ML20247D657
| ML20247D657 | |
| Person / Time | |
|---|---|
| Site: | National Bureau of Standards Reactor |
| Issue date: | 03/24/1989 |
| From: | Zech L NRC COMMISSION (OCM) |
| To: | Mikulski B, Sarbanes P SENATE |
| Shared Package | |
| ML19316F137 | List: |
| References | |
| NUDOCS 8903310175 | |
| Download: ML20247D657 (2) | |
See also: IR 05000184/1989001
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l [" o UNITED STATES i
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NUCLEAR REGULATORY COMMISSION l
o, WASHINGTON, D.C. 20666
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CHA R N '
The Honorable Paul S. Sarbanes
United States Senate
Washington, D. C. 20510
Dear Senator Sarbanes:
I am responding to your. letter of February 7, 1989, regarding
the low-level radiological release from the National Institute
of Standards and Technology (NIST) during the period August-
October, 1987. Our Region I Office has completed a review of
the event and its technical significance. A copy of the l
Region I follow-up report, which describes the event and 1
subsequent licensee and Nuclear Regulatory Commission (NRC)
actions, is enclosed for your information. ;
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As the February 2, 1989 Inspection Report No. 50-184/89-01
(Enclosure 2 to the Region I Report) makes clear, the NIST
incident involved two separate but related events, neither of
which posed a threat to public health or safety. Initially,
the licensee observed a leak of radioactive primary coolant
water into the secondary side of the heat exchanger. Although
the immediate telephone reporting requirements were met by
notifying NRC Region I of the leak, the licensee has been
cited for failing to submit a two week written repbrt as
specified in the Technical Specifications to its license.
This event did not involve a radiological release to the
environment. Subsequently, the licensee decided to dispose of
this radioactive water by evaporation through the cooling
tower. NRC regulations permit licensees to dispose of radio-
active material'into the environment without advance notice to
the NRC provided that the released radioactivity concentration
is'within the limits specified in 10 CFR Part 20. Because the
NIST release remained within these limits, it posed no undue
risk to public health and safety.
With respect to your concern about notifications to State and
local officials, it is our understanding that the NIST is in
contact with the Montgomery County Executive, representatives
of the Montgomery County Council, and other local officials to
discuss arrangements concerning notifications following
specified events and plans similar discussions with Maryland
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officials. Although our regulations do not require such
notifications unless 10 CFR Part 20 limits are exceeded, the
Commission has no objection to any additional notification
arrangements that may result from these discussions.
I hope the information provided in this letter and its
enclosure will resolve your concerns regarding the 1987 NIST
incident.
Sincerely,
hhl4 (A), * .
Lando W. Zec , Jr. l
Enclosure: As stated ,
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&# UNITED STATES
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a B RESION 1
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- E e 475 ALLENDALE ROAD
/ KING OF PMUSSIA. PENNSYLVANIA 19408
FEB 02 1999
MEMORANDUM FOR: Victor Stello, Jr.
Executive Director for Operations ,
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FROM: William T. Russell
Regional Administrator
Region I
SUBJECT: FOLLOWUP TO AN EVENT AT THE NATIONAL BUREAU OF STANDARDS
RESEARCH REACTOR
This forwards a report on an- event which occurred over the August to
October 1987 timeframe at the National Bureau of Standards (NBS) research
reactor facility in Gaithersburg, Maryland. This report discusses the event
itself, licensee reporting of the event and NRC followup actions.
Enclosure 1 is a synopsis of the event and NRC Region I activities associated
with the NBS reactor. Enclosure 2 is the inspection report issued examining
the technical and licensee management aspects of the 1987 event and Enclosure 3
lists future NRC actions as a result of the event.
If you have any questions, please call me.
William T. Russell
Regional Administrator
Enclosures:
As stated
cc w/encis:
T. Murley, NRR
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ENCLOSURE 1
Review of Event
A. Background
' The National Bureau of Standards Reactor (NBSR) is a reactor-laboratory
complex for providing the means of performing research and standards on i
materials and nuclear processes.
