ML20235Q485
| ML20235Q485 | |
| Person / Time | |
|---|---|
| Issue date: | 09/23/1987 |
| From: | Stello V NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| To: | |
| Shared Package | |
| ML20235Q455 | List: |
| References | |
| RULE-PRM-50-44 NUDOCS 8710070606 | |
| Download: ML20235Q485 (18) | |
Text
.
NUCLEAR REGULATORY COMMISSION 10 CFR 50 Docket No. PRM-50-44
, Committee To Bridge the GAP; Denial of Petition for Rulemaking m
AGENCY:
Nuclear Regulatory Comission.
fl T
ACTION:
Denial of Petition for Rulemaking.
L ll
SUMMARY
- The Nuclear Regulatory Comission (NRC) is denying a petition for rulemaking submitted by the Committee To Bridge the Gap. The petitioner requested that the Commission amend its regulations to require all licensees g
whose reactors employ graphite as a neutron moderator or reflector and whose licensed power is greater than 100 W to:
(1) formulate and submit for NRC approval fire response plans for combating a reactor fire involving graphite and other constituent reactor parts (e.g., fuel); (2) fonnulate and submit for Q
NRC approval evacuation plans in case of a reactor fire; and (3) perform h
measurements of the Wigner energy stored in the graphite of their reactors and j
[
submit these measurements to the NRC for review, together with a revised safety analysis that shall address the risks and consequences of a reactor fire.
The petitioner believes these requirements are necessary because the previous NRC safety evaluations of these reactors allegedly were based on a belief that graphite fires were not cred1bie sind on an inability of the NRC and its contractors
~
to properly calculate Wigner energy in the graphite. The Comission is denying the petition because Fort St. Vrain t.uclear Generating Station and all NRC-licensed research and test (non-power) reactors have approved plans for dealing with emergencies in accordance with existing regulations. The protective actions are based on conservative dose calculations consistent with those proposed by the petitioner.
Graphite burning is a very low-probability (i.e., noncredible) event and its potential is essentially independent cf stored energy in graphite. Empirical 8710070606 870923 PDR PRM 50-44 PDR
measurements of stored energy in graphite are not needed to perform an evaluation of the releasable stored energy.
Furthermore, the requirement for such measure-ments could result in personnel exposures that would be inconsistent with NRC's as low as is reasonably achievable (ALARA) principle.
ADDRESSES: Copies of the petition, public comments and abstracts of the comments received on the petition, and the Brookhaven National Laboratory Report NUREG/CR-4981 are available for inspection and copying under Docket No. PRM-50-44 in the NRC Public Document Room, 1717 H Street NW, Washington, DC. Copies of NUREG/CR-4981 may be purchased through the U.S. Government Printing Office by calling (202)275-2060 or by writing to the U.S. Government Printing Office, P.O. Box 37082, Washington, DC 20013-7082. Copies may also be purchased frcm the National Technical Information Service, U.S. Department of Commerce, 5285 Port Royal Road, Springfield, VA 22161.
FOR FURTHER INFORMATION CONTACT: Theodore S. Michaels, Standardization and Non-Power Reactor Project Directorate, Office of Nuclear Reactor Regulation, U.S. Nuclear Regulatory Commission, Washington, DC 20555, Telephone (301) l l
492-8251.
(
SUPPLEMENTARY INFORMATION:
I The Petition l
A petition for rulemaking was filed by the Committee To Bridge the GAP (CBG) on l
July 7, 1986. The petition was docketed by the Comission on July 7,1986 and was assigned Docket No. PRM-50-44. A notice requesting comments on the peti-tion was printed in the Federal Register on September 3,1986(51FR31341).
The petition requests that the Commission amend its regulations.
l Basis for the Request 1
The petitioner offered the following justification for the proposed revision of the regulations:
l 1
The occurrence of a graphite fire at the Chernobyl plant in the l
Soviet Union demonstrates that such fires are credible events. The 2
1 l
j NRC and its licensees have mistakenly dismissed graphite fires as noncredible events.
