ML20031H368

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Testimony of M Weingart Re Addl Tx Pirg Contention A-40 Re Hydrogen Monitoring
ML20031H368
Person / Time
Site: Allens Creek File:Houston Lighting and Power Company icon.png
Issue date: 09/18/1981
From: Weingart M
HOUSTON LIGHTING & POWER CO.
To:
Shared Package
ML20031H319 List:
References
NUDOCS 8110270417
Download: ML20031H368 (7)
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4 Septcmbar 18, 1981 1

UNITED STATES OF AMERICN NUCLEAR REGULATORY COMMISS. TON 2

BEFORE THE ATOMIC SAFETE AND LICENSING BOARD 3

In the Matter of S

S HOUSTON LIGHTING & POWER COMPANY S

Docket No. 50-466 5

S (Allens Creek Nuclear Generating S

g i Station, Unit 1)

S DIRECT TESTIMONY OF MELVYN WEINGART 3

REGARDING ADDITIONAL CONTENTION TEXPIRG A HYDROGEN MONITORING 9

10 Q.

Mr. Weingart, have you previously testified in this proceeding?

A.

Yes.

I testified in connection with that portion of TexPirg AC 36 (McCorkle 17) regarding charcoal adsorber 13 fires and on Board Question 4A regarding combustible gas 14 control.

O Q.

What is the purpose of this testimony?

16 A.

The purpose of this testimony is to address TexPirg 17 Contention A-40 regsrding the adequacy of the Combustible 13 Gas Control System being provided for ACNGS.

It should be noted chat my testimony presented on August 25, 1981, con-g cerning Board Question 4A/ Combustible C.s Control (Tr. 15986-15923) also addresses the hydrogen control concerns identified 21 in TexPirg Contention A-40.

TexPirg Contention A-40 reads 77

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as follows:

(

en TexPirg contends that the Applicant monitoring of

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in containment building events during LOCA or similar events.is not adequate to detect immediately the oc-currences of hydrogen explosions.

That the recent i,

I 8110270417 810918" PDR ADOCK 05000466 T

PDR _.

1 Three Mile Island incident shows that current approved containment building monitoring apparatus did not bring 2

such an event to the attention of operators immediately, and that therefore the strong possibility existed 3

that actions which would prevent a second hydrogen explosion were not taken.

There is danger that hydrogen explosions will endanger TexPirg members because o the containment building during a LOCA is likely to contain radioactive gases which would be released from*the building damaged even lightly I

by the explosion and in excess of 40 CFR 190 or 10 6 i CFR 20.

Q.

Is it accurate to compare the ACNGS Hydrogen 7

Monitoring System to TMI?

g A.

No.

The ACNGS Hydroge.. Monitoring Subsystem (see PSAR Sections 6. 2. 5. 2. 2 and 7. 5.1. 4. 2. ll(d) ) of the 10 Combustible Gas Control System will be capable of withdrawing ti and analyzing samples from the ACNGS drywell and containment

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17 in order to provide sufficient information to the plant

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13 operators regarding hydrogen buildup inside the containment 14 and drywell during accident conditions so that they can maintain the concentration of hydrogen below the flammability 15 limit (4% by volume).

6 The hydrogen monitoring sabsystem for ACNGS is significantly different than the system provided at TMI-2.

18 To determine hydrogen concentration inside the containment lo at TMI-2, personnel had to go to the sample room, manually

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20 draw a sample of the containment atmosphere into a container, 21 take the container to another area, and 3isert-the content 22 into a gas analyzer.

As I will point out in the following 33 discussion, the hydrogen monitoring. system at ACNGS is i

substantially different.

.,_w 1,

s O

Q.

Can you answer the questions raised by the Board 1

at pages 21 and 22 of the September 1 Order?

2 A.

I believe the Board's questions can best be 7

answered by describing the integrated combustible gas control

~

system.

The Hydrogen Monitoring Subsystem for ACNGS will be 3 l actuated from the Control Room after an accident and will 6 j then automatically provide a record over time of the hydrogen concentration at various locations within the containment and drywell for the operator's use in the Control Room.

An e

alarm will actuate if the hydrogen analyzer detects a 9

concentration of 3.0 volume percent.

As indicated in Mr. Hucik's 10 testimony, in connection with Doherty Contention 5, this 99 alarm setting will provide adequate time to initiate the

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97 hydrogen control systems before the flammability limit (4%

13 by volume) is, reached.

14 The ACNGS Hydrogen Monitoring Subsystem, which is designed to the requirements of Regulatory Guide 1.7, will 13 have the ability to obtain samples from various locations 6

within the drywell and the containment.

These points are selected to provide complete coverage of the drywell and 13 containment.

The system consists of two identical analyzer 9~9 trains each powered from a different emergency bus, and each 20 having the ability to monitor any of the sample points.

21 Redundant connections will be provided at each 22 sampling location (one for each analyzer).

The redundant analyzer equipment will be located in the Reactor Auxiliary 33 Building approximately 135 apart.

Readouts and control I

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capability will be provided in the Control Poom.

The analyzer systems will be periodically calibrated (tested) using a 'zero' gas, i.e.

a gas that does not contain 3

hydrogen, and a span gas, i.e. a gas that contains a known j

4 hydrogen concentration.

It should be noted that calibration can be accomplished remotely from the main control room.