The reactor is a heavy water moderated and cooled Argonne CP-5 class tank- !
type reactor using enriched (93%) fuel. The reactor is licensed for oper- .
ation up to 20 MWt. The reactor is housed in a confinement building l
designed and tested to withstand the maximum anticipated internal pressure
of 8 inches of water. Potentially contaminated drains from the confine-
ment. building and laboratory sinks are routed to a sump tank and then
pumped to a radioactive waste system in an adjacent building. '
The reactor operates at a pressure of four inches of water maintained by a
helium blanket. Primary outlet temperature is 112'F. The volume of pri-
mary coolant is approximately 13,000 gallons. The primary coolant is
cooled by means of one of two heat exchangers. The secondary water flow-
ing through the shell side of the heat exchanger is cooled by means of a !
mechanical draft cooling tower. The volume of the secondary coolant sys-
tem is approximately 100,000 gallons of treated potable water forced
through the main and other heat exchangers by a combination of six pumps. ,
Blowdown from the cooling tower basin goes to the sewage system which 1
provides a dilution flow rate of about 300,000-400,000 gallons per day.
Secondary coolant is monitored by an N-16 detector to provide indication
of primary-to-secondary leaks at 100% power. Analysis of the secondary
water for tritium contamination provides a back-up leak detection method.
It should be noted that, based on the design of the reactor, there is no
credible accident which poses a significant risk to the health and safety
of the public beyond the site boundary. The licensee's Emergency Plan, i
therefore, does not include a General Emergency.
Organization
The reactor is operated by employees of the Department of Commerce,
National Institute of Standards and Technology (formerly, the National
Bureau of Standards). At the facility, the Chief, Reactor Radiation
Division, and the Chief Nuclear Engineer, Reactor Operations, have line
responsibility for direction and operation of the reactor facility,
including safeguarding the general public and facility personnel from
radiation exposure and adhering to all requirements of the Operating
License and Technical Specifications.
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Enclosure 1 - Review of Event 2 l
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The Safety Evaluation Committee and the Safety Audit Committee provide
oversight of the facility's operations.
Current Management Personnel include:
l Chief, Reactor Radiation Division -
Dr. Robert S. Carter
Deputy Chief, Reactor Radiation
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Division and Chief, Reactor
Operations Section -
Tawfik M. Raby
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Deputy Chief, Reactor Radiation .
Division and Chief, Technical
Support Section -
James Torrence :
B. Recent Regulatory History
l * Routine inspection history since 1986:
Report No. Dates Area Inspected
50-184/86-01 6/25-26/86 Radiation Protection
50-184/86-02 10/1-2/86 Operator Licensing Exam
70-398/86-01 2/13/86 Nuclear Material Control
70-398/86-02 4/14-17/86 Nuclear Material Control
70-398/86-03 6/25-26/86 Radiation Protection
50-184/87-01 7/7/87 Safeguards
50-184/87-02 7/6-9/87 Radiation Protection
50-184/87-03 11/5/87 Emergency Preparedness :
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70-398/87-01 3/12/87 Nuclear Material Control
70-398/87-02 3/16-18/87 Nuclear Material Control
70-398/87-03 5/11-14/87 Nuclear Material Control
70-398/87-04 12/7-9/87 Nuclear Material Control
50-184/88-01 6/6-7/88 Operator Licensing Exam
50-184/88-02 8/9-11/88 Radiation Protection
IR 70-398/87-04 identified one Level IV violation for failure to
properly post an area containing radioactive material.
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- Reports submitted - The following reports were submitted since 1986
pursuant to license requirements:
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Event Reports
9/23/87
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Reported 9/11/87 - failure of shim arm No. I to
move out/in.
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Enclosure 1 - P.eview of Event 3
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Annual Reports
3/20/86 -
Operations Report No. 38 for CY 85
- 3/20/87 -
Operations Report No. 39 for CY 86
3/28/88 -
Operations Report No. 40 for CY 87
j (Resubmitted 4/21/88 to correct typo errors)
Note: The above reports were all correctly addressed.
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l C. Chronology of Events
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A series of events occurred in the August-October 1987 timeframe that has
recently received substantial interest. An event chronology follows:
1987
5/17 Reactor shutdown for anticipated three-month shutdown for in-
stallation of experiment and major maintenance, j
7/7 Plugged 7 tubes in heat exchanger HE-1A.
7/15 HE-1A passed leak rate test.
8/20 Refilled primary system
8/26-27 Loaded core
8/27 Refilled secondary system
8/28 AM - Licensee logs show that the cooling systems were started
and a loss of "several hundred gallons of heavy water" was
noted. Analyzed spent fuel pool, liquid waste system, and
secondary coolant system; tritium found in secondary system.