New experimental data show that NRC's generic analysis of stored i
energy in research reactor graphite significantly underestimates the I
actual amount of stored energy, and thus underestimates the associ-l ated risk of graphite fire.
The NRC failed to require basic safety measures that could help to reduce the threat of such a fire. Licensees whose reactors use graphite, including dozens of non-power reactors and one commercial j
power reactor, have no fire response plans for combating graphi1e fires in their reactors. Non-power reactor licensees do not have I
4 adequate emergency plans to evacuate members of the public in the i
event of a graphite fire or other severe accident.
For these reasons, the petitioner would require all licensees whose reactors employ graphite as a neutron moderator or reflector and whose licensed power is greater than 100 W to:
(a) Formulate and submit for NRC approval fire response plans for
{
j combating a reactor fire involving graphite and other constituent reactor parts (e.g., fuel) which might be involved in such a fire, l
taking into consideration the potential for explosive reactions.
Response plans shall identify precisely which materials will be used to suppress a fire without increasing the risk of explosion, and shall indicate where and in what quantities these materials l
will be stored.
J (b) Formulate and submit for NRC approval evacuation plans for a reactor fire.
Plans should include evacuation out to a sufficient distance from the reactor such that no member of the public receives a dose to the thyroid greater than 5 rem, assuming a release to the environment of 25% of the equilibrium radioactive iodine inventory.
I (c) Perfom measurements of the "Wigner energy" stored in the graphite of their reactor, and submit these measurements to NRC for review 3
i
I l
together with a revised safety analysis, which shall' address the risks and consequences of a reactor fire. A sufficient number of J
graphite samples shall be measured to identify the location of
. maximum stored energy, and to detemine the maximum quantity of stored energy within 10%.
)
l Public Comments on the Petition On September 3, 1986, the' Commission published a notice in the Federal Register (51 FR 31341) requesting comments on the petition. The NRC received nine requests for an extension of the coment period. An extension of the comment period was granted, changing the closing date for the comments from November 3, 1986, to February 2,1987. A total of 27 comments were received, six of which supported the petition and 21 of which opposed the petition. Of the six comenters supporting the petition, two were individual citizens and four were from citizen's groups. Of the 21 comenters opposed to the petition,15 were universities or university-related organizations, four were companies involved s
with the nuclear industry, one was a state government agency, and one was an individual citizen.
J Of the comments in support of the petition, none offered any specific technical insights but rather simply endorsed the information and basis of the petition.
e These coments covered general concerns that include:
the potential for graphite fires,
?;
training of firefighters to manage graphite fires, evacuation of persons on-site and in nearby areas in the event of an accident.
. Highlights from the comments opposing the petition are as follows:
CBG's comparison of research reactors to the Chernobyl-4 (RBMK) reactor ignores the extreme differences in power level, core size, fission product inventory, operating temperature, reactor control systems, and inherent design characteristics.
4
I CBG's inference that graphite fires were the initiating events in both the Chernobyl and Windscale accidents cannot be substantiated.
The operating temperature of the Chernobyl graphite (700 C) dismisses CBG's contention that stored energy in the irradiated graphite played any role in the Chernobyl accident.
CBG ignores the necessity for an initiating event to raise the graphite temperature 50C'-100C* above its normal operating temperature before any Wigner(stored)energyingraphitecanbereleased.
h~'
CBG 1.gnores the fact that only the releasable stored energy, not the total d
i stored energy, in graphite, in accordance with the annealing temperature, R
can contribute to a graphite temperature increase.
i 7
The conditions necessary for graphite burning do not exist nor can they i
I be created by random events in non-power reactors.
h$
The conditions necessary for graphite burning do not exist in the Fort St. Vrain reactor.
lh Operating temperatures of the graphite in the Fort St. Vrain reactor jg!
preclude the accumulation of any significant quantity of stored energy (i.e., the graphite is self-annealing).