I 5

The sample withdrawal system will also be functionally 7

tested on a periodic basis.

3 The Drywell-Containment Mixing Subsystem (see PSAn Section 6.2.5.2.3) is part of the Combustible Gas Control a

System.

Its function is to dilute the hydrogen content in the drywell by mixing the drywell and containment atmospheres 11 after LOCA.

This safety related system is completely 9n

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redundant with duplicate piping, equipm'ent and instrumentation.

3 1

The mixing subsystem capacity is 500 cfm for each 14 of the redundant subsystems.

The compressor in each subsystem 15 has the capability of transferring the containment atmosphere 16 inte the drywell and discharging it at sufficient pressure to depress the water level in the drywell weir, expose the 3-al drywell suppresssion pool vents and cause the air flow to g

exit through the vents.

The hydrogen air mixture bubbles through the suppression pool and is then dispersed within 20 the containment.

7-The ACNGS Mark III containment utilizes thermal

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22 convective mixing to assure that the hydrogen concentration 22 throughout the containment is uniform.

The mixing of the i

I' 24 l

t

1 containment atmospherc is further discussed by Mr. Hucik in 2

his testimony.

PSAR Section 6.2.5.3.3 describes the various analyses performed to demonstrate drywell and 3

containmen hydrogen mixing, and hydrogen redistribution from the drywell to the containment due to the operation of the Drywell-Containment Hydrogen Mixing Subsystem.

i 6 i The Hydrogen Recombiner Subsystem (see PSAR Sections 7

6.2.5.1 and 6.2.5.2.4) will be manually activated from the O

Control Room as early as 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> following a design basis 9

loss-of-ctolant accident but before the hydrogen concentration 10 in the containment reaches 3.5 volume percent, to ensure that the four volume percent is never exceeded following 11 a design basis LOCA.

The Hydrogen Recombiner Subsystem consists of 13 two redundant thermal units (such as the recombiners 14 manufactured by Westinghouse Electric Corp.) located inside 1

the containment; one at elevation 207.33 feet and the

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16 other at 232.25 feet, approximately 150' apart.

The power 17 supply panels are located in the Reactor Auxiliary Building 18 at elevation 164,00 feet.

Controls for the Hydrogen Re-combiner are located in the Control Room.

gg Hydrogen recombination is a thermal process, O

using heat to cause recombination of the hydrogen and the

,,s-The recombiners for oxygen in air to form water vapor.

22 ACMGS utilize natural convection as the driving force to j

i' circulate containment atmosphere through equipment for

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I, 24' I.

t

processing.

The recombiners are designed to maintain containment hydrogen concentration below 4 percent by volume.

3 The subsystem consists of an inlet preheater section, a heater-recombination section and an exhaust chamber.

When the recombining subsystem is initiated from i

6 I the Control Room, the heating elements wichin the recombiner 7

are energized, increasing the temperature of the recombination 3

section.

Containment atmosphere is drawn first into the preheater section at a controlled flow rate, then into the e

i heater-recombination section where water vapor is formed t

due to the high temperature of approximately 1,150 F.

LL Following the high temperature section, the hot water vapor / air is mixture is cooled down to approximately'50 F above the

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11 ambient temperature in the containment.

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14 There are no moving parts or piping between sections.

15 The unit is completely enclosed and the internals are 16 protected from impingement by containment spray.

The inlet and outlet ports employ a louver arrangement to permit 3

1 containment atmosphere to flow tnrough the unit.

In addition, a major advantage of this design is that there are no l

19 l

catalysts employed which could be subject to degradation l

20 by " poisoning".

3, The Westinghouse recombiner design has been i

22 thoroughlj tested to assure their performance during post 23 LOCA conditions.

Westinghouse Document WCAP-9347 entitled i

I

" Qualification Testing for Model B Electric Hydrogen Recombiner" l

34 t

l l

i, l <

7 e

l 1-dated July, 1978 and reports referenced therein, reports the 1

results of the latest testing program for this' type of re-l2 1

I combiner.

These test results confirm that the hydrogen recombiner 3

of the size and type to be used at ACNGS will perform as s

F indicated on PSAR Figure 6.2-29.

I For testing pur-oses, each recombiner will be energized i

6 !

once every six months at 10KW for five minutes, to. check the i

7 electronics and to apply voltage to all other electrical components.

In 7ddition, once a year, a heating test will be performed, g

3 allowing temperature to stabilize at operating conditions, to check calibration of the unit and proper operation 'or heaters, s

10 K4 The Containment Hydrogen Purge Sub-System, PSAR Section

~

11 6.2.5.2.5, (CHPSS) is a part of the Combustible Gas Control 17 System and has the capability to purge the Containment atmosphere -

w

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13 throagh the Stand-by Gas Treatment System (SGTS) at a sufficient s

14 rate (equivalent to the processing capability of the' hydrogen

,7 13 recombiners) to control hydrogen concentration below-4% by volu e.

j This post accident purge capcbility as a backup to the'hydrog6n 6

3 o

recombiner is provided in accordance with Item C4 of Reg. Guide s

1.7, Rev. 1 (September 1976).

The CHPSS is designed to exhaust s

18 the air-hydrogen mixture from the Containment to'the Shield 19 Building Annulus for dilution and " hold-up" and replace it

O with filtered air.

The Air-Hydrogen mixture in the annulus is 21 then filtered through the SGTS before final release to the 22 environment.

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