8/28 12:00 - Telephone notification to Region I reporting:
- Loss of "several hundred gallons" of primary coolant
- Tritium detected only in secondary system
- No release to surroundings
- No Technical Specification limit exceeded '
Isolated and drained the two main heat exchangers and drained
secondary sides. (HE-1A showed higher tritium concentration).
Tested HE-1B and HE-2 (purification HX) satisfactorily.
Drained primary side of HE-1A, pressure tested secondary side
with results indicative of leaks.
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1987(Continued)
8/31 Plugged 15 tubes in HE-1A following numerous leak checks.
Licensee operated cooling tower fans "
... to aid in
evaporation."
< 9/3 Established 70 gpm dilution flow from potable water to sanitary
sewers.
9/4 10:30 - Telephone followup notification to Region I reporting:
- Detection of leaks in 15 tubes in heat exchanger and
plugging of affected tubes.
- Having restored secondary flow on 9/3 to check for
vibration.
- Estimated loss of 300 gallons (within factor of 2) of
heavy water (late calculations indicated 400 gallons).
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No indication of tritium releases provided.
9/5 Detected and plugged additional leaking tube in HE-1A.
9/10 Re-routed secondary N-16 sample return to pump suction header
to minimize liquid discharge to storm sewers.
9/? Licensee believes a telephone report was made to NRC to discuss
method of tritium disposal. No NRC records exist of this phone
call.
9/12-13 Operated reactor at 5 MWt to release tritium via evaporation.
9/14 Operated reactor at 5 MWt (approximately 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />) to release
tritium via evaporation.
9/25-30 Operated reactor at 5 MWt to release tritium via evaporation.
Secured 70 gpm sanitary system dilution flow and established
normal 20 gpm cooling tower blowdown.
10/? Telephone report from licensee informing Region I that written
report was about to be sent. Licensee believes the call
involved a discussion of report content details. No record
. exists of this call.
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Enclosure 1 - Review of Event 5
1988-
12/? A reporter from the Montgomery County Sentinel toured the
reactor facility with the licensee. The reporter is told of an
event involving a radiological release which is said to have
occurred "last August".
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1989
1/5 Region I Public Affairs Officer receives an inquiry from the.
Montgomery County Sentinel reporter regarding the leak. Region I
determines an event occurred in August 1988, which involved
leakage from a cooling system for the biological shield wall.
No records of a primary system leak occurring in August 1988
were located.
1/18 Based on phone conversations with the licensee, Region I deter-
mined that an event consistent with that described to the
reporter occurred in the summer of 1987 and that the licensee
submitted an informal event report in a letter- dated
October 26, 1987; however, no record exists that this letter was
received in Region I.
1/23 * Region I received a copy of the licensee's October 26, 1987
letter.
- Press inquiries are received about the event from the
Washington Post indicating the Post was developing this
story.
- PNO-I-89-005 was issued around 4:45 p.m.
- The Commissioners' Assistants were briefed at about
8:15 p.m.
1/24 Region I Public Affairs Officer provided copies of the
October 26, 1987 letter to the two reporters he had been dealing
with on this event.
1/26 Region dispatched two man team to investigate the event.
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Enclosure 1 - Review of Event 6
D. NRC Followup to the Event
NRC Region I was notified of the degradation of the tubes in one of two
primary-to-secondary system heat exchangers in phone calls made by the NBS
licensee on August 28 and September 4,1987. No mention of radiological
releases were made during either of these calls. The licensee did not
indicate that either call was being made pursuant to Technical Specifica-
tion reporting requirements. In January 1989, when Region I became aware
of the tritium releases which occurred, a two-man team was dispatched to
the site to review the event and its technical significance and to deter-
mine if the licensee properly reported the event. The results of this
review are provided in Inspection Report No. 50-184/89-01.
In addition, Region I reviewed its records and practices to determine
how the original phone reports were handled and to attempt to determine
the disposition of the licensee's October 26, 1987 letter.
E. Conclusions
1. Region I concluded that the event discussed by the NBS licensee in
its August 28 and September 4, 1987, phone calls and in its
October 26, 1987, letter occurred as it was described.
2. Region I verified that the event involved a degradation of the l
primary-to-secondary heat exchanger tubes which resulted in a leak
rate substantially in excess of that allowed by Technical
Specification.