{(
1'\\$hj[
NRC-approved emergency plans (required by 10 CFR 50, Appendix E) are in
[
place at all NRC-licensed reactors and are adequate and acceptable.
Measurement of stored energy is not consistent with the ALARA philos-ophy, since it requires the unnecessary exposure of reactor personnel.
CBG fails to provide a technical basis for any of the petition's proposed requirements.
The comments opposing the petition are too numerous to address individually.
However, each comment has been considered by the staff and its contractors in analyzing the petition and in developing the NRC position. Abstracts of all 5
1 comments received and the full text are available at the NRC Public Document j
Room in the Docket file PRM-50-44, as noted in the address section above.
I Analysis of the Petition k
i (1) The petitioner asserts that "the occurrence of a graphite fire at the Chernobyl plant demonstrates that such fires are indeed credible events."
l CBG filed its petition on July 7, 1986. Consequently, only fragmentary information, mostly conjecture, was available before the petition was filed. More detailed and definitive information was first made available, outside the Soviet Union, hl during a meeting held by the International Atomic Energy Agency (IAEA) in Vienna, i
Austria, on August 25 to 29, 1986. Without the benefit of the detailed Soviet report, the basis of the petition is seriously flawed.
In response to the CBG assertion regarding the Chernobyl event, the NRC selected
(
Brookhaven National Laboratory (BNL), operator of the Brookhaven Graphite Research Reactor, whose staff is recognized internationally for its research on reactor-grade graphite and its properties, to review the published information and x
determine its relevancy to the use of graphite in NRC-licensed reactors.
In addition, BNL personnel reviewed the Chernobyl and Windscale accidents and the o
role, if any, of the graphite moderator in these events. The results of this p
review are contained in NUREG/CR-4981, "A Safety Assessment of the Use of Graphite (h
in Nuclear Reactors Licensed by the U.S. NRC," July 1987. This report is f
available as noted in the address section above.
I
.m t The staff has used the BNL report, comments received from the public, and its F
own understanding of and expertise relevant to the use of graphite in non-power reactors and Foit St. Vrain to evaluate and respond to the assertions and proposed b
requirements of the CBG petition (PRM-50-44).
In their evaluations of the Chernobyl accident, both Soviet and international scientists agree that graphite burning did occur during this accident. However, most of the experts, including the scientists at BNL, consider the graphite burning a secondary or corollary event resulting from the explosions that occurred as a result of a very rapid reactivity insertion that overheated the fuel and cladding. The explosion created the conditions necessary to initiate and 6
I l
f l
sustain graphite burning (e.g., fragmentation of fuel and graphite, rupture of the moderator inert gas boundary, admission of air, a favorable ratio of graph-ite volume-to-surface area, sustained heat input from asphalt fires, and decay heat). Although the petition considers the Chernobyl accident a demonstration of graphite fire credibility, the accident confirms that initiation and sustained burning of graphite require the existence of a complex combination of ideal conditions, which are extremely difficult to achieve in any real situation and are virtually incredible in the reactors being considered under this petition.
The words " credible" and incredible" have been used in many AEC/NRC safety analyses. As used by the staff, these words have always been a qualitative statement of the likelihood or probability ci an event or condition occurring.
Accordingly, the staff's conclusion that sustained or self-sustained graphite j
h burning is not a credible event in NRC-licensed reactors is still valid (i.e.,
l the random simultaneous occurrence of the several conditions necessary for h
sustained graphite burning or self-sustained graphite burning is an event with a very small probability of occurring). The staff thus concurs in the conclu-T sion reached in the BNL report:
"There is no new evidence associated with the I
analyses of either the Windscale accident or the Chernobyl accident that indi-cates a credible potential for a graphite burning accident in any of the J
f reactors considered in this review. Nor is there any new evidence that detailed case-by-case safety analyses of the role of graphite in NRC-licensed reactors Accordingly, there has been no change in the staff's assessment are warranted."
y$1 of graphite burning, the Chernobyl accident notwithstanding, in NRC-licensed U
reactors, and no changes are required in the staff's previous findings in the h[
j safety evaluation reports prepared for these reactors.
