 4

v

~

7 Answer The containment personnel airlock consists of a cylindrical shell fitted with bulkhead doors at each end.

By design, these doors are mechanically inter-locked so that neither can be operated unless the other $s completely closed, latched and sealed.

Prior to containment entry this interlock would be bypassed.

This action would allow the opposite (outer) bulkhead door to be opened and closed in the event the inne,r door is left open or only partially closed.

In this case, containment integrity would be maintained by the second bulkhead door.

Also, note that the containment is maintained at a slight negative pressure creating a suction effect so that air flow would be directed into the containment.

The licensee is working expenditiously to remedy the problems associated with the personnel airlock so that the containment entry program can proceed.

The staff estimates that the containment entry will take place within 2 months.

l l

k

)

, =..

j}

?nu

i::

N!S.~ *

7 a.:..- ~.

u.EE ---

.un:.

nuit

.. ]

us.

g

';.==::

u

uu une 1

{

j,;. "

,y j

.=:===

}

g t

AEE

's w:: -

gll.+h

.)

E-

?.it Il n:

jdp

69i liF" tm i

1--

m??-

G.

imii ii.,

Congit%% of tf)t Bnittb blatts

%>ouse et Erpetsentatibts m{

gu.

- ~~

="gn:

=

asastinaren, m.c.

=.. =.. =..

f.=),s?.

.g May 28, 1980

!f k...

Mr. Carlton Kanunerer, Dir5ctor Nuclear Regulatory Conunission

~

U ??$;.

=r::-

, ll4 L ~~

2.j

$5 Office of Cong. Affairs V.=i

~"'

vce.n Washington, D.C.

20555 une j

Sir:

us;......

The attached communication 5ll

!i

~

q.;c;.

utss!

~

==

i aun is sent for your consideration.

"~

Please investigate the statements

"r::'

.z,

^

contained therein and forward me

' "[......

~

5!

a::

n- :==

'jii5.

.h the necessary information for re-9;s!EEE as:

?4

~'

~

(;;

ply, returning the enclosed corre-

-ljg.:f 7;

=

i.,

.:.gg

.,, j.

iaz.ag;;=.

==::n spondence vith your answer.

w;.;:.+=

~

Y

-1

.sv ours truly,

= = -

;

=vi;:

' pq: -

[

.?'5 :*

^~

j}h

~ :-Ni?

'.+E

==!

3 R

K

==::

16th District, Pa.

~

.NI "h

i#F==-

= m :.

=.tl.'.

u==--

~ - *

'r.'.---

[.-*Nhh.*:

,

ib.

?"*C n

,a, ti *t.

o.

h::

- sj.g"gif

m,

M 4 gi: " "i " ' *" '====

.........-....=:

~

g.(

.E i ?q

~

g

'~

13..:

i

[g,;,

uai:

a.g" ua

~

t~

's..-...-..

• .f c

~

~

ub.,.

Rol>ert G. Gray 3:+.

1270 Wilson Avenue

s M g%

j Lancaster, Penn ylvania 17603 sa 21 May 1980

=m

+:4:+ -

u =..g;;jr..

":j Honorable Robert Walker

~

House of Representatives

Subject:

Three Mile Island g

Waahington, D.C.

- !d m!i si.: -

Dear Congressman Walker:

"2:

I am writing to inquire if you have information from

~::

the NRC on several issues that concern me about the 4

3/

damaged reactor at Three Mile Island.

It may be that

~

r::.

• BY:

fi these concerns have been addressed in central Fennsylvania J.q news coverage. But because I am working in Washington, D.C. this year -- and have been since September -- I

~

= :.

have not followed local press coverage.

It is my impression,

"-~' i1 however, that the answ0rs to my questions are not clear

,"4 from the public record, and I solicit ynur assistance.

- +:s ~

The following questions are urfemost in my mind:

, :;gsg

j 1.