3. Region I verified that the radiological releases associated with the
event were within Technical Specification and 10 CFR 20 limits and
were not reportable based upon the quantities released. The radio- !
logical significance of these releases was minimal.
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4. The licensee failed to formally report the event pursuant to Tech-
nical Specification requirements associated with degradation of pri- !
mary system barriers. Consequently, a Notice of Violation is being
issued.
5. Region I did not fully recognize the Technical Specification
implication of the leak rate when it was informed of the event in
1987. The Region did not promptly followup the initial phone call l
with the licensee. As a result, although the licensee claims to have
made two additional phone notifications regarding the event, with the
release plans discussed during at least one of them, the NRC has no
records of receiving these subsequent calls or the licensee's
Octcber 26, 1987 letter.
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UNITED STATES
y , NUCLEAR REGULATORY COMMISSION
_g ,j REGION I
- 476 ALLENDALE ROAD !
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KING OF PRUSSIA, PENNSYLVANIA 19408
- "* FEB 0 21 gag
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Docket No. 50-184
U. S. Department of Commerce
National Institute for Standards and Technology
l ATTN: Dr. R. S. Carter, Chief
l Reactor Radiation Divisior,
Gaithersburg, Maryland 20899 i
Gentlemen:
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Subject: Inspection Report No. 50-184/89-01
An announced, reactive inspection was conducted on January 26, 1989 at the
research reactor facility in Gaithersburg, Maryland. The purpose of the
inspection was to review the circumstances connected with a controlled but
non-rcutine release of tritium in September,1987. This release occurred via the
mechanical draft cooling tower associated with the reactor secondary cooling
system, as well as via a storm drain at the facility. . The tritium released in
this manner originated from a primary to secondary leak in the reactor cooling.
system, in one of the two main reactor heat exchangers. Some water contaminated
with tritium was also released into the sanitary sewer system during this
period.
The findings of this inspection indicate that the corrective actions following
discovery of the primary to secondary leak in the ' heat exchanger were timely and ,
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well executed. The release of the tritium contaminant in the secondary coolant
via the cooling tower also appears to have been carefully reviewed for safety
and compliance prior to the release. The monitoring program that was implemented
during the release appears to have been adequate to support the release
calculations, and showed that the concentrations of tritium at the site boundary
were well below the applicable NRC limits for the general public.
Although you met the immediate telephone reporting requirements of your
Technical Specifications by notifying NRC Region I of the occurrence of the
leak, you failed to submit the required two week written report. This failure to
submit a written report to the U. S. Nuclear Regulatory Commission, ATTN:
Document Control Desk, Washington, DC 20555, as required by Section 7.8 of your
Technical Specifications and 10 CFR 50.4 constitutes an apparent violation of
the Technical Specifications reporting requirements. Details are provided
in the enclosed Appendix A and the enclosed report. You are required to respond
to the violation in accordance with the instructions contained in the enclosed
Appendix A.
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'U S. Department of Commerce 2 B 0 2.1989
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Your cooperation with us is appreciated. -
Sincerely,
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Ronald R. Bellamy, Chief M
Facilities Radiological Safety.
and Safeguards
Division.of Radiation Safety and
Safeguards
Enclosures:
1. Appendix A, Notice of Violation
2. Inspection Report No. 50-184/89-01
cc w/encis:
J. Torrence, Deputy Chief, Reactor Operations
T. Raby, Reactor Supervisor
Public Document Room (PDR)
local Public Document Room (LPDR)
Nuclear Safety Information Center (NSIC)
State of Maryland (2).
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APPENDIX A -
NOTICE OF VIOLATION
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National Bureau of Standards Docket No. 50-184
Gaithersburg, Maryland
As a result of the inspection conducted on January 26, 1989, and in accordance
with the " General Statement of Policy and Procedure for NRC Enforcement
Actions," 10 CFR Part 2, Appendix C (Enforcement Policy,1986), the following
violation was identified:
-Technical Specification Section 7.7 requires, in part, that a
major degradation of one of the several boundaries which are
designed to contain radioactive materials resulting from the
fission process, shall be reported to the NRC in accordance with
Section 7.8(1). Technical Specification Section 7.8(1) requires,
in part, that the reports required by Section 7.7 be submitted,
in writing, within 2 weeks to the U. S. Nuclear Regulatory
Commission, ATTN: Document Control Desk, Washington DC 20555, as
required by 10 CFR 50.4.