r-(2) The petitioner states that "the NRC has failed to require basic safety
)
measures to reduce the threat of a graphite fire."
e cw 1
The petitioner did not identify the " basic measures" the NRC has failed to require and provided no basis for this statement. The staff considers that the elements of the NRC regulatory and licensing process represent the basic safety measures required of licensees to ensure the safe design and operation of their reactors as well as to provide specific plans and procedures for managing and responding to off-normal conditions and accidents. Some examples that are l
relevant to fire detection, protection, and mitigation are listed below:
Covers all types of fires, including graphite fires.
7 r
Safety reviews of non-power reactors include an assessment of the fire protection systems at each facility.
Fire detection, fire extinguishers, l
fire alarms, fire prevention, fire fighting training of facility personnel, and onsite and offsite response to fire alarms are typical
)
areas included in the safety review.
Inadequacies identified during the review must be corrected before a license is granted.
~
Each non-power reactor licensee is required by conditions of the license t
(Technical Specifications) to provide a safety review for experiments
- ~
to be inserted in their reactors and for changes in reactor operation.
g Among many other safety considerations, an assessment of fire potential l t hi (e.g..flammablematerials)isincluded.
Each non-power reactor licensee has responded to the requirements of 10 CFR 50.54(q) and 10 CFR 50, Appendix E, in submitting an emergency-
!]
f plan for NRC review and approval. All licensed non-power reactors now have approved emergency plans and the necessary implementing l
procedures. These plans were reviewed against ANSI /ANS-15.16-1982 and q
Regulatory Guide 2.6, proposed Revision 1, as outlined in NUREG-0849,
" Standard Review Plan for the Review and Evaluation of Emergency Plans U
for Research and Test Reactors."
SQ Examples of the evaluation items that are relevant to " basic safety measures p-to reduce the threat of... fire" are listed below:
k (e) The [ emergency] plan should also describe non-radiological monitorsorindicators....(2)Firedetectors....
(.
(b) The emergency plan should describe an initial training and periodic retraining program designed.to maintain the ability of emergency response personnel to perfonn assigned functions for the following:
...f.
Police security, ambulance, and fire fighting personnel....
(NUREG-0849, Sections 8.0 and 10.0)
The licensee for Fort St. Vrain has satisfactorily met the requirements of 10 CFR 50.48 and 10 CFR 50, Appendix R.
Appendix R, " Fire Protection Program 8
L-- _
1 l
for Nuclear Power Facilities Operating Prior to January 1,1979," sets forth fire. protection features required to satisfy Criterion 3 of Appendi_x A to 10'CFR 50. These NRC requirements include _the " basic safety measdres to l
reduce the threat of a... fire."
i It is the staff's judgment that the NRC has required adequate basic safety j
measures to reduce the threat of. fire as well as to mitigate the consequences of any fires that do occur. These measures have been reviewed, approved, and
. c,.,_-
implemented for all licensed reactors. They generally apply to all fires and.
a h
have been found to provide acceptable protection for'the health and safety of hdj the public.
i
[]
The petitioner alleges that " licensees have no fire response plans for 3d (3)
.f af.I graphite fires."
As discussed in item 2, above, all licensees have NRC-approved emergency plans inaccordancewith10CFR50.54(q)and10CFR50,AppendixE. These plans provide for response to fires, for training of fire fighting personnel, and for periodic drills to demonstrate proper operation of the plan in accordance with procedures developed for each facility. One commenter opposing the petition l
reported that the offsite fire fighters and their supervisors were regularly j) j trained in fire fighting procedures for their facilities and that the fire fighters-y Fh were confident that they were prepared to deal with the type of fires they could encounter, including a fire involving graphite. This is consistent with BNL research,2 which recomends a basic fire fighting technique for graphite fires, k
that is, exclude air or oxygen and cool the graphite. Success in using this i
[I basic " cool-and-smother" technique was demonstrated during the Chernobyl accident, k
Cold nitrogen gas was pumped into the bottom of the reactor to successfully cool the graphite and fuel debris while excluding oxygen to smother any burning.