Given possible (indeed, pivuaise) damage to instruments and equipment in the reactor building, would there now

...,, =..

be warning of an absence of water over the core?

qq g

j.;- i s

-==

=

2.

What is the NRC risk assessment of catastrophic f!! ~ ~ '

~"

. ))

consequencesofinstrument/equipmentfailureaseach EB 2....

.?-

month passes?

~

Vi 3

If, as seems likely, the passage of time degrades instruments and equipment, shouldn't the highest priority sE be attached to entering the reactor building to determine the status of conditions, followed by the swiftest possible action to bring the core to a safe and confidently

.. ME

=;::

moditored status? (I recognize this as a loaded question - sorry.)d "3}

.. a 1,. DidNRC/MetEdhaveaplaniftheyhadopenedthe

"" il door yestirday and been unable to close it? Will it really tese months to plan the next move, as press repbrts

~""'

indicate? Should it take this long?

.. y;y

. ))

5 A question for you: Are you persuaded that every

.4 significant action being taken has in mind public safety I

,2:';

^:.1 and not the economic or public relations interests of

ujj Met Ed and/or the civilian nuclear power industry?

.._.."=- ::i.1

=,

!!.**.i:

-- continued --

':;;;;3

~

us-3.5

. nl nk.al

"' ~

.h.

u

= =..

'"2

.,f"'(:

fiCh"-? "i.U."f.

Robert G. Gr.y

~ :.*?

h 1270 Wilson Avenu.

~

"~2l en '

9 y?'"

d L.ncaster, Penn.ylvani.17603

==:==r);j

==

1 Page 2 9

=u=.

3=

4p.3

f3 Although I have concerns about long-term health

!#15:.:=;

EFE4 consequences of low-level radiation, that problem strikes

• M

~

4 me as secondary as long as the reactor '.s in its f,g.fevel,

"~

.. ;d uun current uncertain condition. Moreover, while theAlong-

~

==.

term health consequences are unknown, the consequences

==gi

=.{

._ u...;,;.u of a melt-down or sudden release of large amounts of

~ " " " " "- EE

- B1 radiation are clearly awful to ccecprehend.

Thus, I

'T.5.

EE A believe that the venting of gases necessary to permit

~=".,,.u.'~"

-.x. (

entry into the reactor building is necessary to achieve

[sz the highest priority objective : the swiftest possible (h-" ~~~~

action to bring the core of the reactor to a safe and EE confidently monitored state.

En I appreciate any efforts you make ta provide answers

["

~~"

".I.f to the questions on the preceding page. And, assuming E..

s= -

7 that the answers will be in line with my expectations Bil' 5"-

"I'.5 (to wit, that degradation of instruments and equipment g~,

,....., ;. " ="_._

as time passes is a threat), I urge you te press

"' (,....:l;lll" for action as soon as possible on an absolutely J-urgent, top priority basis to bring the core under i

confident control.

It is difficult for me to believe

$.=.guuY -., _

--indeed, it is inconceivable -- that the citizens of k.

~ " " "

'!)f::

[

central Pennsylvania will be forced to live for an g

indefinite period of time with the un;ertainty of the

4==

.=uff si current situation and with the spectre of potentially HE En catastrophic destruction of the area.

~

I appreciate your continuing efforts cn behalf of your fj==

" ~ '

constituents on a problem that clearly transcends politics.

p

,.;:j.,,.,.._ ;;;. :.g..

Like me, you have a wife living in Lancaster, and I fi:+

"~==i

"'S personal and congressiunal perspeative.

.... 9 respect your judgments on these issues from both a

""E

.g; u

.*:....... ::=::

=

Sincerely yours, f):[ "~

~

e

.m g

==:=nn,

Robert C. Gray

==j.:f!

.5 Assistant Professor of Govt.

.. 55..

Franklin and Marshsll College

~ ~ 55E (On leave, 1979-60) as===

.. =

q

=

=

?"-:E 1

^;)

.

5.W

s=.

....g

((EN ~

Eu.

==:,

)