Contrary to the above, on or about August 28, 1987, a major
degradation of the primary coolant boundary, was not reported, in
writing, to the NRC as required.
This is a Severity Level V violation (Supplement IV).
Pursuant to the provisions of 10 CFR 2.201, the National Bureau of Standards, is
hereby required to submit to this office within thirty days of the date of the
letter which transmitted this Notice, a written statement or explanation in
reply, including: (1) the corrective steps which have been taken and the results
achieved; (2) corrective steps which will be taken to avoid further violations;
and (3) the date when full compliance will be achieved. Where good cause is
shown, consideration will be given to extending this response time.
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U. S. NUCLEAR REGULATORY COMMISSION
I REGION I
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Report No. 50-184/89-01
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Docket No. 50-184
License No. TR5
Licensee: U. S. Department of Commerce
National Bureau of Standards
Gaithersburg, Maryland 20899
Facility Name: National Bureau of Standards
Inspection At: Gaithersburg, Maryland
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Inspection Conducted: January 26, 1989
Inspector: /
[. Limr'oth, Project Engineer, Section 3A
2 / f /80)
date
Branch 3, Di ision o Reactor Projects l
O 'Z-/2-/ f 7
date
5. sherbini, senior Radiation Specialist
Facilities Radiation Protection Section
Approved by: M5 O
M. Shanbaky, Chief , tacMities Radiation
2 M /P'f
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Protection Section i
Inspection Summary: Inspection on January 26, 1989 (Report No. 50-184/89-01)
Areas Inspected: Announced, reactive inspection to review the circumstances
connected with the release of tritium to the atmosphere, to a storm drain, and
to the sanitary sewer, in September 1987.
Results: One apparent violation was identified: failure to submit a written
re
S. port of the
Nuclear primaryCommission,
Regulatory to secondary leak
ATTN: within two
Document weeks
Control of Washington
Desk, the event toDCthe U.
20555, as required by Section 7.8 of the Technical Specifications and 10 CFR
50.4.
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DETAILS
1.0 Personnel Contacted
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- R. Carter, Chief, Reactor Radiation Division J
T. Hobbs, Chief, Health Physics i
- T. Michaels, NRC, NRR
- T. Raby, Deputy Chief, Reactor Radiation Division
- L. Slaback, Supervisory. Health Physicist
- denotes. attendance at the exit interview.
2.0 Event Description
The reactor was shut down on May 17, 1987 and the core unloaded for a.
period that was expected to last about three' months. The purpose of the
shutdown was to install an experiment at the reactor. The shutdown period I
was also to be used for major maintenance on the reactor systems. One of I
these maintenance items was .to locate and repair a small leak in heat
exchanger HE-1A,.one of the two main reactor system heat exchangers. The l
1eak had-been identified on the basis of sampling of the secondary system 1
for tritium content.
Following shutdown, both the primary and secondary systems were drained.
The primary system contained approximately 13,000 gallons of heavy water
(deuterium oxide), and was drained to a storage tank. The secondary system
contained a total of about 100,000 gallons of water, and was drained to the
cooling tower basin or to holdup tanks and then to the sanitary sewer. The
basin normally contains most of the secondary water, the balance being in -
the secondary system piping. The cooling tower is a mechanical ~ draft :
cooling tower equipped with three fans. Water is pumped to the top of the
tower and then allowed to cascade down a series of louvers while cooling
air flows past the water. The top of the cooling tower is about 21' above
ground level. The licensee stated that at full reactor power (20 MW
thermal) the heat output from the reactor will evaporate approximately
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100,000 gallons of water' to the atmosphere in a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> period. The
evaporated water is replaced by fresh makeup water, either continuously or
intermittently. The cooling tower basin is located directly below the tower
and is open to the atmosphere. During repair of the small leak following
shutdown, several tubes in the heat exchanger were identified as possibly
contributing to the leak, and seven tubes were plugged. The system was
successfully pressure tested on July 15, 1987, using high pressure air.