Also at Chernobyl, graphite blocks were successfully quenched using water (NUREG-1250,pp.4-12,4-21,and7-23). Since this basic cool-and-smother 1
2
.W. Powell, R. A. Meyer, and R. G. Bourdeau, " Control Radiation Effects in R
a Graphite Reactor Structure," Proceedings of the Second United Nations International Conference on the Peaceful Uses of Atomic Enerqy, Vol. 7, 1958,
- p. 293.
9
technique is effective for most fires, the staff has concluded that the licensee' existing emergency plans provide an adequate response for graphite fires as well as any other type of fire.
(4) The petitioner asserts that "non-power reactors do not have adequate emergency plans to evacuate members of the public in the event of a graphite fire."
Neither the petitioner nor any of the citizens' groups or individuals support-ing the petition provided a basis in support of this assertion. The staff has reconsidered the need to provide a plan to evacuate members of the public located off site in the very unlikely event of a graphite fire and, in the j
gl course of evaluating this petition, has not identified any such need, e
li ;
a 0
As stated in Regulatory Guide 2.6, Revision 1:
[
. d vjj In the judgement of the NRC staff, the potential radiological hazards to the public associated with the operation of research and test reactors are considerably less than those involved with nuclear power plants.
In addition, because there are many different kinds of non-power reactors, the potential for emergency situations arising and the f
consequences thereof vary from facility to facility. These differences j
$9 and variations are expected to be reflected realistically in the h
emergency plans and procedures developed for each research and test h
reactor facility.
$ fM Accordingly, each non-power reactor licensee has developed an emergency plan
~
based on the identified characteristics of its reactor facility. To assist licensees in meeting the requirements of 10 CFR 50, Appendix E, Regulatory Guide 2.6 (ANSI /ANS-15.16-1982 Table 2) provides an " Alternate Method for Determining the Size of an Emergency Planning Zone (EPZ)." Table 2 is based on highly conservative dose calculations that are generically applicable to non-power reactors. These calculations include the very conservative assumption for non-power reactors that 25% of the equilibrium radioactive iodine is gaseous and will escape from the reactor building into the environment.
It is the current and standard practice of the NRC staff to use the 25% iodine source tem with regard to 10 CFR 20 recommended dose considerations in its safety evaluations of non-power reactors. Table 2, which is based on power level, recomends 10
that reactors with power levels less than or equal to 2 MW use their " operations boundary" for their EPZs, which essentially recognizes that a reactor of this power level will only need to initiate protective actions for members of the general public on site and will not pose an unacceptable radiological hazard to members of the public off site. There are only five licensed non-power reactors containing graphite that have power levels greater than 2 MW. Three of the reactors have power levels less than 10 MW, one has a power level of 10 MW, and one has a power level of 20 MW. Table 2 recommends an EPZ of 100 meters for non-power reactors with power levels greater than 2 MW and equal to or less than 10 MW, and 400 meters for those with power levels greater than 10 MW and equal to or less than 20 MW. The licensee for each of these reactors has an hij NRC-approved emergency plan that takes into consideration the specific charac-teristics of each reactor (e.g., fission product inventory and engineered safety features) in the development of the action levels, procedures, and protective l
actions necessary to protect all members of the public within its EPZ. Regula-
[
tory Guides 1.3 and 1.4 recommend the use of the 25% radioactive iodine source term in determining the compliance of power reactors with the siting, containment, f
and dose guidelines of 10 CFR 100. The staff believes the current regulatory practices are suitable to ensure that the basic statutory requirement, for adequate protection of public health and safety, is met.
4jj These emergency planning considerations are appropriate for reactors utilizing hh graphite components. Because the graphite contains no fission products and h
very few activation products, even the remote possibility of the graphite h
burning would not contribute to the radiological source term. Therefore, a k
graphite fire in and of itself presents essentially no radiological hazard to
+4 the public.
P Because of the major differences in design, power level, core size, fission product inventory, reactor control systems, and inherent reactor neutronics, comparison of the Chernobyl accident and its consequences with accidents and the resulting consequences for non-power reactors is not appropriate, nor is it meaningful. Many of the coments received in opposition to the petition speak
(
of the impropriety of comparing NRC-licensed non-power reactors with the Chernobyl RBMK-1000 reactor.
l The petitioner has not provided any proof of inadequacy in the emergency plans for non-power reactors. On the basis of a review of the guidance for 11
emergency planning contained in Regulatory Guide 2.6 and ANSI /ANS 15.16-1982 t
and the requirements fo 10 CFR 50, Appendix E, the staff has concluded that the 3
emergency plans previously approved by NRC are still appropriate and adequate.
Neither the petitioner nor the commenters supporting the petition have supplied infonnation that demonstrates that, even in the remote case of graphite burn-ing, there is a need to modify any existing emergency plans.
(5) The petitioner states that "NRC's generic analysis of stored energy in research reactor graphite significantly underestimates the actual amount of j
stored energy and thus underestimates the associated risk of graph 1te fire."
{
%~
The conditions necessary for stored energy releases in graphite are described h
in Section 3 of the BNL report. The staff agrees with the methodology derived i
q for estimating the stored energy that can be released from graphite and in the analysis applied to the estimation of stored energy releases in Section 6 of E'
the BNL report.
i L
I In Section 2 of the BNL report, the necessary conditions for graphite to burn fd are discussed in detail. A reassessment of the literature on the experiments
[
previously performed at BNL and the reported details of the Windscale and Chernobyl accidents are included in the BNL study. The conclusions reached as y
a result of these analyses are:
y@fh d}
[T]he potential to initiate or maintain a graphite burning incident y l }
is essentially independent of the stored energy in the graphite, h
and depends on other factors that are unique for each research reactor and for Fort St. Vrain.
In order to have self-sustained g-rapid graphite oxidation in any of these reactors, certain necessary conditions of geometry, temperature, oxygen supply, reaction product removal and a favorable heat balance must be maintained. There is no new evidence associated with either the Windscale Accident or the Chernobyl Accident that indicates a credible potential for a graphite burning accident in any of the reactors considered in this review.
On the basis of its review of the BNL report, the literature on BNL experiments, and the information on the Windscale and Chernobyl events, the staff finds that the conclusions reached by BNL are correct and adopts them as its own.
12
(6) The petitioner asserts that " actual empirical measurements of Wigner energy will be required to assess the magnitude of the energy stored in research reactor graphite."
Measurements of stored energy in its research reactor graphite were made by the University of California, Los Angeles, in the course of decommissioning its Argonaut research reactor. Several things learned from its program of sampling and measuring stored energy were reported by a comenter who opposed the petition. This information was also reported in a paper by Ashbaugh,
"~~
3 Ostrander, and Pearlman at the American Nuclear Society annual meeting in 1
7 June 1986, hh
.{
Stored energy decreases with increasing distance from the fuel region
-[- j (e.g., 5.61 cal /gm at 18 inches, 1.34 cal /gm at 22 inches, and an unmeas-l L
urable amount at 26 inches).
f Within the graphite island, stored energy decreases from 33.3 cal /gm at j
l the fuel box graphite interface to 19.2 cal /gm about 3 inches from the
{
fuel box toward the center of the graphite island.
f g
j J
These results illustrate the principles associated with the proposed requirement to measure the Wigner energy stored in the research and test reactor graphite, j
g The significant changes in stored energy with relatively small differences in MP location demonstrate the difficulty in select?ng the locations and the number of samples needed to characterize the " maximum stored energy and to determine b
the maximum quantity of stored energy to within *10%."