On August 20, 1987, after completion of the maintenance work, the heavy
water was returned to the primary system, and by August 27 the core was
loaded into the reactor. It was found necessary to add 55 gallons of heavy
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water to bring the water in the system to the desired level. The licensee l
stated that this is normal and expected as a result of minor leaks and
evaporation during the lengthy shutdown period. The secondary system was
then filled on August 27, and the primary system pumps were operated for ;
testing purposes. A second 55 gallons of heavy water were added to maintain 4
the desired level. The licensee stated that this addition was still not I
unusual. On the morning of August 28, it was discovered after operating the {
system pumps that the level of the heavy water in the primary system had
dropped overnight. Visual inspection of all systems did not reveal any
leaks. The licensee, however, did not check the tritium concentrations in
the secondary side for possible primary to secondary leaks. A third 55
gallon quantity of heavy water was then added to the primary system, but
the water level could not be maintained. The licensee then decided to
analyze samples of water taken from several locations in the system for
tritium content. The locations were chosen as being likely points of
contamination in case of a primary system leak. Elevated tritium
concentrations were found in the samples taken from the secondary cooling
system, indicating a heat exchanger leak. The heat exchangers were then
isolated and drained and the water from each was analyzed. In this way, it
was found that the leak was in main heat exchanger WE-1A, the sane heat l
exchanger that was repaired earlier. The primary system was then drained
and repairs started. Sixteen tubes in HE-1A were plugged before repairs
were completed. The licensee believes that the leak probably occurred after
the primary pumps were started on August 27. The reactor was operated for
the first time following the May shutdown on September 12, 1987.
Following discovery of the primary to secondary leak in the heat exchanger,
the licensee analyzed the secondary water for radioactivity content and
found a tritium concentration of slightly over 2 uCi/ml, which is about
four orders of magnitude higher than normal operating levels. Using a total
secondary volume of 100,000 gallons, the licensee estimated that the
tritium leak was approximately 800 curies (Ci). The secondary water also
contained about 2-3 millicuries (mci) of nongaseous radioactive material,
mostly cobalt (Co-60). An analysis of the pr' mary coolant at that time ,
showed a tritium activity of 0.53 mC1/ml. Based on this value and the total
activity calculated to be in the secondary system, the licensee estimated
the magnftude of the leak to be. approximately 400 gallons of heavy water.
3.0 Review of the Events Connected With The Release of Radioactivity
On September 9, 1987, the licensee had approximately 100,000 gallons of
secondary water contaminated with about 800 Ci of tritium and about 3 mci
of Co-60. About 690 Ci of the tritium were in the cooling tower basin, and
the remaining 110 Ci were in holdup tanks containing secondary water
drained from the heat exchangers. The licensee stated that they evaluated
the various possibilities available to them at the time for disposing of
this contaminated water. Based on their evaluations, it was decided that
evaporation into the atmosphere via che cooling tower would have the least
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er,vironmental impact and that the released radioactivity concentrations
would be well below allowable limits. The licensee's records indicated that
the options were discussed by the Reactor Hea.th Physics Supervisor and the
Chief of Health Physics at the National Bureau of Standards (NBS, now
NIST). According to these records, the timing of the release, the most
favorable meteorological conditions, and environmental monitoring were
discussed on August 31 and again on September 3. The record also shows that
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the matter was discussed during the September 9, 1987 meeting-of the Safety
Evaluation Committee. According to the minutes of the September 9 meeting,
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the Reactor Health Physicist stated that his calculations showed that it
was not'likely for the tritium concentration in the atmosphere to exceed
the concentration limits for air specified by NRC regulations (10 CFR Part
20.106).
The licensee initially decided to evaporate the water in the basin by
,
heating it with steam supplied directly to the basin. However, this method
did not work, and evaporation was minimal. It was then decided to heat the
water by operating the reactor at low power and using the normal reactor
cooling system to evaporate the water. According to the reactor's log book.
the reactor was operated at a power level of 5 W from 1343 on September 12
to 1444 on September 13, 1987, a total of a little over 25 hours2.893519e-4 days <br />0.00694 hours <br />4.133598e-5 weeks <br />9.5125e-6 months <br />. The
reactor was operated at 5 MW for about two hours on September 14, and again
at 5 MW from 2012 on September 25 to 0700 on September 30, 1987. for a
total of about four days and 11 hours1.273148e-4 days <br />0.00306 hours <br />1.818783e-5 weeks <br />4.1855e-6 months <br />. Practically all the tritium in the
secondary cooling system ( approximately 680 C1) was evaporated during
these periods of low power reactor operation.