NL; c5 P
The bases for storage and release of Wigner energy in graphite are delineated b'
in the BNL report, which shows that there is no unique connection between total
]
stored energy and the releasable energy. Thus, establishing the magnitude of
{
the stored energy in non-power reactor graphite by empirical measurements would not provide the information needed to evaluate this potential. Because the releasable stored energy saturates, an upper bound on the stored energy that C. E. Ashbaugh, N. C. Ostrander, and H. Perlman, " Graphite Stored Energy in the 3
I UCLA Research Reactor," Transactions of the ANS, Vol. 52, 1986, p. 372.
13 1
8 4
can be released to 700 C can be determined from existing data. Therefore, no measurement of stored energy is required.
Also, because of the several conditions required to initiate graphite burning in addition to a graphite temperature of 650*C, the potential to initiate or l
maintain a graphite-burning incident is essentially independent of stored energy in the graphite. This further supports the conclusion that no measure-ment of stored energy is needed.
Many of the commenters who opposed the petition cited a violation of ALARA considerations because stored energy measurements would not provide needed
- lg 1
information, but would incur radiological exposures. The impracticality of For taking the samples and making the measurements was also pointed out.
ah' example, sampling the graphite reflector pieces in the ends of a TRIGA fuel pin would require breaching the fuel pin cladding as well as providing f]
shielding against the fuel pin's radioactivity. Similar challenges would be f
associated in taking a sample from graphite reflector components clad with In addition, it was pointed out that numerous samples would be required metal.
j to establish the true magnitude of stored energy in the various graphite j
II l
components.
L' f)
The staff has considered the relevant BNL findings and the comments received Jh and has concluded that empirical measurement of stored energy in non-power hh reactor graphite components is not practical nor is it necessary to ensure the health and safety of the public, b
(7) The petitioner refers to "one commercial power reactor," indicating that it has no fire response plans for combating graphite fires. The petitioner also states that " graphite is used as a moderator in the Fort St. Vrain l
nuclear power plant in Colorado."
Other than the lack of graphite fire response plans, the petitioner does not j
However, it is implied identify specific concerns related to Fort St. Vrain.
that all reactors using graphite components are subject to CBG's concerns and In reality, the petition and requirements are really directed at l
assertions.
NRC-licensed non-power reactors.
14
Fort St. Vrain it a high-temperature gas-cooled reactor (HTGR) owned and oper-ated by Public Service Company of Colorado.
Its design capacity is 330 MWe.
It uses a ceramic fuel particle (uranium and thorium carbide) clad with silicon carbide and multiple layers of pyrolytic carbon. The fuel particles are compacted into small rods and installed in fuel holes in the hexagonal graphite fuel blocks.
Including the reflectors there are 500 tons of reactor graphite in the core. The reactor coolant is helium with an average inlet temperatureof762*F(405"C)andanoutlettemperatureof1445*F(785*C). The average graphite moderator temperature is 1380*F (749'C). These characteristics are far different than those of the non-power reactors. BNL has reviewed Fort g
St. Vrain parameters in relation to graphite stored energy and concludes in g
Section 7 of its report, " Fort St. Vrain operates at temperatures that preclude accumulation of stored energy. There are no known problems associated with j
stored energy in graphite for operating temperatures associated with HTGRs."
The staff agrees with BNL's conclusion and can find no reason to empirically measure the stored energy in Fort St. Vrain's graphite components.
L l
In response to an NRC request, Public Service Company of Colorado addressed the implications of the Chernobyl accident for Fort St. Vrain. The licensee J{
submitted a final report entitled " Design Differences, Air Ingress and Graphite Oxidation, and Steam Ingress and Water Gas Generation" (P-86641,
- f[
December 4,1986). The staff has reviewed the report and concludes that the Q
only significant similarity between Chernobyl and Fort St. Vrain reactors is f
that they both contain a large amount of graphite moderator. There are
[
design differences between these reactors that preclude an accident similar to k;
the Chernobyl accident at Fort St. Vrain.
Furthemore, on the basis of its review, the staff concluded that the structural integrity of the Fort St. Vrain prestressed concrete reactor vessel would be maintained during and after the assumed accident scenarios. Although the initiating events are beyond the plant's original design basis, the plant design appears to have an adequate margin of safety to withstand these events.