The. licensee's, analysis of the secondary water on September 12 showed about
2 uCi/ml of tritium. The water analysis after shutdown on September 13'
showed-about 0.9 uti/mi of tritium, and it dropped to 0.8 uCi/mi on
September 14. The tritium level at restart on September 25 was about 0.8
uC1/ml and at shutdown on September 30 was about 0.05 uCi/ml. The reactor
was subsequently operated at 10 and then 15 MW during October, and the
tritium levels in the secondary system had dropped to essentially normal
operating levels of 0.0002 uC1/ml by October 6, 1987.
During the period of reactor operation on September 29, 1987, the temporary
piping connecting the N-16 monitor outlet to the cooling tower basin broke,
allowing the secondary water flowing through the monitor to flow into a
storm drain at the reactor site. The system used by the licensee to ensure
the quality of temporary modifications will be reviewed during a future
inspection. The N-16 monitor is th immersion type GM detector connected to
the secondary system and used to detect primary to secondary leaks during
reactor operation. Part of the secondary system flow is routed through this
monitor (about 2-4 gallons per minute) and the dis::harge from the monitor
is routed'to a local storm drain. Following discovery of the heat exchanger
leak, the licensee had temporarily re-routed the monitor outlet back to the
basin. The licensee estimated that when this temporary connection broke on
September 29, about 4000 gallons of secondary water went into the storm
..;
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_i____.._._._ .i_m._. __ _ _ _ . _ . !
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drain. Based on a' water analysis at the time of the break that showed about
0.4 uCi/ml, the licensee conservatively estimated a total release'of-10 Ci-
of tritium. Approximately 100 uCf of Co-60 would have also been released to
the storm drain. The licensee has permanently re-routed the N-16 monitor
discharge to the cooling tower basin. The licensee stated that in an
attempt to dilute the activity in the storm drain, a total of 2 million
gallons of clean water was pumped into the storm drain over a nine-day
period'following the spill.
4.0 Radiological Consequence
Based on analyces of the secondary reactor $ooling system water, about half
of the tritium activity, approximately 400 Ci, was released to the -
atmosphere via the cooling tower during the 25 hour2.893519e-4 days <br />0.00694 hours <br />4.133598e-5 weeks <br />9.5125e-6 months <br /> period of September
12-13. According to the minutes of the Safety Evaluation Committee meeting,
the licensee calculations indicated that the tritium concentration in:the
atmosphere would not exceed the maximum permissible concentration.in 10 CFR
Part 20. The release on September 12-13 was conducted over a weekend
because public access to National Institute for Standards and Technology
(NIST) grounds is restricted during periods. outside of normal working
hours. Releases during the period from. September 25 to September 30
averaged from about 100 Ci/ day during the first day to about 10 C1/ day
during the last day.-These releases were carried out during periods that
included norma 1' working hours at NIST. The licensee stated that the-
extensive air sampling during the first period of release on September
12-13, had shown' that the tritium concentrations -in the air within i.he NIST
facility fence were substantially below allowable 10 CFR 20.106 limits.
Since the second period of release from September 25-30 involved much lower
release. rates than those that occurred during the first period, the
licensee determined that it was not necessary to limit the September 25-30
releases to periods of restricted access to NIST facilities'. Only.'a small
quantity of tritium was released during the brief period of operation on
September 14.
l The inspector reviewed the licensee's records of the results of the
environmental monitoring and performed independent calculations to verify
the licensee's analysis predicting the expected concentrations as a result
of the releases. The calculations supported the licensee's conclusions that
the annual average concentration of tritium was not likely to exceed the
l allowable concentrations for the general public as specified in 10 CFR part
20.106.
The reactor Technical Specifications place limits on the allowable
concentration of radioactive material at the point of release. The
L inspector made independent calculations that showed that the' average daily
concentration of tritium in the air leaving the tower, assuming one cooling
tower fan operating at the rated flow rate, was substantially below the
permissible Technical Specification limits for concentrations at the point
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of release to the atmosphere. However, the limits in the Technical-
l Specifications apply to releases from the reactor stack (elevated release)
whereas the releases' in question were from the cooling tower (ground . level
release). The top of the tower is 21 high whereas the top of the stack'is
about 100' high. The applicability of the Technical Specification limits to
such ground level releases will be reviewed during a future inspection.
The. releases of' radioactive gases to the atmosphere during normal reactor
operation over the past'several years is shown below to provide a
perspective. The table shows the quantities released and the average annual
- concentrations at the point of release. Argon-41 is generated in the
reactor by neutron capture in naturally occurring argon in the air.
Argon-41 Tri tium
Ci pCi/cc Ci pCi/cc
(annual average) (annual average)
1983 477 1.2 728 1.8
1984 274 0.7 768 1.9
1985 852 2.1 234 0.6
1986 1087 2.7 450 1.1
1987 727 1.6 1154 2.6
1988 900 2.3 393 1.0
The average annual concentrations for Ar-41 and tritium shown in the table i
are substantially below the limits specified in the reactor's Technical
Specifications.
The break in the N-16 monitor released about 10 Ci os tritium and-about 100
uCi of Co-60 to the storm drain..The licensee added about 2 million gallons
of clean water to the storm drain over a nine-day period in an attempt.to
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dilute this activity. Independent calculations by the inspector showed that
the average concentration of radioactivity 1i the drain resulting from this
release, without' allowing for the dilution, was less than the maximum
allowable concentrations for liquid offluents to unrestricted areas
specified in 10 CFR Part 20.106.
The licensee also released about 110 Ci of tritium and about 2 mci of Co-60
to the sanitary sewer during the three month period of reactor shutdown.
Most of this activity originated mostly from draining the heat exchangers
after shutdown, the remainder coming mostly from blowdown from the cooling
tower. The water is drained from the heat exchanger to a sump, analyzed for
radioactivity, and then released to the sewer. The water released in this
manner is then diluted by the daily flow of water in the sewers, which
j
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averages about 340,000 gallons per day. The daily average concentration of
tritium after allowing for this dilution, was below the maximum
concentration permitted by 10 CFR Part 20.303.
.
5.0 Reporting Requirements
According to the reactor's Technical Specifications, Section 7.7, " Action-
To Be Taken in the Event of a Reportable Occurrence", all reportable
occurrences shall be reported to the NRC in accordance with Section 7.8(1)
of the Specifications. According to Section 7.8 " Reporting Requirements",
Part (1), reports shall be made to the NRC no later than the following day
by telephone or telegraph to the Director, NRC Region I. In addition, a
report is to be submitted within 2 weeks, in writing, to the Director,
Division of Reactor Licensii.g, NRC, Washington DC. It should be noted that
the NRC forwarding address for such a reportable event was amended by 10
CFR 50.4 to "U. S. Nuclear Regulatory Commission, Document Control Desk, <
Vashington DC 20555".
According to section 7.7 (4) of the Specifications, reportable occurrences
- *
shall i'aclude "(f) major degradation of one of the_ several boundaries which
are designed to contain the radioactive materials resulting from the
fission process". The -inspector determined that the leak identified on
August 28 constituted a major degradation of a boundary to contain
radioactive materials. This is based on the Technical Specifications
requirement that the reactor be shut down and corrective action taken if
~
primary coolant leakage in the heat exchanger exceeds 36 gallons per day.
The leak in question was estimated to be 400 gallons which most probably
occurred within a period of about 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. The inspector stated that
although a telephone notification to Region I was made, failure to submit
the required two-week writtr.n report to the NRC constitutes an apparent
violation of Technical Specifications reporting requirements
_
(50-184/89-01-01).
6.0 Exit Meeting
The inspector met with licensee representatives at the conclusion of the
inspection. The inspector presented the inspection findings to licensee
management. Licensee management stated that they believe they had conducted i
repair of the leak and subsequent effluent release in accordance with j
applicable safety principles i.nd regulatory requirements. ]
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ENCLOSURE 3 j
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Future Region I Actions j
l
As a result of our review of the 1987 tritium release event at. a National
Bureau of Standards reactor, the following actions are deemed appropriate: ,
i
1. NRC Region I will hold a management meeting with the National Bureau of
Standards licensee to discuss the event, its significance and the licen-
'
see's reporting of the event.
2. NRC Region I has been planning a seminar with Test and Research Reactor
licensees. The NBS event and Lessons Learned will be discussed during
this seminar.
4
3. NRC Region I Division of Reactor Projects and Division of Radiation Safety.
and Safeguards will hold training sessions to sensitize their respective l
staffs on the special handling considerations for non-routine reports
from test and research reactor licensees.
,