The staff's coments and conclusions can be found in the NRC Public Document Room under Docket No. 50-267, in a letter dated April 1, 1987, Accession No.
8704090248.
15
)4 The petitioner's assertion that graphite burning and oxidation were not included in the staff's evaluation for Fort St. Vrain is in error,.This subject was thoroughly reviewed in both the construction permit and operating 3
license safety evaluations. These staff evaluations may be found in the Public l
Document Room in the 50-267 docket file. The licensee's updated Fort St.
Vrain Final Safety Analysis Report, Section 14, contains much of the information and analyses submitted for NRC review. The staff concluded that significant graphite oxidation at Fort St. Vrain was not credible.
(Note:
In
/
addition to the previously discussed conditions necessary for graphite burning, Fort St. Vrain must suffer simultaneous independent structural failures li!
resulting in the release of the inert helium and the subsequent supply of an f
adequate' air /oxygenflow). The staff finds no basis for changing its previous conclusions. The licensee for Fort St. Vrain has met the requirements of f
10 CFR 50, Appendix R (which sets forth fire protection features required to satisfy Criterion 3 of 10 CFR 50, Appendix A) and has an NRC-approved emergency
~
plan that meets 10 CFR 50, Appendix E.
The Fort St. Vrain fire protection
]
program and emergency plan specify the necessary organization. plans. and j
procedures to provide the necessary protection of the health anc safety of the public even in the very unlikely event of a graphite fire.
T Q9 L
d.
16
1 9
i
.r i
BASIS FOR DENIAL o
The NRC denies the petitioner's request to amend 10 CFR 50 to require
, licensees whose reactors employ graphite as a neutron moderator or reflector I
and whose licensed power is greater than 100 W to:
(1) formulate and submit for NRC approval fire response plans for combating a reactor fire: involving graphite and other constituent reactor parts j
(e.g., fuel);
(2) formulate and submit for NRC approval evacuation plans in case of a h
reactor fire; and i i I95f t
d !'
(3) perform measurements of the Wigner energy stored in the graphite of their reactors, and submit these measurements to the NRC for review together with a revised safety analysis that shall address the risk and consequences p
of a reactor fire.
I.,.
This denial is based on the following:
':q s ji h[
(1) Each licensee of a non-power reactor has submitted an emergency plan that M
has been approved as meeting the requirements of 10 CFR 50, Appendix E.
k,k The petitioner has not demonstrated that these plans do.not provide an e
appropriate level of protection of the health and safety of the public.
(2) The licensee for Fort St. Vrain has an approved emergency plan that meets the requirements of 10 CFR 50, Appendix E, as well as an approved fire protection program that meets the requirements of 10 CFR 50, Appendix R.
In addition, at the request of the NRC, the licensee has submitted a report addressing the implications of the Chernobyl accident for Fort St.
Vrain. The report has been reviewed and approved by the staff. The petitioner has not provided a technical basis that would show that an additional fire response plan would enhance the protection provided for the health and safety of the public by the existing emergency plan and fire protection program.
17
4 (3) Measurement of maximum stored energy in.on-power reactors are not neces-sary to ascertain the releasable stored energy in graphite components below 650 C.
Existing knowledge provides this information which is adequate for 3 safety evaluation of the effect of stored energy on the potential for graphite burning and the associated danger to the health and
~
safety of the public. Additionally, such measurem uts are contrary to the NRC's ALARA principle, since unneeded knowledge would be sought at the j@
' expense of unnecessary personnel exposure.
Accordingly, the Commission denies the petition.
hO cdb day o y j y 1987.
Dated at '3ethesda, Maryland, this
'g.
(,
For the Nuclear Regulatory Commission M
f
. n, -
lt
-t jh
[p.
</
~
vict_r Stells d r.
g o
og Executive Directo.
for Operations q
f l
)
18
- - _ _ _ _ _ _ _ _ _ _ _ _ _